Carburetor EGR port question
Simpson
on a carburetor with the engine revved to about 2000rpm?
I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
Dakota V6 engine and failed the NO part of the California smog test. The
HC and CO tests passed well below average. I came back home and
checked the action on the EGR valve. No movement on the visible piston
when the engine was revved.
The EGR valve checked out okay when tested. It opened with less than 10
inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
are all in good shape, no leaks.
I checked the vacuum at the EGR port on the brand spanking new
carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
Manifold vacuum is 19 inches at a 700rpm idle.
What gives?
Mike Romain
I don't know that particular carb, but have seen that kind of failure
before. When I saw it it was a gasket in wrong or the wrong one in so a
notch in the base plate was covered when it was supposed to be open.
The other times I have seen the base plate in upside down. There are
notches in some that need to be on the carb side, not the manifold side
and if folks don't know this, the plate can be in wrong.
I would figure the port you are using was blocked or it would have one
or the other types of vacuum.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
'New' frame in the works for '08. Some Canadian Bush Trip and Build
Photos: http://mikeromainjeeptrips.shutterfly.com
Simpson
> "Simpson" wrote
I'm absolutely sure. I have a spare carb of the same design that is
disassembled. There are not many who are more familiar with the guts of
this carb than I am. I became knowledgeable about it through necessity.
The truck came stock with a Holley 6280, which is the electronic
feedback version of the 2280, the main difference being a fuel mixture
control solenoid. The solenoid is no longer available as a replacement
part and when it goes the only recourse is to locate a used one, which
in my experience is no better than the one that went south. So I decided
to replace the feedback 6280 with the non-feedback 2280. The problem
with the mixture control solenoid first surfaced about eight years ago.
After sleeping on it, I think the problem may be a leak in the purge
line to the charcoal canister. This purge line enters the carb through a
port in the exact same place as the EGR port, just above the closed
throttle plates. This would explain the low vacuum at the EGR port. The
lack of EGR function, plus the vacuum leak, which would cause a lean
condition, would combine to create a higher than normal temperature in
the combustion chamber resulting in the abnormally high NO readings. The
ceramic insulators on the plugs have that very white look caused by a
lean fuel mix. Soon as I finish my morning cup I'm going to warm up the
engine, disconnect the purge line, plug the purge line port in the carb
and test the EGR function again.
>
> A few pages of 2280 info a quick search found.....
> http://www.slantsix.org/articles/choke-adjust/carb-info/2280-info.jpg
> http://www.slantsix.org/articles/choke-adjust/carb-info/2280-info2.jpg
> http://www.slantsix.org/articles/choke-adjust/carb-info/2280-info3.jpg
> http://www.slantsix.org/articles/choke-adjust/carb-info/2280-info4.jpg
>
>
--
Chuck Norris can fool all of the people all of the time and Chuck Norris
supports McCain.
McCain -- it rhymes with Hussein, Bahrain, cocaine, insane, wolfbane,
chest pain and chow mein.
Simpson
> Simpson wrote:
>> Does anyone have any idea how much vacuum should develop at an EGR port
>> on a carburetor with the engine revved to about 2000rpm?
>>
>> I installed a brand spanking new Holley 2280 carburetor on my 87 Dodge
>> Dakota V6 engine and failed the NO part of the California smog test. The
>> HC and CO tests passed well below average. I came back home and checked
>> the action on the EGR valve. No movement on the visible piston when the
>> engine was revved.
>>
>> The EGR valve checked out okay when tested. It opened with less than 10
>> inches of vacuum and stayed open indefinitely. The Coolant Vacuum Switch
>> Cold Closed (CVSCC) is operating correctly. The vacuum hoses involved
>> are all in good shape, no leaks.
>>
>> I checked the vacuum at the EGR port on the brand spanking new
>> carburetor and only got about 1 or 2 inches of vacuum at about 2000 rpm.
>>
>> Manifold vacuum is 19 inches at a 700rpm idle.
>>
>> What gives?
>>
>
> I don't know that particular carb, but have seen that kind of failure
> before. When I saw it it was a gasket in wrong or the wrong one in so a
> notch in the base plate was covered when it was supposed to be open.
>
> The other times I have seen the base plate in upside down. There are
> notches in some that need to be on the carb side, not the manifold side
> and if folks don't know this, the plate can be in wrong.
Could this 'base plate' be a one inch aluminum spacer with a single
manifold vacuum port? Or are you referring to the actual throttle
portion of the carb? That would be kind of hard to put in upside down.
In any case, as in my reply to MasterBlaster, I suspect a leak in the
canister purge line, which enters the carb just above the closed
throttle plates, same as the EGR port.
>
> I would figure the port you are using was blocked or it would have one
> or the other types of vacuum.
It's brand new, straight from the Holley factory, after sitting on some
shelf for about 20 years or more.
Mike Romain
Yes it could. Sometimes the kits come with multiple types of base
gaskets with different holes or slots.
Or are you referring to the actual throttle
> portion of the carb? That would be kind of hard to put in upside down.
> In any case, as in my reply to MasterBlaster, I suspect a leak in the
> canister purge line, which enters the carb just above the closed
> throttle plates, same as the EGR port.
There is an easy test for that though I don't think it can be the
trouble unless you were measuring the vacuum downstream vs at the carb
nipple, just pinch the line closed.
BigIronRam
"Simpson" <aso-...@epoxy.com> wrote in message
news:wwaEj.14577$5K1....@newssvr12.news.prodigy.net...
Are you absolutely certain you haven't bypassed the vacuum amplifier? As I
recall, venturi vacuum only generates around two inches vacuum max and thus
needs the vacuum amplifier to operate the EGR valve. Again, if I recall
correctly, the amplifier will boost it to around 8 inches.
Simpson
I found the problem. There are two available ports that tap into the
carb just below the closed throttle plates. One develops vacuum and the
other doesn't. The one that doesn't develop vacuum is designated in the
installation sheet that came packed with this new carb as the 'EGR
vacuum line'. The one that does develop vacuum is designated as the
'spark vacuum line'.
On this version of the 2280, the designated EGR port is tied into
another port that is much higher up in the venturi via an external
vacuum hose with a tee fitting, and this tee fitting is then supposed to
connect to the EGR valve. However, the designated EGR port just doesn't
develop sufficient vacuum as measured directly with a vacuum meter. With
or without the connection to the higher port, the vacuum is the same,
less than two pounds at over 2000rpm. The EGR valve begins to open at
about 3 pounds and is fully opened at about 5 pounds.
The port designated as the spark vacuum line *does* develop the proper
vacuum to operate the EGR valve. The spark vacuum on this truck is
supplied directly from the manifold vacuum. I've got the factory manual
which shows this in the same vacuum hose routing diagram that is pasted
to the underside of the hood.
So whatever the problem is with the designated EGR port on this carb,
the designated spark vacuum port has the proper vacuum characteristics
to operate the EGR valve: no vacuum at idle, increasing vacuum as the
throttle is opened. If I connect the EGR valve directly to the
designated spark vacuum port the EGR valve responds to the throttle as
it is supposed to. However, if I connect the designated spark vacuum
port to the higher port via the tee fitting, the response is sluggish to
non-existent. Therefore, in the interest of proper EGR operation and
passing the smog test, I am chucking what's in the instructions and
going with my gut on this one.
Simpson
Mike, I solved the problem. See my detailed reply to BigIronRam in this
thread.
Thanks, for the help. You were on the right track as far as the port
probably being blocked goes. Whatever the reason, it just wasn't
developing EGR vacuum characteristics and would not even make it to 2
pounds at 2,000rpm.
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> This would explain the low vacuum at the EGR port. The
> lack of EGR function, plus the vacuum leak, which would cause a lean
> condition, would combine to create a higher than normal temperature in
> the combustion chamber resulting in the abnormally high NO readings.
Not to nit pick but lean air fuel mixtures don't burn hotter.
They burn slower which causes associated component temperatures
to rise. Lean doesn't cause higher NOx, the extra O2 in the
exhaust from a lean mixture makes the reduction bed of a 3 way
catalyst less efficient resulting in higher NOx at the tail pipe.
Simpson
Nit picking appreciated! It's always valuable to learn more precisely
what is going on. It makes perfect sense to me the way that you
explained it. Perhaps you could enlighten me on the effect of ignition
timing on emissions.
I just got back from passing the smog test after initially failing it.
The failure was caused by improper vacuum to the EGR valve deom the
carburetor and a minor manifold vacuum leak. The vacuum being supplied
to the EGR valve by the Holley 2280 carburetor was insufficient to open
the EGR valve, even at over 2000rpm. This non-functioning EGR valve and
the minor manifold vacuum leak caused a measurement of over 3600 PPM of
NOx. Anything over 1195 PPM is a failure. Below is the failed test results.
--------------------
Percent of CO2
15mph 1333rpm - 10.8
25mph 1309rpm - 10.7
--------------------
Percent of O2
15mph 1333rpm - 5.9
25mph 1309rpm - 6.0
-------------------
HC PPM
15mph 1333rpm - 34 - PASS (maximum allowable is 134)
25mph 1309rpm - 26 - PASS (maximum allowable is 106)
-------------------------
Percent of CO
15mph 1333rpm - 0.01 - PASS (maximum allowable is 0.90%)
25mph 1309rpm - 0.01 - PASS (maximum allowable is 1.14%)
--------------------------------------------------------
NOx PPM
15mph 1333rpm - 3641 - GROSS POLLUTER (maximum allowable is 1095)
25mph 1309rpm - 3225 - GROSS POLLUTER (maximum allowable is 1140)
-----------------------------------------------------------------
After failing the test, I checked the action of the EGR valve and found
the condition I described above. After correcting the condition I took
the truck back and passed the test with the following results.
--------------------
Percent of CO2
15mph 1333rpm - 10.4
25mph 1309rpm - 10.7
--------------------
Percent of O2
15mph 1333rpm - 6.7
25mph 1309rpm - 6.1
-------------------
HC PPM
*15mph 1333rpm - 132 - PASS (maximum allowable is 134)*
25mph 1309rpm - 65 - PASS (maximum allowable is 106)
-------------------------
Percent of CO
15mph 1333rpm - 0.01 - PASS (maximum allowable is 0.90%)
25mph 1309rpm - 0.04 - PASS (maximum allowable is 1.14%)
--------------------------------------------------------
NOx PPM
15mph 1333rpm - 626 - PASS (maximum allowable is 1095)
25mph 1309rpm - 606 - PASS (maximum allowable is 1140)
------------------------------------------------------
I'm a bit concerned that the truck passed the 15mph test for HC by only
2 PPM. I would like to try to lower the HCs from the tailpipe. The
catalytic converter is a brand new replacement. Would changing the
ignition timing lower the HC reading? Or changing the air fuel ratio
through either resizing the main jets or adjusting the float level? The
ignition timing is currently set at 7 degrees BTDC with the vacuum line
disconnected from the transducer at the computer, as per the shop manual.
The carb is a new (not rebuilt) Holley 2280. It is the non-feedback
version of the Holley 6280 that came stock with this 87 Dakota V6. The
mixture control solenoid for the Holley 6280 is no longer available as a
replacement part so I tracked down a new 2280 on eBay and bolted it on.
This configuration no longer benefits from the input from the O2 sensor,
but it was the best I could do on short notice.
The way I see it I have three main ways to lower HCs:
1. Advance or retard the ignition timing
2. Enrich or lean out the fuel mixture by increasing or decreasing the
size of the main jets in the carb.
3. Enrich or lean out the fuel mixture by raising or lowering the level
of fuel in the bowl via the float setting, which is currently stock.
From the test results, I have more room to increase NOx than HCs so if
lowering HCs cause NOX to rise, there is some headroom there.
Please feel free to nitpick away. It would go unappreciated.
Jack
Mike
I don't know why your HC's went up just from fixing an inop EGR valve ? High
HC is from a rich mixture. Did you also mess with the charcoal canister vent
line ? I would first try to lower the HC reading by leaning out the idle
mixture screws, if that doesn't work then try the float level before you try
switching main jets.
One other question, was the engine and converter fully warmed up before the
test ?
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
Hi Jack,
Does this truck have an air pump? The reason I ask is because
there is an awful lot of O2 in the exhaust sample.
If the truck has an air pump, that would account for it, but
unfortunately the dilution from the air pump makes analyzing the
gas samples difficult.
If there is NO air pump, here;s what I think; too much O2, too
much HC, not enough CO2 and not enough CO. That is a lean
mixture. Richening it up a bit will drop the HCs, lower the O2
and increase the CO2. A richer mixture doesn't contribute to more
NOx typically as long as the other NOx treatments are functioning
as they should.
Advancing ignition timing hurts NOx, it tends to hurt HC and CO
also, the exception being if the ignition system is marginal and
HCs are caused by an ignition misfire, this is because it takes
less voltage to ionize the plug gap the farther the piston is
away from TDC (advanced). Late ignition timing tends to help HC
and CO for the exact reasons given in my first post, hotter
combustion chamber wall, hotter exhaust valve and port, but late
timing can reveal marginal ignition components.
CO2 is the best indicator of combustion efficiency, higher is
better so anything you do that raises CO2 shows you're headed in
the right direction. I mention this because your CO2 reading are
low, by about 3 percent or more.
An efficient catalytic converter lowers CO and HC and raises CO2
by its very nature, OEM catalysts are usually 90%+ efficient,
aftermarket catalysts are usually only 40%-50% efficient.
The only way to tell if the tailpipe readings are due to an
inefficient catalyst is to take pre-cat and post cat gas samples
and calculate the efficiency.
Without an air pump diluting the sample a stoichiometric air/fuel
ratio would read .5% CO and .5% O2 give or take .1% either way.
Simpson
Hi Mike,
As to the last question, yes, the engine was fully warmed up as
indicated by the temp gauge. I don't know what constitutes 'fully warmed
up' for the cat. The engine was fully warmed up when the smog tech drove
it onto the dynamometer. He did a 15mph test and a 25mph test, during
which the engine was turning at about 1340 rpm, as indicated on the test
result sheet. I am somewhat mystified by that. I would expect the rpms
to be higher during the 25mph test, but it was actually lower by 22
rpms. Another one of life's unexplained mysteries. The test was long
enough to warm up the cat, I would guess.
There may also have been a minor manifold vacuum leak. The bolts fixing
the EGR valve to the intake manifold were slightly loose. If I had a
manifold vacuum leak during the first test, that would have introduced a
lean mix. Fixing the leak would richen up the mix. That would explain
the higher HC on the second test.
One bolt on the EGR was so loose that when I tried to loosen it with
what appeared to my eye to be a 1/2" hex head socket, I thought I must
have got it wrong as there was no resistance, so I put on a 7/16" socket
and that didn't fit. I tried metric and nothing that fit on the bolt
head gripped. That's when I tried my fingers and the bolt unscrewed easy
as pie. Being as I am my own mechanic I felt somewhat stupid, but soon
got over it, remembering that shit happens. So I probably had a vacuum leak.
I didn't mess with the charcoal vent line except to put a hose clamp
(damn, you're good) on where it connected to the carb. But to be honest,
I don't think it was all that loose, but I had a couple of extra small
hose clamps knocking around and figured what the hey.
As far as leaning out the idle mixture screws goes, how much does the
idle circuit figure in at 1350 rpm on the engine and 15 and 25 mph on
the speedometer?
Roger on adjusting the float level before changing the jets. I like that
because it doesn't require getting new jets, just bending metal.
The Holley 2280 carb that I put on this 3.9L (239 cu) engine was used on
Chrysler's 318 engine. It's the same body as the Holley 6280 that came
stock on the 87 Dakota, but it doesn't have the mixture control
solenoid, which is no longer available as a replacement part. As this
part went south on the original carb, and any rebuilt 6280 will have an
old mixture control solenoid, those of us who have this carb are left to
our own devices. My solution, as was that of others with the know-how,
was to install a non-feedback 2280. Just so ya know...
Do you have any light to shed on adjusting the timing either way,
advanced or retarded, to bring down HCs? I have found arguments both
ways while googling the web and the groups.
Thanks for your sharing your knowledge.
Jack
Simpson
Yes it does. It injects air directly into the cat.
> The reason I ask is because
> there is an awful lot of O2 in the exhaust sample.
That's what I thought.
> If the truck has an air pump, that would account for it, but
> unfortunately the dilution from the air pump makes analyzing the
> gas samples difficult.
> If there is NO air pump, here;s what I think; too much O2, too
> much HC, not enough CO2 and not enough CO. That is a lean
> mixture. Richening it up a bit will drop the HCs, lower the O2
> and increase the CO2.
I'm confused. If there is excess O2 and excess HC, what prevents them
from combining in a burn to produce more CO2?
> A richer mixture doesn't contribute to more
> NOx typically as long as the other NOx treatments are functioning
> as they should.
That's seems to be in line what what I have read concerning the
formation of NOx, which is mainly a factor of a too hot combustion chamber.
>
> Advancing ignition timing hurts NOx, it tends to hurt HC and CO
> also, the exception being if the ignition system is marginal and
> HCs are caused by an ignition misfire, this is because it takes
> less voltage to ionize the plug gap the farther the piston is
> away from TDC (advanced).
I can't quite follow you on this. Did you mean that "it takes *more*
voltage to ionize the plug gap the farther the piston is away from TDC
(advanced)."?
> Late ignition timing tends to help HC
> and CO for the exact reasons given in my first post, hotter
> combustion chamber wall, hotter exhaust valve and port, but late
> timing can reveal marginal ignition components.
Plugs, cap and rotor are all very healthy looking, but the resistance of
the wires all measure below the lower spec for resistance in the shop
manual. 250 ohms per inch is the minimum spec. Mine are at about 200.
At this point, I should probably mention that I have an MSD Blaster
Ignition, model PN 5900, installed:
http://www.msdignition.com/ignition_1_5900.htm
More precisely, it was installed when the truck failed the test and not
installed when it passed, but I don't think it had anything to do with
the failure. The non-functioning EGR system definitely played the major
role, IMO. I unconnected the MSD unit for the retest because I thought
that perhaps the more powerful and longer duration spark it supplied
might be contributing to the hot combustion chamber conditions that
caused the high NOx reading.
>
> CO2 is the best indicator of combustion efficiency, higher is
> better so anything you do that raises CO2 shows you're headed in
> the right direction. I mention this because your CO2 reading are
> low, by about 3 percent or more.
>
> An efficient catalytic converter lowers CO and HC and raises CO2
> by its very nature, OEM catalysts are usually 90%+ efficient,
> aftermarket catalysts are usually only 40%-50% efficient.
> The only way to tell if the tailpipe readings are due to an
> inefficient catalyst is to take pre-cat and post cat gas samples
> and calculate the efficiency.
>
> Without an air pump diluting the sample a stoichiometric air/fuel
> ratio would read .5% CO and .5% O2 give or take .1% either way.
So the truck has an air pump, and given what we have hashed through here
so far, I feel that, just to be sure, I should replace the plugs, wires,
cap and rotor before concerning myself with the jets or the float level,
even if I think they are in good shape.
BTW, do you happen to know if plug wires can *lose* resistance over time?
I hope all is well in your part of the world.
Jack
aarcuda69062
"Mike" <m...@localnet.com> wrote:
Why wouldn't the HCs increase? When the exhaust gas
recirculation valve opens, what is it allowing into the intake
manifold/ combustion chamber?
CO2, CO, O2, NOx and HC.
When the exhaust gas recirculation valve opens what happens to
manifold pressure?
It goes up.
What does the power valve do when manifold pressure goes up?
It opens and allows more HC (gasoline) to flow into the venturi
in the carb.
Simpson
Yes, it is reasonable to assume that these gases would increase in the
exhaust stream over their presence in a non-EGR exhaust stream, but only
in proportion to the total EGR gases that are reintroduced to a fresh
intake fuel mixture, 5 to 15 percent from what I have read. In my case,
the HC content increased 388% at 15 mph.
>
> When the exhaust gas recirculation valve opens what happens to
> manifold pressure?
> It goes up.
> What does the power valve do when manifold pressure goes up?
> It opens and allows more HC (gasoline) to flow into the venturi
> in the carb.
My source tell me you got that backwards. As manifold pressure goes up,
the power valve is closed. As manifold pressure goes down, the power
valve opens.
My source is "Holley Carburetors and Manifolds" by Mike Urich and Bill
Fisher. HPBooks, 1987:
When the engine is called upon to produce power in excess of normal
cruising requirements, the carburetor has to provide a richer mixture.
Added fuel for power operation is supplied by the power system
controlled by manifold vacuum.
Manifold vacuum accurately indicates engine load. Vacuum is usually
strongest at idle. As load increases, the throttle valve must be opened
wider to maintain a given speed. This offers less restriction to air
entering the intake manifold and reduces manifold vacuum.
A vacuum passage in the carburetor applies manifold vacuum to a
power-valve piston or diaphragm. At idle or normal cruising conditions,
manifold vacuum acting against a spring holds the valve closed. As high
power demands load the engine, manifold vacuum drops.
Below a preset point, usually about 6 inches of mercury (in.Hg), the
power valve spring overcomes manifold vacuum and opens the power valve.
Fuel flows through the power valve and through a power-valve restriction
to join fuel already flowing through the main metering system from the
main jet. The mixture is richened.
Scroll down to the yellow hi-lited text
Jack
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> > Why wouldn't the HCs increase? When the exhaust gas
> > recirculation valve opens, what is it allowing into the intake
> > manifold/ combustion chamber?
> > CO2, CO, O2, NOx and HC.
>
> Yes, it is reasonable to assume that these gases would increase in the
> exhaust stream over their presence in a non-EGR exhaust stream, but only
> in proportion to the total EGR gases that are reintroduced to a fresh
> intake fuel mixture, 5 to 15 percent from what I have read. In my case,
> the HC content increased 388% at 15 mph.
My reply to Mike wasn't based upon your readings, it was based
upon his statement.
In your case, if the engine is running lean to begin with, the
addition of EGR is going to displace any burnable mixture that
might have stood a chance of combusting.
> >
> > When the exhaust gas recirculation valve opens what happens to
> > manifold pressure?
> > It goes up.
> > What does the power valve do when manifold pressure goes up?
> > It opens and allows more HC (gasoline) to flow into the venturi
> > in the carb.
>
> My source tell me you got that backwards.
Nope.
> As manifold pressure goes up,
> the power valve is closed.
As manifold -vacuum- goes -up- the power valve closes.
Manifold vacuum is a great way to determine engine health, it's a
lousy way to refer to how an engine and fuel system operate.
Right now assuming your truck is parked and not running, the
manifold pressure is high and the power valve is open.
Assuming that you're somewhere below 1000 feet altitude, the
pressure inside your manifold parked and engine not running is
probably somewhere near 28 or 29 inches of mercury.
If you were to then start the engine, the manifold pressure might
drop to 10 inches of mercury. If we subtract the 10 inches of
mercury running from the 29 inches of mercury measured with the
engine not running, we get 19 inches which would be a fairly
healthy "manifold vacuum" reading.
> As manifold pressure goes down, the power
> valve opens.
>
> My source is "Holley Carburetors and Manifolds" by Mike Urich and Bill
> Fisher. HPBooks, 1987:
I know the book.
> When the engine is called upon to produce power in excess of normal
> cruising requirements, the carburetor has to provide a richer mixture.
> Added fuel for power operation is supplied by the power system
> controlled by manifold vacuum.
>
> Manifold vacuum accurately indicates engine load. Vacuum is usually
> strongest at idle. As load increases, the throttle valve must be opened
> wider to maintain a given speed. This offers less restriction to air
> entering the intake manifold and reduces manifold vacuum.
>
> A vacuum passage in the carburetor applies manifold vacuum to a
> power-valve piston or diaphragm. At idle or normal cruising conditions,
> manifold vacuum acting against a spring holds the valve closed. As high
> power demands load the engine, manifold vacuum drops.
>
> Below a preset point, usually about 6 inches of mercury (in.Hg), the
> power valve spring overcomes manifold vacuum and opens the power valve.
> Fuel flows through the power valve and through a power-valve restriction
> to join fuel already flowing through the main metering system from the
> main jet. The mixture is richened.
>
> http://books.google.com/books?id=ClyzQHlQbjYC&pg=PA28&lpg=PA28&dq=%22When+the+
> engine+is+called+upon+to+produce+power%22&source=web&ots=SdPf9kX1c4&sig=bDsxQZ
> oaKdSk_aQ98Kxp41-vp4k&hl=en
Please understand, I'm not referring to manifold vacuum.
Simpson
Ahn... you're right.
You referred to manifold pressure, not vacuum.
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> > Hi Jack,
> > Does this truck have an air pump?
>
> Yes it does. It injects air directly into the cat.
I suspected so. The only way to make meaningful determination of
the gas readings is to take the gas readings again with the air
pump disabled.
> > The reason I ask is because
> > there is an awful lot of O2 in the exhaust sample.
>
> That's what I thought.
At this point, it's nether good or bad until you attempt to use
the gas readings as a diagnostic aid.
There's a thing called the Brettschneider equation which allows
with the input of 4 or 5 gas reading to accurately calculate the
air fuel ratio. The equation works whether or not there is a
catalytic converter ahead of where the sample is taken.
What the Brettschneider equation can not compensate for however
is false air introduced either by leaks in the exhaust pipes or
joints or an auxiliary air system such as is on your truck.
> > If the truck has an air pump, that would account for it, but
> > unfortunately the dilution from the air pump makes analyzing the
> > gas samples difficult.
> > If there is NO air pump, here;s what I think; too much O2, too
> > much HC, not enough CO2 and not enough CO. That is a lean
> > mixture. Richening it up a bit will drop the HCs, lower the O2
> > and increase the CO2.
>
> I'm confused. If there is excess O2 and excess HC, what prevents them
> from combining in a burn to produce more CO2?
Low catalytic converter efficiency.
The excess gases are in the wrong ratio.
Ever use a cutting torch?
If you set the flame as oxidizing, you won't get the results you
need. If you set the flame as carburizing, you won't get the
results you need.
One size fits all replacement parts...
I've seen vehicles fail emissions tests because the air pump was
too small, I've seen vehicles fail emissions test because the air
pump was too big. (the OEMs rate/size them by CFM)
> > A richer mixture doesn't contribute to more
> > NOx typically as long as the other NOx treatments are functioning
> > as they should.
>
> That's seems to be in line what what I have read concerning the
> formation of NOx, which is mainly a factor of a too hot combustion chamber.
>
> >
> > Advancing ignition timing hurts NOx, it tends to hurt HC and CO
> > also, the exception being if the ignition system is marginal and
> > HCs are caused by an ignition misfire, this is because it takes
> > less voltage to ionize the plug gap the farther the piston is
> > away from TDC (advanced).
>
> I can't quite follow you on this. Did you mean that "it takes *more*
> voltage to ionize the plug gap the farther the piston is away from TDC
> (advanced)."?
No, opposite that. If you have a weak ignition system, chances
are it will present itself or be more problematic with less
ignition advance.
if I see low firing voltage on a secondary waveform on a scope
and no indication of plug fouling, I first grab my timing light
and check ignition timing.
You can search for my posts in either of the Chevy truck groups,
you want to focus on exchanges between myself and a poster named
"snoman" for my attempts to get him to understand why his truck
runs better with the ignition timing jacked sky high contrary to
the hundreds of identical trucks I've worked on in the last 20
years that would just ping, rattle and set ESC codes when set the
same or similar.
> > Late ignition timing tends to help HC
> > and CO for the exact reasons given in my first post, hotter
> > combustion chamber wall, hotter exhaust valve and port, but late
> > timing can reveal marginal ignition components.
>
> Plugs, cap and rotor are all very healthy looking, but the resistance of
> the wires all measure below the lower spec for resistance in the shop
> manual. 250 ohms per inch is the minimum spec. Mine are at about 200.
Which shop manual specifies ohms per inch?
> At this point, I should probably mention that I have an MSD Blaster
> Ignition, model PN 5900, installed:
>
> http://www.msdignition.com/ignition_1_5900.htm
>
> More precisely, it was installed when the truck failed the test and not
> installed when it passed, but I don't think it had anything to do with
> the failure. The non-functioning EGR system definitely played the major
> role, IMO. I unconnected the MSD unit for the retest because I thought
> that perhaps the more powerful and longer duration spark it supplied
> might be contributing to the hot combustion chamber conditions that
> caused the high NOx reading.
Again, hot combustion chambers do not contribute to NOx formation.
Hotter combustion does contribute to NOx formation.
Hottest combustion typically occurs if the mixture is 2 percent
richer than stoichiometric.
> > Without an air pump diluting the sample a stoichiometric air/fuel
> > ratio would read .5% CO and .5% O2 give or take .1% either way.
>
> So the truck has an air pump, and given what we have hashed through here
> so far, I feel that, just to be sure, I should replace the plugs, wires,
> cap and rotor before concerning myself with the jets or the float level,
> even if I think they are in good shape.
It's cheap enough to do on that engine.
My hunch however is that the carb is a little lean.
> BTW, do you happen to know if plug wires can *lose* resistance over time?
Outside of leaking insulation, I can't say I've ever seen it in
37 years in the trade. The typical failure that would account
for high HCs would be an open plug wire.
> I hope all is well in your part of the world.
Ask me again tomorrow 8-) they're forecasting 8-14 inches of snow
for our area. We've already had over 100 inches this season
though most of it had melted in the last two weeks.
Good wrenching and let us know the results.
Mike Romain
>
> The way I see it I have three main ways to lower HCs:
>
One more way, a fresh oil change using conventional oil.
High HC's can come from oil getting past the rings also so a really thin
oil or old oil that goes 'thin' can bump them up.
Simpson
> Simpson wrote:.
>> The way I see it I have three main ways to lower HCs:
>>
>
> One more way, a fresh oil change using conventional oil.
>
> High HC's can come from oil getting past the rings also so a really thin
> oil or old oil that goes 'thin' can bump them up.
Oil is fresh and the rings seem to be in good shape. I can go all the
way between oil changes at 3,000 miles without having to add a quart. I
bought it new and changed oil and filter fairly regularly.
Simpson
Page 8D-10 of the
Chrysler Motors 1987 Shop Manual
2WD and 4WD Pickups
Dakota Trucks
Like the one shown here:
From the manual:
CABLE RESISTANCE CHART
Minimum---------------------Maximum
250 Ohms Per Inch 600 Ohms Per Inch
>
>> At this point, I should probably mention that I have an MSD Blaster
>> Ignition, model PN 5900, installed:
>>
>> http://www.msdignition.com/ignition_1_5900.htm
>>
>> More precisely, it was installed when the truck failed the test and not
>> installed when it passed, but I don't think it had anything to do with
>> the failure. The non-functioning EGR system definitely played the major
>> role, IMO. I unconnected the MSD unit for the retest because I thought
>> that perhaps the more powerful and longer duration spark it supplied
>> might be contributing to the hot combustion chamber conditions that
>> caused the high NOx reading.
>
> Again, hot combustion chambers do not contribute to NOx formation.
> Hotter combustion does contribute to NOx formation.
> Hottest combustion typically occurs if the mixture is 2 percent
> richer than stoichiometric.
Right... I went and re-read what you wrote about it in your first post.
>
>>> Without an air pump diluting the sample a stoichiometric air/fuel
>>> ratio would read .5% CO and .5% O2 give or take .1% either way.
>> So the truck has an air pump, and given what we have hashed through here
>> so far, I feel that, just to be sure, I should replace the plugs, wires,
>> cap and rotor before concerning myself with the jets or the float level,
>> even if I think they are in good shape.
>
> It's cheap enough to do on that engine.
> My hunch however is that the carb is a little lean.
I feel certain that the reasoning for this must be in one of your past
posts. It appears counterintuitive at first glance, though... a richer
mix to lower HCs at the tailpipe.
Would you suggest bigger main jets or a higher float?
Mike suggested leaning out the idle mixture screws to get lower HCs.
At this point I am a bit more knowledgeable, but not quite sure what to
do with it. What I need is tailpipe emissions wand like the one at the
shop so i can monitor the changes that take place for a given tweak.
>
>> BTW, do you happen to know if plug wires can *lose* resistance over time?
>
> Outside of leaking insulation, I can't say I've ever seen it in
> 37 years in the trade. The typical failure that would account
> for high HCs would be an open plug wire.
>
>> I hope all is well in your part of the world.
>
> Ask me again tomorrow 8-) they're forecasting 8-14 inches of snow
> for our area. We've already had over 100 inches this season
> though most of it had melted in the last two weeks.
>
> Good wrenching and let us know the results.
Will do, and thanks for all the input.
Mike
"aarcuda69062" <none...@sbcglobal.net> wrote in message
news:nonelson-F22BAF...@news.chi.sbcglobal.net...
Yep, the EGR valve allows exhaust gas back into the combustion chamber, but,
it is only a very small percentage of the total combution chamber volume. The
exhaust gas was already burnt once in the combustion chamber, how does running
it through the combustion chamber a second time cause the HC to increase even
further ? Isn't the HC reading from the smog test unburned hydrocarbons ?
>
> When the exhaust gas recirculation valve opens what happens to
> manifold pressure?
> It goes up.
> What does the power valve do when manifold pressure goes up?
> It opens and allows more HC (gasoline) to flow into the venturi
> in the carb.
Yep, that's how the power enrichment works as well but why such a jump in
HC ? This is the first time I remember seeing a NOx problem fixed were the HC
reading jumped up like that. Does this have anything to do with the vehicle
being equiped with an air pump ? We don't see too many air pumps on the east
coast.
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> From the manual:
>
> CABLE RESISTANCE CHART
>
> Minimum---------------------Maximum
> 250 Ohms Per Inch 600 Ohms Per Inch
Okay, if Chrysler says so.
> > Again, hot combustion chambers do not contribute to NOx formation.
> > Hotter combustion does contribute to NOx formation.
> > Hottest combustion typically occurs if the mixture is 2 percent
> > richer than stoichiometric.
>
> Right... I went and re-read what you wrote about it in your first post.
>
> >
> >>> Without an air pump diluting the sample a stoichiometric air/fuel
> >>> ratio would read .5% CO and .5% O2 give or take .1% either way.
> >> So the truck has an air pump, and given what we have hashed through here
> >> so far, I feel that, just to be sure, I should replace the plugs, wires,
> >> cap and rotor before concerning myself with the jets or the float level,
> >> even if I think they are in good shape.
> >
> > It's cheap enough to do on that engine.
> > My hunch however is that the carb is a little lean.
>
> I feel certain that the reasoning for this must be in one of your past
> posts. It appears counterintuitive at first glance, though... a richer
> mix to lower HCs at the tailpipe.
When a cylinder gets lean enough it begins to misfire and HC goes
up. The whole thing is a teeter totter balancing act.
> Would you suggest bigger main jets or a higher float?
I'd play with the main jets. A higher float can cause other not
so desirable results. (like dripping upon shut down)
> Mike suggested leaning out the idle mixture screws to get lower HCs.
Both of you should look at the chart on the first page of this PDF
http://www.autoshop101.com/forms/h56.pdf
See what I mean about teeter totter?
Which side of the bold black line is your high HC on?
Then look at the chart on page 2, pay attention to where O2 and
CO converge at stoichiometric, like I said earlier, .5% give or
take tenth.
Mike is certain that your high HC is because the mix is rich,
based upon -what- I have no idea since your gas numbers are
skewed by the false air from the air pump.
I'm saying that I "suspect" that it's actually too lean, maybe in
part because I thought you had mentioned that the plugs were
white.
> At this point I am a bit more knowledgeable, but not quite sure what to
> do with it. What I need is tailpipe emissions wand like the one at the
> shop so i can monitor the changes that take place for a given tweak.
http://www.autologicco.com/AllProducts/GasAnalyzer.shtm#GasPortabl
e
(sorry about the line wrap)
This is (IMHO) the best deal out there.
Simpson
Mike,
I just popped the top off the carb and removed the boost venturi to get
at the area around the throttle plates. The barrel that has the
designated EGR port has a perforation just above the closed throttle
plate just as I expected. When I attach a hose to the designated EGR
port I can blow air through the perforation. When I plug up the
perforation inside the venturi with my finger, the air flow stops. This
is the case with the other barrel that has the designated spark vacuum
port. The only difference between the two seems to be the relative size
of the venturi perforations, the EGR side being slightly smaller and the
height relative to the closed throttle plate.
three hours later... I just got back from ripping the carb out of its
moorings and teraing it down and comparing it with the old original.
Same body - different porting. I cut a new slot for the EGR port and
widened the holes that feed the canister purge line into the the venturi
just above the throttle plates, both mods to conform to the original.
The new carb also differed from the original through a hole in the
gasket that connects the throttle body to the main body. This hole in
the gasket on the new carb connected the EGR hole in the throttle body
just above the throttle plate in one barrel to a hole in the base of the
venturi. The original carb did not have this hole in the gasket or the
hole in the base of the venturi, so I flipped the gasket to put the hole
on the other side where nothing is happening and the hole is not
connecting anything to anything.
I am about to go out now and take it for a test drive to see what
happens after it warms up and the EGR circuit kicks in. I have a vacuum
meter teed into the vacuum line to the EGR valve so I should be able to
see if the mod works like the original. If not, I will negate that
particular mod in some fashion and go back to running the EGR valve from
the park vacuum port, which is what got me passed smog.
It's a frikken obsession, but I bought this truck new and I refuse to
let it die for want of a replacement mixture control solenoid.
Thanks Chrysler.
Thanks Holley.
Way to stand behind your products.
aarcuda69062
wrote:
> > Why wouldn't the HCs increase? When the exhaust gas
> > recirculation valve opens, what is it allowing into the intake
> > manifold/ combustion chamber?
> > CO2, CO, O2, NOx and HC.
>
> Yep, the EGR valve allows exhaust gas back into the combustion chamber,
> but,
> it is only a very small percentage of the total combution chamber volume.
So? If the air fuel mixture is lean to begin with, how does adding
exhaust gas make the flame propagate better?
> The exhaust gas was already burnt once in the combustion chamber, how does
> running
> it through the combustion chamber a second time cause the HC to increase even
> further ?
See above.
> Isn't the HC reading from the smog test unburned hydrocarbons ?
Yes it is.
Ever open an EGR valve at idle?
Did the engine run better or worse?
Do you suppose HC goes up or down if you open the EGR at idle?
> >
> > When the exhaust gas recirculation valve opens what happens to
> > manifold pressure?
> > It goes up.
> > What does the power valve do when manifold pressure goes up?
> > It opens and allows more HC (gasoline) to flow into the venturi
> > in the carb.
>
> Yep, that's how the power enrichment works as well but why such a jump in
> HC ? This is the first time I remember seeing a NOx problem fixed were the
> HC reading jumped up like that.
Not for me.
It's very common on some engines to repair a non functioning EGR for a
NOx failure and have the car fail on HC. Typical 4 cylinder where the
EGR feeds into the intake ports individually (4 separate EGR passages)
and 2 or 3 are plugged. The 1 or 2 that do flow EGR are over fed and
cause a misfire. Roto-Root the passages and everything is fine...
> Does this have anything to do with the vehicle
> being equiped with an air pump ?
The high HC? Maybe yes, maybe no. That's why there's a thing called
'diagnostics.' I'd watch the reading with the air pump disabled.
The OP has a 21 year old truck, what are the odds hat the air pump is
original? I couldn't get the air pump on my bought new 85 F-150 to last
more than three years.
Air pumps tend to have a generic universal design, what if instead of a
4 CFM air pump made for a 3.9 liter engine, he got a 10 CFM replacement
pump made for a 7.4 liter engine.
You -can- pump too much air into a catalytic converter and snuff out the
fire.
> We don't see too many air pumps on the east
> coast.
Dunno why, they were pretty common in the day that the OPs truck was
built.
Now they're likely to be electric.
Simpson
I just got back from modding the carb. See my last reply to Mike.
While I had the carb off, I removed the limiter caps and will try
readjusting the idle mixture screws as I have a rough idle. Apparently,
this truck has always idled rough, from what I hear and read. The HCs on
the successful test at 15mph test are double those at 25mph test - 132
to 65. The engine rpms for both tests reads virtually the same, though,
which is a mystery. But that mystery aside, I would guess that the idle
circuit plays more of a part in the fuel mixture at 15mph than at 25mph
and this transmission will go all day in third gear at 15 mph. Anyway,
what I guess I'm trying to say is that I will try riching up the idle
circuit first. Being as it would cost me up to 30 bucks for a dry run on
the dynamometer, I want to try everything that I can to get the ideal
adjustments lined for a try.
>
>> Would you suggest bigger main jets or a higher float?
>
> I'd play with the main jets. A higher float can cause other not
> so desirable results. (like dripping upon shut down)
I have some smaller jets from the old carb that worked in conjunction
with the mixture control solenoid. I hear that it's not always a good
idea to drill out jets because the shape of the jets is important to the
flow of the fuel, but is it always a bad idea?
I guess I should mention again that the carb that I put on this 3.9L
(239 cu) V6 was designed for a 318 from the early seventies. It probably
was designed for a Lean Burn system as it had a throttle position sensor
on it, which I took off, as this 87 Dakota is not a Lean Burn system, I
don't think. Anyway, there was no throttle position sensor on the
original carb, so off it came from the new one.
In any case, this 2280 Holley that was used on the 318 V8 is the same
body and capacity as the 6280 that came original on the 239 V6, so I am
assuming that it can be tweaked to run the 239 just fine.
>
>> Mike suggested leaning out the idle mixture screws to get lower HCs.
>
> Both of you should look at the chart on the first page of this PDF
>
> http://www.autoshop101.com/forms/h56.pdf
Wow, love it! Thanks for posting that!
>
> See what I mean about teeter totter?
>
> Which side of the bold black line is your high HC on?
The 15mph test, 132 PPM, is on the left, but the HC line on the graph
does not come down to 65 PPM, which was the result of the 25mph test.
>
> Then look at the chart on page 2, pay attention to where O2 and
> CO converge at stoichiometric, like I said earlier, .5% give or
> take tenth.
>
> Mike is certain that your high HC is because the mix is rich,
> based upon -what- I have no idea since your gas numbers are
> skewed by the false air from the air pump.
> I'm saying that I "suspect" that it's actually too lean, maybe in
> part because I thought you had mentioned that the plugs were
> white.
I will pay this the attention it deserves after I get back from a test
drive, or maybe tomorrow morning after a big mug of tea
>
>> At this point I am a bit more knowledgeable, but not quite sure what to
>> do with it. What I need is tailpipe emissions wand like the one at the
>> shop so i can monitor the changes that take place for a given tweak.
>
> http://www.autologicco.com/AllProducts/GasAnalyzer.shtm#GasPortabl
> e
> (sorry about the line wrap)
Not a problem.
>
> This is (IMHO) the best deal out there.
Yeow! Prices are on the high side for shade tree mechanic.
Mike Romain
> Mike Romain wrote:
>> Simpson wrote:.
>>> The way I see it I have three main ways to lower HCs:
>>>
>>
>> One more way, a fresh oil change using conventional oil.
>>
>> High HC's can come from oil getting past the rings also so a really
>> thin oil or old oil that goes 'thin' can bump them up.
>
> Oil is fresh and the rings seem to be in good shape. I can go all the
> way between oil changes at 3,000 miles without having to add a quart. I
> bought it new and changed oil and filter fairly regularly.
Mine has read high HC's with a lean miss on mine once.
Mike Romain
>
>
> When a cylinder gets lean enough it begins to misfire and HC goes
> up. The whole thing is a teeter totter balancing act.
I have had that happen to mine once.
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> I just got back from modding the carb. See my last reply to Mike.
>
> While I had the carb off, I removed the limiter caps and will try
> readjusting the idle mixture screws as I have a rough idle. Apparently,
> this truck has always idled rough, from what I hear and read. The HCs on
> the successful test at 15mph test are double those at 25mph test - 132
> to 65. The engine rpms for both tests reads virtually the same, though,
> which is a mystery. But that mystery aside, I would guess that the idle
> circuit plays more of a part in the fuel mixture at 15mph than at 25mph
> and this transmission will go all day in third gear at 15 mph. Anyway,
> what I guess I'm trying to say is that I will try riching up the idle
> circuit first. Being as it would cost me up to 30 bucks for a dry run on
> the dynamometer, I want to try everything that I can to get the ideal
> adjustments lined for a try.
>
> >
> >> Would you suggest bigger main jets or a higher float?
> >
> > I'd play with the main jets. A higher float can cause other not
> > so desirable results. (like dripping upon shut down)
>
> I have some smaller jets from the old carb that worked in conjunction
> with the mixture control solenoid. I hear that it's not always a good
> idea to drill out jets because the shape of the jets is important to the
> flow of the fuel, but is it always a bad idea?
Ya gotta do what ya gotta do.
Last fall had a guy bring me one of those kit cars that's a replica of a
20s something Mercedes Benz, the drive train is 78 or 79 Mustang V-6
with a 2 barrel Motorcraft carb. All stock engine wise, all emissions
equipment present and functioning. The car couldn't pass the state
IM-240 test. The only thing non-stock emissions related was the
exhaust, he had one of those small universal catalytic converters on it.
The original Mustangs had a 3 cat system.
Thing is way rich, CO is sky high. No way to fit two more cats on it.
Shoot the moon, pull the carb top off, remove the jets, solder 'em shut
and re-drill them .008" smaller. Why .008"? That was the next smallest
drill size in my number drill set. Re-assemble and took it to the test
station 2 miles away. The car fast passed which means it's running
significantly cleaner then it was before.
Is soldering and drilling a set of jets a kludge repair? Absolutely!
Did it fix the car? Hell yes. It passed the emissions test and he
called back 2 days later and said the car had never ran so good.
> I guess I should mention again that the carb that I put on this 3.9L
> (239 cu) V6 was designed for a 318 from the early seventies. It probably
> was designed for a Lean Burn system as it had a throttle position sensor
> on it, which I took off, as this 87 Dakota is not a Lean Burn system, I
> don't think. Anyway, there was no throttle position sensor on the
> original carb, so off it came from the new one.
So, a lean jetted carb is high on HC.
> In any case, this 2280 Holley that was used on the 318 V8 is the same
> body and capacity as the 6280 that came original on the 239 V6, so I am
> assuming that it can be tweaked to run the 239 just fine.
>
> >
> >> Mike suggested leaning out the idle mixture screws to get lower HCs.
> >
> > Both of you should look at the chart on the first page of this PDF
> >
> > http://www.autoshop101.com/forms/h56.pdf
>
>
> Wow, love it! Thanks for posting that!
>
>
> >
> > See what I mean about teeter totter?
> >
> > Which side of the bold black line is your high HC on?
>
> The 15mph test, 132 PPM, is on the left,
How do you know that? Maybe your HC reading is to the right of the bold
black line. The HC graph represented on that chart is "U" shaped isn't
it? High rich of stoichiometric, drops near stoichiometric and rises
again lean of stoichiometric.
> but the HC line on the graph
> does not come down to 65 PPM, which was the result of the 25mph test.
Your test sample was taken after the catalytic converter. so naturally
the numbers would be lower.
The specific number aren't what I was pointing out, it's the
relationships of the different gasses at different air fuel ratios,
i.e., is the HC high because it's too rich or because it's too lean.
Some here seem to think that HC can only be high due to a too rich fuel
mixture. The only way to know which side of stoichiometric your HC
numbers represent is to know what the actual unadulterated O2
measurement is.
Simpson
Got it! Using that way of looking at the graph, especially for CO, CO2
and O2, which are expressed in percentages, I can easily see that my
passing test was on the lean side, the CO being a dead giveaway.
> Some here seem to think that HC can only be high due to a too rich fuel
> mixture. The only way to know which side of stoichiometric your HC
> numbers represent is to know what the actual unadulterated O2
> measurement is.
>
>>> Then look at the chart on page 2, pay attention to where O2 and
>>> CO converge at stoichiometric, like I said earlier, .5% give or
>>> take tenth.
Okay, now I see why you place so much store in the O2 reading. I need to
richen up the mix a bit. The only tool I have at my disposal to judge
The mix is the color of the ceramic insulators on the plugs and they
have been pure white of late.
Is plug insulator color a good indicator of proper fuel mix? That's all
I have for now. If it's a good indicator, when I get a good color I will
take it to the smog shop for a dry run.
jim
Simpson wrote:
>
> Okay, now I see why you place so much store in the O2 reading. I need to
> richen up the mix a bit. The only tool I have at my disposal to judge
> The mix is the color of the ceramic insulators on the plugs and they
> have been pure white of late.
>
> Is plug insulator color a good indicator of proper fuel mix? That's all
> I have for now. If it's a good indicator, when I get a good color I will
> take it to the smog shop for a dry run.
Your issue may be timing. The vehicle is designed to run with EGR. It
sounds like your engine performs well without it (ignoring NOX) and with
EGR it does not do as well (other than NOX). That suggests you may be able
to advance the timing a degree or 2. Doing that will probably increase NOX
a little but may bring the other readings back in line.
-jim
>
> >>>
> >>> Mike is certain that your high HC is because the mix is rich,
> >>> based upon -what- I have no idea since your gas numbers are
> >>> skewed by the false air from the air pump.
> >>> I'm saying that I "suspect" that it's actually too lean, maybe in
> >>> part because I thought you had mentioned that the plugs were
> >>> white.
> >> I will pay this the attention it deserves after I get back from a test
> >> drive, or maybe tomorrow morning after a big mug of tea
> >>
> >>>
> >>>> At this point I am a bit more knowledgeable, but not quite sure what to
> >>>> do with it. What I need is tailpipe emissions wand like the one at the
> >>>> shop so i can monitor the changes that take place for a given tweak.
> >>> http://www.autologicco.com/AllProducts/GasAnalyzer.shtm#GasPortabl
> >>> e
> >>> (sorry about the line wrap)
> >> Not a problem.
> >>
> >>> This is (IMHO) the best deal out there.
> >> Yeow! Prices are on the high side for shade tree mechanic.
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jim
Simpson wrote:
> Mike, I solved the problem. See my detailed reply to BigIronRam in this
> thread.
Your response was to ignore the advice given. The suggestion was made that
the EGR was designed to run off the very low vacuum port. From there it
goes to a vacuum amplifier which uses the low vacuum signal to control the
EGR using vacuum coming from intake manifold. If I understood your
response - you ignored that advice and hooked it up in a different way.
The low vacuum plus amplifier may or may not be how your engine vacuum
lines are supposed to be configured. But it does sound like the carb was
designed to work with that configuration. Is there an under-the-hood
vacuum line diagram?
-jim
>
> Thanks, for the help. You were on the right track as far as the port
> probably being blocked goes. Whatever the reason, it just wasn't
> developing EGR vacuum characteristics and would not even make it to 2
> pounds at 2,000rpm.
Simpson
>
> Simpson wrote:
>
>> Mike, I solved the problem. See my detailed reply to BigIronRam in this
>> thread.
>
> Your response was to ignore the advice given.
My response was to investigate what a vacuum amplifier was and then to
determine that the EGR system on the 87 Dakota V6 did not incorporate one.
> The suggestion was made
And that is *all* that it was... a suggestion.
that
> the EGR was designed to run off the very low vacuum port. From there it
> goes to a vacuum amplifier which uses the low vacuum signal to control the
> EGR using vacuum coming from intake manifold.
But not in this case.
I hooked up the EGR valve the way it was hooked up stock. There is no
vacuum amplifier. The vacuum hose from the EGR port on the carb goes
directly to the CVSCC (coolant vacuum switch cold closed) which prevents
the EGR system from kicking in when the engine is closed. The vacuum
line then goes directly to the EGR valve.
> If I understood your
> response - you ignored that advice
You're starting to repeat yourself.
> and hooked it up in a different way.
I hooked it up in such a way that passed the smog inspection.
> The low vacuum plus amplifier may or may not be how your engine vacuum
> lines are supposed to be configured.
Now you're getting it.
> But it does sound like the carb was
> designed to work with that configuration.
It may be that the *carb* was designed to work that way, but the EGR
system on my truck was designed to to work without a vacuum amplifier.
I made it clear in the thread that the mixture control solenoid for the
original, stock carb can longer be purchased and that the carb I am
working with is the non-feedback version of that carb. I also made it
clear in my last post to Mike Romain that I modified the carb to work
like the original as far as the EGR function goes and that the mod was
successful.
> Is there an under-the-hood
> vacuum line diagram?
Of course there is. There is also one in the shop service manual.
>
> -jim
Are you the hall monitor for this group? Do you go around busting people
for not following the advice of others to the letter? If so, you have
too much time on your hands.
>
>> Thanks, for the help. You were on the right track as far as the port
>> probably being blocked goes. Whatever the reason, it just wasn't
>> developing EGR vacuum characteristics and would not even make it to 2
>> pounds at 2,000rpm.
>
>
> ----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==----
> http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
> ---= - Total Privacy via Encryption =---
jim
Simpson wrote:
>
> jim wrote:
> >
> > Simpson wrote:
> >
> >> Mike, I solved the problem. See my detailed reply to BigIronRam in this
> >> thread.
> >
> > Your response was to ignore the advice given.
>
> My response was to investigate what a vacuum amplifier was and then to
> determine that the EGR system on the 87 Dakota V6 did not incorporate one.
Your reply made no mention of that. That is you completely ignored the
advice and didn't explain why you ignored it until now. You didn't even
give a hint that you comprehended what was said.
>
> > The suggestion was made
>
> And that is *all* that it was... a suggestion.
>
> that
> > the EGR was designed to run off the very low vacuum port. From there it
> > goes to a vacuum amplifier which uses the low vacuum signal to control the
> > EGR using vacuum coming from intake manifold.
>
> But not in this case.
Maybe - Maybe not. How the hell would I know.
>
> I hooked up the EGR valve the way it was hooked up stock. There is no
> vacuum amplifier. The vacuum hose from the EGR port on the carb goes
> directly to the CVSCC (coolant vacuum switch cold closed) which prevents
> the EGR system from kicking in when the engine is closed. The vacuum
> line then goes directly to the EGR valve.
>
> > If I understood your
> > response - you ignored that advice
>
> You're starting to repeat yourself.
When people fail to indicate they understand the advice the tendency is to
repeat it. No??
>
> > and hooked it up in a different way.
>
> I hooked it up in such a way that passed the smog inspection.
Then why are you trying to do additional modification? You've made a half
dozen posting since you passed the test asking for help with
modifications. What's that all about?
>
> > The low vacuum plus amplifier may or may not be how your engine vacuum
> > lines are supposed to be configured.
>
> Now you're getting it.
You still don't "get" that when you fail to provide adequate information
the reader has no choice but to guess what the actual facts are.
>
> > But it does sound like the carb was
> > designed to work with that configuration.
>
> It may be that the *carb* was designed to work that way, but the EGR
> system on my truck was designed to to work without a vacuum amplifier.
But given that you now have a different carburetor the range of vacuum
coming from the EGR port will not be exactly the same as the original and
it is possible that the way it was hooked up in connection with a vacuum
amplifier might give you better performance. The EGR affects the mixture
that the carb delivers. If the flow thru the EGR is not in synch with the
carb mixture controls you may not be getting optimum mixture at all the
different possible engine loads and RPMs. So the original advice to hook
the EGR thru a vacuum amplifier still may have produced better results
than you got.
>
> I made it clear in the thread that the mixture control solenoid for the
> original, stock carb can longer be purchased and that the carb I am
> working with is the non-feedback version of that carb. I also made it
> clear in my last post to Mike Romain that I modified the carb to work
> like the original as far as the EGR function goes and that the mod was
> successful.
>
> > Is there an under-the-hood
> > vacuum line diagram?
>
> Of course there is. There is also one in the shop service manual.
>
> >
> > -jim
>
> Are you the hall monitor for this group? Do you go around busting people
> for not following the advice of others to the letter? If so, you have
> too much time on your hands.
You implied that you replied to the advice given. You did not reply to
that advice you ignored it completely. You didn't even give the slightest
hint that you understood what the advice was. Since my crystal ball is in
the shop for repairs this week - I thought maybe you didn't understand the
advice and perhaps maybe you would want to be aware of that. But
apparently you're not interested.
-jim
Mike Romain
>
> It's a frikken obsession, but I bought this truck new and I refuse to
> let it die for want of a replacement mixture control solenoid.
>
> Thanks Chrysler.
>
> Thanks Holley.
>
> Way to stand behind your products.
When we mod our Jeeps to take out the feedback carb, we can run the
ignition module or even a replacement stand alone distributor or
ignition replacement without the rest of the smog computer controls.
The reason is or 'ford' emissions control box goes into 'limp home' mode
basically clamping down on the timing advance.
When we wire our ignition control modules directly to the distributor in
whatever form, we bypass this, our timing jumps about 15 deg and has to
be reset and we get a sweet 'seat of the pants' 25% boost in power.
We can have 'fun' with the new vacuum line layouts as well.
aarcuda69062
Simpson <"tinauxide butylflex"@epoxy.com> wrote:
> Chuck Norris can fool all of the people all of the time and Chuck Norris
> supports McCain.
Chuck Norris once roundhouse kicked someone so hard that his foot broke
the speed of light, went back in time, and killed Amelia Earhart while
she was flying over the Pacific Ocean.
Crop circles are Chuck Norris' way of telling the world that sometimes
corn needs to lie down.
Chuck Norris is ten feet tall, weighs two-tons, breathes fire, and could
eat a hammer and take a shotgun blast standing.
The Great Wall of China was originally created to keep Chuck Norris out.
It failed miserably.
Contrary to popular belief, Chuck Norris, not the box jellyfish of
northern Australia, is the most venomous creature on earth. Within 3
minutes of being bitten, a human being experiences the following
symptoms: fever, blurred vision, beard rash, tightness of the jeans, and
the feeling of being repeatedly kicked through a car windshield.
Most people have 23 pairs of chromosomes. Chuck Norris has 72... and
they're all poisonous.
If you ask Chuck Norris what time it is, he always says, "Two seconds
'til." After you ask, "Two seconds 'til what?" he roundhouse kicks you
in the face.
Chuck Norris drives an ice cream truck covered in human skulls.
When Chuck Norris sends in his taxes, he sends blank forms and includes
only a picture of himself, crouched and ready to attack. Chuck Norris
has not had to pay taxes, ever.
The quickest way to a man's heart is with Chuck Norris' fist.
Chuck Norris invented Kentucky Fried Chicken's famous secret recipe,
with eleven herbs and spices. But nobody ever mentions the twelfth
ingredient: Fear.
CNN was originally created as the "Chuck Norris Network" to update
Americans with on-the-spot ass kicking in real-time.
Chuck Norris can win a game of Connect Four in only three moves.
There is no theory of evolution, just a list of creatures Chuck Norris
allows to live.
Chuck Norris once ate three 72 oz. steaks in one hour. He spent the
first 45 minutes having sex with his waitress.
What was going through the minds of all of Chuck Norris' victims before
they died? His shoe.
Chuck Norris is the only man to ever defeat a brick wall in a game of
tennis.
Police label anyone attacking Chuck Norris as a Code 45-11.... a suicide.
Chuck Norris doesn't churn butter. He roundhouse kicks the cows and the
butter comes straight out.
Chuck Norris doesnšt wash his clothes, he disembowels them.
A Handicapped parking sign does not signify that this spot is for
handicapped people. It is actually in fact a warning, that the spot
belongs to Chuck Norris and that you will be handicapped if you park
there.
Chuck Norris will attain statehood in 2009. His state flower will be the
Magnolia.
Someone once videotaped Chuck Norris getting pissed off. It was called
Walker: Texas Chain Saw Masacre.
If you spell Chuck Norris in Scrabble, you win. Forever.
Chuck Norris originally appeared in the "Street Fighter II" video game,
but was removed by Beta Testers because every button caused him to do a
roundhouse kick. When asked bout this "glitch," Norris replied, "That's
no glitch."
Fool me once, shame on you. Fool Chuck Norris once and he will
roundhouse you in the face.
The opening scene of the movie "Saving Private Ryan" is loosely based on
games of dodgeball Chuck Norris played in second grade.
Chuck Norris once shot down a German fighter plane with his finger, by
yelling, "Bang!"
Chuck Norris once bet NASA he could survive re-entry without a
spacesuit. On July 19th, 1999, a naked Chuck Norris re-entered the
earth's atmosphere, streaking over 14 states and reaching a temperature
of 3000 degrees. An embarrassed NASA publically claimed it was a meteor,
and still owes him a beer.
Chuck Norris has two speeds: Walk and Kill.
Someone once tried to tell Chuck Norris that roundhouse kicks aren't the
best way to kick someone. This has been recorded by historians as the
worst mistake anyone has ever made.
Contrary to popular belief, America is not a democracy, it is a
Chucktatorship.
Teenage Mutant Ninja Turtles is based on a true story: Chuck Norris once
swallowed a turtle whole, and when he crapped it out, the turtle was six
feet tall and had learned karate.
Chuck Norris is not hung like a horse... horses are hung like Chuck
Norris.
Faster than a speeding bullet ... more powerful than a locomotive ...
able to leap tall buildings in a single bound... yes, these are some of
Chuck Norris's warm-up exercises.
Chuck Norris is the only human being to display the Heisenberg
uncertainty principle -- you can never know both exactly where and how
quickly he will roundhouse-kick you in the face.
In the Bible, Jesus turned water into wine. But then Chuck Norris turned
that wine into beer.
Chuck Norris can hit you so hard that he can actually alter your DNA.
Decades from now your descendants will occasionally clutch their heads
and yell "What The Hell was That?"
Time waits for no man. Unless that man is Chuck Norris.
Chuck Norris discovered a new theory of relativity involving multiple
universes in which Chuck Norris is even more badass than in this one.
When it was discovered by Albert Einstein and made public, Chuck Norris
roundhouse-kicked him in the face. We know Albert Einstein today as
Stephen Hawking.
Chuck Norris doesn't shower, he only takes blood baths.
aarcuda69062
wrote:
> Then why are you trying to do additional modification? You've made a half
> dozen posting since you passed the test asking for help with
> modifications. What's that all about?
He has already stated that with the replacement carb installed the HC
emissions are barely within limits.
> But given that you now have a different carburetor the range of vacuum
> coming from the EGR port will not be exactly the same as the original and
> it is possible that the way it was hooked up in connection with a vacuum
> amplifier might give you better performance.
He has already explained that he reconfigured the vacuum slots to match
the old carb. And what's to say that his current EGR valve is
calibrated to be used on a system that employs a vacuum amplifier?
Where does it end? It's a 21 year old truck.
> The EGR affects the mixture
> that the carb delivers.
Actually, no.
When you say mixture associated with carburetor (or any fuel metering
device), It's assumed you mean the air/fuel ratio. Exhaust gas is
neither air nor fuel, it's supposed to be inert. EGR doesn't alter
air/fuel mixture, it displaces it.
> If the flow thru the EGR is not in synch with the
> carb mixture controls you may not be getting optimum mixture at all the
> different possible engine loads and RPMs.
He's not getting optimum mixture because he's using a lean burn carb in
a non lean burn application. But what do I know, I only worked on them
every day in a dealership in the late 70s.
> So the original advice to hook
> the EGR thru a vacuum amplifier still may have produced better results
> than you got.
And if there's an underhood inspection involved with the emissions test,
he gets an automatic fail.
aarcuda69062
Simpson <aso-...@epoxy.com> wrote:
> > Your test sample was taken after the catalytic converter. so naturally
> > the numbers would be lower.
> > The specific number aren't what I was pointing out, it's the
> > relationships of the different gasses at different air fuel ratios,
> > i.e., is the HC high because it's too rich or because it's too lean.
>
> Got it! Using that way of looking at the graph, especially for CO, CO2
> and O2, which are expressed in percentages, I can easily see that my
> passing test was on the lean side, the CO being a dead giveaway.
Atta boy!
> >>> Then look at the chart on page 2, pay attention to where O2 and
> >>> CO converge at stoichiometric, like I said earlier, .5% give or
> >>> take tenth.
>
> Okay, now I see why you place so much store in the O2 reading. I need to
> richen up the mix a bit. The only tool I have at my disposal to judge
> The mix is the color of the ceramic insulators on the plugs and they
> have been pure white of late.
>
> Is plug insulator color a good indicator of proper fuel mix? That's all
> I have for now. If it's a good indicator, when I get a good color I will
> take it to the smog shop for a dry run.
Plug color is a method, it's naturally not going to be as accurate as a
gas analyzer. Hell, it worked for Smokey Yunik for years.
jim
aarcuda69062 wrote:
>
> In article <1206200329_650@isp.n>, jim <".sjedgingN0sp"@m...@mwt.net>
> wrote:
>
> > Then why are you trying to do additional modification? You've made a half
> > dozen posting since you passed the test asking for help with
> > modifications. What's that all about?
>
> He has already stated that with the replacement carb installed the HC
> emissions are barely within limits.
The 15 mph test was barely within limits. The other was well within
limits.
>
> > But given that you now have a different carburetor the range of vacuum
> > coming from the EGR port will not be exactly the same as the original and
> > it is possible that the way it was hooked up in connection with a vacuum
> > amplifier might give you better performance.
>
> He has already explained that he reconfigured the vacuum slots to match
> the old carb. And what's to say that his current EGR valve is
> calibrated to be used on a system that employs a vacuum amplifier?
Not a very difficult thing to check if you have a vacuum gauge.
> Where does it end? It's a 21 year old truck.
>
> > The EGR affects the mixture
> > that the carb delivers.
>
> Actually, no.
Actually yes.
> When you say mixture associated with carburetor (or any fuel metering
> device), It's assumed you mean the air/fuel ratio. Exhaust gas is
> neither air nor fuel, it's supposed to be inert. EGR doesn't alter
> air/fuel mixture, it displaces it.
How is "displace" different than "alter" ? Do you think the engine is
concerned with semantics?
>
> > If the flow thru the EGR is not in synch with the
> > carb mixture controls you may not be getting optimum mixture at all the
> > different possible engine loads and RPMs.
>
> He's not getting optimum mixture because he's using a lean burn carb in
> a non lean burn application. But what do I know, I only worked on them
> every day in a dealership in the late 70s.
You are revealing how little you know. Besides his engine is new enough to
be beyond some of the stupidity of the 70's lean burn applications. The
reality is the EGR will affect mixture on a carb because it does affect
airflow. Even some of your statements seem to be claiming that it was not
too lean before the EGR was hooked up but now after it is.
Now if the EGR is the only thing different from the failed test to the
passed one (a doubtful theory in itself). He may simply not need as much
EGR at 15 mph than he is getting with his current setup. That might
entirely account for the higher HC. The carb was designed to work with an
EGR that followed venturi vacuum - I'm not saying it will work better if
configured like that but it does seem likely. Given that he doesn't have a
standard setup. The only way to find out is to experiment.
>
> > So the original advice to hook
> > the EGR thru a vacuum amplifier still may have produced better results
> > than you got.
>
> And if there's an underhood inspection involved with the emissions test,
> he gets an automatic fail.
He will fail for not having the OEM carb?
Simpson
Dodge Dakota V6 with a non-stock, non-feedback carburetor, and the
differences in the emissions configuration for each test.
The third test brought down HCs considerably for the 15mph test, which
was my aim. However, CO measurement skyrocketed and failed at 15mph and
barely passed at 25mph. O2 measurements came down by about half for both
speeds and CO2 was up 17% in both tests.
The difference in EGR function between using the spark vaccuum port and
the modified EGR port was measured using a vacuum meter teed into the
EGR vacuum line just before the EGR diaphragm. The spark vacuum port
responded more strongly to the throttle and was higher at steady speeds
from 15 mph through freeway speeds than the modified EGR port. However,
the modified EGR port presented what appeared to me to be favorable EGR
vacuum characteristics so I used that port in the third test.
I am not sure which of the three modifications that I made (listed below
under '3rd test') contributed to the changes in measurement of the
various emissions gases, but I think it is safe to assume that I should
lean out the idle mixture to bring down CO. From the looks of the CO
line on this graph: http://www.autoshop101.com/forms/h56.pdf I should
not have to lean it out much as that line is very steep. I would guess
that between 1/4 and 1/2 half turn of each screw would do it. I set the
idle mixture by the conventional method of starting with each screw 2
full turns out from fully closed and then screwing each on in until the
engine starts to stumble and then backing out 1/2 turn. I backed out
each screw from there about another half turn. So 1/4 to 1/2 turn in
should do it. I may get another reading after that and then try what jim
suggested and advance the timing 2 degrees to see how that changes the
readings. That's all for now. I have to go earn some money to pay for
all these tests. 30 bucks a pop for a pre-test. Not bad.
Best displayed with Courier, or some other monospace font:
%CO2 %O2 HC PPM %CO NOx PPM
15mph
1st test 10.8 5.9 34 .01 3641-FAIL
2nd test 10.4 6.7 132* .01 626
3rd test 12.2 3.6 82 1.02-FAIL 358
25mph
1st test 10.7 6.0 26 .01 3225-FAIL
2nd test 10.7 6.1 65 .04 606
3rd test 12.5 2.9 73 1.14** 191
1st test - EGR run from EGR port on carb resulting in essentially
no EGR function
2nd test - EGR run from spark advance port on carb
3rd test - 1. EGR run from modified EGR port on carb
2. Idle mixture enriched.
3. The ports entering both barrels from the canister
purge hose were enlarged to correspond to those in the
original stock carb.
* passing is 134, measured 132
** passing is 1.14, measured 1.14
Simpson
>
> Simpson wrote:
>
>> Okay, now I see why you place so much store in the O2 reading. I need to
>> richen up the mix a bit. The only tool I have at my disposal to judge
>> The mix is the color of the ceramic insulators on the plugs and they
>> have been pure white of late.
>>
>> Is plug insulator color a good indicator of proper fuel mix? That's all
>> I have for now. If it's a good indicator, when I get a good color I will
>> take it to the smog shop for a dry run.
>
> Your issue may be timing. The vehicle is designed to run with EGR. It
> sounds like your engine performs well without it (ignoring NOX) and with
> EGR it does not do as well (other than NOX). That suggests you may be able
> to advance the timing a degree or 2. Doing that will probably increase NOX
> a little but may bring the other readings back in line.
Considering that in the last test from the smog shop (posted as my last
reply to aarcuda69062) about an hour ago showed the NOx well below
average, I have room to spare on that measurement. I will try your
suggestion of advancing the timing two degrees and leaning out the idle
mixture a bit and get another reading, but not today.
Simpson
>
> Simpson wrote:
>> jim wrote:
>>> Simpson wrote:
>>>
>>>> Mike, I solved the problem. See my detailed reply to BigIronRam in this
>>>> thread.
>>> Your response was to ignore the advice given.
>> My response was to investigate what a vacuum amplifier was and then to
>> determine that the EGR system on the 87 Dakota V6 did not incorporate one.
>
> Your reply made no mention of that. That is you completely ignored the
> advice and didn't explain why you ignored it until now. You didn't even
> give a hint that you comprehended what was said.
You can't possibly realize how quickly this situation has progressed
since I first posted. I stopped mid-post in my 3/21 4:19pm reply to Mike
Romain in order to pull the carb, tear it down and make modifications to
the ports in the throttle body based on the ongoing suggestions that I
was given and my own very intimate knowledge of this carb and it's
various configurations. I am doing this work as I see fit based on my
understanding of the situation at any given moment. I am also trying to
reply to all posts and explain the work that I have done, the reasons
for doing it and the results I have gotten.
I'm sorry if I don't do it in a way that you deem proper.
jim
Simpson wrote:
>
> You can't possibly realize how quickly this situation has progressed
> since I first posted. I stopped mid-post in my 3/21 4:19pm reply to Mike
> Romain in order to pull the carb, tear it down and make modifications to
> the ports in the throttle body based on the ongoing suggestions that I
> was given and my own very intimate knowledge of this carb and it's
> various configurations. I am doing this work as I see fit based on my
> understanding of the situation at any given moment. I am also trying to
> reply to all posts and explain the work that I have done, the reasons
> for doing it and the results I have gotten.
>
> I'm sorry if I don't do it in a way that you deem proper.
I don't particularly care much how you do it. I was trying to empress upon
you that the advice you get is only as good as the information you supply.
For instance why is it you changed the carb in the first place? And how
much have you driven with the new one? If someone cared, they might guess
that the old carb was running very rich and you haven't driven very many
miles on this one. It may pay off to just drive it a few hundred miles. It
may take a while to recover from whatever was previously wrong. Also
fiddling with the idle mixture is not likely to help much. When your going
down the road the throttle is usually open enough that the idle circuit is
no longer doing anything.
-jim
Simpson
> Simpson wrote:
>> It's a frikken obsession, but I bought this truck new and I refuse to
>> let it die for want of a replacement mixture control solenoid.
>>
>> Thanks Chrysler.
>>
>> Thanks Holley.
>>
>> Way to stand behind your products.
>
> When we mod our Jeeps to take out the feedback carb, we can run the
> ignition module or even a replacement stand alone distributor or
> ignition replacement without the rest of the smog computer controls.
>
> The reason is or 'ford' emissions control box goes into 'limp home' mode
> basically clamping down on the timing advance.
Good point, Mike. There is a 'open loop' mode that this computer may
default to if it senses a value outside of its programmed parameters.
This computer controls spark advance timing and fuel mixture, but now
that the carb no longer has a mixture control solenoid, that aspect of
control is gone and only the spark timing is left.
Your post raises an important point for me. I have the code reader for
this beast. It's almost prehistoric but it works great. I got it used
on eBay because good luck trying to find one new. When I had the old
original feedback carb installed, the mixture control solenoid would get
stuck. At one point, I screwed down the allen screw on top of the
solenoid to close the auxiliary main jet and the auxiliary air bleed in
an attempt to convert the feedback carb into a convention carb. Even
with the solenoid modified so that the electrical pulses to it were
doing nothing, the computer failed to set any codes. I would have
expected a code set for the the O2 sensor perhaps because it was no
longer controlling the fuel mix, but the computer seemed not to mind.
When I disconnected the wires to the feedback solenoid, however the
computer set a code for it.
Getting back to the 'limp-home mode' question. The only thing that the
computer now controls is the spark advance. The service manual spells
out the procedure for testing the spark advance at 2000rpm. After setup,
it says that I should be reading 38 degrees plus or minus 4. The only
trouble is, how will I read 38 degrees I don't have a magnetic timing
unit, which I assume will allow one to read that far off the scale used
with a timing light, which only goes plus and minus 10 degrees from TDC.
I guess I can wire the failed solenoid the computer. The windings are
still good. This way the computer will still read it as working and, if
the computer is working okay, the advance timing should working okay. If
I read the service manual correctly, there are only two spark advance
curves, one for cold and one for warmed up. I had a problem with the
coolant temperature sensor recently that caused the vehicle to only
operate in cold mode which was too retarded. Gas mileage sucked until I
discovered the problem. If there are only two modes I should be able to
tell if the computer is ignoring the absence of the mixture solenoid and
continuing to use the warmed up spark advance curve.
>
> When we wire our ignition control modules directly to the distributor in
> whatever form, we bypass this, our timing jumps about 15 deg and has to
> be reset and we get a sweet 'seat of the pants' 25% boost in power.
How does the situation you are describing dealing with spark advance? Is
this controlled by the 'ignition control modules' you mentioned?
>
> We can have 'fun' with the new vacuum line layouts as well.
Sounds like a real party :-)
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 'New' frame in the works for '08. Some Canadian Bush Trip and Build
> Photos: http://mikeromainjeeptrips.shutterfly.com
Simpson
>
> Simpson wrote:
>
>> You can't possibly realize how quickly this situation has progressed
>> since I first posted. I stopped mid-post in my 3/21 4:19pm reply to Mike
>> Romain in order to pull the carb, tear it down and make modifications to
>> the ports in the throttle body based on the ongoing suggestions that I
>> was given and my own very intimate knowledge of this carb and it's
>> various configurations. I am doing this work as I see fit based on my
>> understanding of the situation at any given moment. I am also trying to
>> reply to all posts and explain the work that I have done, the reasons
>> for doing it and the results I have gotten.
>>
>> I'm sorry if I don't do it in a way that you deem proper.
>
> I don't particularly care much how you do it. I was trying to empress upon
> you that the advice you get is only as good as the information you supply.
Actually, I'm doing quite well, thank you. I appreciate your suggestion
about advancing the timing. Perhaps you should limit your posts to
asking questions and making suggestions instead of trying to correct
what you seem to regard as my inappropriate posting methods in my
communications with others.
jim
Simpson wrote:
> Perhaps you should limit your posts to
> asking questions and making suggestions instead of trying to correct
> what you seem to regard as my inappropriate posting methods in my
> communications with others.
I can assure you I haven't given much thought to your posting methods. I
did ask a couple of questions and have made some suggestions.....
aarcuda69062
wrote:
> > He has already stated that with the replacement carb installed the HC
> > emissions are barely within limits.
>
> The 15 mph test was barely within limits. The other was well within
> limits.
And he wasn't satisfied with "barely."
I wouldn't be either.
The frickin cut points are so loose that if it's not below 50% of cut
point, something isn't right.
> > He has already explained that he reconfigured the vacuum slots to match
> > the old carb. And what's to say that his current EGR valve is
> > calibrated to be used on a system that employs a vacuum amplifier?
>
> Not a very difficult thing to check if you have a vacuum gauge.
Okay, publish the vacuum specs for both types of EGR systems.
That ought to help him considerably.
>
> > Where does it end? It's a 21 year old truck.
> >
> > > The EGR affects the mixture
> > > that the carb delivers.
> >
> > Actually, no.
>
> Actually yes.
It's the twenty first century Jim, the old beliefs that you're
subscribing to here have been long refuted.
> > When you say mixture associated with carburetor (or any fuel metering
> > device), It's assumed you mean the air/fuel ratio. Exhaust gas is
> > neither air nor fuel, it's supposed to be inert. EGR doesn't alter
> > air/fuel mixture, it displaces it.
>
> How is "displace" different than "alter" ?
Main Entry:
dis?place
Pronunciation:
\(?)dis-?pla?s, di-?spla?s\
Function:
transitive verb
1 a: to remove from the usual or proper place; specifically : to expel
or force to flee from home or homeland <displaced persons> b: to remove
from an office, status, or job cobsolete : to drive out : banish
2 a: to move physically out of position <a floating object displaces
water> b: to take the place of (as in a chemical reaction) : supplant
Main Entry:
al?ter
Pronunciation:
\?o?l-t?r\
Function:
verb
transitive verb
1 : to make different without changing into something else
2 : castrate, spay
intransitive verb
: to become different
> Do you think the engine is concerned with semantics?
Do you think a boat floating in water makes the water different?
Your wet sidewalks cause rain fan club membership card is in the mail.
>
> >
> > > If the flow thru the EGR is not in synch with the
> > > carb mixture controls you may not be getting optimum mixture at all the
> > > different possible engine loads and RPMs.
> >
> > He's not getting optimum mixture because he's using a lean burn carb in
> > a non lean burn application. But what do I know, I only worked on them
> > every day in a dealership in the late 70s.
>
> You are revealing how little you know.
Really? The results of his third test show differently.
> Besides his engine is new enough to
> be beyond some of the stupidity of the 70's lean burn applications.
Couldn't figure out how to fix them, 'eh?
> The reality is the EGR will affect mixture on a carb because it does affect
> airflow.
Not even close to plausible.
> Even some of your statements seem to be claiming that it was not
> too lean before the EGR was hooked up but now after it is.
Cite?
> Now if the EGR is the only thing different from the failed test to the
> passed one (a doubtful theory in itself).
Gee, I'm pretty sure there was a carburetor change in there.
> He may simply not need as much
> EGR at 15 mph than he is getting with his current setup. That might
> entirely account for the higher HC.
It might if the CO weren't so low.
I will admit to not having fully realized that he connected the EGR to
the vacuum fitting for the spark transducer which well would cause an
over EGR condition. Should have run like crap at cruise though...
> The carb was designed to work with an
> EGR that followed venturi vacuum -
And he has since modified the carb and tested it configured with ported
vacuum with positive results.
> I'm not saying it will work better if
> configured like that but it does seem likely. Given that he doesn't have a
> standard setup. The only way to find out is to experiment.
True that.
> > And if there's an underhood inspection involved with the emissions test,
> > he gets an automatic fail.
>
> He will fail for not having the OEM carb?
Not necessarily due to there no longer being any service parts.
I don't know what your problem is, Simpson has demonstrated amazing
ingenuity, intuition and desire to learn and understand.
Simpson
>
> Simpson wrote:
>> Perhaps you should limit your posts to
>> asking questions and making suggestions instead of trying to correct
>> what you seem to regard as my inappropriate posting methods in my
>> communications with others.
>
> I can assure you I haven't given much thought to your posting methods.
You can go crawl back into your hole, jim. You've expended your good will.
Simpson
For the 3rd test, I reconnected the MSD Blaster Ignition. It was present
on the 1st and 3rd tests, but not on the 2nd.
http://www.msdignition.com/ignition_1_5900.htm
jim
aarcuda69062 wrote:
>
> In article <1206214594_660@isp.n>, jim <"sjedgingN0sp"@m...@mwt.net>
> wrote:
>
> > > He has already stated that with the replacement carb installed the HC
> > > emissions are barely within limits.
> >
> > The 15 mph test was barely within limits. The other was well within
> > limits.
>
> And he wasn't satisfied with "barely."
> I wouldn't be either.
But the point was that only under certain load and RPM it was well within
limits.
> The frickin cut points are so loose that if it's not below 50% of cut
> point, something isn't right.
>
> > > He has already explained that he reconfigured the vacuum slots to match
> > > the old carb. And what's to say that his current EGR valve is
> > > calibrated to be used on a system that employs a vacuum amplifier?
The reason they introduced the vacuum amplifier was not because they
changed the way the EGR worked but because they changed the location that
the vacuum signal that operated the EGR came from. The EGR valve for his
vehicle probably was the same for a 10 or 15 year period. During that time
they had all sorts of different carbs and vacuum line configurations.
The signal from venturi vacuum was to weak to operate an EGR valve in a
reliable way so it needed to be amplified and then the same old EGR could
be used. The reason it was tied to the weaker venturi vacuum was that
would allow for more accurate metering of air and fuel under a wider
range of operating conditions. The feedback carberator wouldn't need that
because the feedback system itself would be able to compensate for any
changes in airflow that affected the air/fuel mixture.
As for the Chrysler lean burn crap - that was easy to fix. What was so
incredibly stupid was it took Chrysler engineers 10 years and near
bankruptcy to figure out how to fix it.
-jim
> >
> > Not a very difficult thing to check if you have a vacuum gauge.
>
> Okay, publish the vacuum specs for both types of EGR systems.
> That ought to help him considerably.
>
> >
> > > Where does it end? It's a 21 year old truck.
> > >
> > > > The EGR affects the mixture
> > > > that the carb delivers.
> > >
> > > Actually, no.
> >
> > Actually yes.
>
> It's the twenty first century Jim, the old beliefs that you're
> subscribing to here have been long refuted.
Air fuel mixture is controlled by the flow
Mike Romain
> trouble is, how will I read 38 degrees I don't have a magnetic timing
> unit, which I assume will allow one to read that far off the scale used
> with a timing light, which only goes plus and minus 10 degrees from TDC.
The newer timing lights have a digital display that gives the advance also
>
>
>
> How does the situation you are describing dealing with spark advance? Is
> this controlled by the 'ignition control modules' you mentioned?
>
Yes, you can get stand alone distributors and/or ignition modules to put
in so your timing works like the pre-computer engine does.
Someone on AADT should know what ones plug in or what junkyard swaps are
easy?
>>
>> We can have 'fun' with the new vacuum line layouts as well.
>
> Sounds like a real party :-)
I have the PCV and canister (gas tank and carb float vent) hooked up,
the EGR, the distributor advance and the air filter flaps all properly
plumbed for a manual tune. I am set up to pass emissions with my
feedback carb manually set.
I got on one ASM 2525 test, 589 NOx, 16 ppm HC and 0.11% CO and my 1986
CJ7 'Utility Vehicle' doesn't have nor need a Cat up here in Canada...
aarcuda69062
wrote:
> > And he wasn't satisfied with "barely."
> > I wouldn't be either.
>
> But the point was that only under certain load and RPM it was well within
> limits.
No one drives at only 15 and 25 miles per hour. There is no data for
other speed ranges so, the word "only" is a bit disingenuous.
> > > > He has already explained that he reconfigured the vacuum slots to match
> > > > the old carb. And what's to say that his current EGR valve is
> > > > calibrated to be used on a system that employs a vacuum amplifier?
>
> The reason they introduced the vacuum amplifier was not because they
> changed the way the EGR worked but because they changed the location that
> the vacuum signal that operated the EGR came from. The EGR valve for his
> vehicle probably was the same for a 10 or 15 year period.
It couldn't possibly be. His was the first year of production for both
the chassis and the engine, the year following his was throttle body
fuel injection and used a SMEC controlled pulse width modulated solenoid
and back pressure transducer to control the EGR.
> During that time
> they had all sorts of different carbs and vacuum line configurations.
No they didn't. One year only. 4 cylinder or six cylinder.
> The signal from venturi vacuum was to weak to operate an EGR valve in a
> reliable way so it needed to be amplified and then the same old EGR could
> be used. The reason it was tied to the weaker venturi vacuum was that
> would allow for more accurate metering of air and fuel under a wider
> range of operating conditions.
That was Chrysler's way of doing it. That's all that can be said.
> The feedback carberator wouldn't need that
> because the feedback system itself would be able to compensate for any
> changes in airflow that affected the air/fuel mixture.
Love to hear about it some time. Hope you research it better then your
claims about the 10-15 year spread where they used that exact EGR
valve/scheme on a vehicle that was produced in that configuration for
only one year.
> As for the Chrysler lean burn crap - that was easy to fix. What was so
> incredibly stupid was it took Chrysler engineers 10 years and near
> bankruptcy to figure out how to fix it.
That's the way innovation is.
aarcuda69062
Simpson <"tinauxide butylflex"@epoxy.com> wrote:
> The only trouble is, how will I read 38 degrees I don't have a magnetic timing
> unit, which I assume will allow one to read that far off the scale used
> with a timing light, which only goes plus and minus 10 degrees from TDC.
Quite easily.
Hand turn the engine until the #1 TDC timing mark on the balancer is
aligned with the minus 10 mark on the front cover scale. Make a mark
(sharpie) on the balancer adjacent to the plus 10 timing mark on the
front cover scale.
Hand turn the engine again until your new balancer mark aligns with the
minus 10 mark on the front cover timing scale. Make another new mark
(sharpie) on the balancer adjacent to the plus 10 mark on the front
cover scale. Take a knife edged file and make this last mark more
permanent.
You've just marked your balancer 40 degrees advanced from the TDC mark.
The 2 degrees error you can work out easy enough.
Simpson
Some times the simplest solution is the hardest to see.
Thanks for all your help and patience.
Steve W.
As long as you do the run/ chop the throttle/ and shut down a plug
reading is pretty good. The problem is that you don't want it to idle
much if you want a good reading. Now if you really want to play with it
at idle a gas analyzer works. So does a set of color tune plugs. But on
an installed engine where you can't see the plugs real well they are no
fun to use. But they do show how well the manifold actually spreads the
mix around, or not in the case of some engines.
--
Steve W.
mr.som ting wong
please explain why melted holes in pistons don't result from leaned out
fuel mixtures?????
aarcuda69062 wrote:
> In article <wwaEj.14577$5K1....@newssvr12.news.prodigy.net>,
> Simpson <aso-...@epoxy.com> wrote:
>
> > This would explain the low vacuum at the EGR port. The
> > lack of EGR function, plus the vacuum leak, which would cause a lean
> > condition, would combine to create a higher than normal temperature in
> > the combustion chamber resulting in the abnormally high NO readings.
>
> Not to nit pick but lean air fuel mixtures don't burn hotter.
> They burn slower which causes associated component temperatures
> to rise. Lean doesn't cause higher NOx, the extra O2 in the
> exhaust from a lean mixture makes the reduction bed of a 3 way
> catalyst less efficient resulting in higher NOx at the tail pipe.
aarcuda69062
"mr.som ting wong" <dbr...@cac.net> wrote:
> really lean conditions don't burn hotter
> please explain why melted holes in pistons don't result from leaned out
> fuel mixtures?????
The explanation is in the post you're responding to.
jim
aarcuda69062 wrote:
>
> > The signal from venturi vacuum was to weak to operate an EGR valve in a
> > reliable way so it needed to be amplified and then the same old EGR could
> > be used. The reason it was tied to the weaker venturi vacuum was that
> > would allow for more accurate metering of air and fuel under a wider
> > range of operating conditions.
>
> That was Chrysler's way of doing it. That's all that can be said.
For someone who claims to know something that is as good as saying you
don't. I didn't say chrysler used the same engines for all those years I
said the EGR's were all pretty much the same in that era. The means of
controlling the vacuum, which determined how much exhaust gas was
delivered and when it was delivered is what changed depending on make,
model and year.
That was the purpose of vacuum hose configurations, vacuum amplifiers or
transducers and different vacuum ports. The difference in the valve itself
had more to do with how they fit on the engine rather than how they
behaved.
At any rate EGR clearly has a huge effect on NOX emissions and does
completely change the way air and fuel burn inside an engine. That mains
the entire way the engine is tuned needs to change to accompany the
changes that EGR creates. For the most part EGR is beneficial. It is a lot
like getting an octane boost (at no extra cost) and does allow for better
fuel economy as well as overall better emissions *if* the engine is tuned
to accommodate the changes in burn characteristics. That means changing
air/fuel ratio as well as timing. The modern vehicle's computer takes care
of all of that for you so yes you can get along quite nicely with any
knowledge of it.
-jim
Mike
"aarcuda69062" <none...@sbcglobal.net> wrote in message
news:nonelson-C07182...@news.chi.sbcglobal.net...
> In article <%PSEj.267$Cn4...@news02.roc.ny>, "Mike" <m...@localnet.com>
> wrote:
>
>> > Why wouldn't the HCs increase? When the exhaust gas
>> > recirculation valve opens, what is it allowing into the intake
>> > manifold/ combustion chamber?
>> > CO2, CO, O2, NOx and HC.
>>
>> Yep, the EGR valve allows exhaust gas back into the combustion chamber,
>> but,
>> it is only a very small percentage of the total combution chamber volume.
>
> So? If the air fuel mixture is lean to begin with, how does adding
> exhaust gas make the flame propagate better?
>
>> The exhaust gas was already burnt once in the combustion chamber, how does
>> running
>> it through the combustion chamber a second time cause the HC to increase
>> even
>> further ?
>
> See above.
>
>> Isn't the HC reading from the smog test unburned hydrocarbons ?
>
> Yes it is.
> Ever open an EGR valve at idle?
Yep.
> Did the engine run better or worse?
Didn't run at all, they don't run well on an inert gas.
> Do you suppose HC goes up or down if you open the EGR at idle?
Being the engine wouldn't stay running I would say it went down. ;) If it
would stay running it would have a lean misfire that would lead to an increase
in HC.
>
>> >
>> > When the exhaust gas recirculation valve opens what happens to
>> > manifold pressure?
>> > It goes up.
>> > What does the power valve do when manifold pressure goes up?
>> > It opens and allows more HC (gasoline) to flow into the venturi
>> > in the carb
>>
>> Yep, that's how the power enrichment works as well but why such a jump
>> in
>> HC ? This is the first time I remember seeing a NOx problem fixed were the
>> HC reading jumped up like that.
>
> Not for me.
> It's very common on some engines to repair a non functioning EGR for a
> NOx failure and have the car fail on HC. Typical 4 cylinder where the
> EGR feeds into the intake ports individually (4 separate EGR passages)
> and 2 or 3 are plugged. The 1 or 2 that do flow EGR are over fed and
> cause a misfire. Roto-Root the passages and everything is fine...
>
>> Does this have anything to do with the vehicle
>> being equiped with an air pump ?
>
> The high HC? Maybe yes, maybe no. That's why there's a thing called
> 'diagnostics.' I'd watch the reading with the air pump disabled.
Yes, I'd like to see the results with the air pump disabled.
> The OP has a 21 year old truck, what are the odds hat the air pump is
> original? I couldn't get the air pump on my bought new 85 F-150 to last
> more than three years.
> Air pumps tend to have a generic universal design, what if instead of a
> 4 CFM air pump made for a 3.9 liter engine, he got a 10 CFM replacement
> pump made for a 7.4 liter engine.
> You -can- pump too much air into a catalytic converter and snuff out the
> fire.
Yep, I see your point here. My experience has been that aftermarket
emission parts are junk.
>
>> We don't see too many air pumps on the east
>> coast.
>
> Dunno why, they were pretty common in the day that the OPs truck was
> built.
They sure were, but living in the rust belt they don't last very long and
are long ago rusted away.
> Now they're likely to be electric.
aarcuda69062
wrote:
> aarcuda69062 wrote:
>
> >
> > > The signal from venturi vacuum was to weak to operate an EGR valve
> > > in a
> > > reliable way so it needed to be amplified and then the same old EGR could
> > > be used. The reason it was tied to the weaker venturi vacuum was that
> > > would allow for more accurate metering of air and fuel under a wider
> > > range of operating conditions.
> >
> > That was Chrysler's way of doing it. That's all that can be said.
>
> For someone who claims to know something that is as good as saying you
> don't.
That's hilarious coming from someone who's above statement describes the
EGR as metering air and fuel.
> I didn't say chrysler used the same engines for all those years I
> said the EGR's were all pretty much the same in that era.
Must be why they all had the same part number (not).
> The means of
> controlling the vacuum, which determined how much exhaust gas was
> delivered and when it was delivered is what changed depending on make,
> model and year.
Now you're getting it.
Did the 87 Dakota V-6 use a vacuum amplifier?
> That was the purpose of vacuum hose configurations, vacuum amplifiers or
> transducers and different vacuum ports. The difference in the valve itself
> had more to do with how they fit on the engine rather than how they
> behaved.
Sounds like something the guy at the junkyard would say.
> At any rate EGR clearly has a huge effect on NOX emissions and does
> completely change the way air and fuel burn inside an engine.
Never said otherwise.
> That mains
> the entire way the engine is tuned needs to change to accompany the
> changes that EGR creates.
Indeed.
> For the most part EGR is beneficial. It is a lot
> like getting an octane boost (at no extra cost) and does allow for better
> fuel economy as well as overall better emissions *if* the engine is tuned
> to accommodate the changes in burn characteristics. That means changing
> air/fuel ratio as well as timing.
Which is not the same as asserting that the EGR changes the air fuel
ratio.
> The modern vehicle's computer takes care
> of all of that for you so yes you can get along quite nicely with any
> knowledge of it.
Absolutely.
aarcuda69062
wrote:
> > Yes it is.
> > Ever open an EGR valve at idle?
>
> Yep.
>
> > Did the engine run better or worse?
>
> Didn't run at all, they don't run well on an inert gas.
Next time, don't open it so far. Try a 10% or 20% command on your scn
tool instead of 80% .
>
> > Do you suppose HC goes up or down if you open the EGR at idle?
>
> Being the engine wouldn't stay running I would say it went down. ;) If
> it
> would stay running it would have a lean misfire that would lead to an
> increase
> in HC.
No, it wouldn't be a lean misfire. Lean misfire comes from too much air
and not enough fuel. Opening the EGR does not add more air.
The exhaust gasses displace what would have been combustible mixture in
the combustion chamber, the actual ratio of that combustible mixture
doesn't change.
If you have an engine with a leaking EGR valve at idle, fattening up the
mixture doesn't improve how the engine will idle.
Comparing secondary spark lines on a ignition scope, a lean mixture
looks completely different than a stuck open or leaking EGR valve.
> > Air pumps tend to have a generic universal design, what if instead of a
> > 4 CFM air pump made for a 3.9 liter engine, he got a 10 CFM replacement
> > pump made for a 7.4 liter engine.
> > You -can- pump too much air into a catalytic converter and snuff out the
> > fire.
>
> Yep, I see your point here. My experience has been that aftermarket
> emission parts are junk.
Yup.
beer...@whoever.com
Ultradrive innovation?
Simpson
The air pump is original equipment. I bought the truck new and I have
done all my own work on it, including changing the lifters and changing
a blown head gasket, two separate operations. So I know the air pump is
original. Whether it's working as it should today, I can't say. I tested
it a few years ago according to the manual and it seemed to be working then.
What has me puzzled at this point is which of the 4 operations I
performed on the fuel and ignition systems contributed to the
skyrocketing of CO emissions on the third test (test results reprinted
below). HC and NO came down significantly, as did O2, but at the expense
of CO.
Only the enrichening of the idle mixture and the widening of the
canister purge line ports in the wall of the carb throttle body could
have fattened up the mix, which would have resulted in the higher CO and
lower O2 readings. Assuming no freakishly timed breakdown of the air
pump, it's operation would have been the same for all 3 tests, whether
working or not.
If the guy who owns the smog shop will allow it, I would like to run
another pre-test and see if clamping down the canister purge hose
changes the readings mid-test.
I leaned out the idle mixture screws just a bit after the third test.
They were pretty close to lean best idle as it was. I can't imagine that
the small change that I made to the idle mix could have such a strong
affect on the emissions with the engine running at 1325 rpms. So the
enlarging of the canister purge line ports into the venturi just above
the throttle plates is the likely suspect, IMO.
%CO2 %O2 HC PPM %CO NOx PPM
15mph
1st test 10.8 5.9 34 .01 3641-FAIL
2nd test 10.4 6.7 132* .01 626
3rd test 12.2 3.6 82 1.02-FAIL 358
25mph
1st test 10.7 6.0 26 .01 3225-FAIL
2nd test 10.7 6.1 65 .04 606
3rd test 12.5 2.9 73 1.14** 191
1st test - 1. EGR run from EGR port on carb resulting in essentially
no EGR function
2. MSD ignition hooked up
2nd test - 1. EGR run from spark advance port on carb
2. MSD ignition not hooked up
3rd test - 1. EGR run from modified EGR port on carb
2. Idle mixture enriched slightly
3. The ports entering both barrels from the canister
purge hose were enlarged to correspond to those in the
original stock carb.
4. MSD ignition hooked up
* passing is 134, measured 132
** passing is 1.14, measured 1.14
aarcuda69062
jim
aarcuda69062 wrote:
>
> In article <_NtFj.364$NU2...@news01.roc.ny>, "Mike" <m...@localnet.com>
> wrote:
>
> > > Yes it is.
> > > Ever open an EGR valve at idle?
> >
> > Yep.
> >
> > > Did the engine run better or worse?
> >
> > Didn't run at all, they don't run well on an inert gas.
>
> Next time, don't open it so far. Try a 10% or 20% command on your scn
> tool instead of 80% .
> >
> > > Do you suppose HC goes up or down if you open the EGR at idle?
> >
> > Being the engine wouldn't stay running I would say it went down. ;) If
> > it
> > would stay running it would have a lean misfire that would lead to an
> > increase
> > in HC.
>
> No, it wouldn't be a lean misfire. Lean misfire comes from too much air
> and not enough fuel. Opening the EGR does not add more air.
It does add gas which displaces air. That would mean less air going into
the cylinders. At least that is what would happen in the first fractions
of a second. So for a very brief period of time you get a rich condition.
> The exhaust gasses displace what would have been combustible mixture in
> the combustion chamber, the actual ratio of that combustible mixture
> doesn't change.
How can the mixture not change if you just took away some of the air. Of
course in about the time it takes you to blink the dynamic system that
controls fuel, air, timing and idle speed is going to react to those
changes - so any conclusions you draw from this experiment are more than
likely to be completely wrong.
-jim
> If you have an engine with a leaking EGR valve at idle, fattening up the
> mixture doesn't improve how the engine will idle.
> Comparing secondary spark lines on a ignition scope, a lean mixture
> looks completely different than a stuck open or leaking EGR valve.
>
> > > Air pumps tend to have a generic universal design, what if instead of a
> > > 4 CFM air pump made for a 3.9 liter engine, he got a 10 CFM replacement
> > > pump made for a 7.4 liter engine.
> > > You -can- pump too much air into a catalytic converter and snuff out the
> > > fire.
> >
> > Yep, I see your point here. My experience has been that aftermarket
> > emission parts are junk.
>
> Yup.
aarcuda69062
wrote:
> > No, it wouldn't be a lean misfire. Lean misfire comes from too much air
> > and not enough fuel. Opening the EGR does not add more air.
>
> It does add gas which displaces air.
Displaces air -and- fuel.
> That would mean less air going into
> the cylinders.
Less air -and- fuel going into the cylinder.
> At least that is what would happen in the first fractions
> of a second. So for a very brief period of time you get a rich condition.
>
>
> > The exhaust gasses displace what would have been combustible mixture in
> > the combustion chamber, the actual ratio of that combustible mixture
> > doesn't change.
>
> How can the mixture not change if you just took away some of the air.
What makes you think that EGR only takes away air.
What makes you think that EGR takes away anything?
EGR displaces a volume in a cylinder.
> Of
> course in about the time it takes you to blink the dynamic system that
> controls fuel, air, timing and idle speed is going to react to those
> changes - so any conclusions you draw from this experiment are more than
> likely to be completely wrong.
None of what I've said are mine nor are they conclusions.
IOWs, you assume wrong again
They are the physics of the internal combustion engine, documented and
published (but probably not in Popular Mechanics).
Don't take my word for it, feel free to run Simpson's non operating EGR
valve gas readings and his operating EGR valve gas readings thru a
Lambda calculator.
You'll find that the air fuel ratio changes by .01 which is well within
the expected sampling error of the type of equipment being used for his
tests.
jim
aarcuda69062 wrote:
>
> In article <1206361375_763@isp.n>, jim <"sjedgingN0sp"@m...@mwt.net>
> wrote:
>
> > > No, it wouldn't be a lean misfire. Lean misfire comes from too much air
> > > and not enough fuel. Opening the EGR does not add more air.
> >
> > It does add gas which displaces air.
>
> Displaces air -and- fuel.
One can only guess what it is you are talking about. Let's assume you were
talking about a modern car with fuel injection. Air gets displaced
meaning less will enter intake (at least for an instant). The fuel at the
same time doesn't get displaced. There is nothing physical to cause the
fuel to be displaced. If the end result is less fuel is delivered it is
only because the engine's control system delivers less fuel (but it could
deliver more air or both).
On a vehicle with carb it's different because airflow is part of the
physical process that delivers fuel. But that still doesn't mean the
air/fuel ratio will stay the same without some engineering effort to make
that happen.
>
> > That would mean less air going into
> > the cylinders.
>
> Less air -and- fuel going into the cylinder.
Maybe or maybe not. All depends how a particular system is designed.
Hopefully it's designed well enough that it won't change the air/fuel
ratio very much in your scenario since EGR failures are not rare
occurrences.
>
> > At least that is what would happen in the first fractions
> > of a second. So for a very brief period of time you get a rich condition.
> >
> >
> > > The exhaust gasses displace what would have been combustible mixture in
> > > the combustion chamber, the actual ratio of that combustible mixture
> > > doesn't change.
> >
> > How can the mixture not change if you just took away some of the air.
>
> What makes you think that EGR only takes away air.
> What makes you think that EGR takes away anything?
> EGR displaces a volume in a cylinder.
That was your terminology. Air is a gas. So is the exhaust coming from EGR
- fuel is not. If you say some of the volume of gas is displaced that
equivalent to saying some is taken away.
>
> > Of
> > course in about the time it takes you to blink the dynamic system that
> > controls fuel, air, timing and idle speed is going to react to those
> > changes - so any conclusions you draw from this experiment are more than
> > likely to be completely wrong.
>
> None of what I've said are mine nor are they conclusions.
It sounded like it was your experiment. It also sounded like your
conclusion or at least you hoped others would reach from the experiment.
The only reason your experiment would lead to that erroneous conclusion is
because that is the way it is engineered to work. If the controls are
working as they should then it won't affect air/fuel because it is
designed not to.
> IOWs, you assume wrong again
> They are the physics of the internal combustion engine, documented and
> published (but probably not in Popular Mechanics).
>
> Don't take my word for it, feel free to run Simpson's non operating EGR
> valve gas readings and his operating EGR valve gas readings thru a
> Lambda calculator.
> You'll find that the air fuel ratio changes by .01 which is well within
> the expected sampling error of the type of equipment being used for his
> tests.
I suspect that Chrysler had a good bit of data on the vacuum controls for
EGR in the 80's also. And that data is what they used to design EGR
controls so that didn't throw the air/fuel ratio out of wack. But when you
start doing your own design on an engine as the OP is doing it is
extremely unlikely that you will end up not changing air/fuel ratio if you
just slap any EGR control onto the system any which way and simply hope.
-jim
Tegger
>
>
> aarcuda69062 wrote:
>>
>> In article <1206361375_763@isp.n>, jim <"sjedgingN0sp"@m...@mwt.net>
>> wrote:
>>
>> > > No, it wouldn't be a lean misfire. Lean misfire comes from too
>> > > much air and not enough fuel. Opening the EGR does not add more
>> > > air.
>> >
>> > It does add gas which displaces air.
>>
>> Displaces air -and- fuel.
>
> One can only guess what it is you are talking about. Let's assume you
> were talking about a modern car with fuel injection. Air gets
> displaced meaning less will enter intake (at least for an instant).
> The fuel at the same time doesn't get displaced. There is nothing
> physical to cause the fuel to be displaced.
I'd think the engine's computer would sense the decrease in fresh air
intake and reduce fuel delivery accordingly.
--
Tegger