[GMCnet] Fi Tech - any downwsides

[Gordon Gibson]

Hello all

Reassembly of my coach has is now well underway. Frank Borrmann (Borrmann's Garage, Bluevale, Ontario) has done a great job of insulating the
underneath of the cockpit (rubber sound deadener membrane, half inch of aluminum-backed foam paneling and stainless steel), and the new frame was
married to the coach early this week. Les Burt graciously put me in touch with Marcus Miller, who supplied two used fuel tanks to replace mine which
were thoroughly corroded through. The JMK 4-bag rear suspension and Dave Lenzie upper control arms and hubs are ready to bolt on. A Honda EV6010
patiently awaits installation in a slide tray.

I am now at the stage where decisions have to be made about fuel delivery. The PO had swapped out the Quadrajet for an Edelbrock carb, I will either
revert to a Quadrajet, or go the throttle-body fuel injection route. Since I have no re-buildable core, a Patterson rebuilt Quadrajet from Applied
will set me back $395 + $285 core charge. My conclusion is that I would be crazy not to at least consider FI, and the recent spate of write-ups on the
FiTech system sound very compelling. Given that there is no real free lunch, my question is whether anyone has bumped up up against the inevitable
downsides? Installation sounds simple enough, but is there a "give-up" because the unit has so few sensors? Is it easy to hook up the legacy GMC
cruise control to it? If not, what else has to be bought to get cruise control working? Which would be the unit of choice - the 400 or the 600?
Finally, I have heard stories about people having to debug their Howell FI systems - but the comments about FiTech don't seem to mention this. Is the
FiTech really plug&play? I have an Applied low-pressure electric fuel pump, and so the Commander option that obviates the need for return hoses
sounds appealing. Once again, is there a "give-up" associated with this. Finally, are there any alternatives to FiTech that I should be considering.


I am torn between staying with old technology that has proven itself, and new technology which (to me at least) will probably be better understood by
a higher percentage of mechanics currently plying their trade in North America - although I have read affirmations to the contrary..


Just throwing these questions out there, in the hopes of seeing a feeding frenzy of responses. And thanking all responders in advance.

Gordon Gibson
23' Norris Upfit
Montreal West, Qc. Canada
--
1976 23" Norris Upfit

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[A.]

This one is for a 403, but I would try it if I needed a carb for a 455 and was fiscally constrained.

http://www.ebay.com/itm/1978-GMC-CHEVY-MOTORHOME-CARBURETOR-ROCHESTER-M4MC-4BBL-403ci-6-6L-8cyl-7021-/201552530797?hash=item2eed778d6d:g:1TYAAOSw-jhT-MMW&vxp=mtr
--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Jim Kanomata]

Gorden,
You'll find some people with problem with the Howell/EBL True EFI units as
there are considerably more of them out there.They should contact me as I
have people that can solve problems.
A good rebuilt carburetor and a Patterson distributor will perform almost
as well as the FiTech unit.
Reason why the carb units do not fire up immediately is because of leaking
fuel bowel and exhaust cross over that has not been plugged to cut down on
excess heat.
On My 403 carbed unit I run a electric pump and turn the key on for about 5
seconds then push the throttle half way to set the choke then engage the
starter.It fires up immidiatly.
Should your engine continues to run after shutting off the key, it is
because your engine idle speed is too high.
True EFI should sense have knock sensor, Oxygen sensor and correct timing
when engine temperature gets extra high on a long hill.
Ignition timing is more important than fuel delivery. The EBL does that so
well that our customers are getting 1-2 mpg improvement.
Another plus is the technical assistance 7 days a week from people that not
only understand the EBL system, but can analyze the problem .
95% of parts are available at automotive parts stores.




On Thu, Apr 14, 2016 at 3:14 PM, Gordon Gibson <gordon...@videotron.ca>
wrote:

--
Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Jim Kanomata]

I have run several EFI units since 1990 so I know these units or know
people that know how to analyze units when they develope issues.

[Espen Heitmann]

Gordon go with the Fitech, I restore Rochester and other carbs and will have a Fitech or simular on my coach.
I would go for the 600 due to the ignition control but the 400 looks to be more than good for the GMC
--
1973 26'-3 # 1460 Parrot green Seqouia Known as the Big Mean Green Machine,
And just sold my 1973 26'-2 # 581 White Canyon lands under the name Dobbelt trøbbel
in Norway

[Gordon Gibson]

Loffen

A quick question if I may - while at the same time I ask for your indulgence with regard to my mechanical ignorance.

As you mention, the 600 has a few more bells and whistles, including ignition control. I assume that this means the FI somehow controls the degree of
spark advance to optimize combustion, reduce pinging, etc.

My understanding is that there are two models of distributor installed on GMCs - one is the classic old style with breaker points, which I guess uses
intake manifold vacuum to control the advance. The second is "pointless" - presumably triggering the spark with some kind of sensor. I have no idea
how the advance is controlled with this type of distributor - but assume it is done electronically.

My coach is an early 1976 with the 455. Think that Frank Borrman (the mechanic doing the work on the coach) told me that my distributor was of the
"pointless" variety. When I searched the forum for Fitech entries I thought I saw some mention of the fact that the ignition control on the Fitech 600
works with one type of distributor and not the other.

Am I safe to assume that the 600 ignition control would work with the more modern "pointless" distributor...but perhaps not with the other model?

Thanks in advance for your response...and your patience.

Regards

Gordon

--
1976 23" Norris Upfit

[jhb1]

Hi Gordon

I originally ordered the 400hp unit but kept getting the delivery pushed back. I ended up ordering the 600hp unit the differences between the two are
injector sizes and the 400hp unit does not support ignition control. The ignition control only works on points type distributors early models non-HEI.
Hope this helps
--
John H. Bell
77 Royale; QuadBag,Manny OneTon,Honda EV4010
Montreal Qc.

[Ken Henderson]

John,

In addition to the restriction to points type distributors, it's my
understanding that the only ignition "control" is that the advance curve is
controlled by software tables. That is, there is no knock detector
providing feedback and real time control of advance.

Is that correct?

Thanks,

Ken H.

On Fri, Apr 22, 2016 at 8:53 AM, jhb1 <jhb...@gmail.com> wrote:

> Hi Gordon
>
> I originally ordered the 400hp unit but kept getting the delivery pushed
> back. I ended up ordering the 600hp unit the differences between the two are
> injector sizes and the 400hp unit does not support ignition control. The
> ignition control only works on points type distributors early models
> non-HEI.
> Hope this helps
> --
>

[Gerald Work]

I’m not John,

But, the answer is yes, the FiTech ignition control is an advance curve programmed into a table without a knock sensor. It needs a locked out standard distributor (not HEI) to work. Most of the FiTech support people with whom I have spoken say they run their own classic/muscle cars using the HEI distributor. When Dick Patterson discussed this with FiTech at a trade show, he found the curve to be about what he programs into his HEI units designed for our GMCs. I had him curve one of his HEI distributors for my FiTech application in the Clasco and it seems to perform well.

The 400hp unit was not available when I purchased my 600 hp unit from FiTech - or at least I was unaware of it at that time if it did exist then. The design of the throttle body is the injectors do not squirt directly into the area of the throttle butterfly plates. Instead they squirt into an annular chamber that runs all around the throttle body. Small holes in the inside of the throttle body direct the pressurized fuel from the injectors into the throttle body all around on top of the throttle butterfly plates which they say delivers better atomization. It is not clear to me whether there is any real world difference between the two sizes of injectors given this delivery mechanism. All I know is the 600 hp unit works very well for me. I had one person off line tell me I should be experiencing bogging issues given the size of the injectors in the 600 hp unit. I am not. The only anomaly I have experienced is on two occasions while trying to reset the manual idle air back to the factory setting (I improperly moved that adjustment during installation) I experienced a bog right off idle when first firing up the engine from a cold state and driving off immediately. I have not experienced that since I think I got the manual idle air back close to where it belongs.

Most of the folks who are using computer based spark control with a knock sensor say they are able to achieve more advance without pre-ignition and so experience perhaps a 1 (some even say 2) mpg gain in fuel mileage. Some say they do not. Using the HEI distributor curve in both the Clasco with the FiTech EFI and the Royale with a Patterson Qjet I can’t readily tell any difference in fuel mileage. There is a lot of difference in throttle response, altitude compensation, immediate starting, etc. Lots of variation in our old beasts, I guess.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR

glw...@mac.com
http://jerrywork.com

==============
Message: 12
Date: Fri, 22 Apr 2016 09:37:58 -0400
From: Ken Henderson <hend...@bellsouth.net>
To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] Fi Tech - any downwsides
Message-ID:
<CANsh1i1Beq51qmT+per-7h_ix=hDeZJEL_GL1O...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

John,

In addition to the restriction to points type distributors, it's my
understanding that the only ignition "control" is that the advance curve is
controlled by software tables. That is, there is no knock detector
providing feedback and real time control of advance.

Is that correct?

Thanks,

Ken H.

On Fri, Apr 22, 2016 at 8:53 AM, jhb1 <jhb...@gmail.com> wrote:

> Hi Gordon
>
> I originally ordered the 400hp unit but kept getting the delivery pushed
> back. I ended up ordering the 600hp unit the differences between the two are
> injector sizes and the 400hp unit does not support ignition control. The
> ignition control only works on points type distributors early models
> non-HEI.
> Hope this helps

> —
=================

[Ken Henderson]

Thanks, Jerry.

If I weren't already deeply into TBI with EBL, I'd probably be going with
that system also. I don't see the dramatic mileage improvement with CCD
that some claim, but then I don't track MPG much either. I do enjoy
knowing I have full advance without having to worry about not being able to
hear knocking though.

Ken H.

On Fri, Apr 22, 2016 at 12:43 PM, Gerald Work <glw...@mac.com> wrote:

> I’m not John,
>
> But, the answer is yes, the FiTech ignition control is an advance curve
> programmed into a table without a knock sensor. It needs a locked out
> standard distributor (not HEI) to work. Most of the FiTech support people
> with whom I have spoken say they run their own classic/muscle cars using
> the HEI distributor. When Dick Patterson discussed this with FiTech at a
> trade show, he found the curve to be about what he programs into his HEI
> units designed for our GMCs. I had him curve one of his HEI distributors
> for my FiTech application in the Clasco and it seems to perform well.

> ...

[James Hupy]

Lots of engineering went into both the frequency of and amptitude of, as
well as the placement of knock sensors. GM spent a huge bundle on it, and
the other manufacturers did also. If you consider firing order of the
various engines involved, as well as construction materials, engine mounts,
exhaust manifolds, rpm, loads, etc. You get the idea. Fi Tec probably does
not quite have the engineering department that the big 3 have. Might have
more than a little bit to do with the product that they produce.
Their fuel module with internal submerged electric pump is as bright an
idea as I have seen in recent years, and should be adaptable to the Howell
system. I am going to try one as soon as the opportunity presents itself.
We need all the help that we can get to combat fuel vapor lock, especially
with blended fuels with low Reid pressure points. The problem will persist
as long as there is alcohol blended into gasoline, and I suspect that will
be a very long time.
Just what it is. We need to adapt to it.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

[jhb1]

Yup pretty simple control if I was looking for more control I would have kept the airsensor system and gone with megasquirt with coil paks for full
ignition control

Ken Henderson wrote on Fri, 22 April 2016 13:37

> John,
>
> In addition to the restriction to points type distributors, it's my
> understanding that the only ignition "control" is that the advance curve is
> controlled by software tables. That is, there is no knock detector
> providing feedback and real time control of advance.
>
> Is that correct?
>
> Thanks,
>
> Ken H.
>

> On Fri, Apr 22, 2016 at 8:53 AM, jhb1 wrote:
>
> > Hi Gordon
> >
> > I originally ordered the 400hp unit but kept getting the delivery pushed
> > back. I ended up ordering the 600hp unit the differences between the two are
> > injector sizes and the 400hp unit does not support ignition control. The
> > ignition control only works on points type distributors early models
> > non-HEI.
> > Hope this helps
> > --
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

--
John H. Bell
77 Royale; QuadBag,Manny OneTon,Honda EV4010
Montreal Qc.

[Larry]

Jerry,
I don't get it. Exactly how does the FiTech hook up and then control the spark? What does "locked out"... "standard distributor" mean? I have a
points distributor converted to Hall effect and curved by Patterson....or would my EFI distributor plug directly into the FiTech?
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

[Billy Massey]

Me to. And how does altitude compensation work without connecting to the
distributor?

bdub

On Sat, Apr 23, 2016 at 7:51 AM, Larry wrote:

> Jerry,
> I don't get it. Exactly how does the FiTech hook up and then control the
> spark? What does "locked out"... "standard distributor" mean? I have a
> points distributor converted to Hall effect and curved by Patterson....or
> would my EFI distributor plug directly into the FiTech?
>
>

[Armand Minnie]

go to http://fitechefi.com/virtualoffice_files/30001.30002%20Instructionsm%2012.9.15.pdf for a PDF of the instructions for the FiTech unit. The last
page has a diagram of what all the connections are.

--
Armand Minnie
Marana, AZ
'76 Eleganza II TZE166V103202
http://www.minniebiz.com
http://www.gmcws.org

[Billy Massey]

Jerry said in February that he didn't used "spark is via an HEI Dick
Patterson curved for this EfI". So, the schematic on page 11 would be
correct. Still don't see any means of altitude compensation which would be
one of my main objectives. I suppose the air / fuel mixture would be
compensated for with the oxygen sensor.
http://fitechefi.com/virtualoffice_files/30001.30002%20Instructionsm%2012.9.15.pdf#page=11

bdub ... EFI Dummy

On Sat, Apr 23, 2016 at 10:22 AM, Armand Minnie wrote:

> go to
> http://fitechefi.com/virtualoffice_files/30001.30002%20Instructionsm%2012.9.15.pdf
> for a PDF of the instructions for the FiTech unit. The last
> page has a diagram of what all the connections are.
>

[James Hupy]

Normally, altitude compensation is done by decreasing pulse width in the
fuel injection along with an increase in spark advance. If the distributor
is locked or fixed, then a timing module is incorporated to accomplish the
same effect. All attenuated by barometric pressure changes. (altitude
compensation). Lacking more sophisticated sensors, then the ECU takes over
more control. Lacking that, I suppose nothing gets done but fuel
management. Without more technical information, this is just educated
guesswork on my part.
Jim Hupy

[Gerald Work]

Good question for FiTech, Larry. Since I did not use their spark control I don’t know the ins and outs of which distributors work with their system. They show examples using an MSD distributor where the mechanical advance mechanism is locked so it no longer functions. The timing of the spark is set by the electronics instead of the mechanical advance mechanism.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR

glw...@mac.com
http://jerrywork.com

=============
Message: 8
Date: Sat, 23 Apr 2016 06:51:16 -0600
From: Larry <weid...@wwt.net>

To: gmc...@list.gmcnet.org
Subject: Re: [GMCnet] Fi Tech - any downwsides

Message-ID: <49203.5...@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="utf-8"

Jerry,
I don't get it. Exactly how does the FiTech hook up and then control the spark? What does "locked out"... "standard distributor" mean? I have a
points distributor converted to Hall effect and curved by Patterson....or would my EFI distributor plug directly into the FiTech?

--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

=============

[Gerald Work]

Hi Billy,

As I understand it, where a carb uses vacuum and springs to control the amount of fuel introduced into the air stream entering the carb, EFI uses an O2 sensor in the exhaust after combustion to maintain the desired air/fuel ratio for the load. The oxygen content of the air decreases the higher you go so in a conventional carb the relative amount of fuel introduced remains the same. At higher altitudes you run richer and power decreases. With EFI, since it is measuring the fuel to oxygen ratio directly, it can compensate for the change in oxygen available at different altitudes to keep the air/fuel ratio relatively the same. A conventional distributor only knows initial advance, speed of rotation and vacuum and uses those three pieces of information to determine spark advance at any given moment so advance would be the same for the same speed and load at any altitude.

One of our other posters with far more experience with the intricacies of EFI and computer controlled spark advance may be able to give a more compete explanation.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR

glw...@mac.com
http://jerrywork.com
============

Message: 11
Date: Sat, 23 Apr 2016 08:39:14 -0500
From: Billy Massey <bd...@bdub.net>
To: "gmc...@list.gmcnet.org" <gmc...@list.gmcnet.org>

Subject: Re: [GMCnet] Fi Tech - any downwsides
Message-ID:

<CANi-gHfPPCxR2rdscUC6=CAh6+eSCi+=EKEmgJXbr...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8

Me to. And how does altitude compensation work without connecting to the
distributor?

bdub

==============

[Terry]

The unit can adjust fuel mixture for altitude and load using a MAP sensor built into the ECU.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

[Billy Massey]

That's about the way I understand it. Seems like the computer controlled
spark advance would be a big improvement. Please let us all know if / when
you make that leap. :-)

bdub

On Sat, Apr 23, 2016 at 11:23 AM, Gerald Work wrote:

>
> As I understand it, where a carb uses vacuum and springs to control the
> amount of fuel introduced into the air stream entering the carb, EFI uses
> an O2 sensor in the exhaust after combustion to maintain the desired
> air/fuel ratio for the load. The oxygen content of the air decreases the
> higher you go so in a conventional carb the relative amount of fuel
> introduced remains the same. At higher altitudes you run richer and power
> decreases. With EFI, since it is measuring the fuel to oxygen ratio
> directly, it can compensate for the change in oxygen available at different
> altitudes to keep the air/fuel ratio relatively the same. A conventional
> distributor only knows initial advance, speed of rotation and vacuum and
> uses those three pieces of information to determine spark advance at any
> given moment so advance would be the same for the same speed and load at
> any altitude.
>
> One of our other posters with far more experience with the intricacies of
> EFI and computer controlled spark advance may be able to give a more
> compete explanation.
>
>

[Ken Henderson]

Perhaps a simplified explanation of how EBL works will help: A spark
advance table is pre-programmed to, hopefully, correspond closely to the
engine's load, as recognized by MAP (vacuum) and RPM. The table grid
contains spark advance settings for all likely combinations of those two.
AFAIK, the FiTech system uses the same type table. The difference is what
happens when the table is wrong:

With the EBL (and basic GMC system WITH spark control -- not all have it),
there is a knock sensor and associated circuitry and software. When knocks
(pings) are detected, the ECU (Engine Control Unit -- "computer") subtracts
a set bias value from the spark advance extracted from the table. It then
"listens" for more knocks and either holds its setting or subtracts more
advance. After a programmed period of no knocks, the bias is removed.
There is also a programmed maximum which can be removed. Since this
process is operating continuously, knocks are reduced to those few required
to trigger the retard process. This is true regardless of altitude,
temperature, fuel quality, or other factors.

Since the FiTech has no knock detector, it cannot automatically retard
spark to reduce knocks. Therefore, in this regard it can offer no more
than a convenient way to "manually" curve a mechanical distributor.

Feel free to add details about either system; hopefully this is sufficient
to clarify the differences.

Ken H.

On Sat, Apr 23, 2016 at 12:23 PM, Gerald Work <glw...@mac.com> wrote:

> Hi Billy,
>
> As I understand it, where a carb uses vacuum and springs to control the
> amount of fuel introduced into the air stream entering the carb, EFI uses
> an O2 sensor in the exhaust after combustion to maintain the desired
> air/fuel ratio for the load. The oxygen content of the air decreases the
> higher you go so in a conventional carb the relative amount of fuel
> introduced remains the same. At higher altitudes you run richer and power
> decreases. With EFI, since it is measuring the fuel to oxygen ratio
> directly, it can compensate for the change in oxygen available at different
> altitudes to keep the air/fuel ratio relatively the same. A conventional
> distributor only knows initial advance, speed of rotation and vacuum and
> uses those three pieces of information to determine spark advance at any
> given moment so advance would be the same for the same speed and load at
> any altitude.
>
> One of our other posters with far more experience with the intricacies of
> EFI and computer controlled spark advance may be able to give a more
> compete explanation.

[Justin Brady]

True on all counts.
In its most basic form the FiTech is an AFR controller. It manipulates the amount of fuel in the combustion chamber to maintain the desired AFR at all
times.

Ken is right. The FiTech uses a 3x3 table setup for timing control (at least on the models we will be using, the higher power models have bigger
tables). This is less than ideal, and you may in fact have just as good or better results with a nice hei curved properly and professionally for your
coach. The advantage is if you have an off the shelf distributor or worn out parts etc that would be difficult to detect without having a professional
work over your distributor the FiTech can control it with the table and be almost as good as a well tuned distributor.

There is no knock sensor, so the FiTech spark control in my opinion should not be used to try to eek out the maximum power from your engine or to try
to get a 2mpg boost. In my eyes it's purpose is to give piece of mind that your engine is tuned to a good stable level and all is functioning
properly. Since it's solid state there's nothing to wear out over time reducing things that you have to keep an eye on or worry about. This is my view
on the whole system, it's purpose is not to turn your Motorhome into a drag car, but to increase convenience (cold starting, altitude changes etc) and
to give piece of mind that all is functioning as best it can (or near to it)


Ken, have you (or others) done any data logging that shows the spark curve a d how often the knock sensor actually comes into play? Id be curious to
see the numbers on whether it's being used to maximize power and mileage or if it's just there as an extra sefety measure.
--
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455

[Ken Henderson]

Justin,

I have done very little data logging, none over the past couple of years.
Randy Van Winkle and George Beckman are the guru's on the EBL system and
have done a lot of logging. Whether they've concentrated on the spark
tables, I don't know.

You and others interested in EFI, whether FiTech or others, may want to
join our Google EFI Group:
https://groups.google.com/forum/#!forum/gmcmh-efi
Since we don't cover anything except EFI, there's not much traffic and
practically all of it is valuable.

Ken H.

On Sat, Apr 23, 2016 at 2:16 PM, Justin Brady <jbr...@gmail.com> wrote:

> True on all counts.
> In its most basic form the FiTech is an AFR controller. It manipulates the
> amount of fuel in the combustion chamber to maintain the desired AFR at all
> times.
>

...

> Ken, have you (or others) done any data logging that shows the spark curve
> a d how often the knock sensor actually comes into play? Id be curious to
> see the numbers on whether it's being used to maximize power and mileage
> or if it's just there as an extra sefety measure.
> --
>

[Randy Van Winkle]

SONICJK wrote on Sat, 23 April 2016 13:16

> True on all counts.
> In its most basic form the FiTech is an AFR controller. It manipulates the amount of fuel in the combustion chamber to maintain the desired AFR at
> all times.
>

> ...

>
> Ken is right. The FiTech uses a 3x3 table setup for timing control (at least on the models we will be using, the higher power models have bigger
> tables). This is less than ideal, and you may in fact have just as good or better results with a nice hei curved properly and professionally for

> your coach. Ken, have you (or others) done any data logging that shows the spark curve a d how often the knock sensor actually comes into play? Id

> be curious to see the numbers on whether it's being used to maximize power and mileage or if it's just there as an extra sefety measure.

A couple of us have done extensive testing with fuel (Air Fuel Ratio (AFR)) and spark control with the Howell/EBL setup. EmBedded Locker system
(EBL)is an add-on to the 80s and 90s Electronic Fuel Injection (EFI) systems that many of us have retrofitted to the 455 or 403 that makes the
original Electronic Control Modules (ECM) very similar in function to modern day ECMs and aftermarket EFI systems with self learning. There is not a
lot that can be done with fuel. Most carbs and EFI units will mix fuel and air for a good burn. However, EFI units of whatever variety does do a
better job of mixing fuel and air under a variety of different conditions, such as altitude, heat, cold, load, no loads, etc. whereas, a carb is
limited to mixtures based on the particular metering rod. Under load, a carb opens the secondaries and pours in the fuel. EFI is a bit more precise.
One other thing with the EBL setup, is the ability to run lean when just cruising (no load). In testing for the GMC MH, we have found that around
16.5 to 1 is the appropriate ratio when under no load. Engine combustion temps will actually cool some in this mode as measured by Exhaust Gas
Temperature (EGT) probes that I have on my engine. The important point here is when load starts to increase, the AFR needs to quickly get richer or
engine combustion temps will rise and it rises very quickly. The EBL allows tuning of this situation so that ratios are getting richer fast enough to
keep temps under control.

The other component to running leaner is that spark must also be advanced. The flame front is harder to start and spreads slower when the AFR is lean.
Again, in our tuning we have found that 5 degrees of additional advance is needed to keep producing enough power to keep the engine running
efficiently and to maintain cruise speed. Once load is encountered, then Spark Advance (SA) needs to drop back. Again, the EBL allows tuning of these
parameters. When I'm cruising at 65, AFR is around 16.5 and SA is 48 degrees. I do have a 403 and it likes a tad more advance than a 455 but not by a
bunch. My friend, George has a 455 and we have done testing with my 403 and his 455 and have ended up with similar spark curves with mine perhaps
being a couple of degrees more advanced.

Our engines are not spark limited under most conditions with the exception of when under hard pulls. The EBL has many cells (as Ken indicated, each
cell is defined by Manifold Absolute Pressure (MAP), which is sort of a measure of vacuum, and Revolutions Per Minute (RPM))which allows for SA to be
calibrated in those cells were pinging or knocks are prevalent when under load. The advantage over a non computer controlled distributor, or computer
controlled that is only mimicking a manual distributor (eg, very small spark table), is that you can tune only the cells where the knocks are
occurring (I let the knock sensor tell me where those are). With a manual distributor, if you hear a knock, you twist the distributor in retard
direction a couple of degrees to correct. The problem is you have now adjusted the whole spark curve those two degrees affecting advance in the cruise
area which is where the miles per gallon is obtained. I always want to make sure the SA is tuned to avoid any pinging then rely on the knock sensor to
"protect" the engine if I get a tank of bad gas (which happens), or if a spark plug starts producing a hot spot (which has happened to me). Modern day
knock sensing is sophisticated enough where engines can run equally well on high octane or low octane gas. A lot of engineering goes into knock
sensor technology and probably why these more inexpensive aftermarket EFI systems do not include knock sensor technology. For that reason, I do not
totally trust the knock sensor technology from the 80s and 90s that we are using so I tune to avoid knocks and use the knock sensor to "protect" the
engine from bad gas, etc. That being said, I always marvel at the fact that the knock indicator starts to show knocks before I actually hear any.
--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO

[Justin Brady]

Randy,
Good information,
That's basically what I was getting at.
My question is what is the lean cruise netting you? Slightly higher mpg? More power? These are my my personal reasons for going efi in the first
place, neither is a primary concern of mine. I am curious though.
There are certainly better efi systems available than the FiTech. There's no debate there, but the question becomes why are you going efi? For me it's
so I dont have to worry about the spark tables or if I'm running lean or if I'm going to overheat going over the pass because my AFR is off due to
altitude. For me it's all about ease of use, convenience, and piece of mind. I have zero desire to constantly tweak things, that's not why I want my
GMC.
For my weekend toy 69 GMC stepside sure, more power more torque more everything and tweaking is half the fun, but for the Motorhome I want to set it
and forget it if you know what I mean.

Again this is all personal opinion, but I'd wager that this is the reason the FiTech is so popular, because people share these sentiments.

--
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455

[James Hupy]

What Randy said! I tried to hint around at the complexities, but he has a
way of condensing the subjects. Whenever I try to do that, I get cut off at
the pockets by the network administrator for using too much bandwidth. The
place for these technical subjects is not the GMCnet. The efi forum will
get as specific as any sane person needs. (Grin)
Jim Hupy
Salem, Or
78 GMC ROYALE 403.

[Billy Massey]

Hi Randy

Thank you for this excellent explanation.

Just excellent!
bdub

[Jeremy]

That was excellent. Thanks!
--
Thanks,
Jeremy Knezek
1976 Glenbrook
Birmingham, AL

[Randy Van Winkle]

SONICJK wrote on Sat, 23 April 2016 15:13

> Randy,
> Good information,
> That's basically what I was getting at.
> My question is what is the lean cruise netting you? Slightly higher mpg? More power? These are my my personal reasons for going efi in the first
> place, neither is a primary concern of mine. I am curious though.
> There are certainly better efi systems available than the FiTech. There's no debate there, but the question becomes why are you going efi? For me
> it's so I dont have to worry about the spark tables or if I'm running lean or if I'm going to overheat going over the pass because my AFR is off due
> to altitude. For me it's all about ease of use, convenience, and piece of mind. I have zero desire to constantly tweak things, that's not why I want
> my GMC.
> For my weekend toy 69 GMC stepside sure, more power more torque more everything and tweaking is half the fun, but for the Motorhome I want to set
> it and forget it if you know what I mean.
>
> Again this is all personal opinion, but I'd wager that this is the reason the FiTech is so popular, because people share these sentiments.

First, the lean cruise does help with miles per gallon. With my display tied to the EBL, I have instantaneous mpg readout. When the EBL goes into
lean cruise the mpg goes up by 1. Overall, that does not net a tremendous increase but it is fun. And with Spark Control, I can probably eek out a
little more. Keep in mind, a 12,000 pound motorhome pushing a lot of air is going to consume a lot of gas no matter the type of EFI or Carb or
whatever...

Now, to address the constant tweaking issue. The EBL setup gives you the tools and knobs to allow easy tweaking of the system. Doesn't mean you have
to do it. I do because it is (or was) fun. I probably have not touched my setup for at least 3 to 5 years - it just works. My coach has around
120,000 miles and I have run my EFI setup for about 80,000 of those miles. And for anyone new, the basic setup that comes out of the box for a
Howell/EBL system is a good conservative setup and will run years without issue providing all the benefits of EFI. I have nothing against the FITech
system. I think it is an excellent setup and easy to install. It provides most of the benefits of going EFI without too much hassle. I just wish it
had a better setup for handling spark control. For most, the easy install will make this an excellent choice.

I had two WOW moments. One was when I installed EFI with fuel control only. I went for my first test drive. The instant start up and responsiveness
led me to say "WOW". A few months later, I added spark control. Responsiveness jumped a notch not only off the line, but especially when rolling and
you punch it a little. My second "WOW".

BTW...I have no dog in the hunt here, just my experience talking.

--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO

[Jim Kanomata]

Our Howell EBL system is plug and play.
85% of our customers never touch a thing as we pre program the ECM either
the 455/403.
Should there be a problem, we have several people like Randy,Ken and Walt
that are running them on their coaches and can assist you 7 days a week.
There are lot of people that have the basic Howell system and are not aware
of the EBL system we sell.
I just feel that if your going to go with the EFI way, step up and take
advantage of the more advanced feature.
We do sell the MSD Throttle Body unit, which is very similar to the Fi Tech
unit, so I understand the difference.
Lean run is always misunderstood, Less fuel, cooler the combustion .
Think about it, first time I heard that, I raised my hand and questioned
that and soon realized why it works with our burning up the valves,etc.
We do not have the Lean Run feature activated when we sell or units. We
leave that up to the customer to contact others that are running it that
way.

On Sat, Apr 23, 2016 at 3:25 PM, Randy Van Winkle <rlva...@gmail.com>
wrote:

--
Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[Carl Stouffer]

For about the last five years, I have had an MSD adjustable timing unit in my coach, courtesy of Steve Ferguson. It allows me to adjust the timing
from the dash. This makes it possible for me to retard the timing under heavy towing loads and/or at low elevations, or advance the timing under
light loads and at high elevations.

This sounds like it would work well with the FiTech system, the only down side being that you would need to manually adjust the timing. After five
years of using the MSD spark control, it has become automatic for me anyway.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.

[A.]

Carl S. wrote on Sun, 24 April 2016 09:53
> ...I have...adjustable timing...from the dash. ...
My dad had a gizmo in a pickup truck that he tried to use to get max power going over the continental divide. Burned a valve. Spark advance can't be
done manually with any expectation of success. It needs a knock sensor, or mechanical/vacuum advance that is not too aggressive.
--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Gerald Work]

Interesting that I have not seen any mention of the aftermarket automatic spark controllers with knock sensors like the one JimK sells for $595 called “Safeguard Knock Controller” . On paper it sounds like it may do something like what the EBL does for the Howell EFI and if memory serves me correctly the EBL adder is that price or perhaps more. Anyone have experience with any of these? Do they accomplish the same thing? Do they work with HEI? Are they worth considering for use with the self learning EFI systems like FiTech or MSD Atomic?

Here is a comment the owner of the Safeguard company made a few years ago when asked about the knock sensor hearing pre-detonation or piston slap on race engines. Not sure it has any applicability for our GMCs, but sure sounds like after market knock sensors can be a touchy subject:

"Our latest units are calibrated for Bosch or other brand "donut" style knock sensors. We no longer use GM "one wire" sensors, as included with the MSD Knock Alert. That's a clever analog design from the 1980's and works well with a quiet engine, but it has no micro-processor or other logic.

John Pizzuto
J&S Electronics”

I am also wondering about the base economics of trying to eek out another mpg or so by trying to advance timing more than a properly curved HEI will do under similar circumstances. Not trying to sell any thing here as I have no dog in this hunt. Just thinking through all I am reading -

A new engine costs somewhere between $3500 and $15000 with the R&R depending on lots of things. I will use $5000 as a rough average. We drive our two coaches a lot each year, but I doubt if most of our owners drive more than 10,000 miles a year, if that. Depending on how fast one drives, how loaded the coach is and where they drive (mountain west or flatlander) most GMCs will get 8 to 10 mpg. Lets use 9mpg as an average for this purpose. At 9mpg over 10,000 miles one will burn about 1100 gallons of fuel. At, say, $2.50 per gallon that is about $2,750 per year. With absolutely perfect spark control what is hear is the gain could be maybe 1 to as much as 2 mpg. Lets use 1.5mpg. 1.5 on 9 is an increase of a bit over 15% which would mean a savings of around $400 or so per year. At this rate the perfect spark control savings would take somewhere around 9 to 30+ years to equal the cost of one engine R&R if the spark control was not perfect and/or the aftermarket knock sensor failed to retard adequately or fast enough to keep from burning a hole in a piston or worse. Hmmmm…..

Food for thought, anyway.

Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR

glw...@mac.com
http://jerrywork.com

================

[Wally Anderson]

glwgmc wrote on Sun, 24 April 2016 12:43

> Interesting that I have not seen any mention of the aftermarket automatic spark controllers with knock sensors like the one JimK sells for $595
> called "Safeguard Knock Controller" . On paper it sounds like it may do something like what the EBL does for the Howell EFI and if memory serves me
> correctly the EBL adder is that price or perhaps more. Anyone have experience with any of these? Do they accomplish the same thing? Do they work
> with HEI? Are they worth considering for use with the self learning EFI systems like FiTech or MSD Atomic?
>
> Here is a comment the owner of the Safeguard company made a few years ago when asked about the knock sensor hearing pre-detonation or piston slap
> on race engines. Not sure it has any applicability for our GMCs, but sure sounds like after market knock sensors can be a touchy subject:
>
> "Our latest units are calibrated for Bosch or other brand "donut" style knock sensors. We no longer use GM "one wire" sensors, as included with
> the MSD Knock Alert. That's a clever analog design from the 1980's and works well with a quiet engine, but it has no micro-processor or other
> logic.
>
> John Pizzuto
> J&S Electronics"
>
> I am also wondering about the base economics of trying to eek out another mpg or so by trying to advance timing more than a properly curved HEI
> will do under similar circumstances. Not trying to sell any thing here as I have no dog in this hunt. Just thinking through all I am reading -
>
> A new engine costs somewhere between $3500 and $15000 with the R&R depending on lots of things. I will use $5000 as a rough average. We drive
> our two coaches a lot each year, but I doubt if most of our owners drive more than 10,000 miles a year, if that. Depending on how fast one drives,
> how loaded the coach is and where they drive (mountain west or flatlander) most GMCs will get 8 to 10 mpg. Lets use 9mpg as an average for this
> purpose. At 9mpg over 10,000 miles one will burn about 1100 gallons of fuel. At, say, $2.50 per gallon that is about $2,750 per year. With
> absolutely perfect spark control what is hear is the gain could be maybe 1 to as much as 2 mpg. Lets use 1.5mpg. 1.5 on 9 is an increase of a bit
> over 15% which would mean a savings of around $400 or so per year. At this rate the perfect spark control savings would take somewhere around 9 to
> 30+ years to equal the cost of one engine R&R if the spark control was not perfect and/or the aftermarket knock sensor failed to retard adequately

> or fast enough to keep from burning a hole in a piston or worse. Hmmmm.....

>
> Food for thought, anyway.
>
> Jerry
> Jerry Work
> The Dovetail Joint
> Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
>
> glw...@mac.com
> http://jerrywork.com
> ================
>
>
>
>
>
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

We have been running a J&S safeguard since 2011. Individual cylinder retard with "windowed" sensing. It is stand alone no matter what ignition scheme
you are using. We have the Vampire with remote display.
http://wallyandsue.blogspot.com/search/label/J%20S%20safeguard
http://wallyandsue.blogspot.com/search/label/Knock%20control
--
Wally Anderson
1975 Glenbrook
Megasquirt 455 port injection science project
Omaha Nebraska
Bob Stone hydroBOOOOST
Greater Midwest Classics
GMCES
http://wallyandsue.blogspot.com/

[Carl Stouffer]

A Hamilto wrote on Sun, 24 April 2016 08:03

> Carl S. wrote on Sun, 24 April 2016 09:53
> > ...I have...adjustable timing...from the dash. ...
> My dad had a gizmo in a pickup truck that he tried to use to get max power going over the continental divide. Burned a valve. Spark advance can't

> be done manually with any expectation of success. It needs a knock sensor coupled with the electronic ignition, or mechanical/vacuum advance that is
> not too aggressive.



I stand corrected. I'm not sure how one burns a valve by retarding the timing six or eight degrees to eliminate detonation on a hard climb, but I
always defer to the

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.

[A.]

Carl S. wrote on Sun, 24 April 2016 17:16

> A Hamilto wrote on Sun, 24 April 2016 08:03
> > Carl S. wrote on Sun, 24 April 2016 09:53
> > > ...I have...adjustable timing...from the dash. ...
> > My dad had a gizmo in a pickup truck that he tried to use to get max power going over the continental divide. Burned a valve. Spark advance
> > can't be done manually with any expectation of success. It needs a knock sensor coupled with the electronic ignition, or mechanical/vacuum advance
> > that is not too aggressive.
> I stand corrected. I'm not sure how one burns a valve by retarding the timing six or eight degrees to eliminate detonation on a hard climb, but I
> always defer to the

Not retarding. He was advancing it for power and trying to back off when it knocked. It didn't work. Manual control can't do enough fast enough.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Carl Stouffer]

A Hamilto wrote on Sun, 24 April 2016 15:30

> Carl S. wrote on Sun, 24 April 2016 17:16
> > A Hamilto wrote on Sun, 24 April 2016 08:03
> > > Carl S. wrote on Sun, 24 April 2016 09:53
> > > > ...I have...adjustable timing...from the dash. ...
> > > My dad had a gizmo in a pickup truck that he tried to use to get max power going over the continental divide. Burned a valve. Spark
> > > advance can't be done manually with any expectation of success. It needs a knock sensor coupled with the electronic ignition, or
> > > mechanical/vacuum advance that is not too aggressive.
> > I stand corrected. I'm not sure how one burns a valve by retarding the timing six or eight degrees to eliminate detonation on a hard climb,
> > but I always defer to the
> Not retarding. He was advancing it for power and trying to back off when it knocked. It didn't work. Manual control can't do enough fast enough.

His mistake.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.

[Johnny Bridges via Gmclist]

Retarding the timing means the mixture lights later and burns later. Leaning from altitude makes the mixture burn slower. Combine the two and you
can be blowing fire past the valve when it opens.

--johnny
--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[James Hupy]

Hmmmm? Let me see if I got this. Intake opens, piston travels down and
atmospheric pressure forces air/fuel mix into cylinder as long as there is
a difference in pressure between the two areas. Intake valve closes, piston
travels up compresses the mix, 8 or 10 degrees before tdc at idle speed,
plug fires, mixture expands and shoves the piston down. Few degrees before
bottom, exhaust valve starts to open. By this time, no Ox left to oxidize
the valve seat or valve face. Inert gasses are not the cause of oxidation.
Valves can run red hot without burning and do a lot of the time under heavy
loads. Thermodynamics teaches us that as long as heat is exchanged to the
exhaust and cooling systems at a greater rate than combustion heats them
up, the valves and seats can survive in that environment, AS LONG AS NO
OXYGEN IS PRESENT.

Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Apr 24, 2016 3:33 PM, "Johnny Bridges via Gmclist" <

[A.]

Carl S. wrote on Sun, 24 April 2016 17:32
> His mistake.
No argument there. And the mistake was trying to control the spark advance manually expecting better results than OEM. A human can't do it. You are
most likely human.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Johnny Bridges via Gmclist]

That's the way it was 'splained to me. And supported by the fact that retarded idle spark using ported vacuum makes the engine run way hotter.
particularly exhaust valves and downstream components.
Maybe one of the engineering types will take this further.

--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[Jim Kanomata]

That is one of the test question on the ASE test.
Correct answer is what Jim H said.

--
Jim Kanomata
Applied/GMC, Fremont,CA
ji...@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502

[A.]

jimk wrote on Sun, 24 April 2016 20:24

> That is one of the test question on the ASE test.
> Correct answer is what Jim H said.

I am glad you joined the conversation. I am a bit dense. Are you and Mr. Hupy saying that no matter how late the spark occurs, all the A/F is
completely consumed before the exhaust valve opens? If that is NOT what you are saying, can you tell us what happens when combustion is still in
progress when the exhaust valve opens?

I guess what I want to know is, knowing that too much advance can burn a valve, what happens with not enough advance?

--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Johnny Bridges via Gmclist]

OK, so getting it hot doesn't hurt unless it's over lean and there's spare oxygen present? Makes sense, I had a manifold leak in a Ranger chew up
both heads eventually.

--johnny

--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[James Hupy]

It can best be understood when expressed in degrees of crankshaft rotation.
Gasoline engines have a limited amount of time when heat is applied ,
(combustion) usually less than 40° out of 720°. When valves are in contact
with the seats, combustion heat is transferred by direct conduction to the
cooling system. When the valves are off the seats, they are exposed to
combustion gasses whose temperature is above the melting point of the
materials involved, and the only way they can dispose of heat is down the
stem and through the oil film to the guides. Not very efficient. If ANY
OXYGEN IS PRESENT, valves will oxidize an atom or molecule at a time until
they cannot seal against the seat. Then bad stuff happens quickly.

Jim Hupy
Salem, Or
78 GMC ROYALE 403

On Apr 24, 2016 6:58 PM, "Johnny Bridges via Gmclist" <

[George Beckman]

James Hupy wrote on Sun, 24 April 2016 15:55

> Thermodynamics teaches us that as long as heat is exchanged to the
> exhaust and cooling systems at a greater rate than combustion heats them
> up, the valves and seats can survive in that environment, AS LONG AS NO
> OXYGEN IS PRESENT.
> Jim Hupy
> Salem, Or
> 78 GMC ROYALE 403

And thanks to Jim Hupy, I finally understand.that oxygen is present in greater quantities when the mixture is lean. Combine a retarded spark and lean
fuel mixture and I am thinking the engine is going to burn valves and it happens in seconds.

This creates a big problem for EFI like my EBL. I only use a narrowband O2 sensor to control fuel. A narrow band only knows one thing: 14.7 to 1. If
the mixture moves off 14.7, such as climbing a hill, and the O2 sensor is clueless other than to say "It is rich". So during a climb, I am at the
mercy of injectors just as Carb guys are at the mercy of the jets. We can only "hope that the mixture is rich.

This is where a Wide Band O2 sensor can be handy for Carb and EFI. It tells us what is really happening. I was climbing a grade (not a hill) in Nevada
and suddenly the throttle felt like I was stepping on a grapefruit. The EBL said it was in Power Enrichment, meaning the mixture should be at least
12.8 to 1. The WideBand said 19 to 1. A quick look at fuel pressure showed 5lbs rather than 17lbs.

I know these gauges are expensive and I am supposed to look out the windows and enjoy. I changed a fuel pump that sounded like it was grinding bolts
and then enjoyed not having to buy a new engine. Besides, I have seen Nevada on I-80.
--
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George

[Matt Colie]

OK Guys,

I am not really sure where to start or how much to explain here, but....
Definitions:
MAP - Manifold Absolute Pressure - Kind of the inverse of vacuum and very related to altitude.
Initial Cylinder Pressure - the absolute pressure peak in the cylinder before the fire starts.

I will be referring to a single all mechanical engine.

Flame propagation gets slower with lower ICP. This is why the typical plan is to retard the ignition at higher MAP.
There is ALWAYS loose oxygen present in any IC engine exhaust stream. Regardless of the current A/F ratio.
There are ALWAYS unburned hydrocarbons present in any IC engine exhaust stream.
Exhaust valves are cooled both by the seat contact and the stem/guide transfer.
Exhaust valves are usually operating at a temperature that could be moments away from self destruction.
If the seat gets fouled by the unburned hydrocarbons or by failing to seat properly, it may fail to seal. In this case, valve failure is a small
number of combustion cycles away.

Lean is typically a slower propagation rate than rich.* (A broad generality)

How do OEs do this?
With the engine in a development dynamometer cell (this is no relation to a speed shop dyno), they run spark and fuel loops with conditioned intake
air. These loops are when they run the engine band with an ignition timing and a known fuel delivery. When that run is complete, they change
something a little and run it again, and again and again and then again. (Does this sound boring? We used to do this by hand and now the cell
controller does most of it.) They also don't usually use a stock block. We would get a special block cast that has a collection of extra bosses that
got machined off-line (the block would go down the standard machine line if it existed) and then knock sensors would be on as many of those bosses as
we could manage and the cell controller would listen to all of them. (this also used to get done with headphones and a band-pass filter) Then people
get to look at a telephone book of data.

Matt - off to the dentist - If there are questions, I will fill them in later.
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit

[A.]

Matt Colie wrote on Mon, 25 April 2016 08:35

> OK Guys,
> I am not really sure where to start or how much to explain here, but....
> Definitions:
> MAP - Manifold Absolute Pressure - Kind of the inverse of vacuum and very related to altitude.
> Initial Cylinder Pressure - the absolute pressure peak in the cylinder before the fire starts.
>
> I will be referring to a single all mechanical engine.
>
> Flame propagation gets slower with lower ICP. This is why the typical plan is to retard the ignition at higher MAP.
> There is ALWAYS loose oxygen present in any IC engine exhaust stream. Regardless of the current A/F ratio.
> There are ALWAYS unburned hydrocarbons present in any IC engine exhaust stream.
> Exhaust valves are cooled both by the seat contact and the stem/guide transfer.
> Exhaust valves are usually operating at a temperature that could be moments away from self destruction.
> If the seat gets fouled by the unburned hydrocarbons or by failing to seat properly, it may fail to seal. In this case, valve failure is a small
> number of combustion cycles away.
>
> Lean is typically a slower propagation rate than rich.* (A broad generality)
>
> How do OEs do this?
> With the engine in a development dynamometer cell (this is no relation to a speed shop dyno), they run spark and fuel loops with conditioned
> intake air. These loops are when they run the engine band with an ignition timing and a known fuel delivery. When that run is complete, they
> change something a little and run it again, and again and again and then again. (Does this sound boring? We used to do this by hand and now the
> cell controller does most of it.) They also don't usually use a stock block. We would get a special block cast that has a collection of extra
> bosses that got machined off-line (the block would go down the standard machine line if it existed) and then knock sensors would be on as many of
> those bosses as we could manage and the cell controller would listen to all of them. (this also used to get done with headphones and a band-pass
> filter) Then people get to look at a telephone book of data.
>
> Matt - off to the dentist - If there are questions, I will fill them in later.

My question is this: If the spark is not adequately advanced at a higher altitude (low barometric pressure) is the engine in any danger of damage from
combustion that is still in progress when the exhaust valve opens? Of course I am not talking about a single stroke, I mean thousands of times per
minute. Backing up a step, is it even possible that the combustion process is still in progress when the exhaust valve opens?

--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Matt Colie]

Response to what Matt Colie wrote on Mon, 25 April 2016 08:35
A Hamilto wrote on Mon, 25 April 2016 12:36

> My question is this: If the spark is not adequately advanced at a higher altitude (low barometric pressure) is the engine in any danger of damage
> from combustion that is still in progress when the exhaust valve opens? Of course I am not talking about a single stroke, I mean thousands of times
> per minute. Backing up a step, is it even possible that the combustion process is still in progress when the exhaust valve opens?

I completely understand how your effective thinking could cause the question order as you wrote.

So, I am going to answer the second question first as that will shed some light on the answer to the first.
Yes, in most SI (Spark Ignition) engines operating above idle power the combustion process is still going when the exhaust valve opens.
And
We have a saving grace in physics that keeps SI engines from being destroyed by small issues. The operation of an SI (Otto cycle) engine depends
heavily on the expansion ratio of the burned charge. That expansion, while possibly increasing the measured temperature, actually decreases that
amount of heat that can be transferred to metal parts during the cycle. A thermocouple in the exhaust stream (lab rats do this all the time) can
indicate a very high gas temperature at idle. It won't seem that hot if you are near it. But, darken a test cell with an engine at WOT and look at
the glowing exhaust while the indicated exhaust temperature is no higher than it was at idle. This is why our lab exhausts were always stainless.
Carbon steel will just give up and leave....

Thought starter . . .
Thousands of times a minute?
Yes - When you are running 2400RPM at road load, the crankshaft is doing 40 revolutions per SECOND!
Spark plugs are firing 160 times a second.

I have had the luxury of having high speed data acquisition running during a few engine failures.
No, you can't back off the throttle in the 100ms it takes for an engine to grenade.

Matt

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit

[Johnny Bridges via Gmclist]

We used to call that 'Lunching the mill'. Buds left a couple scattered along the Montgomery dragstrip Back When.

--johnny
--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon

[A.]

Matt Colie wrote on Tue, 26 April 2016 08:47
> ...Yes, in most SI (Spark Ignition) engines operating above idle power the combustion process is still going when the exhaust valve opens. ...
So we get back to what Mr. Hupy said: Oxygen burns the valve. I am going to be satisfied that the later the spark occurs, the more unburned A/F is
trying to get past the exhaust valve, and it is the oxygen in that mix, not the heat or flame, that will burn the valve when spark is not adequately
advanced.

If I got that wrong, any combustion guru should chime in, because the premise is that either too much OR too little advance will burn a valve.

--
'73 23' Sequoia For Sale
'73 23' CanyonLands Parts Unit For Sale
Upper Alabama
Why don't they sell spray paint that washes off with soap and water for graffiti vandals to use?

[Matt Colie]

A Hamilto wrote on Tue, 26 April 2016 12:26

> Matt Colie wrote on Tue, 26 April 2016 08:47
> > ...Yes, in most SI (Spark Ignition) engines operating above idle power the combustion process is still going when the exhaust valve opens. ...
> So we get back to what Mr. Hupy said: Oxygen burns the valve. I am going to be satisfied that the later the spark occurs, the more unburned A/F is
> trying to get past the exhaust valve, and it is the oxygen in that mix, not the heat or flame, that will burn the valve when spark is not adequately
> advanced.
>
> If I got that wrong, any combustion guru should chime in, because the premise is that either too much OR too little advance will burn a valve.

A,

Jim Hupy didn't get it wrong, but he didn't quite get it right either. (No offense intended Jim.)

The error in your premise is that it should and would burn the entire valve face. That is not what usually happens. The typical failed exhaust valve
tends to look like somebody found a beaver with tungsten-carbide teeth to take a bight out of it. However, do not completely discount this as it can
be a contributor to a valve head cracking situation.

Remember I said that the exhaust valves count on the seat face for cooling? Well if there is any problem getting that cooling, lots of bad things can
happen. One of the first is a crack in the valve face. As nearly as we could determine, this is a result of the thermal cycling of the valve
material. The valve alloy can have a great effect on this, but heat resisting alloys are never a first choice ($).
When that crack happens, it causes two things:
The combustion gasses that are near plasma temperature squirt though the smallest of gaps.
And, the valve is now not able to cool the face in that area.

Most people are not aware that the peak cylinder pressure of an SI engine (within a few degrees hopefully after top center) can easily be in the
500PSI region. That does not last long, but it doesn't have to be long to rip out a few iron atoms. It is really hard to not have any O2 in an
exhaust stream.

If there is loose O2 there, it will be like a rich flame cutting torch, but it doesn't need the O2s help at all. With the metal hot, it looses some
of its mechanical strength and now it is even more easily ripped apart by the passing by passing plasma stream. I have seen "burned" parts in a steam
plant, and there is NO O2 in a process steam system. (Right Wally?)
While I have assembled the above scenario based on a crack in the exhaust valve head, the same can be accomplished by anything that fouls the
face/seat area. Anything that makes it leak can do it. A valve that fails to rotate in operation is a good start. The list is pretty long.

As to early or late timing, that is simple.
Early timing will hammer parts into submission. Even when running an engine in a continues knock mode valve failures are rare. Either with ignition
timing or preignition (Same - Same). The abuse will take out top lands and/or rings and cylinder head gaskets give time. But it can only take out a
valve by causing it or the seat to crack and usually the other damage done will cause a shutdown first.
Late timing can be bad, because the operator will increase the manifold pressure to makeup for the lost power. This will make the end of cycle
pressure and temperature both higher and that is something that those poor exhaust valves just don't need. If everything is as it should be, things
should be good. (Notice I said SHOULD) It doesn't take much for it to not be good.

I may be the only person you will ever know that made a valve burn on purpose. The really funny part of the entire program is that early on I was
working with experience from being a steam engineer. A Detroit OE was having a warranty issue and they didn't understand the problem. They were
throwing heads on to keep customers happy, but shareholders were not happy. In a typical valve gear train, the valves rotate largely as a result of
the spring winding up and unwinding. But in this case, cylinder head line had been reworked and some critical measurements changed so some of the
rocker arms were fighting the spring rotation.

Matt - the refugee from dynoland

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit

[James Hupy]

Matt, I intentionally did not get into strength of materials, and crude
beyond belief castings, and no hardened valve seats, and on and on. Every
time I try to give exact specific detail on very technical subjects, my
posts are so long, that I exceed bandwidth limits. Not to mention the level
of comprehension of some of our readers. I try to get my point across
without getting cut off at the pockets. As a result, accuracy in my posts
lacks a bit of the finer points. Most readers, but not all, still get their
questions answered. I know full well the chain of events, as well as the
causes of, valve failures in Olds 455 engines. Seen far too many of them in
my 75 plus years, and I owned my first Olds V8 in 1959. I won't even go
into heat exchange cycles and air fuel ratios. Just what the limits are,
varies nanosecond by nanosecond, and we both know that. No argument from me.
Jim Hupy
Salem, OR
78 GMC Royale 403

[KB]

Matt Colie wrote on Tue, 26 April 2016 18:19

> In a typical valve gear train, the valves rotate largely as a result of the spring winding up and unwinding.

So will the valves rotate even if they don't have rotator type retainers?
We used a set of C heads on our latest build, which have shallower spring seats,
and weren't able to use rotators (which are thicker than regular retainers).
I was also told that a lot of modern engines don't use them anymore so wondered why not.

thanks,
Karen
1975 26'

[Carl Stouffer]

A Hamilto wrote on Sun, 24 April 2016 16:09

> Carl S. wrote on Sun, 24 April 2016 17:32
> > His mistake.
> No argument there. And the mistake was trying to control the spark advance manually expecting better results than OEM. A human can't do it. You
> are most likely human.

Ha! Last time I checked I was. That's not the way I use the timing control though. I make small adjustments as conditions change and try to think
ahead.

--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.

[Matt Colie]

KB wrote on Wed, 27 April 2016 17:40

> Matt Colie wrote on Tue, 26 April 2016 18:19
> > In a typical valve gear train, the valves rotate largely as a result of the spring winding up and unwinding.
>
>
> So will the valves rotate even if they don't have rotator type retainers?
> We used a set of C heads on our latest build, which have shallower spring seats,
> and weren't able to use rotators (which are thicker than regular retainers).
> I was also told that a lot of modern engines don't use them anymore so wondered why not.
>
> thanks,
> Karen
> 1975 26'

Karen,

I regret to tell you that I don't know if your engine really needs rotators.
Many engines survive without actual rotators. The modern engines don't need them because the action is now well understood and the machining and
processing is much better than it used to be. I can even advise you where to go for an answer. My best bet would be to ask someone at Mondelo.

Sorry -

Matt

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit

[Johnny Bridges via Gmclist]

I realize these discussions often get a bit off track and wordy, but I find them worth reading. I've learnt a bunch from this discussion.

--johnny

--
'76 23' transmode Norris upfit
Braselton, Ga.

"Sometimes I wonder what tomorrow's gonna bring when I think about my dirty life and times" --Warren Zevon