[GMCnet] Final Drives and MPG

[Richard MacDonald]

Our FD is starting to make a little noise and assume it will just get louder, so am thinking about a replacement.

Is there a factual Analysis showing the best Engine/FD combination as it relates to MPG? If not, what parameters should be used to make a decision?

We have a 455/307 with Howell EBL/ESC and still do not get 9 MPG,
although it is much improved from the 6.5 to 7 that the Carb. gave us.
We seldom exceed 60 MPH or 2100 RPM. We do not Tow. Very little Hill climbing in Fl, Ga, and Al.

Thank you,
Richard





--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL


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[James Hupy]

A little noise can sometimes go a long way before it gets to making
grinding and clunking sounds. It will take a very long time to cover the
cost of a lower geared final drive with a fuel savings of one mile per
gallon. That being said, for your use, I would think that the 3.55:1 ratio
would be nearly ideal with the 455 engine.
Jim Hupy
Salem, Or
78 Gmc Royale 403

[Ray Erspamer]

Not sure if there is any scientific data out there. Here is our
experience......

We have the 403 engine and when we purchased the coach it had a 3:46 final
drive. Performance was good and mileage was about 8.9 mpg.

After I wrecked the final drive I replaced it with a 3:70, mileage improved,
performance is outstanding. As of last trip and fill the average was 9.3 mpg.
I typically run about 70 MPH on the highways.

Along with the 3:70 final drive we have the Patterson Ignition System and I've
had the Quadrajet carb rebuilt by Patterson.

Ray


Ray & Lisa
78 Royale "Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMC-...@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/




________________________________
From: Richard MacDonald <rm1...@gmail.com>
To: gmc...@temp.gmcnet.org
Sent: Tue, April 16, 2013 12:37:29 PM
Subject: [GMCnet] Final Drives and MPG

[Ray Erspamer]

I would agree with Jim. From all I've heard, with the 403 the 3:70 is the way
to go and with the 455 the 3:55 is great.

I wouldn't let a little noise bother me, you'll know without a doubt if it's
failing.

Ray


Ray & Lisa
78 Royale "Great Lakes Eagle"
Center Kitchen TZE368V101144
Wauwatosa, Wisconsin 53226
Email: 78GMC-...@att.net
414-745-3188
Web Site: http://ray-lisa.page.tl/




________________________________

From: James Hupy <james...@gmail.com>
To: gmc...@temp.gmcnet.org
Sent: Tue, April 16, 2013 12:52:09 PM
Subject: Re: [GMCnet] Final Drives and MPG

[Richard MacDonald]

Thanks Jim, Ray, I appreciate your replies.

[Gary Berry]

Hey Richard;

I had a FD start making noise on me as I was north of Madras,OR (at
least that is when I first noticed it). I went to Bend, OR, got on the net,
and most everyone said to drive it to Applied GMC to get it fixed and that
it would make it there. I decided that since I had an extra 3:07 FD at home
(5 hours away) and that I was still 10 hours away from Applied GMC and that
this thing was howling like crazy that I would call my brother and see if
he would pick up the FD for me and drive it to Prineville, OR where I had a
friend that would let me use his driveway to do the R&R. I drove to
Prineville, and by the time my brother showed up we had the old FD pulled.
The pinion bearing was shot. Threw the other FD in and away I went. From
the time I noticed the whine until it started to howl was about 100 miles.
I later swapped the 3:07 for a 3:70. MPG didn't change, but it has been a
lot more fun going up hills.
--
Gary and Diana Berry
73 CL Stretch in Wa.

On Tue, Apr 16, 2013 at 10:37 AM, Richard MacDonald <rm1...@gmail.com>wrote:

>
> Our FD is starting to make a little noise and assume it will just get
> louder, so am thinking about a replacement.

> Thank you,
> Richard

[George Beckman]

Oldngray wrote on Tue, 16 April 2013 10:37

> Is there a factual Analysis showing the best Engine/FD combination as it relates to MPG? If not, what parameters should be used to make a decision?
>
> We have a 455/307 with Howell EBL/ESC and still do not get 9 MPG,
> although it is much improved from the 6.5 to 7 that the Carb. gave us.
> We seldom exceed 60 MPH or 2100 RPM. We do not Tow. Very little Hill climbing in Fl, Ga, and Al.
>
> Thank you,
> Richard

As others have said, this is all conjecture, although after 40K miles in a GMC, some things become fairly evident.

One thing that might be happening here is the 2100 RPM. The Original stock torque converter had a stall of 2200 RPMs. (Lock the brakes and step on the gas and the RPMs go to 2200 with the coach not moving.) While torque converters without lockup clutches don't ever quit slipping, the stock unit is built to slip at 2100. You might try several tanks at 64 mph or so to see if this helps any. (I chose 64 because our coach really likes 64... everything seems to settle in.)

If you ever have to do a transmission, Manny's Switch Pitch will lower that stall to about 1600, unless in Switch which places it at about 2600. THe tighter torque converter is very responsive, even without lower gears. (Wouldn't want to try to maneuver into a steep camping site with it and a 3.07.) The last big trip I got 10.7 mpg, not towing. That was pump vs. actual miles traveled for 5400 miles. We were from CA to Washington to Montana to Canada to the Dakotas to Iowa and then home, so lots of variety. (Towing I seem to be more around 9.6, but I do it so seldom I only have 1200 miles experience since the switch pitch was installed.)

Also, with your EBL, do you have Vehicle Speed Sensor? The VSS allows the EBL to go into Highway Mode with is usually called Lean Cruise. The EBL will cut back on the air/fuel from 14.7:1 to 16.4:1 and at the same time advance the spark 4+ degrees. (These are according to settings but these are good averages.)

Each time our coach goes into Lean Cruise, the instant MPG goes up 1 MPG. VSS may be one of the cheaper items to help realize your mpg possibilities.

I believe with some more EBL tuning you will break the 10 mpg limit most of the time, regardless of the final drive.
--
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George

[Richard MacDonald]

Hi George, Do not understand what Stall, Slip, Tight etc means
when you speak of the Converter.
I have given some thought to VSS, just not sure what all is entailed to add it.

Richard
--
Richard MacDonald
Punta Gorda, Florida
76 Edgemonte TZE 266V102313
Howell TBI EBL

[James Hupy]

Richard, the torque converter is a two part fluid coupling between the
engine and the transmission. Think of it like a clutch that is driven by
the engine, has fluid inside it, and when you spin the engine fast enough,
turns the input shaft to the transmission by the force of the fluid acting
upon the finned wheel attached to the input shaft. At a certain rpm, both
the engine and input shafts are turning nearly the same speed. That is
called converter lockup. Around 2400 rpm in the Gmc. If you run below the
lockup rpm, there is some disparity in the speed of the two shafts. This is
called slip. If it is great enough, fluid will heat excessively which is a
bad thing. Fuel economy is poorer when you have slippage as well. In
theory, if you run the engine at or above the lockup point, you should be
able to achieve better fuel economy. OPINIONS VARY WIDELY ON THIS POINT.
That is a thumbnail sketch of torque converters. Much more to it than what
I have talked about here.
Jim Hupy
Salem, Or
78 Gmc Royale 403 w/Manny Tranny and 3:70 - 1 final drive.p

[Bob de Kruyff]

Oldngray wrote on Tue, 16 April 2013 11:37

> Our FD is starting to make a little noise and assume it will just get louder, so am thinking about a replacement.
>
> Is there a factual Analysis showing the best Engine/FD combination as it relates to MPG? If not, what parameters should be used to make a decision?
>
> We have a 455/307 with Howell EBL/ESC and still do not get 9 MPG,
> although it is much improved from the 6.5 to 7 that the Carb. gave us.
> We seldom exceed 60 MPH or 2100 RPM. We do not Tow. Very little Hill climbing in Fl, Ga, and Al.
>
> Thank you,
> Richard
>

> Energy is energy so depending on where you drive, you want the engine to be in its prime area of efficiency.Higher speeds mean more friction and pumping losses, but I'm convinced that a tall final drive (3.07) and liberal use of 2cnd and 1 st works best for me in the mountains mixed with long flat runs at around 70 mph. It's not necessary nor benefical to be able to climb grades without downshifting. I suppose it's great for bragging rights but in the end it may be the wrong approach. We have great ratio coverage and it is greatest with a tall final drive. If you go to higher final drives, you are reducing your ratio coverage which I feel is the wrong thing to do. The higher (numerically) that you gear your coach, the less ratio spread and subsequently flexibility you have.


--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Bob de Kruyff]

James Hupy wrote on Tue, 16 April 2013 18:34

James, I have to disagree with you on this. Our stall(WOT engine and 0 output RPM) rpm is indeed around 2200 to 2400 rpm but the hydraulic lock-up point is much closer to 4000 rpm. Even at that rpm, we still have around 500 rpm slippage.

--
Bob de Kruyff
78 Eleganza
Chandler, AZ

[Jim Kanomata]

Jim Bounds drove the newly painted coach of Jim Decheine with 455 from
Orlando to Arizona and commented how well the 3.70 performed.
Up to this time, Jim B felt that 3.55 was the ideal ratio, but now he felt
that even small hills were not noticeable.
When we have over 3,000 units with 2,000 with3.70, we get feed back
constantly of power gain and no decrease in mileage.
We have over 50 with the 4.10 ratio that are pulling over 11mpg at 55-60
mph speed

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

[Ronald Pottol]

I cannot argue with your data, but I'd love to understand why it is at such
variance with theory. I mean, in general, lower rpms should be more
efficient, but that isn't how it seems to be working out.

Any idea why?

Ron

[Johnny Bridges]

OK, a practical approach - I got to run up to STL in a couple of weeks, with the toadstone clipped on the coach.   Going up Monteagle on I 24, the overflow bottle is boiling steam at the top.  Am I better off to hang it in S at the bottom, and run it up at 2800 or so and whatever speed I get, as opposed to letting it downshift itself about halfway up?  It's a 23' with the original 3:07 as far as I can tell - 62 per gets about 2250 or so on the tach, just under 2500 usually gives around 67 on the flat.

I don't like to see it get that hot, I'm toying with simply running West to Birmingspam and going that way, which skips the mountains entirely and gets a nice run up The Great River Road. 
Thoughts?
 
--johnny
'76 23' transmode norris
'76 palm beach

________________________________
From: Mark Grueninger <mark...@hotmail.com>
To: gmc...@temp.gmcnet.org
Sent: Wednesday, April 17, 2013 8:20 AM

Subject: Re: [GMCnet] Final Drives and MPG

 The best way to do that is to match the transmission and final drive with the speed you are traveling.  If you drive 60 you will need a lower final drive to keep the RPM up.  If you drive 75 you will need a bit higher final drive to keep the RPM in the best efficiency range.  On the 455 I seem to remember that range is fairly wide so a 3 speed transmission is ok for it.  The trick is though to keep the torque converter turning fast enough to minimize slippage.  That can be done by dropping a gear when you drive slower such as going up a hill but constant shifting down from 3rd to 2nd is hard on the transmission because of the way it changes gears...  I know I have oversimplified this but bottom line keep the RPM in the "sweet spot" and mileage will improve.  Final drive is the way to do that best with stock engine and transmission.  Just my opinion though,

Mark

[quote title=Ronald Pottol wrote on Tue, 16 April 2013 23:50]I cannot argue with your data, but I'd love to understand why it is at such

variance with theory. I mean, in general, lower rpms should be more
efficient, but that isn't how it seems to be working out.

Any idea why?

Ron

[Mark Grueninger]

An engine (Really just a self powered air pump) will have an rpm at which it operates most efficiently. This RPM is dictated by valve sizes, intake and exauust port size and length piston dome shape, bore and stroke and several other factors. This RPM is usually not variable without physical engine work. Yes variable valve timing will change it but we don't need to worry about that with our engines. That RPM is normally the RPM at which the engine achives peak torque. I am not certain what it is on a 455 but I think it is around 2800 RPM on a stock engine. At that point the airflow is moving through the engine with the least losses and the parasitic losses are the lowest as a whole. It is also the RPM where the ignition and flame propagation in the cylinders is the best for that engine. In other words the fuel all gets burned before the exauust valve opens and the spent gasses are expelled just before the intake valve opens. If you can operate it at that RPM const
antly you will get peak efficiency. The best way to do that is to match the transmission and final drive with the speed you are traveling. If you drive 60 you will need a lower final drive to keep the RPM up. If you drive 75 you will need a bit higher final drive to keep the RPM in the best efficiency range. On the 455 I seem to remember that range is fairly wide so a 3 speed transmission is ok for it. The trick is though to keep the torque converter turning fast enough to minimize slippage. That can be done by dropping a gear when you drive slower such as going up a hill but constant shifting down from 3rd to 2nd is hard on the transmission because of the way it changes gears... I know I have oversimplified this but bottom line keep the RPM in the "sweet spot" and mileage will improve. Final drive is the way to do that best with stock engine and transmission. Just my opinion though,

Mark

[quote title=Ronald Pottol wrote on Tue, 16 April 2013 23:50]I cannot argue with your data, but I'd love to understand why it is at such

variance with theory. I mean, in general, lower rpms should be more
efficient, but that isn't how it seems to be working out.

Any idea why?

Ron

On Apr 16, 2013 8:53 PM, "Jim Kanomata" <mailto:jimka...@gmail.com> wrote:


--
Mark Grueninger 76 Palm Beach
Valmeyer IL

[Matt Colie]

mgrue wrote on Wed, 17 April 2013 08:20
> An engine (Really just a self powered air pump) will have an rpm at which it operates most efficiently. This RPM is dictated by valve sizes, intake and exauust port size and length piston dome shape, bore and stroke and several other factors. This RPM is usually not variable without physical engine work. Yes variable valve timing will change it but we don't need to worry about that with our engines. That RPM is normally the RPM at which the engine achives peak torque. I am not certain what it is on a 455 but I think it is around 2800 RPM on a stock engine. At that point the airflow is moving through the engine with the least losses and the parasitic losses are the lowest as a whole. It is also the RPM where the ignition and flame propagation in the cylinders is the best for that engine. In other words the fuel all gets burned before the exauust valve opens and the spent gasses are expelled just before the intake valve opens. If you can operate it at that RPM constantly you will get peak efficiency. The best way to do that is to match the transmission and final drive with the speed you are traveling. If you drive 60 you will need a lower final drive to keep the RPM up. If you drive 75 you will need a bit higher final drive to keep the RPM in the best efficiency range. On the 455 I seem to remember that range is fairly wide so a 3 speed transmission is ok for it. The trick is though to keep the torque converter turning fast enough to minimize slippage. That can be done by dropping a gear when you drive slower such as going up a hill but constant shifting down from 3rd to 2nd is hard on the transmission because of the way it changes gears... I know I have oversimplified this but bottom line keep the RPM in the "sweet spot" and mileage will improve. Final drive is the way to do that best with stock engine and transmission. Just my opinion though,
>
> Mark

Mark,

Thank you for saving me the writing time. The only thing I might change is the remark about downshifting. It should also be noted that every transmission person I know (more than a few) recommends manually shift to lower gears as opposed to letting the electric kick-down do this.

If you had been at Jimk's talk at Dothan, you would have heard me say that it was my (professional) opinion that the 3.07 was the wrong rear-end for our coaches.

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit

[Michael]

I am not a transmission guy, but in losing my transmission I now know the reason for manually downshifting vs. letting it downshift on it's own.

The pressures applied on the internal clutches changes when you manually downshift, if left in "D", the clutches will start slipping, which is part of what is causing you to lose speed. At the point where it automatically downshifts, you have already began to wear out your Drive and Reverse Clutches, they share the same pack. By manually downshifting, you eliminate the clutch slippage and apply a greater force to the lower clutch pack to prevent them from slipping.

I wish I had known the reason why you should downshift going up a grade instead of letting it downshift on it's own before driving cross country and back.
--
1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive :)

[Rob Mueller]

Matt,

The 3.07 was for a 4000lb car and that sure ain't the right ration for even the lightest GMC at say 8000 lbs!

"Rumor" has it that GMC had a 3.42 to 1 Final Drive "on the drawing board" when production ceased.

Regards,
Rob M.

-----Original Message-----
From: Matt Colie

Mark,

Thank you for saving me the writing time. The only thing I might change is the remark about downshifting. It should also be noted
that every transmission person I know (more than a few) recommends manually shift to lower gears as opposed to letting the electric
kick-down do this.

If you had been at Jimk's talk at Dothan, you would have heard me say that it was my (professional) opinion that the 3.07 was the
wrong rear-end for our coaches.

Matt

[James Hupy]

Bob, I had not noticed that you had been offnet until recently. Are you
still gainfully employed by U-haul or some such? When I noticed that you
were in disagreement with my ALL TOO SIMPLE explanation of torque
converters, it seemed like you had never been away.(grin) Every time I try
to offer a far too simple answer to complex problems you or Ken H or others
are quick to remind me of the HUGE BRAIN TRUST that exits in the GMC
community. I do know far more about torque converters than my simple answer
would indicate. I was trying to keep it simple. Should have known better
by now. Wait until next time!! (grin)

Jim Hupy
Salem, Or
78 Gmc Royale 403

[Kerry Pinkerton]

James Hupy wrote on Wed, 17 April 2013 10:56
> ... I was trying to keep it simple. ....


Please keep keeping it simple Jim. If you're concerned about it, just say something like..."While it is actually more complex than the following, a simplified description is..."

That will keep you out of trouble with the sticklers for detail (God bless them!) while allowing us mere mortals to begin to comprehend some things without having a degree and a lifetime of experience in automotive/electrical/nuclear/etc engineering. :lol:
--
Kerry Pinkerton

North Alabama, near Huntsville,

77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as an Art Deco car hauler

[Rob Mueller]

Kerry,

Please don't be insulted by what I'm about to write but you can Google anything and find a lot of different levels of explanation on
just about anything.

I acknowledge there's a lot of chaff out there but a reasonably intelligent person can separate it from the wheat.

Or as Mr. ERF says; "Google is your friend."

Rob M.

-----Original Message-----
From: Kerry Pinkerton

Please keep keeping it simple Jim. If you're concerned about it, just say something like..."While it is actually more complex than
the following, a simplified description is..."

That will keep you out of trouble with the sticklers for detail (God bless them!) while allowing us mere mortals to begin to
comprehend some things without having a degree and a lifetime of experience in automotive/electrical/nuclear/etc engineering. :lol:

--
Kerry

[Mark Grueninger]

Please don't let my lack of writing skills mess up the message. I certainly advocate downshifting when pulling a hill or anytime you need the extra torque. When you do downshift with the 425 or any GM 3 speed it should be done manually and you should let off the gas a bit as you do it. Not all the way but most of the way. My reasoning is this: In 3rd gear the clutches lock the planetary gears to the output so it all turns as one. As such the band releases the ring gear at the same time. When you downshift from 3rd to 2nd gear the ring is spinning at output shaft speed and the band has to stop the spinning and then hold what ever torque is applied from the engine either positive if you are pulling hard or negative if the coach is pushing the engine as running down a hill. The band is not designed tough enough to handle that much torque and it will slip a bit. When this is done over and over it will destroy it and you will not have 1st and 2nd gear. So my suggestion
is to shift manually down when pulling a lot of torque so you can minimize the torque from the engine until the band has the chance to stop the band and lock it up with full pressure before you apply torque to it. Just let your foot up off the gas most of the way before you pull the lever down. When going down hill against the engine apply just a bit of throttle when pulling it into 2nd. Again just my opinion but it cant hurt....

Mark

Matt Colie wrote on Wed, 17 April 2013 09:19

> mgrue wrote on Wed, 17 April 2013 08:20
> > An engine (Really just a self powered air pump) will have an rpm at which it operates most efficiently. This RPM is dictated by valve sizes, intake and exauust port size and length piston dome shape, bore and stroke and several other factors. This RPM is usually not variable without physical engine work. Yes variable valve timing will change it but we don't need to worry about that with our engines. That RPM is normally the RPM at which the engine achives peak torque. I am not certain what it is on a 455 but I think it is around 2800 RPM on a stock engine. At that point the airflow is moving through the engine with the least losses and the parasitic losses are the lowest as a whole. It is also the RPM where the ignition and flame propagation in the cylinders is the best for that engine. In other words the fuel all gets burned before the exauust valve opens and the spent gasses are expelled just before the intake valve opens. If you can operate it at that RPM c
onstantly you will get peak efficiency. The best way to do that is to match the transmission and final drive with the speed you are traveling. If you drive 60 you will need a lower final drive to keep the RPM up. If you drive 75 you will need a bit higher final drive to keep the RPM in the best efficiency range. On the 455 I seem to remember that range is fairly wide so a 3 speed transmission is ok for it. The trick is though to keep the torque converter turning fast enough to minimize slippage. That can be done by dropping a gear when you drive slower such as going up a hill but constant shifting down from 3rd to 2nd is hard on the transmission because of the way it changes gears... I know I have oversimplified this but bottom line keep the RPM in the "sweet spot" and mileage will improve. Final drive is the way to do that best with stock engine and transmission. Just my opinion though,
> >
> > Mark
>
> Mark,
>
> Thank you for saving me the writing time. The only thing I might change is the remark about downshifting. It should also be noted that every transmission person I know (more than a few) recommends manually shift to lower gears as opposed to letting the electric kick-down do this.
>
> If you had been at Jimk's talk at Dothan, you would have heard me say that it was my (professional) opinion that the 3.07 was the wrong rear-end for our coaches.
>
> Matt


--

Mark Grueninger 76 Palm Beach
Valmeyer IL

[Dave King]

Kerry, don't feel bad about not being an engine or transmission designer/engineer, you can probably spin circles around most people on the forum about metal working and the tricks to do seemingly impossible metal working tasks.
--
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada

[George Beckman]

Johnny Bridges wrote on Wed, 17 April 2013 05:48

> OK, a practical approach - I got to run up to STL in a couple of weeks, with the toadstone clipped on the coach.   Going up Monteagle on I 24, the overflow bottle is boiling steam at the top.  Am I better off to hang it in S at the bottom, and run it up at 2800 or so and whatever speed I get, as opposed to letting it downshift itself about halfway up?  It's a 23' with the original 3:07 as far as I can tell - 62 per gets about 2250 or so on the tach, just under 2500 usually gives around 67 on the flat.
>
> I don't like to see it get that hot, I'm toying with simply running West to Birmingspam and going that way, which skips the mountains entirely and gets a nice run up The Great River Road. 
> Thoughts?
>  
> --johnny
> '76 23' transmode norris
> '76 palm beach

Another reason for shifting down on a hill gets us back to the torque converter slippage. Manual transmissions usually do not have trans cooler lines that go into the radiator. Automatics do and for one reason... the torque converter slips and that causes super heat. ( if you slipped a manual clutch that much you would burn it up )

So, if on a hill you can keep your RPMs up, there will be less slippage and less heat being dumped into the radiator. Every little bit helps.

--
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George

[A.]

Johnny Bridges wrote on Wed, 17 April 2013 07:48

> OK, a practical approach - I got to run up to STL in a couple of weeks, with the toadstone clipped on the coach.   Going up Monteagle on I 24, the overflow bottle is boiling steam at the top.  Am I better off to hang it in S at the bottom, and run it up at 2800 or so and whatever speed I get, as opposed to letting it downshift itself about halfway up?  It's a 23' with the original 3:07 as far as I can tell - 62 per gets about 2250 or so on the tach, just under 2500 usually gives around 67 on the flat.
>
> I don't like to see it get that hot, I'm toying with simply running West to Birmingspam and going that way, which skips the mountains entirely and gets a nice run up The Great River Road. 
> Thoughts?
>  
> --johnny
> '76 23' transmode norris
> '76 palm beach

Check this link to see if it helps: http://gmcmotorhome.info/transmission.html#shift
--
'73 23' Sequoia For Camping
'73 23' CanyonLands For Sale
UA (Upper Alabama)
"Time is money. If you use YOUR time, you get to keep YOUR money."

[Johnny Bridges]

The consensus seems to be, "Stuff it in S and motor over the mountain."
 
--johnny
Just up from Kim Basinger's little city
 


________________________________
From: A. <mar...@netzero.com>
To: gmc...@temp.gmcnet.org
Sent: Thursday, April 18, 2013 12:02 PM

Subject: Re: [GMCnet] Final Drives and MPG

[Larry Davick]

Modern cars have 6+ speed transmissions. GM and Ford are doing a joint venture on a 10 speed transmission.
<http://www.gizmag.com/ford-gm-9-10-speed-transmissions/27103>
I wonder what the point is? Are modern engines tuned to a very narrow torque band?
It seems to me that all those gears can offer a small difference in RPM's. Then again, as it's been stated in another post, low RPM's and wide-open-throttle put a big strain on the engine's components. Perhaps a higher revving engine would last longer and provide better MPG.
--
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca

[Craig Lechowicz]

Well, there are lots of smarter powertrain guys out there than me, but I did work in Corporate Average Fuel Economy (CAFE) for 2 years. When automakers are required by political fiat to "double" average fuel economy to 54.5 mpg every little bit helps. There is a diminishing return to adding automatic transmission speeds, maybe at best case, 2 mpg highway going from 4 speed to 5 speeds, on an "average" car, down to probably a few tenths of a mile per gallon by the time you are out around 8 speeds. But with a $5 fine per tenth of a mile per gallon miss in CAFE times 3 million vehicles a year for a large manufacturer's production, it adds up to a pretty good chunk of change. And, every manufacturer is forced to do it, so there isn't a competitive disadvantage. It just increases the country's use of fuel and adds to "greenhouse" gases, since cars cost more, fewer are replaced (average age is now out past 11 years) and 13 mpg vehicles stay in use longer.

Why do the added speeds help? Part of it has to do with the specific EPA drive cycles used to derive fuel economy ratings, that don't use very high speeds, very high loads, or very fast acceleration. Although loading the engine heavily at slow speeds may not be good from a durability standpoint on an old design engine like our motorhome, most of those concerns are mitigated by design on new vehicles through things like variable displacement oil pumps, required synthetic oils, and basic design. Meanwhile, on newish engines, low engine speeds are a good fuel economy enabler on those EPA tests. The strategy is to get the engine speed as low as possible as quickly as possible to minimize frictional losses, and to get the throttle open as wide as possible to lower "pumping losses" caused by throttle restriction (vacuum).

There was a good comment on one of the engine replacement threads that talked about the engines being at highest "efficiency" at or near the torque peak. That is true, but it is only true when every engine rpm is being evaluated at wide open throttle, and therefore low throttle restriction. At low amounts of engine output and therefore low throttle openings, lower rpm's are better from an overall efficiency standpoint.
--
Craig Lechowicz
'77 Kingsley, Waterford, MI

[Mark]

Craig Lechowicz wrote on Thu, 18 April 2013 18:47

> When automakers are required by political fiat to "double" average fuel economy to 54.5 mpg every little bit helps.

I suspect this is all just political gamesmanship, and will never happen (or at least, not for a long, long time). It's essentially just a matter of poisoning the well for the subsequent administration(s).

The same thing was done in the not too distant past. One president set physically impossible emissions standards for power plants the last month or two of his administration, after not having done anything on the subject for eight years. The next administration had to relax the unobtainable goals, but actually implemented changes that significantly reduced the actual emissions. But president one goes down as a green champion, and president two as a villain. It's just how the game is played in DC (sadly, it's played with our money).

Since there's no realistic way that the corporate average is going to reach 54.5mpg without Congress repealing the laws of physics, it's just a matter of who blinks first. Or of writing in a big pile of exclusions, exceptions, and amendments that allow them to buy "MPG credits" from other politicians who start up businesses selling them...
--
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen

[Keith V]

Quote:

> Since there's no realistic way that the corporate average is going to reach 54.5mpg without Congress repealing the laws of physics, it's just a matter of who blinks first.

Oh there is a way...I mean I had a 1982 Plymouth Horizon Miser with the VW 1.7 engine. That old piece of junk got 45 mpg on the freeway, in 198 using a carburetor !

Take that same car, make it more aerodynamic, add a small modern engine and THEN tell me you cant reach 54mpg...

But, it had no power windows, no AC, no airbags and it wasn't a 5000lb SUV.

and emissions are good enough now, lets focus on fuel usage.

--
Keith
69 Vette
29 Dodge
75 Royale GMC

[Rob Mueller]

G'day,

Speaking of power plants . . . . . .

Downunder the current Prime Minister Julia Gillard noted (before she took office) that under her administration "there would be NO
carbon tax." Then along came the global financial crisis and "they" needed money so a carbon tax was instituted @ $23 per ton of CO2
dumped into the atmosphere. The Greens were jubilant, the UN Chief lauded Julia's taking the right ecological stand and leading the
world.

Unfortunately 90% of Australia's power is generated by burning fossil fuels. Therefore everybody's power bills went up big time. The
government came to the rescue and people on low income receive stipends from the government. All the rest of us get screwed!

By the way Australia produces 1.5% of the world's carbon dioxide! BIG DEAL when it is reduced to 1% - NOT!

The good news is I can still buy petrol WITHOUT ethanol at most stations!

Regards,
Rob M.
USAussie - Downunder

PS - Three guesses at who the number 1 and number 2 CO2 dumpers are and the first two don't count!

-----Original Message-----
From: Mark

I suspect this is all just political gamesmanship, and will never happen (or at least, not for a long, long time). It's essentially
just a matter of poisoning the well for the subsequent administration(s).

The same thing was done in the not too distant past. One president set physically impossible emissions standards for power plants
the last month or two of his administration, after not having done anything on the subject for eight years. The next administration
had to relax the unobtainable goals, but actually implemented changes that significantly reduced the actual emissions. But
president one goes down as a green champion, and president two as a villain. It's just how the game is played in DC (sadly, it's
played with our money).

Since there's no realistic way that the corporate average is going to reach 54.5mpg without Congress repealing the laws of physics,
it's just a matter of who blinks first. Or of writing in a big pile of exclusions, exceptions, and amendments that allow them to
buy "MPG credits" from other politicians who start up businesses selling them...
--
Mark

[Mark]

Keith V wrote on Fri, 19 April 2013 07:55

> Take that same car, make it more aerodynamic, add a small modern engine and THEN tell me you cant reach 54mpg...
>
> But, it had no power windows, no AC, no airbags and it wasn't a 5000lb SUV.
>
> and emissions are good enough now, lets focus on fuel usage.

I don't disagree that it's possible to make a car that gets 54mpg, just that there's no realistic way that the corporate average of the entire fleet of vehicles sold in a single year is going to get there without some draconian changes. Sure, if we all agree to drive the 2015 equivalent of the Geo Metro, we're there. But look at the average size, weight and equipment of what Joe Q. Public is driving today and it's an unobtainable goal.

Alternatively, if we make an unexpected quantum leap in battery technology, we can get there too (since we get to average all those electric vehicles in).

But right now it would be like setting an average goal of 17mpg for the entire fleet of existing GMC motorhomes. Yes, it would be "possible" to get that with a single motorhome (if money is no object) but since most of us will continue to get 8-10mpg the 17mpg average would remain a pipe dream since it would mean that a lot of us would need to average 25-30mpg to bring the "corporate average" up to 17mpg.

--
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen

[Thomas Phipps]

My guess for number one and number two. China and India. And, they will not change their ways to make Western Greenies happy.
What's the next standard? 100 mpg?
Tom, MS II
--
1975 GMC Avion, under forever re-construction
Vicksburg, MS. 3.7 miles from I-20

[Rob Mueller]

Tom,

You got number 1 and 4. Number 2 is a lot closer to home. ;-)

http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions

Regards,
Rob M.

-----Original Message-----
From: Thomas Phipps

My guess for number one and number two. China and India. And, they will not change their ways to make Western Greenies happy.
What's the next standard? 100 mpg?
Tom, MS II

[Matt Colie]

Robert Mueller wrote on Fri, 19 April 2013 12:59
> Tom,
>
> You got number 1 and 4. Number 2 is a lot closer to home. ;)

>
> http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions
>
> Regards,
> Rob M.

Rob,

There are some problems with those numbers. First is that the UN numbers are not supported by any known data and are wrong big time. Next is that another view is "greenhouse" (since proven fallacious) gasses emitted as a function of GDP. The US is not even near the top on this one. What is interesting unless you are part of it is that the US has remarkably decreased CO2 emissions since 2009. Just not quite as much as the GDP has declined. So, there is an easy solution that BH0 and the UN both seem to be working on. Fewer American's with jobs means less "Green House" emissions. Too bad that anthropogenic climate change has been absolutely ruled out by the available data. But that never bothers people with an agenda like redistributing the world's wealth (misery). (Please read the resume and history of IPCC Chair Rajendra Pachauri.)

The above is fact and not any kind of rant.....

Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will find
SE Michigan - Twixt A2 and Detroit