[Gmecm] GMECM Question related to fuel economy

[BNRVL at aol.com]

Hello Rick ..I read your email to Dunvagen..and i have   a 1933  Dodge 
Truck ..very light weight   with a 69 Corvette  350 that has a an  Sig Erson  
unknown  cam number.but will  idle @ 700 rpm and runs OK .,we just installed a 
92 Camaro type TPI  Fuel  Inj. system  and it runs like a haint ...!!!   
WOW  what a  nice drive now...!!!  cant believe the performance compared to 
the Carter 4  bbl. 
 
Do you think the Lean burn chio by Bob will increase the MPG   performance 
..??
 
Thanks 
 
Bob
 
 
In a message dated 3/2/2010 8:59:13 A.M. Central Daylight Time,  
dunvegan at sbcglobal.net writes:

Slight  disagreement in terms, cruise is more of a toruqe thing, not 
horespower thing.  Torque keeps things in motion, horespower is really delta of  
motion.

Matching the build of the engine torque curve to the desired  application 
is key to mileage.

My experiences:
I targeted a '87  Camaro build using a 5.7 at a 2400 to 3000 torque peak, 
and geared  to cruise 70 MPH at the lower end of the curve. Result, at 75 MPH 
it  turned right at 2500 and knocked down over 30MPG through rolling 
interstate  thru central Missouri, so it can be done. My '86 vette does even 
better,  due in part to being lighter weight. Don't believe you must have tiny 
engines  to bang big mileage, torque is your partner, along w/ a smart tune in 
the  ecm.

So, I'd go for a bigger small engine, something that is designed  or 
rebuilt to develop low end torque - you may need to design intakes for  that, 
which is what the TPI maximizes w/ it's long runner design. And, a good  lockup 
converter goes a long way to mileage, but consider a higher stall to  allow 
it to build torque RPM on launch (a relative term) to maximize stoplight  
mileage.
Most of the advantage is gained from getting the most from a load  of fuel, 
and not doing it as frequently (think about diesels) so the more  torque at 
least RPM and then gearing is really where a mileage monger is  happy. Goes 
to the less frictin at lower RPM as well, the less strokes per  minute is 
less friciton actions per minute, friction doesn't increase w/ RPM,  but 
double the RPM and you double the friction events thereby doubling the  required 
effort to overcome friction per minute. 

cheers
-rick  




________________________________
From: Scot Sealander  <ssealander at stny.rr.com>
To: A list for discussing General Motors EFI  <gmecm at diy-efi.org>
Sent: Mon, March 1, 2010 7:27:46 PM
Subject:  Re: [Gmecm] GMECM Question related to fuel economy


That being said,  a constant cruise requires a certain amount of horsepower
just to maintain  that speed, but luckily that number is not large.  So my
conclusion is  that you need to minimize any parasitic losses, such as 
engine
friction,  rolling friction and so on to get the best mileage.  Engine
friction  losses rise rapidly with engine speed, so I think a slow engine
speed is  needed to keep those losses low.  

I have a 90 Vette with TPI and  a six speed, and the gas mileage it gets 
when
driven to try and get mileage  is just amazing.  At 55 mph in 6th gear, the
engine is just turning  over at 1250 RPM.

My thoughts are that you may not need the smallest  engine you can find, but
an engine that makes enough torque at a low engine  speed to allow it to
cruise at a low engine speed.  Oh, and use a  manual transmission so you can
control what gear it is  in.

Scot
_______________________________________________
Gmecm  mailing  list
Gmecm at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/gmecm

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.diy-efi.org/pipermail/gmecm/attachments/20120517/bc4241f7/attachment.html