From: brooks@mcnc.org (Ted Brooks)
Subject: Re: Carburetors, gasoline, and why I don't recycle
Organization: MCNC Center for Microelectronics, RTP, NC
Date: Wed, 2 Sep 1992 18:07:13 GMT

In article <VBREAULT.92Sep2104354@rinhp750.gmr.com> vbreault@rinhp750.gmr.com (Val Breault) writes:
>In article <1992Sep02.010828.24870@rs6000.cmp.ilstu.edu> ejhupper@rs6000.cmp.ilstu.edu (Eric Huppertz) writes:
>
><some provocative flame bait deleted>
>   You see, carburetors have been the subject of much study for decades.
>   And there have been several enterprising groups who have developed
>   carburetors and engine systems which are hyper-efficient by 
>   comparison to today's standards, but only par for the course where
>   scientific development is concerned.  I once read an article which
>   stated, as I recall, that one such fuel-injection system promised
>   to double the effective power of its engine, while extending gas
>   mileage to well over 130 (that's one hundred thirty) miles per
>   gallon.  On a news program years ago, I saw a group of college
>   students who had developed a carburetor that guaranteed at least
>   100 miles per gallon of regular unleaded gasoline.
><more provocative flame bait deleted>
>
>Okay, let's bring it up to date.  General Motors recently developed
>a concept vehicle that had these constraints:  It was to be a street
>legal 4 passenger vehicle, Achieve > 100 mpg,  Have all the normal 
>accessories, Accelerate like a "normal" car (I forgot the 0:60 figure) 
>and meet all current and proposed emissions figures.  It made the
>rounds at the auto shows last year.  It had a large antimated display
>with quite a number of people to answer your questions.
>
>GM did it.  Unlike some "high mileage" cars, this one is a serious 
>street legal car.   A lot of VERY bright people worked on it.  It is 
>BRUTALLY expensive.  It will NEVER be produced.  The reason will be 
>clear shortly.
>
>While the engineers were careful to get the most out of every drop
>of fuel, the enabling technology for this project was NOT fuel delivery.
>Fuel delivery systems have been the subject of MUCH development over
>the last couple of decades and further improvement will change things
>only slightly.  The enabling technologies for this project were performance 
>measurement, aerodynamics and materials.  The entire monocoque body, 
>for example, is single piece carbon-fiber unit that weighs something 
>like 400 pounds.  
>
>I don't know whether or not the miracle carburetor urban legend will
>EVER die, but I know that 100 mpg vehicles ARE possible.   It's REALLY
>unlikely that they'll be anything like our current low cost offerings
>though.  The MATERIALS for the concept vehicle (never mind the manpower)
>cost more than several entire production line cars.  
>

>Val Breault - vbreault@gmr.com - N8OEF
>General Motors Research and Environmental Staff.
>The opinions expressed by the author do not necessarily reflect 
>those of the GMRES or the General Motors Corporation.
> 
>
Val, one point you forgot to mention is the basic problem of thermodynamics.
I think our urban legend friend is under the belief that all ya gotta do is
put this newfangled carburetor on your 4000 pound Impala and you'll magically
go from 15 mpg to 100 mpg. 'Cause everybody knows the fool engine's less than
20% efficient right now. Get that efficiency up whar it oughta be an' ya got
the problem licked. Right?

Wrong. Much of the fuel's wasted energy is lost in heat - right out the
ol' radiator & block. This has to do with a couple of things like the concept
of the Carnot cycle (thermodynamics), and the fact that current engine
components can't withstand peak combustion temperatures on a steady state 
without melting, coking the oil, etc. Maybe we could improve things by using
some ultra high temp space-shuttle developed materials to improve the source
vs. sink temperature differential, but then we've blown the economics right
out the window, and created some new field useage & serviceability issues.
Maybe we could figure out a way to trap the lost heat through regenration, and
somehow make it turn the wheels. But I really doubt there's a communist plot - 
or a corporate plot - to keep miracle carburetors off the market. (Since the
USSR fell apart, I'm pretty sure it's not a communist plot :-)    )

Anyone out there who's better versed in thermo than I am want to give us some
numbers on the theoretical maximum efficiency of a modern design gas engine?

 
Ted Brooks
 ______________________________________________________________________
| Disclaimer: The opinions expressed are my own, and do not reflect    |
| those of my employer. Advice is free, but you get what you pay for.  |
|                               ________                               |
|                         _____|  1955  |_______                       |
|                        /      Chevrolet      /                       |
|                       /______  BelAir  _____/                        |
|                              |________|                              |
|______________________________________________________________________|