ssm@cmu-ri-leg.ARPA (Sesh Murthy) (03/06/85)
Why does a diesel give better m.p.g. than a gasoline car. Is it because the effieciency is greater because of the higher compression ratio or because diesel fuel gives out more energy when burnt? By the way I found a very cheap ($50) speed control kit at a farm store in Champaign. It works fine on my diesel Dasher. It is called the Escort II and I will give you the address if you are interested. Also how good is gunk engine cleaner in cleaing your engines insides. My car is making a racket and I thought it would not hurt. What about the additives that are used to improve the diesel fuel. Do they really do anything for you. Sesh -- uucp: seismo!rochester!cmu-ri-leg!ssm arpa: ssm@cmu-ri-leg
doug@terak.UUCP (Doug Pardee) (03/11/85)
> Why does a diesel give better m.p.g. than a gasoline car. Is it because the > effieciency is greater because of the higher compression ratio or because > diesel fuel gives out more energy when burnt? My (admittedly unknowledgable) beliefs are: 1) The Diesel cycle is slightly more efficient than the Otto cycle in "normal" designs; 2) Most Diesel engines are lower-powered than the gasoline engines they're compared to; 3) Gasoline engines are hampered by emission regulations from which Diesels are exempt. -- Doug Pardee -- Terak Corp. -- !{hao,ihnp4,decvax}!noao!terak!doug
ix1037@sdcc6.UUCP (Christopher Latham) (03/14/85)
> > Why does a diesel give better m.p.g. than a gasoline car. Is it because the > > effieciency is greater because of the higher compression ratio or because > > diesel fuel gives out more energy when burnt? > > My (admittedly unknowledgable) beliefs are: > 1) The Diesel cycle is slightly more efficient than the Otto cycle > in "normal" designs; > 2) Most Diesel engines are lower-powered than the gasoline engines > they're compared to; > 3) Gasoline engines are hampered by emission regulations from which > Diesels are exempt. Actually the cycle in diesel engines is less efficient than that in gasoline engines. However the efficiency in both cycles goes up as compression ratio goes up. So since automotive diesels operate at around 20/1 as opposed to 7-10/1 for typical gasoline engines they get their increased efficieny from the higher compression ratio. If gasoline engines could be run at such high compression ratios they would get much higher mileage. Christopher Latham U.C.San Diego Dept. of Applied Mechanics and Engineering Sciences ..sdcsvax!sdcc6!ix1037
ark@alice.UUCP (Andrew Koenig) (03/14/85)
Diesel engines give more MPG than gasoline engines because: 1. Diesel fuel has more energy per gallon than gasoline. 2. Diesel engines are inherently more efficient because of their higher compression ratio (typically 22:1) and consequent higher combustion temperature.
seifert@mako.UUCP (Snoopy) (03/20/85)
A big part of why diesels are more efficient under "normal"
operating conditions is because they don't have a throttle.
Takes power to suck that air past a throttle that's almost shut,
ya know? Above a certain point, gas engines become more efficient.
Thus the quotes around "normal". If crusing flat out on the
autobahn is your idea of normal, than a gas engine will be more
efficient.
This is the same reason that you get better gas mileage by accelerating
quickly up to crusing speed rather than creeping along. The engine
(assuming a gas engine here) is running unthrottled, thus more efficiently.
Also you spend less time in the lower gears.
The above statements are based on research done by BMW. (which doesn't
imply that they agree with my muddy explaination of their work)
_____
|___| the Bavarian Beagle
_|___|_ Snoopy
\_____/ tektronix!mako!seifert
\___/
If God had intended Man to Smoke, He would have set him on Fire.
-the fortune AI projectgmv@cbuxc.UUCP (Mike Vrbanac) (03/22/85)
The reason diesels get approximately one-third better milage than their gasoline counterparts is because the energy content (BTU's) of diesel fuel is about one-third more than gasoline. Mike Vrbanac cbosgd!cbuxc!gmv
hollombe@ttidcc.UUCP (The Polymath) (03/27/85)
In article <209@cbuxc.UUCP> gmv@cbuxc.UUCP (Mike Vrbanac) writes: >The reason diesels get approximately one-third better milage than their >gasoline counterparts is because the energy content (BTU's) of diesel >fuel is about one-third more than gasoline. Diesels also use a much higher compression ratio than gasoline engines (on the order of 20:1 or more vs. ~10:1 for gasoline) which makes for much more efficient use of the energy in the fuel. -- -_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_- The Polymath (aka: Jerry Hollombe) Citicorp TTI 3100 Ocean Park Blvd. Santa Monica, CA 90405 (213) 450-9111, ext. 2483 {philabs,randvax,trwrb,vortex}!ttidca!ttidcc!hollombe