Automobiles powered by gasoline engines are very inefficient machines. Even under ideal conditions, less than 15% of the chemical energy in the fuel is used to power the vehicle. The situation is much worse under stop-and-go driving conditions in a city.
Many mechanisms contribute to energy loss in an automobile. About 67% of the energy available from the fuel is lost in the engine. This energy ends up in the atmosphere, partly via the exhaust system and partly via the cooling system. Approximately 10% of the available energy is lost to friction in the transmission, drive shaft, wheel, and axle bearings, and differential. Friction in other moving parts dissipates approximately 6% of the energy, and 4% of the energy is used to operate fuel and oil pumps and such accessories as power steering and air conditioning. This leaves a mere 13% of the available energy to propel the automobile! This energy is used mainly to balance the energy loss due to flexing of the tires and the friction caused by the air.
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Was studying my physics, and came across this, just wanted to share.

 

i didn't knew that, i tought engines were a lil more efficient, but well, i was wrong, but i've heard that diesel engines are more efficient than gas, is it true?

 

I thought they were a little more efficient as well, like in the 30's % or something.

Diesel engines get better gas mileage, but according to equaations I was shown by my thermo teacher, they should actually be less efficient. I don't know....

Either way, I don't think any engine is all that efficient. Hell, a human being is like 25% efficent from what I heard.


[Modified by Lsos, 5:53 AM 10/8/2002]

 

Heh, so just immagine the HP #s you'ld be putting down if your engine was even 50% efficient

 

word. the gasonline engine is old old outdated technology. something needs to be done, but the large oil/auto conglomerates will not allow such progress cuz--well, they'd lose massive amounts of money.

i ain't complaining though... i love driving.

 

I'll stick with my highly efficient steam powered pneumatic roller.....fuel efficiency at it best!

 

theres a small article in hte las t honda tunning about a concept car that uses 4 electric motors and 1 V6 (propably from the NSX) and was putting down 455hp(or so) and getting 80+mpg....

it was in the same section as the preview for that STUPID new-yuppie-scum-child SUV thing... hondas been disapointig me more and more these days, at the corporate level. BAAHH! "no they dont need any of the type Rs in the states..."

 

that thing is a CRV with 'class/appeal?' same frame same everyghing except body
this is gonna be something weird not really a fan, tehy should just take all that metal and make more s2000's or NSX's

 

No!! Gasoline engines are very very efficient at making heat

 

Don't forget that gasoline engines incur throttling losses (i.e. they're working as vacuum pumps, pumping a leaky container) while diesel engines do not.

 

lol... i loved my thermodynamics class in college

 

I remember a popular mechanics piece many years ago on the rotary engine, saying it's the perfect platform for hydrogen fuel. Something to do with the shape of the combustion chambers. I'd love to see rotaries like, EVERYWHERE! hehe...
If anyone can find information on that, link me up. It's been over 10 years since reading that, and my memory doesn't do the subject justice, really.