Engine Trivia

[GPracer2500]

What (approximate) percentage of the energy contained within gasoline does a normally aspirated engine convert into mechanical work?

If you're not sure, just guess! This is just for fun, after all.

[†2005 400ex†]

i have no idea, i just put a hundred, im curious....what is the answer????

[GPracer2500]

I'll post the answer after folks have a chance to reply.

[300EXrider356]

I think like 65%? this is a good question!

[K_Fulk]

I put 45% , I know a lot gets wasted. I've heard this before just can't remember.

[BlasterEaten250]

45%:macho

*Edit- Just realized K_Fulk had the same guess as me, I didn't copy your answer:p

[underpowered]

lol good quesiton GP. we need to have like a weekly trivia question like this. even if it is a simpler question, it would help many people learn things on here.

[JOEX]

25% I'm guessing most of the energy goes to heat:confused:

[gojk]

Originally posted by JOEX
25% I'm guessing most of the energy goes to heat:confused:

This was my thoughts exactly.

[m.h.s.c.#527]

our science book said 30% so i put 25%

[GPracer2500]

25% is the answer I was looking for. If I could do the poll over again I would have had each choice be a range rather than a set number.

I've found figures that range from 20% up to 38%, but certain qualifiers generally accompany any figure over 30%. For example, an engine might be able to manage over 35% effeciency but only under specific parameters--like staying within a very narrow rpm range. Really, even if you were looking at one specific engine, you might get a different figure depending on how you are determining power output (e.g. at the crank?, at the countershaft sprocket?, at the wheels/propeller/impeller?, an average of all rpm?, an average of "normal" operating rpm?, etc). On average, I'm comfortable with 25% being an accurate figure.

I'm comforable with that figure because that's what Kevin Cameron (http://www.superbikeplanet.com/featurekc.htm) says in a recent article I read titled, Dividing The Pie: Expoloring Where The Energy From Your [Vehicle's] Fuel Actually Goes. Cameron is my favorite powersports technical writer of all time and I've learned to trust his writing. He's held tenure at a variety of magazines as a technical editor and I generally subscribe to whatever mag that may be just to get his articles.

BTW, the remaining ~75% of the energy in our gasoline turns into heat. Most of it goes straight out the exhaust with the exhaust gas. A good portion goes into the cooling system (be it air or water). Some effeciency losses come from friction within the engine--friction which ultimately shows up as heat.

Automotive desiel engines can manage ~40%. Hydrogen fuel cells used on spacecraft by NASA might reach 50% or 60% (so says Cameron). The highest effeciencies for desiel engines (~50%) come with scale. City generating plants and 100,000hp marine desiels sometimes use exhaust gas to not only drive forced induction devices but also to heat water. The heated water can then be used for building heat or turned into steam to run giant electricity producing alternators. Obviously the size/weight/complexity of those systems would make them impractical for all but the largest applications.

Thanks for participating!

[ohsobad_chevy]

GPracer,

We are all smarter becuase of your presence here.......thanks for sharing all your knowledge. One day, I hope to know as much as you. :)

[JOEX]

Now for the hard question... how do atv'ers divert more of the energy to the front sprocket?:D

[ryanh250ex]

25% before i read the thread.

[Kickstarts-suck]

Originally posted by ryanh250ex
25% before i read the thread.

me too :D It was a guess though :p

[ohsobad_chevy]

Originally posted by JOEX
Now for the hard question... how do atv'ers divert more of the energy to the front sprocket?:D

...I got this.......they put more stickers on their quads.....Hooooah, whats my prize? :cool: :p