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How much fuel do various types of engines burn per power output? I'm especially interested in naturally aspirated piston engines, and comparing two-stroke to four-stroke.

The wikipedia article gives the value for several specific engines, but they're mostly for either aircraft or marine applications.

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Sorry. New to the site. Didn't post this under my account. – Jeff Street Apr 30 '13 at 17:57
Hi Jeff, to merge your accounts you can follow this, if that doesn't help then flag the post for moderator attention, and give them the email address of the other account, and let them know it needs merging. – BigHomie Apr 30 '13 at 18:20
Good call. Thank you. – Jeff Street Apr 30 '13 at 18:31
I don't know if engine manufacturers openly publish those specifications. I am sure they have them in a document somewhere but I doubt they are easy to find. Good luck finding them though. – Mike Saull Apr 30 '13 at 18:36
Mayhaps, if none of better, better fit would be on Physics.SE? – theUg May 1 '13 at 19:20

1 Answer 1

2 stroke engines as you know must have gasoline premixed with oil. This is because that oil actually poorly lubricates as the pistons fire constantly. In a four stroke engine every cylinder fires and then makes a full rotation getting lubricated via oil jackets and cooled by water jackets running up through the block and the head of the engine(on top of the block). So a four stroke engine gets better gas mileage because there is less friction.

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How does this in any way answer the OP's question? Jeff is asking about specific fuel input to power output, not why a four stroke gets better gas mileage. On that note, I'd have to say you are incorrect as well. A 2-stroke is less efficient because of how it works, not because of how it's lubricated. A 4-stroke engine can create a lot more compression than it's 2-stroke cousin. For every point of compression there is an ~3% power output increase. This is where the difference lies. – Paulster2 Jan 7 at 11:33
Two strokes have less friction. Four strokes have cams and the various mechanisms needed to be driven from the crank. Four strokes that are liquid cooled have tighter tolerances between piston and bore and therefore additional friction over a two stroke. Two strokes are bearing cranks, less friction. Additionally, two strokes draw their mixture through the crankcase, which is why premix is needed. Gasoline and oil will get on the crank bearings, this is an innate feature of the two stroke combustion process. – DucatiKiller Apr 7 at 16:15
Four strokes have less friction, hence the better gas mileage. They get oiled while 3 other pistons have time to fire. Intead of firing and oiling simultaneously. Two strokes have twice the power, because they are firing twice as often, without the same amount of lubrication as a four stroke. It's very simple. – GettingNifty Apr 8 at 6:24
This is why 125 2 stroke dirt bikes are raced against 250 four strokes – GettingNifty Apr 8 at 6:28

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