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Old 01-23-2009, 03:51 AM   #5
Shmith
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Re: Why diesel consumes less fuel?

Quote:
Originally Posted by MagicRat
I think you mean 'displacement' (aka engine size).
A diesel engine with the same displacement has a smaller combustion chamber that a gasoline engine, due to its higher compression ratio.

Given that, a diesel has a more efficient thermodynamic cycle because the mixture of atomized diesel fuel and air can be compressed significantly more (before combustion begins) than a gasoline and air mixture.

Diesel engines take advantage of this by having higher compression ratios, ~18 to 22:1. Gasoline engines typically have compression ratios of ~8 to 10:1

Also, diesel fuel has slightly more chemical energy per volume than gasoline.
Why then with all the benefits diesel cars run slower and not many prefer them over gasoline englines?
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