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Old 02-07-2008   #14 (permalink)
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alexander
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Re: Why does a lean engine run hot?

Quote:
This is more of a practical question than the typical discussions I've seen here but interesting nontheless. Any mechanic knows an engine which is running lean (less fuel than stoiciometric) runs hotter than one which is properly tuned. 2 stroke motorcycles can actually seize from overheating if run too lean. Normal logic would suggest that with less fuel there would be less heat generated, but it is not the case. My Internal Combustion Engines course professor did not even know about the phenomena (he was the type who knows theory but has someone else change his car's oil).

Any ideas why this happens?
Actually much for the same reason that most drifters run their engines extra rich, especially if they are running a big turbo. Their reason for doing it is so that gas purposely does not all burn up and is ejected out of the engine, for the obvious reason that liquid fuel carries with it a lot of heat, it then burns up in the exhaust pipe, but bottom line is that it is out of the engine, by that cooling the engine down; heat is a big problem on cars that run 600+hp and run almost fully open all the time...

Just like chilehed said, most modern cars are actually ran richer at high loads to cool it down, hence if you run the engine lean, it runs hotter :P

Quote:
Mercedes is supposedly working on a six cycle diesel which uses water alone as fuel on the fifth cycle.
they were supposed to present the engine at the Paris auto show last year, and i thought they did...?


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