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Trailer Trash Engineer
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^that there is the chemical ideal stochiometric(sp?).
Best power at wot will be richer, as in lower number like around 12 or 13:1 and best cruise will be a bit leaner, generally around 15.5:1 or 16:1 I think.
 

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Discussion Starter #4 (Edited)
Ya I thought it was around 15:1 from auto shop back in highschool.

Why I am asking is because I am looking at some Dynos for Mazda 3s and the guys says hes running lean....???????????

A/F is like less than 11:1.
 

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For some reason Mazdas, at least the Protege, and its successor the Mazda3, run rich. I drive a Mazda Protege and it's widely known the system runs pretty rich from the factory. It's gotta be some Mazda way of thinking, perhaps too rich is safer than too lean? I dunno...
 

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camrys blow off too!
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too rich is just as bad as too lean. ive seen many a car have gas washed cyls. perfect way to ruin a block
 

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silverstreakin said:
too rich is just as bad as too lean. ive seen many a car have gas washed cyls. perfect way to ruin a block
Too lean may result in hot spots, detonation, etc., or even melting, right? What does too rich lead to? I have not heard of gas washed cylinder walls before.
 

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Grenaded piston
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gcs118 said:
Too lean may result in hot spots, detonation, etc., or even melting, right?
Yup.

What does too rich lead to?
Fouled plugs, bad fuel economy, etc..

I have not heard of gas washed cylinder walls before.
The cylinder walls get lubricated by oil. If theres to much fuel in the cylinder, the fuel washes away the oil.
 

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fuel washed cylinder walls are real, more ring bore and skirt wear, bad thing, also rich mixture causes cat con to run very hot and may melt internals blocking exhaust. O2 sensor should keep mixture around 14.5:1 (+/- 0.5:1)
 

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running rich will actually cool the engine better; which is why you go richer if you are detonating.

marvelicious, i disagree that optimum power is rich, unless its a turbo engine. if you look at some dyno charts(ones that show a/f at the bottom) for all-motor engines, youll notice they make the a/f leaner to increase power. stoichiometric is not a compromise for power and fuel efficiency, but rather for the gasses coming out of the tail pipe.
 

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I've never really understood how more fuel cools down the cylinder as opposed to leaner conditions? And you say that more power is had from a leaner condition as opposed to a rich one? Why is this?
 

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Discussion Starter #18
A leaner engine will run hotter because when ever you ignite something with more oxygen it will burn more completely, the outcome is a hotter combustion.

Where as a richer engine will not burn all the fuel completely.

A leaner engine isn't necessarily more power, it depends on the engine, that is why people dyno tune. To get the A/F right to obtain max power etc...
 
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