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Originally Posted by greg737
He's saying that 14.7:1 (14.7 to 1 air to fuel ratio) isn't what you always want in a gasoline engine.
For maximum horsepower (in a gasoline powered engine) you tune to achieve a 12.1:1 to 13.1:1 air to fuel ratio.
For maximum fuel efficiency (in a gasoline powered engine) you tune to achieve about a 16.0:1 air to fuel ratio.
Here it is again, copied from a website devoted to fuel injection tuning:
To make maximum power, we want more fuel than stoich. (richer, aka. lower AFR), because we want to be sure to consume ALL the oxygen (even if a little fuel is unburned). Typical full power AFR are 12:1 to 13:1 for gasoline. This is because it is the air flow that limits power (not fuel flow),
To get maximum fuel efficiency, we want to make the mixture a little leaner (higher AFR, about 15:1 to 16:1) than stoich to be sure of burning all the fuel,
To get minimum emissions, we want to run stoich. (14.7:1) as much as possible.
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Thanks, I know how and what to tune for. I didn't understand his first statement
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Thats with the old style O2's, narrow band. With the new wide band O2's, it reads them all the time.
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I'm not sure what "it" he's referring to.
Also, You should note that your numbers refer to naturally aspirated engines. Forced induction engines require richer numbers, unless you run E85.