[darkpuppet]

GFXjamie,Apr 17 2009, 11:46 AM Wrote:I agree, i plan on check AFR as well since i don't have a wide band yet... Will be good for between run tuning as i doubt by AFR is maximized. Quick question tho, what i optimum for HP on a N/A and what is optimal for efficiency? isn't it something like 13.6 for hp and 14.7 for efficiency?
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Ideally, you'd make the most horsepower with a leaner mixture -- but with leaner mixtures comes higher combustion temps.... so for most intents and purposes, running 14.7 is the most efficient ratio.

However, you have to constantly battle against pre-detonation and combustion temps... which you control through octane, spark, and A/F. The easiest thing to do is usually to just richen up the A/F to wet the mixture down -- which cools it down and allows you to run out the engine.

In most N/A applications, I see AFR's in the 13 range. 11-12 for turbo. Much richer than that and you end up blowing black smoke out your tailpipe (which is an indication you're not running efficiently at all).

So the answer is...

Run as lean a mixture you can while avoiding pinging and melting your heads or pistons.