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Buckeye19 Buckeye19 is offline
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Join Date: Mar 2006
Location: Columbus, OH
Posts: 21
Originally Posted by RarlyL8 View Post
From dyno data you have done what is the difference in power when leaning from say 11.8 to 12.6 AFR? I have not done enough runs to see statistically significant results.
I have personally done back to back dyno comparisons and there is no measurable HP difference going from an AFR of 11.5 to a 12.0. This may not be true for every vehicle out there, but this was true on my particular setup (11.3:1 C/R 993 single turbo with 6 psi making 412rwhp), and on several other platforms that I have tuned.

If it were me, I would never run a leaner AFR then 12.0 at WOT on an air cooled CIS turbo motor, too much risk with near zero gain. You have no knock feedback control features on that engine, and it only has to lean out a bit before you start to knock and damage parts very easily. Running mid-high 11's AFR is not rich enough to wash down the cylinder walls or dilute the oil, and it is worth the extra margin of safety, especially on an air cooled engine where head and piston temps can be a problem that leads to failures.
Old 04-28-2008, 11:44 AM
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