Originally Posted by NSFW
I give up. Why?
I have a stock 09 LGT ROM in front of me that calls for 9.65:1 at 6000 RPM and up, and I'd love to know WTF the OEM tuners were thinking.
If that's what it takes to be safe, then those of us running 11:1 must be living on borrowed time.
They put a decent factor of safety on that AFR to protect people from themselves (Derp, 87 is premium right?), if you are careful with putting good fuel in then there is no reason to run that rich.
I have noticed that cars running smaller more restrictive turbines from the factory tend to run excessively rich while cars that came with larger turbos run a touch leaner. Perhaps it has something to do with higher back pressures?
Running leaner also increases the NOx count significantly so the rich AFR could be related to that as well. On my car I target ~11-1 at peak torque then taper down to 10.5-1 at peak RPM, with peak RPM at >8K I feel safer being on the rich side.