what should the A/F ratio be on a tuned car at wide open throttle? I looked around and everything I found said should be close to 12.5 as the 5.0 likes to be more towards the rich side. what is too lean and what is too rich?

I am asking because I was recently at a Dyno day and watching some of the N/A 5.0's the A/F was all over the place.

 

I like 11.5 on a pump gas tune. leaves you some fluff room incase of bad gas. As far as for a race gas tune. 12.0 is the most I would go as the difference between power from 12.0-12.5 is not even noticeabe, it will however keep your EGT's/cylinder temps lower and preserve engine life.

 

11.5 is REALLY safe on an N/A car. Honestly, with PI on this car, 12.5 is totally fine. This car has numerous protection strategies built in and runs closed loop all the time so, there really is very little risk. Split the diff at 12 and be completely confident.

The stock tune can be a bit weird at times from an AFR standpoint. Mine was rock solid ~12.5 all the time but some others report some wandering at different points in the curve.

It'll be whole new ball game in 2015 when DI hits this thing. I predict multiple blown engines as people figure out you can't apply PI tuning knowledge to a DI application.

 

11.9 from bama tunes. Seems to really like it as well

 

11.9 is leaving a lot of meat on the table, fuel-wise. You can counter this with playing around with ignition timing and still have it work out ok feel wise but, that's still pretty fat for a PI N/A application, even taking in a 10% ethanol consideration.