Optimal a/f

[robh]

Now that WB are reasonably available and I was able to pick up a Innovate unit.
What is the optimal a/f for a turbo car? Is there such a thing
I am doing only 3rd gear WOT blast and getting high 11's a/f. But using only a butt dyno how do I know if richer is faster or vice versa.
Before using o2 counts .780 was the magic number I tuned to. Just looking for the same thing.
Any help would be appreciated.

 

[TurboDave]

Well, for forced induction engines, it's generally accepted that something around 12:1 is a good starting point. It may be required to go slightly richer (into the high 11:1's) but it all comes down to what your combo likes.
BTW, using a butt dyno for tuning is not exactly a safe methodl. It's good to dig out driveability issues but not changes in WOT tuning.

 

[robh]

TurboDave,
If I'm using a WBo2 what is not safe?

 

[TurboDave]

There is no magic number. Every car is different. But, I would say that if you're pushing near 12.5-12.7:1 at WOT, you may be getting dangerously lean.

A good EGT would help keep an eye on things, as well as a knock indicator of some sort.

 

[Chuck Leeper]

??????????

At 25#, and WFO, I have my FAST set to a commanded ratio of 11.5... Made well over 800FWHP w/ it, and the engine appears to be "happy".

 

[bruce]

I took my portable WB to the Nats, and hooked it up to +6 different cars. For the guys running in the 10s, seemed to run from 11.3 to 10.5. Was pretty warm, and humid so that needs taken into account.

 

[robh]

Thanks for the replys.
It looks like any where in the 11's is fine. So I will shoot for that and possibly richen until performance loss for safety.
thanks