AFR 10.9 Your Thoughts Please

[FastBlueRoush]

I have a 2006 Roushcharged mustang putting down 422 RWHP.

Last year I had an issue with what looked like detonated Spark Plugs in bank 7 and 8. Was not sure of possible cause, but clearly appeared to have been caused by a lean condition, not sure of root cause.

Over the late winter and early Spring I installed Aeroforce gauges to keep a closer eye on what's happening. I also installed a Wideband 02 sensor pre-cat on drivers side to monitor AFR's as well as a Vacuum/Boost sensor.

I just had a chance to get it out yesterday and peg it out with a few WOT runs in 4th to see where the AFR's were running. I consistently registered 10.9 AFR at WOT on each run.

This seems to be quite rich. Right?

Over the spring I also installed the fuel pump upgraded wiring kit with heavier gauge wiring as well as the 20 amp Kenne Belle boost a pump. It has a dial indicator from 0-100. I've got it cranked to max power 100 and have it closed looped for constant on operation.

Could you guys give me some suggestions at this point? It may be as simple as I need to go in for an updated tune, or maybe I should simply dial back the dial on the BAP to 60 or 80......

Thanks for your suggestions.

FASTBLUEROUSH

 

[hamish]

Pig rich with cats is a recipe for disaster.

 

[stkjock]

Rousch tune? It's a bit rich for WOT, not crazy. 11.4-11.6 would be better and see some gains.

A tune adjustment makes sense to me.

 

[BruceH]

That seems about right for a canned Roush tune. I'd be fairly certain that was their intention. FYI I've seen stock Mustangs at 11.x afr during dyno days.

IMO it's nothing to be concerned with. It's only at wot and is on the safe side but not ridiculous. The variables are fuel injectors. Unless they are flow matched a 6% deviation is the factory spec. 6% leaner would be 11.5. IMO Roush just tuned for the worst case scenario while still being safe. You would benefit from a custom tune though.

 

[Swarzkopf]

^agreed 100%. You'd pick up a little power by getting it to the mid-11s AFR but it's not really that big of a deal. I always liked keeping roots blown cars a little fatter then other blower types due to the generally higher IATs. That little M90 will generate some seriously high outlet temps. Granted it's a little older, but I've had a couple of Gen III M90 blown GMs and outlet temps were just retarded high. A little richer AFR helps cool the cylinder a bit and prevent detonation.