388 H/P at the wheels and A/F SHOWING 12.2 at wot.

[c6r]

I have a 2005 c6, the mods are honker cai, B&B cat-back full exhaust predator 93 tune headers/xpipe with/cats and made 388 at the wheels,on a 12.2 A/F. Installed the predator to lean out the mixture by 3% and the A/F was 12.5 but I lost 6 horses, what gives? I thought leaning it out would help but it did not according to the dyno results, any advice on tweaking for more power or is this a good result for my modifcations

[dynometer]

those are pretty stoudt numbers if it is a dynojet... What was your timing doing (was there knock retard) Intake air temp, timing, and air fuel among many other things can cause losses. Another issue could be how clean the filter was for the wideband, etc (not your deal, but can give inaccurate results)
andy

[jsk06c6]

How were you reading the A/F after the cats?

Plus the dyno is going to give you up to a 5% error between runs, even the same day, right after each other.

[c6r]

The dyno pulls were done at MTI ( IN HOUSTON TX ) and the A/F readings are at the tail pipe. I had a 5.0 Mustang that love to run lean at 13.0 and had also read many magzine articles saying 12.8 A/F was the ideal setting for safe maximum power production with the LS engines.

[jsk06c6]

Yes, about 12.8 IN FRONT OF THE CATS. You have probably a .3 to .5 error from taking the readings after the cats at the tailpipe. That's why most set it at 13.0 when reading at the tailpipe.

[c6r]

Thanks for the time and info, so I'll gather that my true A/F is probably 12.7 and by leaning it out 3% with the predator tuner pushed the ratio to 13.1 or so which is to lean. Before I had the MTI long tube headers install the vette made 370 at the wheels with the cai, b&b and 93 predator tune . I am satisfied with my results but these days you can't afford to leave good horse power on the table.

[jsk06c6]

Thanks for the time and info, so I'll gather that my true A/F is probably 12.7 and by leaning it out 3% with the predator tuner pushed the ratio to 13.1 or so which is to lean. Before I had the MTI long tube headers install the vette made 370 at the wheels with the cai, b&b and 93 predator tune . I am satisfied with my results but these days you can't afford to leave good horse power on the table.

No problem, your making some great power. Makes sense you moved it lean and lost power.

[mikel]

The loss of power is most likely a result of KR, try better fuel.

Thanks