What AFR are you STS guys shooting for on you wideband. I have my wideband after the turbo in the back of the truck like PLX recommends but I don't know how accurate that is. I would imagine that being that far back on the truck and being after the cats would throw off the reading by up to a full point from what the engine is actually seeing. I have been tuning for 11.5 to 1 on all boost levels but it's all by the butt-o-meter. Today I leaned it out 12.5 to 1 with 16.5 degrees of timing at 10psi and the truck felt a lot stronger. I didn't have any KR and I am spraying a ton of meth for safety. What do you guys think? Could my wideband be off by quite a bit?

 

Mine is 11.2afr in boost.
It doesnt matter where the WB is, as long as its not at the very end of the tailpipe.

 

To elaborate a bit on what was said, the wideband has to be far enough away from the exhaust tip so that it does not read any fresh air. How much exhaust pipe is after the wideband?

 

There is about five or six feet of pipe after the wideband.

I know the cats have to affect the reading some. On my TA which is NA I have the wideband pre-cat and it reads about .6 to .7 richer than the sniffer does on the dyno. Theoreticly the cats heat up to burn off left over fuel that is in the spent exhaust coming from the engine. If the cats burn off some of the extra fuel before the wideband reads it then the fuel mixture should be leaner at that point and would give you a false reading. I don't think a lot of the front mount guys have this issue due to there wideband sensor being in the downpipe before the cats so they get a better reading. Am I making any sense or am I crazy?

 

I have my LC-1 after the turbo and I think you are right. When I had cats it read 14.7 almost all the time, when not in PE. Now with no cats and cam/heads it moves around a lot more and reads about .1 to .5 richer than before. This post may just have brought the reason to light. I was thinking it had to do with the cam/heads but may have more to do with the cats straying off.