View Full Version : MAFT tuning issues

05-22-2004, 10:38 PM
My current setup is 14b, 450s, Walbro 255, Buschur/SX AFPR set at
38psi base, SAFC, 3" turboback and MBC @ 16psi. Now I know these are supposed to give your car a lean idle but I had to richen up the idle 25% to get the o2 trims cycling around 100% and my Lo fuel trim is still 120-130%.

As for top end, it was rich as could be. I had to lean that out -35%
to get it running right and my o2 voltage was still around .92. My MID
is set to -25.

Now when I first set these settings I logged a couple of 2nd and 3rd
gear pulls and there was only 2-3 counts of knock max. Without
changing anything except for a new tank of gas, the next day I logged
8-13 counts with my o2s around .89-.90v and airflow up around 2000hz.

Someone mentioned to me that I probably have boost leaks and I
haven't had a chance to test that theory yet, but I did find that my
Tb elbow was held onto my intake by some basically finger tightened
bolts. I tightened them down good and solid and tried a couple more
pulls. Now my knock count is skyrocketing to 14-17 counts with the
same o2v and airflow hz. So I tried richening it up a little and
got all the way up to 25 counts in 2nd gear?

My confusion here is that my car doesn't seem to be running lean or
rich. Maybe it's trying to advance the hell out of the timing
because of how much correction is being made with my translator and
AFC? I don't get it! Any help would be greatly appreciated!

05-22-2004, 10:41 PM
Oh, this was on 92 octane and the MAF is setup blowthrough.

05-23-2004, 05:28 AM
Yeah, sounds like boost leaks. To need to add that much fuel at idle, and take that much out at the higher loads, makes me think you have a boost leak.

Pressure test the intake.