dieselman88

I have a 98 Trans am, 6 speed, 243 ported heads, blower cam, and on3 76mm turbo kit. I have the innovate scg1 boost/wideband and boost controller gauge, but have been noticing that the boost wasn't very steady. Sometimes peak would be 7-8 and sometimes it would hit 12 psi. Has 7 psi wastegate spring and the controller is set to cut it at 10 psi. I decided to put a hallman pro manual boost controller on it. I decide to try out the data logging that the gauge has and noticed that my boost wasn't very smooth, it fluctuated. Still kinda new to this, thought it would build up to what the controller is set at and be nice and steady. I'll try to post a snap shot of the log. Checked for boost leaks and didn't find anything.

In the picture the red line is boost and the black like is rpm, the drop is from 2-3 shift

JoeNova

What's the specs on the cam? Blower cams and turbos don't usually go well together if there is any overlap.

dieselman88

Cam specs are
231/235 617/621 115 LSA

JoeNova

Yeah... That's a pretty big cam for the On3 76mm. Im sure the turbine is having trouble with that one. Any idea how much overlap @.050?

dieselman88

im not real sure, the cam was in the car when I bought it. its a custom grind. so would I have to swap the cam, or get a different turbo to match it better?

dieselman88

would having too big of a cam for the turbo cause the uneven boost psi? I was thinking maybe a faulty wastegate

NitrOmm

iTrader: (1)

If I'm doing the math correctly it looks like 3* overlap.
Maybe someone can verify.