We tuned a CTS-V a few months ago with an overdrive crank pulley. Everything went as expected. The car peaked at 11.8 psi boost.
The customer just brought the car back for retune with a new pulley foir more boost. When we hit 12.8 psi the engine dumps boost back to about 10 psi and then clibs back to 12 psi where it dumpse it again.... repeat cycle every half second or so...
It dosen't look like any belt slip I've ever seen and the tensioner is not visibly jumping. Datalogged Throttle Position is staying at full throttle (84 SAE).
Looking over the tune it looks like I might be hitting a boost limit (in the tune under the supercharger section) but I don't understand the labeling or know how the "Boost Limits," "Boost Disable," or "Boost Control" functions work.
Does anybody have some advice or pointers they could give me?
Thanks,
Dan