I've been running 15 psi for about a month with no problems, and yesterday I had this odd light surging when the turbo first reaches full boost. Almost like its reaching high boost then backing off a bit then reaching it again and then finally stays at 15 and accelerates normally. It all happens very quickly. Feels kinda like a fluttery acceleration.

I have a profec B, and had it set to 12.2 for the start boost (set gain) which seemed to make it spool the fastest without overshooting the target boost. I lowered it to like 11 and the surging seemed to stop. But the turbo also seemed much more laggy. I've read that you should raise the set gain until it either surges or it starts to overshoot the target boost. What causes the surging? I would expect if the set gain was too high that it would just overshoot a bit and come back down smoothly. And what would cause it to start surging now? It never did that before even when i had higher set gain.

I also considered maybe my plugs were about done and I was getting some break up but the afrs didnt get all weird. I assume ignition break up would cause weird afr's?

I'm going to pressurize my intake and make sure I don't have any leaks and that the vacuum source for my tial BOV is good.

 

you mean you have a profec b spec II? did it finally get cold down there for a day? cold weather can cause such things.

 

yeah profec b spec II. It's actually been warmer again. It has been warm, cold, warm, cold, warm, cold the last month or so, so it's had lots of different weather. I changed the BOV vacuum source and it stopped doing it. the hose wasn't sealing against the nipple I had it on even though it was clamped. So i changed its location and made sure it sealed. Maybe the tial BOV was cracking open at first, or maybe it fixed itself and it's just a coincidence. (I didnt test the car today before moving the line)

 

How much is it overshooting on 15psi?
Could be going into maps that are untuned(i.e too lean rich etc) . Have you checked this?

 

Well it wasn't overshooting is why i thought it was strange it would reach 13 or 14 psi and do the surging. I have no idea but i bumped the set gain back up even higher and it won't do it anymore so it seems ok now