zullo

Searched but don't see this discussed...

As the title suggests, instead of steady boost pressure, mine is pulsing. Amount of boost is fine / as expected, but power delivery is obviously not as smooth as it should be. Pulse is about 2-3 psi, roughly 5 times a second. Seems to affect both turbos.

Pettit street port, dp, mp, cb, pfc. Car was tuned by Steve Kan this spring, who tried to tune out the fluctuating boost via pfc but was unable to. We checked and verified pills and actuator function at the time. Hoses and check valves replaced with new engine last winter. Turbos replaced also, fwiw. Behavior is the same whether I run 10 psi boost setting or 14 psi, so it is not a case of turbos running out of breath.

It gives the appearance of pfc adjusting boost only 5 times a second instead of 100 times a second (or whatever), though I don't suspect a lazy pfc is to blame. ;-) I suspect something like a s....l...o...w moving actuator. Has anyone heard of such a thing?

dgeesaman

iTrader: (7)

Boost leaks can pulse, but if it's at normal levels I'd look at the exhaust. I can't recall if it was because an exhaust component was collapsing, or it simply happened, but changing something in the exhaust has worked for at least one owner.

Dave

Mahjik

iTrader: (1)

Kent,

My bet would be on an actuator.

dgeesaman

iTrader: (7)

What boost controller are you running?

zullo

stock boost control

dgeesaman

iTrader: (7)

Then I would move my boost gauge to tee into the line between the actuator and the wastegate solenoid.

If the pressure in that line is surging like the boost pattern was, I would replace the wastegate solenoid.

Dave

jayk

I had a similar problem at the track once, it turned out to be one of the hoses on the green and white check valves that had popped off. Put it back on and everything went back to normal.

zullo

Thanks guys. Dave, I like your diagnostic idea. I will try that.