Boost spikes, what causes this?

[wiked87gn]

WOT causes boost spikes, it goes from 17 to 20 psi back to 16 or 18 and up again to 20 or so, it is never steady, what could be causing this, wastegate is brand new, no leaks on any hoses, turbo is brand new TA60,i am thinking boost control selenoid going bad or sticking, any other Ideas? your imput welcome..

thanks in advance

wikedgn.

 

[stickybones]

Exhaust leak ahead of the turbo (like cracked header or bad crossover connection) may cause this, but...usually just once when boost runs up to maximum with a full throttle acceleration run then hits a spike and settles down to something a bit lower. Once you hit steady WOT, it should stabilize. I've never had boost fluctuate all over the place with a steady WOT run.

You say the wastegate is new. Do you mean the wastegate accuator is new? I also had boost control problems with my old turbo because the leaking oil got in the accuator canister and clogged up the diaphram and all.

 

[gnturbo]

if it is the crossover or cracked header will the little /brief spike to say 20psi hurt anything?mine is doing the same thing.get on it from a roll and it will kick in boost will spike to 20 psi then settle quickly back to 15-17psi.

 

[stickybones]

I'm no expert, but I would think the motor will be fine with a momentary boost spike to 20psi. Always best to fix the problem though.

 

[Russ Merritt]

What is holding the actuator to the swing valve? Could be binding up if it's an "alligator clip" Set up the shop air to 20# and take off the hose from the compressor housing and make the system work to see what's going on.

 

[snoxer]

My car goes to 20 right from the start, then drops to 15-17. Is this normal for these cars?

 

[UNGN]

Originally posted by snoxer
My car goes to 20 right from the start, then drops to 15-17. Is this normal for these cars?

A lot of that could be the chip.

Thrasher Chips for example make the wastegate solenoid (the electronic gizmo on the passenger side valve cover) go to wide open when the car is floored. This part of the "quick spool" feature. When the solenoid is wide open, the wastegate actuator cannot open. After a short period of time, the chip lets the solenoid close and cycle to control boost. If the turbo spools quick enough, it can overboost during this "quick spool" period.

 

[1of1547]

I was having the same problem. Mine was leaking at the exhaust manifold and turbo.

 

[Dean]

Exhaust leaks can, as stickybones mentioned. I went through this a few months ago when my were leaking at all points... didn't hear any of them. This became apparent after I changed turbos.