Stuttering wastegate?Not sure what the problem is.

[WakkoSS]

It's weird, sometimes when I boost up partially, the wastegate starts to stutter or something and the car bucks with the change of boost. Sounds horrible, too. I thought it was my Boost Command, but even with it turned off it still does it. It's set at 22psi by the actuator and I only use the Boost Command to turn it down. Any ideas what would cause this? Car's got 41k miles.

 

[ChrisCairns]

Many years ago I had that same type of stutter. Took me forever to find it as I never suspected it was the actuator. When I removed the actuator I found it was full of oil. Emptied it out and all was normal again.

 

[TurboDave]

Sounds more like you're suffering from compressor surge.

Does it happen mostly at part throttle, mid/low boost levels? If so that's it.

 

[WakkoSS]

Yes, it only occurs at half throttle, and it's inconsistent. If I boost up and slowly release, it's fine...but if I slowly spool up and build to 5 or 7 psi, it bucks and you hear it chug out of the air filter. If that's compressor surge, 1) what causes it, and 2) how can I fix it? It's a fairly new problem.

 

[TurboDave]

It's just a characteristic of the compressor crossing the surge line, and is easy to do at part throttle, light boost conditions.

There are a couple things that can be tried to mitigate the problem.
You can somehow change the volume/size of your intake tract/plumbing. Maybe a change in intercooler plumbing size or length.

You can also change the trigger point on your Boost Command. Try higher trigger points.

 

[WakkoSS]

Hmmm...it's only done it since I installed the LS1 MAF. Am I getting too MUCH air in and not enough air out? I've got stock IC with Dutt neck for now, going to install Mease's upper plenum soon, but otherwise the post turbo track will remain the same for a while.

 

[TurboDave]

Some turbo's can be running so close to the surge line that any small change in the inlet tract from air cleaner to intake valve can push one over the edge.
Did you try moving your BstC trigger point higher?

 

[jastrckl]

I've heard that dropping tension on the wastegate rod and setting up your boost controller to bleed more to compensate helps with surge. Might be worth trying.

 

[WakkoSS]

Even with the BSTC completely off the car will still do it sometimes. I don't think adjusting the turn on point will do anything. What would define the surge point of a turbo? Is it tweakable?

What do you mean about adjusting the tension on the arm? I've got it cranked out to 22psi right now...are you suggesting I go higher and then limit the boost with the BSTC?

I am running no bleeder valve, should I put one in for spool up purposes?

 

[Two Lane]

There's a TON of info on this topic in the Archives...your problem as described is certainly not a rare situation.

What is seemingly rare is a complete "cure" without a significant
"trial-and-error" effort, and/or component changes.

(Many times, it's onset is seemingly most often associated with installing a FMIC...not pertinent in your case.)

Hope you can get rid of it soon...it's a real driveability bastage!