I know this is a total newbie question, but i personally have never dealt with it. Last week on the dyno, I forgot to hook up my vacuum lines to the wastegate and on the dyno the car only built 25-26lbs. Hooked the lines back up and was still only able to get 25.5 lbs out of it at 100% duty cycle on the single mac valve. So i was just curious if only having 12lbs of spring in the wastegate, could it have pushed the gate open enough to bleed off enough to only build 25lbs. Its a precision 66mm wastegate.

 

What turbo, a/r housing, etc?

Back pressure related is the first idea to cross my mind.

 

Yes obviously exhaust backpressure is pushing the gate open.
Is your boost controller adding pressure to the top port?

 

Spit balling another possibility albeit pretty uncommon in our applications.

Do you have a filter on the turbo? I have seen a smaller filter on a compound setup become a restriction and limit the amount of boost the turbo would make.

 

Yes I'm using the top port. Its on a 3 port Mac valve. It built 25 with no lines ran to it and its got 12lb spring in it. And built 26 with the lines on. Just wasn't sure if the gate could have been pushed open with a 12lb spring in it.

 

And its .82 T3

 

sure you built enough backpressure to push the gate open.