hey guys, this is a post from a local forum im in. This guy is having some turbo problems and I just thought i'd try to help him out here and post this to see if anyone else could help. Hes got a z24 cavalier. Any ideas? hes thinking the pressure in his manifold is too high and causing his wastegate to dump it all...


Here is his post:


alright, ive been having issues with my set-up for a few weeks now, i spend a few mins here and there trying different things so its taking me awhile, but ive done all i can to try and fix the issue, im still very new at turbos and am lost on how to fix this.

ive been unable to reach my full desired boost(atleast 8psi, plus thats the spring rating in the WG) tried for boost leaks and pretty sure now its not that. tried my controller and pretty sure its not that. bov is not leaking. and am still not hitting much boost.

here is what its doing while driving:
1st gear i hammer down on the gas i get maybe 2 psi then a sputtering sound and then the boost drops a smidge(the sputtering i thought was a leak but now im thinking its my WG dumping, but at 2psi?)
once in 2nd gear it will climb to 4psi then the sputter noise and drops to about 3psi.
3rd gear im able to get it up to 6.5-7psi then the damn sputter goes.
4th gear i would be going +150km/h so im not trying.


what i dont understand is the whole 2psi in 1st, then 4 in 2nd then 7 in 3rd.
if it was a leak it should be leaking under the smae pressure no matter the gear.
the sputtering could only be the wastegate but doesnt make sence cause its a 8psi spring and i havnt hit 8psi yet.

im hoping its an easy fix that im missing, cause at this point i want to sell the *beep* thing and buy a new car

Had a similar issue with a friend's car. Turned out to be the wastegate actuator was funky. Instead of replacing it we were able to use a cheap mechanical boost controller in line with it's vacuum line to delay when it kicks in (since it was kicking in too early, just like your symptoms).
The loss being different depending on the gear might be explained by different engine load and/or manifold pressure (and flow).
This isn't the smartest thing to do, but you could disconnect the line so that the gate stays shut, and see if you have a loss... while being extremely careful not to overboost (not familiar with how easy that engine can overboost but I'm guessing it wouldn't handle a large spike very well).