When I initially boosted my car, I was seeing boost pressure holding around 9 psi. It seemed to spike to around 9.5, but hold around 8.5 or 9. I had it tuned at that boost level, drove the car for about 6 months, and everything was fine and dandy. The car sat for about another 6 months due to some bad decisions I made, until I finally felt like messing with it again. I was going to strip the engine bay down to have it painted. So I managed to remove the turbo, manifold, wastegate, intercooler, and piping. Some friends bugged me to put it back together to go to the strip. Anyway, to make a long story short, I bolted everything back on, and now it only makes 7 psi with no spiking. I checked, and re-checked everything; pipes, fittings, vaccuum lines, everything. The only conclusion I could come up with that is causing the new, lower boost pressure is my exhaust. A few bolts broke at the exhaust flange where it bolts to the turbo, so the exhaust was never really sealed to the turbo. Since bolting everything back together, I fixed those broken bolts and now have a good seal. My question is, could that exhaust leak at the turbo cause the turbo to build more boost? I always attributed the spike to some inefficiency somewhere, not to the exhaust leak. I have a custom made 3" exhaust, with a high flow cat and a Flowmaster muffler. The downpipe is flattened a little, which could be causing some restriction to the exhaust. Any ideas?

 

What are you using to control boost?

If you had an exhaust leak prior, you would now have more boost due to the fact that all that escaping exhaust is now assisting with the spinning of the turbine, unless you have a boost controller set to a certain level.

The flat spot in the downpipe would affect performance but not boost levels.

 

The only thing that is controlling boost is the wastegate spring. It's a weird situation. I'm going to get a manual boost controller, that I hope will fix the problem.

 

What WG are you running and what spring?

 

38 mm Tial, with a 7 psi spring, I think. It was so long ago since I turbo'd my car that I can't remember which spring I ordered with the wastegate. They are color coded, right? But that would explain why it's boosting 7 psi now, but doesn't explain why it was boosting higher initially. If it's a 9 psi spring, it would explain the initial boost levels, but not the lower levels now. I guess I need to figure out what spring it is to help determine why it's doing what it's doing.

 

Maybe just a fluctuating boost gauge??

 

That was also another thought. I did change where the gauge was getting boost from on the intake manifold.

 

I would be betting on the gauge being off before if you have a 7psi spring. Did you run the WG reference from the same place?

 

The only line that was changed was for my boost gauge. The vaccuum line for the wastegate I ran the same way.

 

Probably just the gauge acting differently.

 

Specail Ed are you still around the Carlisle area? I think I remember your hatch from a few years ago - is it still the same one?

 

Yeah, I'm still around. If you're talking about the army green one with the roll cage, that's me. The car hasn't been on the road in about a year. Stupid DUI's.