unlimited boost, stock turbo/wastegate

[tstkl]

Just like the title says, I had it set to 21 lbs, and the other day it shot up to 24 lbs and was holding there, flustering between 23 and 24. Now today It went up to 28 lbs and didn't seem like it was going to stop anytime soon.

What I've tried: went crazy with teflon tape on my mbc (its a home depot style mbc) so it can't leak anymore (except the bleeder hole), and changed the spring. Before I had a 2 inch .022 gauge spring that I had cut to a little shorter than 1.75 inches, today I bought a 1.75 inch spring thats .016 gauge. Its not as stiff and a tad bit longer. I also unscrewed my mbc as much as possible without the bolt falling out. I also changed the vac line leading to the mbc. Before it was tapped off the bov, but now its from one of the throttle body ports. I checked them for vacume to make sure it was a post tb plate source. (if anyones wondering, the top front port is a boost/vac source, and the top rear port is a boost only source)

I think the wastegate is the only thing left to blame. Its a 14b with the stock wastegate. The exhaust manifold/turbo/o2 housing has never been touched by anyone. I think either the wastegate melted shut (doubt this one), or the spring in the actuator went bad somehow. I'm going to try a different actuator later, but for now, are there any common problems with these turbo's actuators? I'll try eliminating the mbc completely tomorrow to know for sure, but I've had some problems with boost creep in the past, so I dunno how much this can tell me.

 

[tstkl]

shoot, ment to put this in problem diagnosis, can someone move it?

 

[oldman]

1. The BOV line is the worst place to tap because the mbc bleeder hole will affect the proper functioning of your BOV.

2. The closer the pressure source is to the compressor the better, don't you have a fitting on your compressor/j-pipe? Why are you insisting on a vacuum source?

3. Connect the pressure source directly to the actuator. If boost level drops down to the spring setting, the problem is the mbc. If problem persists, the cause is probably actuator/wategate related.

4. Moved to problem diagnosis.

 

[tstkl]

1. thats why I changed to the throttle body port from the bov line, I knew this was an issue and I always thought I didn't have another boost source until I realized one of the tb ports might be a boost/vac source.

2. I don't have a source from my j-pipe, so since I have to use a boost source after the intercooler (the major pressure drop in the intake system), I might as well use a boost/vac source, to increase shift responce, since the vac will cause the ball to close faster and it won't blow the wastegate open even more when the compressor surge starts (since it does infact surge up in psi, until the bov opens, which is aprox. .000001 seconds.) If your using a boost source after the fmic, it might as well be a boost/vac source, I say.

3. I'll do that tomorrow

4. thanks

 

[tstkl]

took the mbc out and, just as expected, this is what happened.

In 3rd gear at about 3.5k, give it 35% tps on the logger, goes up to 10 lbs, and holds, take it up to 40% tps, goes up to 12, 45%, 15, 65%, 18, 85%, 20.... woot, it creeps like none other, still. I think what might be happening is an extreme case of creep, since it has 21 lbs pushing it to start. I think its time I go OLD MAN on my turbine housing and port for creep. Even if I can get it to hold at 18 I'll be happy.