Skyrocketing boost

[xveganxcowboyx]

Recently my MBC fell apart and I had to replace the spring and bolt. The one I originally put in was a little stiff (wouldn't set below 15psi) so I went to replace it today. I put a lighter spring in and got boost that hits 25+psi almost immediately. I have never had boost creep issues so I know it's not that.

The routing was from my compressor outlet to the T fitting that is on the car stock to the wastegate actuator. I tried a couple different setups and settings including my last one which was a line straight from the boost source to the waste gate actuator. It still climbs immediately.

I've also tried to move the wastegate arm. It's stiff, but it moves and feels about the same as the other one I have lying around. Could it still be bad?

 

[CanadianTSi]

A pressure source straight to the Wastegate should result in 10psi if the wastegate is working correctly.

 

[xveganxcowboyx]

That's what i thought (Or maybe a little more on a B16G), but it still climbs exponentially.

 

[Rice Over Wheat]

A pressure source straight to the Wastegate should result in 10psi if the wastegate is working correctly.

Doesn't that depend on what the actuator holds? For example, the stock one held 11 psi, but when I added a 17 psi one, it was 17 psi.

OP: You are saying that even from the compressor outlet to actuator you are still getting 25 psi almost immediately?

 

[CanadianTSi]

Doesn't that depend on what the actuator holds? For example, the stock one held 11 psi, but when I added a 17 psi one, it was 17 psi.

Yes a pressure source will give you whatever the spring inside the WGA is set at, that being around 10 for the Stock actuators.

 

[oldman]

If there is absolutely nothing in between your actuator and compressor fitting but a non leaking vacuum hose, it's either a stucked closed actuator/wastegate or boost creep.

 

[xveganxcowboyx]

I've tried it a few ways. I just hooked it up straight from the compressor to the actuator with only a T fitting to the BOV. I've had just straight hose hooked up as well. It jumps immediately to 25psi+.

I have never had issues with boost creep. I have a 3" exhaust, but the high flow cat adds some back-pressure.

When I turn the actuator with a pliers it turns fine and the rod moves back and forth. Would this eliminate either a stuck wastegate or bad actuator? Is there a way to test either without pulling off the turbo?

 

[No_Skillz]

Remove the T fitting, just have a straight line. If your actuator is stock, then it should stay at 10.

If you can determine that your wastegate is not the problem, look at the spring you bought for your MBC. How long is it? If it's long enough to push against the adjuster/knob and the ball inside (I'm assuming it's a ball and spring mbc) when the adjustment is all the way out, then that will cause your boost to rise higher than stock also. Ideally you want the spring to not touch the ball or adjustment knob when you have it at the lowest setting.

 

[xveganxcowboyx]

The actuator is stock (as far as I know). Came with the B16G and was working fine a couple days ago. It should ieither hold at 10 or a little more depending on which one it is.

Apparently it has to be either the wastegate or the actuator. The MBC cannot be the problem, because I'm not currently using it. (though I know the spring stuff. There is just a tiny bit of room between it and the bolt when it's at the lowest setting. I cut and rebent the end to make it fit nicely)

 

[Rice Over Wheat]

Yes a pressure source will give you whatever the spring inside the WGA is set at, that being around 10 for the Stock actuators.

Ok I thought so, thanks.

Vegancowboy, if your actuator arm has threads and a nut on the end that attaches to the flapper then it is aftermarket because it is adjustable. Stock should be fixed length.

 

[oldman]

I've tried it a few ways. I just hooked it up straight from the compressor to the actuator with only a T fitting to the BOV.

This is very confusing, where exactly are you getting your pressure source from? compressor housing or the BOV line?

To test your actuator/wastegate, apply compressed air (from a compressor with gauge) and see if it opens at around 10 psi like it should.

It jumps immediately to 25psi+.

At what rpm does it hit 25psi? I'm not doubting that you know the difference between uncontrollable boost and boost creep, just making sure because many does not.

 

[xveganxcowboyx]

I'm getting the pressure from the compressor housing. I just happened to T off the line and hook my BOV up this way today, because I wanted to clean up the engine bay a little. The manifold nipple is capped and unused now.

I wanted to try that, but I'm not sure how to hook the compressor to it. What fittings would I use?

It hits it probably before 4k. It normally spools to 15psi just a bit above 3k. It acts just like it did before, but continues to rise at the same rate. No stopping or slowing down, no waiting for higher RPM to climb from the normal boost setting. Or I could put it this way. It hits 25psi at low enough rpm to not max out my stock fuel system and buck. I let off before it gets that high.


*edit* I'm thinking the best thing for me to do is swap the actuator from my old 14b on and see if it solves the problem (unless I can figure out how to hook the compressor to this one)

*edit #2* I figured out the compressor thing. Slow brain or something today... I have to go but a new fitting. I'll try that in the morning.

 

[oldman]

I'm getting the pressure from the compressor housing. I just happened to T off the line and hook my BOV up this way today, because I wanted to clean up the engine bay a little. The manifold nipple is capped and unused now.

You can't do that, BOV requires a vacuum source. If you boost with the way it's setup right now, you can say bye-bye to your turbo.

 

[xveganxcowboyx]

Shouldn't all the piping after the turbo be in vacuum or boost pretty much the same? I know it's blowing off louder and stronger than it was. I thought it might be more responsive this way, take the load off the turbo faster.

I guess the manifold would see vacuum a tiny bit faster, but shouldn't anywhere along the piping be fine?

 

[oldman]

Only areas behind the throttle plate sees vacuum, the extra noise you're hearing is most likely compressor surge.

 

[xveganxcowboyx]

Ok, thanks. That makes sense. The plate would block vacuum. I'll switch that back right away.

 

[xveganxcowboyx]

I've got good news and bad news.

The good news: My car now boosts and holds very well. It was a quick and easy fix.

The bad news: I have the cognitive capacity of sea kelp.

Apparently when I swapped the new spring in and every time I worked on this after I put the intake tube on so that it was pushing against the hose to the wastegate and pinching off air flow. It's always the little things.....


Thanks for all the help in this thread, even if the problem was my own stupidity, which you guys can't help with.