Strange boost issue

[bewstin]

Alright so i viewed a couple similar posts and found nothing to help me .
Basically, first gear WOT the car boosts fine, but if i'm in any other gear at 2-4k RPMS, as soon as i go WOT the boost will hit 5psi, then stay there until it gets up to around 5-5500 RPMS then it will go up to 13psi, which is where i have my MBC set. It seems like the turbo doesn't want to spool unless there's a TON of exhaust flow, hence why it picks up and spools around 5k+ rpms. Its strange too, because i can hear the turbo spooling great even in 3rd gear at like 1500 rpms, I can hear it spooling up. Just confused why it seems to have like a 2 part boost phase. I've done a boost leak test twice in the past 2 days. The only thing i hear is pressure leaking out of the crankcase breather. The car runs great otherwise, doesn't skip a beat, doesn't have cold start problems. Just installed a brand new FP turbo manifold the other day as well, didn't fix my problem though.

I'm Going to take a Video in about 30 min when I go Christmas shopping. Ill put it up when I get back, that way it's easier to understand.

 

[awdtalon4451]

Check your wastegate or for post turbo exhaust leaks.

 

[n0de]

^^ This exactly. I had a 92 talon in the past that had the same symptoms and it was caused by having a small gap between my turbine housing and downpipe.

If this does not fix the issue, try running directly off of the wastegate and see how it acts.

 

[bewstin]

Are you saying, take off my manual boost controller and just run a line from the turbo to the Wastegate actuator? Wont that make my turbo overboost like crazy?

And there's no leaks after the turbo, i checked everything while the car was running, cant hear or feel any leaks. All the bolts are also tight.

 

[n0de]

Are you saying, take off my manual boost controller and just run a line from the turbo to the Wastegate actuator? Wont that make my turbo overboost like crazy?

And there's no leaks after the turbo, i checked everything while the car was running, cant hear or feel any leaks. All the bolts are also tight.

I should have asked what your mods were. What is the wastegates psi rated at? The reason I said this was to see if the boost controller was connected backwards (was a theory for this particular issue).

It depends, running straight wastegate just boosts at wastegate pressure, so whatever you wastegates default spring pressure is rated for, it will boost that much. Do not try this if you are uncertain of the outcome.

 

[Black-Out]

Basically he is suggesting that you check your wastegate to make sure it's not allowing exhaust energy to bleed off before it gets to the turbine.....not check for leaks outside of the system where you would hear or feel air, but to check for the wastegate leaking before the turbo....... If you have a IWG check the swinger on the actuator rod to ensure the e-ring that holds the rod to the swinger is still holding everything together- if it's not then the wastegate will be blown into bypass mode with minimal effort,and it will take ridiculous amounts of air flow to get it to spool to the point where the car will make the power it will produce at wide open throttle.....
Make sense?

 

[bewstin]

Yup makes perfect sense. My internal waste gate seems to be fine, the actuator arm is tight and the c-clip is holding the arm to the flapper still. Boost controller is hooked up properly, I'm sure of that. Here's a video i made. I was starting to think it could be because I'm running so rich. The car vibrates a lot of idle .

VIDEO0069 - YouTube

 

[bewstin]

Still confused, been a couple days now. Even with the new FP manifold and everything 100% tight, still doesn't want to boost up to 12psi before pausing at 5psi for a few 1000 rpms.

 

[Black-Out]

Ok, I watched your video- I think whats going on is the wastegate is cracking open slightly while you're on it and thats why it hangs up at 5psi before it jumps to your set boost. Basically the boost control isn't bleeding off wastegate signal pressure in a linear fashion so it's actually allowing the gate to open when it should be shut and the engine is having to overcome the flow losses until the pressure spikes up high enough to push the wastegate the rest the way open at full boost. If you used a basic electronic boost controller,say a Greddy Profec B Spec II, the way you could remedy this issue would be to adjust the gain percentage up......then adjust set gain for the amount of spike you want or don't want then adjust the actual set to where you want it for the pressure you're trying to achieve-

What MBC is it? because if it's a home grown one then you may have to tune the controller a bit to get the pressure control dialed in. Otherwise I'd pick up an Profec B and call it a day- They're getting cheap second hand and they aren't to pricey brand spankers.

Good luck with it my brotha!

 

[Gerg]

Ok, I watched your video- I think whats going on is the wastegate is cracking open slightly while you're on it and thats why it hangs up at 5psi before it jumps to your set boost. Basically the boost control isn't bleeding off wastegate signal pressure in a linear fashion so it's actually allowing the gate to open when it should be shut and the engine is having to overcome the flow losses until the pressure spikes up high enough to push the wastegate the rest the way open at full boost. If you used a basic electronic boost controller,say a Greddy Profec B Spec II, the way you could remedy this issue would be to adjust the gain percentage up......then adjust set gain for the amount of spike you want or don't want then adjust the actual set to where you want it for the pressure you're trying to achieve-

What MBC is it? because if it's a home grown one then you may have to tune the controller a bit to get the pressure control dialed in. Otherwise I'd pick up an Profec B and call it a day- They're getting cheap second hand and they aren't to pricey brand spankers.

Good luck with it my brotha!

I have a hallman boost controller and I believe I'm having the same problem as the original poster. Do I just adjust the controller until the wastegate will function properly? I have a tial with what I believe is a 11lb spring. Thanks for your help in advance.

 

[Black-Out]

I have a hallman boost controller and I believe I'm having the same problem as the original poster. Do I just adjust the controller until the wastegate will function properly? I have a tial with what I believe is a 11lb spring. Thanks for your help in advance.

Sense you have an external unit, I would do the simplest thing first, which is remove the Hallman and connect the waste gate signal line strait to the intake manifold pressure port, to ensure that the gate is opening at the pressure you suspect the spring is tuned for. Then I would set the Hallman to where it is open allowing full pass through so that with it installed the waste gate opens at it's spring pressure as if the controller isn't even there- (in other words turn the boost controller all the way down, you can actually blow through it to check it.) and then reinstall it in to the waste gate vacuum circuit. If everything is good, the car should build boost the exact same way with the controller in the vacuum circuit as it would with just the waste gate getting the vacuum signal direct. If it builds boost the same way then things are looking up you should then be able to start adjusting the Hallman 1 or 2 turns at a time and make some 3rd or 4rth gear passes and keep a close eye on the gauges (but you know that already) If the car builds boost in a linear fashion then you should be good to go- if not then the vacuum lines may not be connected correctly causing the issue. This will be readily apparent when you just connect the vacuum source pressure to the waste gate signal line and make a few pulls. If that boost comes up quick and smooth and then the gate opens at 11psi the controller or at least it's vacuum connections may have been the culprit.
Either way doing these things will help you pin point if the waste gate is the issue or if the controller or the vacuum connections are the issue,plus itll only take a few minutes to do-

Almost forgot - in the case of an external waste gate the valve seat being left out can also cause the same issue the original poster is complaining about.... make sure that the spring, diaphragm, and any gaskets, along with the valve seat and the source ports are all in good condition and any vacuum points sealed up tight. Basically the obvious stuff.
Hope this helps out-
Will

 

[Gerg]

Sense you have an external unit, I would do the simplest thing first, which is remove the Hallman and connect the waste gate signal line strait to the intake manifold pressure port, to ensure that the gate is opening at the pressure you suspect the spring is tuned for. Then I would set the Hallman to where it is open allowing full pass through so that with it installed the waste gate opens at it's spring pressure as if the controller isn't even there- (in other words turn the boost controller all the way down, you can actually blow through it to check it.) and then reinstall it in to the waste gate vacuum circuit. If everything is good, the car should build boost the exact same way with the controller in the vacuum circuit as it would with just the waste gate getting the vacuum signal direct. If it builds boost the same way then things are looking up you should then be able to start adjusting the Hallman 1 or 2 turns at a time and make some 3rd or 4rth gear passes and keep a close eye on the gauges (but you know that already) If the car builds boost in a linear fashion then you should be good to go- if not then the vacuum lines may not be connected correctly causing the issue. This will be readily apparent when you just connect the vacuum source pressure to the waste gate signal line and make a few pulls. If that boost comes up quick and smooth and then the gate opens at 11psi the controller or at least it's vacuum connections may have been the culprit.
Either way doing these things will help you pin point if the waste gate is the issue or if the controller or the vacuum connections are the issue,plus itll only take a few minutes to do-

Almost forgot - in the case of an external waste gate the valve seat being left out can also cause the same issue the original poster is complaining about.... make sure that the spring, diaphragm, and any gaskets, along with the valve seat and the source ports are all in good condition and any vacuum points sealed up tight. Basically the obvious stuff.
Hope this helps out-
Will

Thanks Will. I'll have to troubleshoot with it some more tomorrow when there is light. I hope one of these is the case!

 

[Black-Out]

Any time sir- hopefully it's something simple....

Anyway Crash89 posted this in an old thread so I think it bears enough to repeat it- get ready for the ol' cut n paste ....

Side port of the wastegate to a direct boost source.. Top port is left open. Whichever turbo you're running should have a pressure source nipple either on the compressor housing or maybe yours is on the IC piping. Closest to the turbo is best.

give this a shot and see what the results are.....it should build boost quickly and smoothly without spike. same if you install the Hallman in between the side port source pressure line and the manifold or compressor signal port on it's lowest setting (which will be default to waste gate spring)

Will-

 

[talon314]

check your throttle body seals

 

[bewstin]

How would i go about checking throttile body seals

 

[WES_393]

A boost leak test would be the quickest way, but if the throttle body doesn't look like it was recently rebuilt then they are most likely leaking some amount. At least I have never seen a stock throttle body that didn't leak.

BUT, that won't cause the boost issues you having. I fully agree with Black-Out, it seems something is going on with your wastegate. My best guess would be that it's sitting open a bit. Since waste gates mainly vent pressure, the tiniest leak can have a big effect on spool. So in order to spool the turbo past a certain point (like 5psi), the volume and pressure of exhaust gas would have to be much greater than the faulty wastegate is letting out. Which won't happen till higher RPM's since you can't boost over X amount.

When I installed an open dump O2 housing on my 16g, I could hear that the wastegate was sitting open a bit at idle. I shimmed the wastegate actuator (added washers under the mounting points) to tighten it up a bit. The wastegate stayed closed which led to much faster spool, and still regulated boost very well. So like Black-Out mentioned, I would try hooking a line straight to the actuator to take the MBC out of the equation. If you still have boost issues, try shimming the actuator like I did.