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Old 07-10-2009, 05:31 PM   #1
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Default Only 2~3 psi boost

Hello all,

Hopefully there is enough info in my signature to be able to troubleshoot this.

I'm only getting about 2 to 3 psi boost under hard acceleration. The turbo I have is a GT2554 from an MSProtege so I would have expected a bit more by 3500 or 4k RMP. I imagine it can be caused be one of the following:

1. Bad Turbo
2. Wastegate leaking
3. Charge pipes leaking
4. BOV leaking
5. Bad boost signal source
6. Bad wastegate actuator

Any idea how to narrow this down? I have a manual boost controller that I've not yet added. I don't want to add it till I figure this out. Any help would be appreciated.

Thanks

Tony
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Old 07-10-2009, 05:34 PM   #2
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Sounds like something in the wastegate.. Is there any noise in the turbo? Like a whine or anything?
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Old 07-10-2009, 05:43 PM   #3
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Not really. I can hear what sounds like air going it to the intake, but that's it. I would need a more educated ear to really understand all of the noises.

Tony

P.S. I'm hoping it's something with the wastegate. That's easily changed (or solved with a manual boost controller).
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Old 07-10-2009, 06:49 PM   #4
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Just out of curiosity, where are you measuring the boost level (where is the reference coming from). Also, what wastegate do you have on your turbo? If it's adjustable, have you checked to make sure the arm is tight? There shouldn't be any slack in the wastegate arm. Does the car otherwise run alright? It appears you still have the mass air flow sensor, so your car would run like poop if you had a boost leak. I'm guessing your car runs fine, so you can cross charge pipe leakin and bov leaking off of the list.

Also, what type of BOV do you have, is it a vent to atmosphere or does it recirculate into the system? If you have a recirc (or bypass valve), where do you get the vacuum /boost reference for that?
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Old 07-10-2009, 07:13 PM   #5
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Quote:
Originally Posted by dustinb View Post
Just out of curiosity, where are you measuring the boost level (where is the reference coming from). Also, what wastegate do you have on your turbo? If it's adjustable, have you checked to make sure the arm is tight? There shouldn't be any slack in the wastegate arm. Does the car otherwise run alright? It appears you still have the mass air flow sensor, so your car would run like poop if you had a boost leak. I'm guessing your car runs fine, so you can cross charge pipe leakin and bov leaking off of the list.

Also, what type of BOV do you have, is it a vent to atmosphere or does it recirculate into the system? If you have a recirc (or bypass valve), where do you get the vacuum /boost reference for that?
I get the same (roughly) readings from the gauge and the emanage. The wastgate actuator is not adjustable, but I have a MBC that I plan on installing. The car idles perfectly and the BOV is actually recirculated. I didn't think it was a leak problem (I would think that I would hear it), but it is a possible cause for this kind of issue so I listed it.

Both the BOV and guage/emanage get their boost source from the engine side of the throttle body. The BOV signal is sourced from just above the throttle body (I believe where the cruise control is normally sourced) and the gauge/emanage is source from the line that normally feeds the automatic transmission (I have a manual so it was capped).

I suspect the wastegate actuator has gotten soft with age and is opening too early. I suspect the addition of the manual boost controller will solve this, but I wanted to see what everyone thought.

Tony
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Old 07-10-2009, 09:49 PM   #6
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pull the line to the wastegate, can you make more? (ps, be careful)
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Old 07-11-2009, 01:31 AM   #7
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Does "hard acceleration" mean wide-open-throttle? Is your foot going to the floor during your pulls?

Is the wastegate actuator new, or OEM from the Protege?
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Old 07-13-2009, 03:42 PM   #8
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If your wastegate signal is sourced from the compressor outlet like the gt2554 I got with my Begi-S kit and your boost gauge signal is sourced from the intake manifold...and it's a 5psi wastegate, then everything is fine and you just need to add boost control.

My boost gauge read 2-3psi with the Begi-S kit bolted on. When I moved the wastegate signal source to the intake manifold, the gauge read 5psi. The discrepancy is due to the diameter change from the compressor outlet to the IM/IC piping. I suppose a bit is also from pressure loss over the IC. There is a decent difference and as such the pressure drops.
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Old 07-13-2009, 06:10 PM   #9
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I was under the impression that the wastegate actuator was not supposed to see vacuum, because it would slam the the wastegate closed and possibly damage the actuator. Is that not right?

The actuator is OEM that came with the turbo.

Brainiac, that is a great and simple idea to determine if the wastegate (or actuator) is the problem. I'll try that on my way home today.

Tony
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Old 07-13-2009, 09:51 PM   #10
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The actuator sees vacuum every time you run the car; basically any time it's not in boost. It won't damage it. I still think your issue is what I described above. I was wondering the same thing when I first got my turbo on and only saw 2-3psi.
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Old 07-13-2009, 09:59 PM   #11
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Did the wg actuator arm come unhooked? That would cause a similar issue.
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Old 07-13-2009, 10:19 PM   #12
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I drove home with the actuator unplugged from the boost signal. Holy cow! It got to 5 psi in seconds! I had to pay attention to make sure that I didn't go too far past 5psi. The acceleration was strong and linear. I'm putting the manual boost controller in now. This is great! This is what I was looking for when I installed the turbo.

Thanks all.

Tony
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