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Peak Boost Issue

Se7eN

Senior Member
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#1
Ok so here's the deal. My friend has a GT2560R he got recently very cheap and his net goal for whp is not all that high.

The issue he is having is that the car does not go above 25psi. He preloaded the stock WGA to 10psi and at 100% it didn't even go past 24psi. Upgraded to a new 16PSI WGA, I did the preload on it and on 0% is giving just about 16psi exactly. On 50% duty for the WGA the car is pushing out 23psi now nearing 90% it's stuck at 25PSI which it hit much lower in the % range. The ATP site does not specify and neither does the 2554 and 2560 thread if the turbo has a peak boost of just around 25. Also searched for similar issues on here and only found one thread with no answers.

My question is what could be the issue. We already did a boost leak test and everything is Ok. Checked all the vacuum lines and the thing we thought was the issue which was the preload. What else could we be missing? Also, is the turbo just limited to that PSI?

PS. I know that most recomendations would be to get a hybrid/GTX or something (it ain't gonna happen due to budget constraints).
 


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Yorktown
#2
What ebcs are you using? That seems to be the one variable that has remained constant and could be your issue.


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Location
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#6
What bypass valve is he using? I don’t believe the turbo is the issue. If the turbo is operating as it should a gt25 series can make more than 25 pounds. Assuming he’s hitting target afr’s, diverter valve or boost control solenoid is where I would look.


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OP
Se7eN

Se7eN

Senior Member
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Thread Starter #7
The BOV is a turbosmart that goes on the symposer delete. I have the same one in my car with no boost issues. I did ask him if he had adjusted it or not though. Said he did.
 


OP
Se7eN

Se7eN

Senior Member
Messages
904
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786
Location
San Juan, Puerto Rico
Thread Starter #8
What bypass valve is he using? I don’t believe the turbo is the issue. If the turbo is operating as it should a gt25 series can make more than 25 pounds. Assuming he’s hitting target afr’s, diverter valve or boost control solenoid is where I would look.


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Yeah, the boost solenoid is about the only thing that hasn't been changed and that I have not actually touched. I did see where it was connected and it was done so propperly, but maybe its having issues.
 


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#10
Hook up the vacuum lines so that it is running only on spring pressure to the waste gate. As in don’t plug in anything to the boost control solenoid and see if it builds anything past spring pressure. If it does more than 1-2 lbs max you have waste gate issue. If it holds fine at spring pressure you have a boost control solenoid issue.


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OP
Se7eN

Se7eN

Senior Member
Messages
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786
Location
San Juan, Puerto Rico
Thread Starter #11
Hook up the vacuum lines so that it is running only on spring pressure to the waste gate. As in don’t plug in anything to the boost control solenoid and see if it builds anything past spring pressure. If it does more than 1-2 lbs max you have waste gate issue. If it holds fine at spring pressure you have a boost control solenoid issue.
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I'll tell him to try that, although that seems similar to running in Economy with 0% WG pressure
 


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Location
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#12
I'll tell him to try that, although that seems similar to running in Economy with 0% WG pressure
Yes but by completely disconnecting the solenoid from the equation you can isolate it to help you determine the problem. All you need is a vacuum line from the internal waste gate hooked to a vacuum source and the turbo should build no more than spring pressure. This isolates any possible hardware issues that may be the problem and depending on what you find one or the other will be the source to investigate


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