Removed HKS EVC = Not boosting past 10.5psi
Okay, here are two simple tests that ANYONE can use to try to isolate boost problems.
If you are not making enough boost, try test number one.
If you are making too much boost, try test number two.
Test #1: Remove the vacuum hose completely from the wastegate actuator. Leave it dangling. (CAUTION! This can be dangerous to your engine, depending on the car and how much boost your turbo will make.) Carefully drive in second gear and get on the throttle. Watch your boost gauge, and let off the gas before the boost gets dangerously high! 18-20 psi should be enough to let you know the turbo and wastegate works, but not so much you blow up your motor. If the car makes lots of boost, your wastegate and turbo is in good shape and the problem is in the control circuit.
If the car won't make substantial boost, you have one of the following problems:
- Your wastegate actuator is broken
- The actuator arm is not attached to the wastegate flapper
- Something has jammed the wastegate open (I've seen gaskets get stuck in there)
- The turbo bearings are shot
- You have a pretty major leak in the intake system (this usually is obvious without doing this test)
Test #2: If you are making TOO MUCH boost, try taking a short vacuum line DIRECTLY from the turbo compressor outlet to the wastegate actuator. (Make sure it's NOT a factory line with any kind of restrictor in it. A spare chunk of vacuum hose is best.) Bypass ALL the boost control stuff. Even with full throttle, you should get the MINIMUM boost level for your turbo -- usually around 10 psi for DSM's, I dunno what it will be for Evos. If you do get a low, steady boost level, your wastegate system is working fine, and your overboost problem has to do with your control circuit.
If you do NOT get a low boost level, but still have uncontrolled boost, you have one of the following problems:
- Wastegate flapper jammed closed
- Wastegate actuator damaged and jamming flapper closed
Remember, if you do Test #1 and let your car boost to 30 psi, I guarantee it'll grenade, so don't blame me if that happens. But these simple tests can really narrow down the troubleshooting around this issue.
Good luck,
Dan
Mach V
MachEVO.com
If you are not making enough boost, try test number one.
If you are making too much boost, try test number two.
Test #1: Remove the vacuum hose completely from the wastegate actuator. Leave it dangling. (CAUTION! This can be dangerous to your engine, depending on the car and how much boost your turbo will make.) Carefully drive in second gear and get on the throttle. Watch your boost gauge, and let off the gas before the boost gets dangerously high! 18-20 psi should be enough to let you know the turbo and wastegate works, but not so much you blow up your motor. If the car makes lots of boost, your wastegate and turbo is in good shape and the problem is in the control circuit.
If the car won't make substantial boost, you have one of the following problems:
- Your wastegate actuator is broken
- The actuator arm is not attached to the wastegate flapper
- Something has jammed the wastegate open (I've seen gaskets get stuck in there)
- The turbo bearings are shot
- You have a pretty major leak in the intake system (this usually is obvious without doing this test)
Test #2: If you are making TOO MUCH boost, try taking a short vacuum line DIRECTLY from the turbo compressor outlet to the wastegate actuator. (Make sure it's NOT a factory line with any kind of restrictor in it. A spare chunk of vacuum hose is best.) Bypass ALL the boost control stuff. Even with full throttle, you should get the MINIMUM boost level for your turbo -- usually around 10 psi for DSM's, I dunno what it will be for Evos. If you do get a low, steady boost level, your wastegate system is working fine, and your overboost problem has to do with your control circuit.
If you do NOT get a low boost level, but still have uncontrolled boost, you have one of the following problems:
- Wastegate flapper jammed closed
- Wastegate actuator damaged and jamming flapper closed
Remember, if you do Test #1 and let your car boost to 30 psi, I guarantee it'll grenade, so don't blame me if that happens. But these simple tests can really narrow down the troubleshooting around this issue.
Good luck,
Dan
Mach V
MachEVO.com
I have also had this problem. I was running an AMS mbc then put it back to stock. I did not use the stock lines with the restrictors on it, I just used regular vacuum lines. I was told that if the stock lines are not used, you will only boost 11psi(which is what I'm boosting now).
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Sounds like Bin-Bin-Bingo! The stock lines with restrictors have been removed in favor of oversized "GIANT" blue hoses. I think we have a winner here.
Last edited by AMSTuning.com; Jun 3, 2004 at 06:36 AM.
Right, make sure you're running the restrictors. I had the same problem where I had swapped out the stock lines. I had put the restrictor that is by the solenoid back, but not the restrictor down by the turbo itself. I was only able to boost 11psi as well until I had both restrictors in place.