Beginner question regarding turbo terms
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This is a discussion on Beginner question regarding turbo terms within the New Member Hangout forums, part of the Community - Meet other Enthusiasts category; what is meant by "turbo creep" and "spiking"...

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    Registered User zeus32's Avatar
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    Beginner question regarding turbo terms

    what is meant by "turbo creep" and "spiking"

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    Registered User 06scoobyrex's Avatar
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    spiking is when there is a vaccum leak somewhere in the line and your boost goes up but it wont hold...

    With the countless threads about boost creep problems with turbobacks on the 2.5l STI, I think this thread should be helpful as a quick summary to those planning on moddifying their STI.

    Q) What is boost creep?
    A) Boost creep occurs when the wastegate is physically unable to bypass enough exhaust around the turbine on the turbo.

    Q) Is boost creep harmful?
    A) Yes, boost creep is one of the worst problems you can have with a turbo engine. Boost creep means that there is NO way for the boost pressure to be controlled. Boost pressures in excess of 20psi!!! have been recorded on STIs with TBE before the ECU cuts fuel.

    Q) What causes boost creep?
    A) Installing a turbo back exhaust whether aftermarket catted or not will in almost all cases cause boost creep to a certain extent.

    Q) Are there any other options to prevent boost creep besides porting the wastegate?
    A) Yes, Installation of an exhaust that either keeps the stock OEM muffler or one of the stock cats should not cause boost creep.

    Q) How do I know if I have boost creep?
    A) If you have a full TBE, then you probably have it. A boost gauge will tell you what pressure you are at as well. Fuel cut occurs when the ECU senses boost in excess of 17.5psi for 2-3s. Fuel cut in my experience is a very violent "stutter" from the engine that resembles extreme knock, followed by CEL.

    Q) What is the overboost CEL?
    A) (P0244) Wastegate malfunction

    Q) Is there anything else I can do besides porting the wastegate to prevent the creeping....MBC, EBC, engine management etc?
    A) This problem is isolated to the wastegate only. The wastegate is a mechanical system. There are no current workarounds or "fixes" besides this. The 2.5l just flows too much exhaust through the turbo once a turbo back has been added for the wastegate to control boost. If you think of it as a hierarchy, then it should make sense.

    level 1) wastegate controls boost pressure
    level 2) boost solenoid controls wastegate
    level 3) MBC/EBC/ECU controls boost solenoid

    Using this logic, if the problem resides on the 1st level, no matter what you do on top of it, you will still have the problem. Whatever (MBC, EBC, UTEC, ECUTEK) is controlling the wastegate CANNOT prevent boost creep if the WASTEGATE is UNABLE TO FLOW ENOUGH EXHAUST to prevent boost creep. A fuel cut defender will not eliminate the boost creep problem, but it will stop the fuel cut. Your boost will still creep up to 20psi, but the ECU won't be able to tell due to the altered signal from the FCD.
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