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No Boost When Cold And Overboosting

rorz

By rorz,
in Engines & Forced Induction

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rorz Enthusiast

rorz

Posted
Posted

Hey guys, i recently purchased a Rb20det R32 coupe (GTS4) converted to manual,

When the car is cold it doesn't want to boost.. i can hear the turbo spooling up hard but the car doesn't go anywhere, then all of a sudden (sometimes) it just hits and goes. i can feel the turbo responding to my throttle and i feel like if i floor it when it's cold the turbo will just explode (even though the car is hardly accelerating)

Additionally, it feels like the car is overboosting. When the car is warm the turbo is really loud and it spools really hard from like 2500 to 4000 then drops off a lot.

Unfortunately i havn't got a boost guage to measure this.

Any ideas?

The car is stock however the cat is removed. Even has factory airbox.

Cheers!

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GTRNUR Grand Master

GTRNUR

Posted
Posted

Best guess is that your BOV might be stuck open/faulty. You need to have the intake system pressure tested by a mechanic to determine where the leak is and precicely what is leaking. You might also find other leaks when doing this test so its well worthwhile having the test done.

As for over boosting.. short of a gauge to verify what is really happening its anyones guess.

For safety sake though you shouldnt be driving the car until its fixed. That is unless you also want to plan on blowing up and replacing the turbo. If it is overboosting, it will blow the ceramic wheel off the turbo pretty quickly. If it doesnt blow the turbo, then your risking detonation, lean running and blowing the engine instead.

GTRNUR Grand Master

GTRNUR

Posted
Posted
Ok thanks for that, assuming the factory BOV or some other part of the intake has a leak, why would this only have a large effect when the car is at cold temperature?

Who knows.. sticky valve that free's up when the temps get warm... but pressure testing it cold will identify the fault and allow you to fix it.

mystery_kid Mentor

mystery_kid

Posted
Posted

you shouldn't be trying to drive on full boost when your car is cold

also that rev range for boosting sounds about right is your car is as stock as you say it is

drive without boosting for the first 5 - 10 minutes or more in winter if you don't want to wreck your engine

rorz Enthusiast

rorz

Posted
  • Author
Posted

That's the thing though, i'm not trying to boost it when it's cold.

I just try and drive nice and slow but the turbo spools up hard even if my foot is 1/5 on the accelerator pedal. The turbo makes noise but the car isn't actually boosting if that makes sence

I bought a boost guage today just need to figure out how to fit it.

rorz Enthusiast

rorz

Posted
  • Author
Posted

I got the boost guage done it's reading -20 at idle and +10 at full boost and doesn't fluctuate so that seems all normal,

Must just have some issue with one of the intake items being blocked/restrictive when cold

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