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Power Cut On R33 Gtst

LRP

By LRP,
in Engines & Forced Induction

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LRP Newbie

LRP

Posted
Posted (edited)

After some thoughts on what could be causing a sudden power cut.

The problem occurs when (for example) I put it into second at say 20kph and fully engage the clutch, then apply full throttle smoothly. The power picks up boost starts to kick in etc, all is fine to this point. Then somwhere around 4.5-5000 rpm the power just dissappears and I get some serious engine braking, if I keep the hammer down the power/boost comes back on again but will eventually cut again.

If I only goto say 75% throttle instead then its fine, smooth power all the way to redline.

So I do some reading around here and I concluded that the aftermarket boost controller was to blame. ECU picks up too much boost and kills the power so as not to blow the engine. Turned it down incrementally a couple of clicks, seemed to raise the rpm of the power cut(not extensively tested). Took that off (now 100% stock under the hood) and the problem persists, if anything its happens at lower rpm.

My housemate suspects that the wastegate is staying open, thus too much boost, running lean ECU does as its job and cuts the power.

Under that theory I found a quiet stretch of straight road and kept a close eye on the (stock) boost gauge. Which went over 7... Housemate reckons it should never go over about 4ish.

Cant really fault my housemates logic at this point, either way Ill probably get it to a mechanic during the week, just after any thoughts/suggestions on what might be going on here.

Thanks guys

Edited by LRP
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govich Community Regular

govich

Posted
Posted

If the boost gauge reads over 7 that corresponds to more than 14psi, which is bad if you're on the stock turbo, and also explains your power loss (ECU cutting power). 75% throttle = not as much air flow (as WOT) and no timing retard from the computer.

Put it on a dyno to see exactly what's wrong.

Rolls Grand Master

Rolls

Posted
Posted

Its definately overboosting, does it have a boost controller or anything?

If not check the vacuum hoses going to the wastegate and make sure they are perished or cracked. 14psi on the stock turbo untuned is asking for trouble.

A proper boost gauge would be a good investment.

R33S2 Grand Master

R33S2

Posted
Posted
suspects that the wastegate is staying open

You mean it's staying closed and not venting excess boost, it is closed untill the set boost level is reached then vents the excess, check your vacuum lines to boost controller and on to wategate actuator. Blow hard into the line with it connected to the actuator and see if it moves.

LRP Newbie

LRP

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Posted

Thanks for the tips guys,

after some head scratching and comparison with my housemates car we determined that some clueless noob put the vaccum hoses on wrong

after about $5 in parts from supercheap and 10 minutes work all is well

thanks again

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