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High RPM problem.

ZERO

By ZERO,
in Engines & Forced Induction

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ZERO Experienced

ZERO

Posted
Posted

Hi Guys i got a problem with my car reving past 4-5 rpms... it starts to splatter... sounds like the pistons is goin to blow out of the block...

R33

RB25 DET

slight mods

- airfilter

- 3 inch all the way

- 9 - 10 psi.

only started not too long after i installed a FMIC.

also my fuel lid isn't pressurized. the seal is cracked would this do anything?

also just had a full 80K service.. all new iridium sparks still not sure why its doin this...

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ZERO Experienced

ZERO

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- Even one cracked coil can cause a lot of hesitation!

- i was getting it between 4500 - 5500 rpm, and after that it was all good, it would rev out nicely...

- When i taped mine the problem went away, but after a week or two, came back b/c the tape shrunk on the coils, exposing parts of the crack once again

- I would be doing this to ALL of the coils, regardless of wheather there is a crack there or not, as it could crack soon anyhow as the others have....

umm... this sounds like wats happening exactly..... (4500 - 5500 rpm) but just a question wat is hesitation? its not like back fire is it? not poping from exhaust right?

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Zahos Mentor

Zahos

Posted
Posted

Yeah, that's what I was implying with that post. It pops, and misfires at around that point at WOT.

Even if you fix your coils, at higher boost, best case scenario is that instead of popping and misfire, you will get a flat spot at around that point.

You will need a new ECU, or a SAFC to retune your air to fuel ratios, as they get VERY rich at around that point with higher boost. I think that timing gets retarded too b/c of the overfuelling, hence the massive flat spot / misfire.

Even with a SAFC, b/c it runs leaner after a tune, the timing does not suffer as much. I only have a SAFC, and I have NO flatspot. In fact, where the flat spot used to be, there is actually a tiny surge or power.

Below is a pic of my dyno graph before and after the SAFC. (Note on the first run - green, my tuner backed off b/c the A/F ratios went crazy. Then sensor he was using to measure the A/F ratios was buggered and he replaced it after a couple of runs.)

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Sime Contributor

Sime

Posted
Posted

Hey Zahos

I am running 12psi and have an SAFC2. It been running great for months. Then on the weekend the car developed the same misfire you guys are talking about. popopop at around 5000rpm and a short drop in power. When I dropped the boost to 10 psi, the problem went away. The spark plugs should be fine as they are new. Would this be a sign the coil packs are on there way out?

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