Jump to content
SAU Community

High RPM problem.

ZERO

By ZERO,
in Engines & Forced Induction

 Share

Recommended Posts

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...

Link to comment
https://www.sau.com.au/forums/topic/52257-high-rpm-problem/
Share on other sites
ZERO Experienced

ZERO

Posted
  • Author
Posted
- 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?

Link to comment
https://www.sau.com.au/forums/topic/52257-high-rpm-problem/#findComment-1032433
Share on other sites
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.)

Link to comment
https://www.sau.com.au/forums/topic/52257-high-rpm-problem/#findComment-1032816
Share on other sites
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?

Link to comment
https://www.sau.com.au/forums/topic/52257-high-rpm-problem/#findComment-1041688
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Lithium
      Garrett G Series

      By Lithium · Posted

      Oof. One of my mates has an R34 GT-R that he initially was a "I want to go twins for response and convenience" on his stock 2.6 with Kelford 272 cams, but his friends are pests and were always in his ear about their place being in the bin.   Eventually one of the 2860-5s decided to add it's own input and force his hand, so he conceded and went for a Pulsar 6262G ("G35 900") with T4 0.85 hotside.    Here's an overlay of the results, same cams, same stock bottom end, same boost, same fuel, just from a pretty tidy 2860-5 install to a Pulsar turbo on a 6boost maniifold on BP98.   Worth mentioning here, it may seem like a dead horse thing but the dyno plot doesn't tell the story of how much better it is to drive - transient response has completely changed the car, he used to have flat foot shifting to stop it having to wind up again on gear changes even at >7000rpm... now it builds boost faster than that even short shifting.   It's 100% transformed the car before you even consider how much better it holds on: Pulsar and Garrett aren't the same, but from our experience if you're just looking for a better drive and the ability to make the same or more power I think the divided G30 770 would probably be the smallest I'd go to.
    • robbo_rb180
      Neil's R33 Gts-t Build

      By robbo_rb180 · Posted

      Great work Duncan, any events local you will give it a test once all done? 
    • robbo_rb180
      Rob's S Chassis track cars. Now with more s15 and less 180sx

      By robbo_rb180 · Posted

      Sweet, yeah hoping stock gears will hold up. May use the transbrake feature on hill climb starts so that will test it.
    • GTSBoy
      What Bucket Seats Do You Have In Your R34 Gtt?

      By GTSBoy · Posted

      Yeah, the thread is only nearly 20 years old.
    • Duncan
      Neil's R33 Gts-t Build

      By Duncan · Posted

      Been down in Tassie for 2 weeks (a cruise, not a race for once) but spent a little time on her when I got back. I worked out the injector settings in the PowerFC were not correct for nismo 555s, set those to 66% +10ms and added a little air at closed throttle, set the timing (approximately, because it has some weird non 15o cells around idle) and now she starts and idles properly. She purrs like a kitten (ignore the co2 alarm in the background, I did  ) 20250518_171052.mp4 Next step, off for run-in, tuning and alignment!
×
×
  • Create New...