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R33 Gtst Flat Spot

bean962

By bean962,
in Engines & Forced Induction

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bean962 Newbie

bean962

Posted
Posted

Hello all.

I am so angry I cant find the reason for this so I'm offering a reasonable reward for the soloutiion.

I have an R33 GTS-T and a massive flat spot at 4500 rpm until 6000.

I have replaced or changed:-

ECU

New Coil packs (for splitfires)

New Iridium plugs

AFM

CAS

Ignition amplifier

Knock sensors

The diagnostics say the ignition retards to about 5Deg at 4500 rpm and then goes back to normal 15/17 deg at 6000. Obviously during this period its running rich, so any ideas?

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https://www.sau.com.au/forums/topic/207039-r33-gtst-flat-spot/
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bean962 Newbie

bean962

Posted
  • Author
Posted

Sorry, I've only had a skyline for a week and I just thought the Aussie club would offer better advise than our UK forums.

The car is completely stock except big bore front pipe and de-cat pipe.

Is the problem likley to be the boost solenoid?

Regards

sik14 Enthusiast

sik14

Posted
Posted
Sorry, I've only had a skyline for a week and I just thought the Aussie club would offer better advise than our UK forums.

The car is completely stock except big bore front pipe and de-cat pipe.

Is the problem likley to be the boost solenoid?

Regards

does it just sound like its missfiring then clears its throat and pulls fine through the rest of the rev range?

bean962 Newbie

bean962

Posted
  • Author
Posted

Thanks for all your constructive replys

Yes it stutters at 4500 and then at 6000 clears its throat and bang....BHP up to 260

I've replaced the o/e ECU with a standard unit

The plugs are greddy

Standard boost

Ignition retards to 4 or 5 deg at 4500 and then goes back to 16/17 at 6000

The voltage on the AFM goes off scale at this RPM but the turbo pipes have been checked and no leaks found.

I'm buggered......

R33silverS2 Mentor

R33silverS2

Posted
Posted
I appreciate I can change the ECU to a Power FC but Nissan didn't design the car to run like this so fitting a power FC will only mask the problem and no diagnose the reason.

it won't 'mask' the problem... it will FIX the problem. The problem is your ecu - the standard nissan ecu is the problem. as covered many times it has factory protection wirtten into it which retards the timing and richens the mixtures when airflow exceedes a certain amount. you obvisoulsy have higher boost than stock to make 260hp, what boost is the car actually running? A power fc is a full replacement engine ecu not a piggy back so thier is no 'masking' so to speak.

edit: do you have a boost gauge or are you just using the standard one? stock should be 7psi and therefore your airflow metre should not be maxing out at this level.

mattymagoo22 Community Regular

mattymagoo22

Posted
Posted

Bean. Nissan designed the car to run exactly how it came off the production line. 3psi<4500 7>4500rpm, no big bore exhaust without a cat. The second you change the exhaust, boost,tubo, fuel pressure etc etc these are things that can potentially harm or in some cases destroy both the engine and the turbo. As mentioned before if boost is raised the cars ECU goes into R&R (richen up and retard timing) to prevent high cylinder temps and detonation which occur when outright power is sort after and none of the supporting systems are considered (AFRs, intake temps, injector duty cycle etc etc).

So to sum up, installing an aftermarket ECU or having a tune done is not masking the problem, it is simply getting the most from what you have SAFELY! the factory tune isn't designed for outright power, its a compromise between power, economy and longevity and by running the way it does its saying something isn't right I got to save myself and so the extra fuel goes in and the timing gets pulled out of it.

Cheers.

SLYDA Community Regular

SLYDA

Posted
Posted

AFM should read up to 5V i believe before maxing out (correct me if wrong) it may be 5.2V - Get a Power FC and a Z32 AFM .. or set ur boost 2 10PSI and dont touch it.. my series had the same problem for about 2 years... try running 14 or 15PSI and it seems fast up to 4500RPM then just died.. Found the car was far faster on 10PSI, now i have a HKS GT3037 Pro S on it.. and at 10PSI with a POWER FC.. all i can say is.. i wish i had of done this 2 years ago..

What you are talking about is called the FACTORY BOOST CUT.

Every member on this forum that has even slightly modified there skyline and upped the boost has encountered this problem

Yo-Yo Grand Master

Yo-Yo

Posted
Posted

As others have already said, it's your factory computer protecting the car from blowing itself up.

Any aftermarket replacement ECU will make full use of your modifications, piggyback air/fuel controllers will do the same thing to an extent, but nowhere near the level of a stand-alone engine management systems.

Most of the guys mention Power FC because it's arguably the most user friendly ECU, other brands are HKS, Trust/Greddy Emanage, Motec etc. just to name a few... all with various costs and pros and cons.

I have a Power FC in my r34 and never had a drama with it, I liked how it already had all the standard ECU maps like cold start and electrics eg. air con control, but let's you re-write the parameters of the factory ecu.

Any competent tuner can install these systems and effectively fix the problems you've been experiencing.

TTT Grand Master

TTT

Posted
Posted
I appreciate I can change the ECU to a Power FC but Nissan didn't design the car to run like this so fitting a power FC will only mask the problem and no diagnose the reason.

bahahaha...

but they designed the car keeping in mind that people would replace the front pipe and remove the Cat convertor all together right?

Brilliant.

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