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air/fuel/boost cut, but not afm!

FATGTS-R

By FATGTS-R,
in Engines & Forced Induction

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FATGTS-R Experienced

FATGTS-R

Posted
Posted

Now, I have a HR31 GTS-R which still has its RB20DET-R. The only mods apart from the factory fitted goodies are a 3 inch exhaust, pod filter, BOV, GTR pump and a non elec. boost controller.

By looking at the terrible state of the wiring, its obvious this car had many gadjets on it in Japan. It came out here with an FCON but it got junked.

The maximum boost I have ever got the car to hit was 10 psi. On average it will cut at about 7-8 psi.

If I am on the freeway in fifth and plant it, it might cut as low as 3-5psi.

Every workshop would just say "your air flow meter has maxed out". But I always thought this was strange because its a friggin GTS-R for f@cks sake, you would not think it would have such a low threshold for the AFM.

I asked another GTS-R owner what boost his car had when standard and he told me it was at about 14psi, thats sounds a lot better and feasible than my 7psi.

It has been on the dyno last week and is cutting as soon as boost starts to come on, like 1-3psi I assume because of the extra load of a dyno.

They put a multi meter on the AFM and it is no where near 5.0 volts when the cut hits. Renewed plug,cleaned element and tried again. Same thing happened.

OK, maybe the AFM is rooted. So different ones were tried and still the cut appears.

Put the ecu into diagnostics mode and it is saying that all is well, didnt give one single error.

WHAT ELSE COULD BE CAUSING THIS?

BTW, the cut is a hard cut. It is instant and brutal. nearly headbutt the steering wheel when it happens.

When it happens the accelerator will die, the revs start dropping as if i have clicked it into neutral.

I have to take my foot completely off the accelerator and apply it again for the engine to come back to life.

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N I B Grand Master

N I B

Posted
Posted

Was the car very rich if it is fit an Safc and tune it,I found that i could lift the cut to 16psi doing this but very cold weather could bring it back to 13psi.We have fitted an aftermarket ECU now as the 31 ECU is a bit old and troublesome.The car stock cut at 12psi but the pod and exhaust cut this back to 4-5 psi.

FATGTS-R Experienced

FATGTS-R

Posted
  • Author
Posted

Funny you say that as my car was on the dyno with a/f ratios of between 9-10:1 so yes , its running extremely rich.

Are you saying the cut is caused by overfuelling and not too much airflow?

Because as I said the afm voltage is fine.

Also note that the cut out is very inconsistent, it will cut at say 7 psi, you back off and get back on and then it will cut at 2psi, then 3psi, then 8 psi then 1psi then........you get the picture.

FATGTS-R Experienced

FATGTS-R

Posted
  • Author
Posted

Thanks for the plug in info Steve.

Got in touch with Steve from AEM and apparently all I need is to have an adapter plug made up to join the pug in to my loom.

Can you verify that the car you are talking about was cutting, but the afm seeing max voltage was not the cause?

croat Mentor

croat

Posted
Posted

FATGTS-R i have same prob. went to a performance shop and they said "airflow meter mmaxing out". so i tried other airflow meter's and still problem and tried mine on mates cars and they ran fine. You know what it is: most performance shops could not give a ****, and cant be bothered putting decent time and effort unless you are mates with them. They all do something different and charge through the roof!

croat Mentor

croat

Posted
Posted

I have r33 gtst. fmic, full exhaust, dump pipe, boost cont. get a safc or full computer as the stock computer goes spastic when u boost it and usually dumps heaps of fuel or retards timing. i have a power fc at home but waiting for my turbo till i put it in.

Sydneykid Grand Master

Sydneykid

Posted
Posted

Hi fatgtsr, there is an endless list of possibilities. Throttle angle sensor, map sensor, water temp sensor, ignitor, coils, plugs, faulty wiring etc etc. As far as I know the GTSR has a Consult port, my first step would be to plug one in and run through all the diagnostics and check the sensor calibrations while driving. Your local Nissan dealer should have a suitable Consult or check with Impakt he has a made a few.....

http://www.skylinesaustralia.com/forums/sh...ead.php?t=42617

Hope that helps

FATGTS-R Experienced

FATGTS-R

Posted
  • Author
Posted

Well the car was taken around to AEM for Steve to have a look and get this plug made up.

He looked at the ecu and said it was different to what he thought and that an R32 and the VL plug in will not work as easily as he thought and with all the mucking around involved I would be better to just get the wire in version.

So I needed to make a decision as to what avenue I would take.

As I have spent a lot of money and time trying to track down this damn cut, so the workshop offered to wire in an Autronic for less than the price of the Wolf and i accepted.

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