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Rb25 Stalling Momentarily

Marcus89

By Marcus89,
in Engines & Forced Induction

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Marcus89 Proficient

Marcus89

Posted
Posted

My r34 rb25det neo has decided to develop a strange issue where I will be drifting and when I shift gears from 2nd to 3rd mid drift it will stall out just for a second causing it to bog down. Initially it happened rarely at the start of the night but got progressively worst as the night went on. It got the to point where clutch kicking it in 3rd (after having shifted 2nd to 3rd and had the stall out) would cause the same issue to happen again rather than for the car to start hooking up like it had done earlier in the night. I went to pits to try and find any potential air leaks or something along those lines but could not find anything and the car idles perfectly beautifully does not hunt. After being in pit for about 10 mins took it out for a run and it seemed to have no issue at all. Went for another go and the issue was back again.

Whenever I drove normally ringing out 1st, 2nd and 3rd gear there was no noticeable issue it only presented when I was drifting.

Engine mods are as follows:
Nistune
3inch turbo back exhaust
Hypergear g2.5
Bosch 550cc injectors
Oil cooler
FMIC
52mm Alum rad
Bosch 023 fuel pump
Still running recirculating BOV

I feel a likely culprit could be the fuel pump being on its way out. Does anyone think a fuel pump that's starting to run out of steam would present with these kind of issues?

Another option I was thinking was that my recirculating BOV could be leaking air out as some of the piping is a bit average and this could be a big enough difference for it to confuse the ECU as it doesn't see the air that it expected to be there.

I really wish the issue was something more obvious/severe as it seems so vague I don't really know where to start and unfortunately don't have the money to just start changing everything (crap job and going back to uni). In the end it is my daily and still drives perfect for daily duties at least at current.

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https://www.sau.com.au/forums/topic/444378-rb25-stalling-momentarily/
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robjen Rookie

robjen

Posted
Posted

Might be completely off track here but a log truck I was driving did this cut out thing. It was too quick to log a fault code so after 12 months of looking poking, trying and several trips to cummins and brown and hurley and anyone else who might know something it ended up being the fuse holder in the battery box. Pliers on the fuse holder, squeeze, insert fuse, never another problem. Maybe not the problem but I always start by shaking fuses.

Ben C34 Grand Master

Ben C34

Posted
Posted

Does it come off boost with gear changes and is the rpm around the 3k mark, if so the mixture could be leaning out slightly when you come back on throttle. Just a thought.

Is that based on something?

If the ecu Is tuned correctly there won't be any weird lean spots.

Ben C34 Grand Master

Ben C34

Posted
Posted

Unless something is not doing/ or can't do what it is being told to do.

Of course.

I just wondered because you were specific with the 3000rpms I thought perhaps you had experienced or heard about something .

XGTRX Veteran

XGTRX

Posted
Posted (edited)

Of course.

I just wondered because you were specific with the 3000rpms I thought perhaps you had experienced or heard about something .

Just mentioned it because especially in the OP's description it seems to be happening at a point where it may be transitioning off boost to on boost where if things aren't spot on a temporary lean condition may occur which is consistent with the occurrences the OP is describing. Just a suggestion anyway.

Oh and a guy with a 200 that was street driven had to add a heap of fuel in this transition area when he started drifting but it couldnt be done on the dyno, had to be done on the street.

Edited by XGTRX
Ben C34 Grand Master

Ben C34

Posted
Posted

Really it could be anything.

It could be reversion in the maf causing a rich conditon.

They are fussy when it comes to how the bov is plumbed back to the inlet.

Mine carries on a bit sometimes due to this, but being an auto doesn't cause problems and doesnt happen often. I am going to change the angle the bov return is attached to the inlet pipe to make it point as much towards the turbo autos possible.

Trex Grand Master

Trex

Posted
Posted

How much fuel did you have?

I had this problem when the filter at the end of the fuel pump was a tiny bit higher than stock, it would get worse the lower the fuel got.

skylines and stageas suffer from a lack of fuel when throwing them around. May need a surge tank?

rondofj Veteran

rondofj

Posted
Posted (edited)

I have a 34gtt that does this on downshifts and especially under load, it bogs down for 3-4 seconds and loses 60% of power or even more, its that bad. I have recently found it sometimes does this on up shifts as well but only under load when shifting a bit early up an incline etc. My tuner found the map tracer cell in my power fc jumps 5 cells when it does this, pinpointing to a high voltage drop in my z32 which is possibly measuring more air from b.o.v. reversion n causing the ecu to retard timing n add more fuel. He said it is most likely my bov angle pipe causing afm reversion- not an ideal entry angle- see pic

post-49401-14028386776606_thumb.jpg

Edited by rondofj
Marcus89 Proficient

Marcus89

Posted
  • Author
Posted

Cheers for the tips guys. I was thinking of BOV reversion being a potential issue rondofj I guess the easiest way to suss that out would be on a dyno although seems a bit strange it only really does it when I am sliding. I have put the BOV return pretty far down the intake pipe but it doesn't point that much towards turbo which isn't good.

I don't think it is fuel surge as I feel it would be even worst when transitioning back the other way and not just grabbing a higher gear while maintaining the same slide which doesn't really slosh the fuel around much.

I've started to think it may actually be a small intake leak that opens up more on boost causing the car to run real rich on boost (Will be doing a intake pressure test soon as it's easy and free)

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