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385 Posts
Hi,
I'm hoping someone else has had this same issue and can give me some ideas.
Firstly my R33 GTR has new GT2860-5 turbos, an Apexi Power FC (mapped by myself) and possibly more important the dump valves blanked off.
When driving the car pulls like a train, all datalogging shows perfect AFR's (AEM wideband fitted) and using datalogit with the Power FC all readings are fine....I run a very conservative tune with knock readings never going above 20.
The issue I have is that if I bring the revs upto around 2,800rpm without any load so just sitting in neutral, the fuelling is perfect around 14.5 and the engine runs sweet but if I hold it there for a few seconds suddenly the wideband reads 10.0, the revs drop and the engine starts misfiring from excessively rich mixture, it then clears after a few seconds and the revs climb back to around 2,800-3,000rpm and the cycle repeats.
I recently fitted the new turbos myself and fitted all new gaskets, I have smoke tested the engine and have no leaks, I have fitted new RB25 MAF's with new Apexi filters and the issue is still there.
It doesn't normally bother me as I drive to the track, spend the day at mostly around full throttle and then drive home but I went for an unusually leisurely drive earlier and every time I was trying to cruise at around 3,000rpm with a very slight amount of throttle I could see the wideband switching to rich and then clearing and I could feel the engine surging slightly.
It isn't a major issue but one I would like to get sorted and after driving backwards and forwards up and down the A5 today datalogging etc I can se no reason for it so hoping someone else may have some ideas I haven't thought of.
Thanks,
Edward.
I'm hoping someone else has had this same issue and can give me some ideas.
Firstly my R33 GTR has new GT2860-5 turbos, an Apexi Power FC (mapped by myself) and possibly more important the dump valves blanked off.
When driving the car pulls like a train, all datalogging shows perfect AFR's (AEM wideband fitted) and using datalogit with the Power FC all readings are fine....I run a very conservative tune with knock readings never going above 20.
The issue I have is that if I bring the revs upto around 2,800rpm without any load so just sitting in neutral, the fuelling is perfect around 14.5 and the engine runs sweet but if I hold it there for a few seconds suddenly the wideband reads 10.0, the revs drop and the engine starts misfiring from excessively rich mixture, it then clears after a few seconds and the revs climb back to around 2,800-3,000rpm and the cycle repeats.
I recently fitted the new turbos myself and fitted all new gaskets, I have smoke tested the engine and have no leaks, I have fitted new RB25 MAF's with new Apexi filters and the issue is still there.
It doesn't normally bother me as I drive to the track, spend the day at mostly around full throttle and then drive home but I went for an unusually leisurely drive earlier and every time I was trying to cruise at around 3,000rpm with a very slight amount of throttle I could see the wideband switching to rich and then clearing and I could feel the engine surging slightly.
It isn't a major issue but one I would like to get sorted and after driving backwards and forwards up and down the A5 today datalogging etc I can se no reason for it so hoping someone else may have some ideas I haven't thought of.
Thanks,
Edward.