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RB25 hitting R&R or air cut?

CGraves
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CGraves Newbie

CGraves

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RB25 hitting R&R or air cut?

Hey guys I'm having a problem where my RB25 is hitting either hitting rich & retard or an air cut based on my research. It's a completey stock RB25 with a manual boost controller, Walbro255 and FMIC.

I had a dyno day today so I got a manual boost controller and turned the boost up to 11 PSI and it made 230hp and 180ftlbs so obviously something is wrong. It will get to about 6000RPM under full throttle and then hit some kind of cut and refuse to rev any higher but if you go partial throttle you can rev all the way to redline but it will hold 11lbs so it's not leaking boost or a broken waste gate. 

I drove it home and tried removing the boost sensor because maybe the ECU was switching to a knock map because it was seeing too much boost but that didn't fix the problem. I turned the boost back down and I'm getting a steady 7 psi but I'm still hitting some type of cut at 6000rpm at full throttle but it will rev fine under partial throttle. 

I read somewhere that it might be a laurel maf which is smaller than the Skyline maf so it would max out on air flow a lot quicker? I was wondering if anyone could corroborate that. I feel like it's maf related either way but a fresh set of eyes on this problem can't hurt regardless. 

Edit: I don't know if it's relevant but I have a printout of the dyno sheet and it's definitely not happy. I can post pictures if it'll help. 

Edited by CGraves
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Bennyr32gtst Rookie

Bennyr32gtst

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I'm having the exact same problem at the moment under throttle at 6000 I'm getting a splitter and boost cut out I thought for some reason it may have to do with wastegate maybe being seized or stuck open going to have a check on it tonight

CGraves Newbie

CGraves

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@nizmo

It's a stock RB25 ECU with no tune. My friend loaded his Nistuned chipped Z32 ECU with a stock map and we tried to run it and it was running so insanely rich that any throttle would flood it. So I'm not sure if there was a problem with his ECU or my car.

CGraves Newbie

CGraves

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@89cal

From my understanding the ECU learns the new map from knock sensors after you reset? I don't have any knock sensors and I put a 500ohm resistor on the knock sensor so the ECU doesn't see anything wrong. Is resetting the ECU still advisable?

CGraves Newbie

CGraves

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@89cal

I didn't get a lower harness with my engine so I don't have anything to plug into the knock sensor. 

I did some reading and it seems like if I reset my ECU then it will keep trying more aggressive maps until it detects knock so I don't think that's gonna work.

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