RB25 loss of power at 6kRPM

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Joined: Wed Apr 05, 2017 6:51 pm
Car: RB25 swapped 260z

RB25 loss of power at 6kRPM

Postby CGraves » Wed Apr 05, 2017 7:01 pm

RB25 hitting R&R or air cut?

Hey guys I'm having a problem where my RB25 is hitting some type of cut based on my research. It's a completely 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 all the way to rev limit under partial throttle.

I feel like it's maf related either way but a fresh set of eyes on this problem can't hurt regardless.

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Posts: 209
Joined: Tue Oct 26, 2004 9:38 am
Car: 1997 Pickup XE 2.4L 4x4 Single cab short box
1991 BNR32 Skyline GTR
1991 240sx SE SR20DET + S13 Silvia Front end swap (Sold)
Location: Stafford, VA

Re: RB25 loss of power at 6kRPM

Postby ericherm1 » Sat Apr 08, 2017 9:22 pm

Sounds like air flow. I would check your MAFs and also check for vacuum leaks.

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