N54 HPFP Crashing


New Member
Aug 23, 2023
Hey guys, having some trouble with my high side fuel pressure and was hoping for some help. I posted before in the troubleshooting forum but didn't get any replies, so was hoping I could get some help here.

The car is a N54 335i, TD03-15T turbo, PR Stage 2 LPFP (retaining venturi). When running 98RON through the motor at 17 psi, my rail pressure is above 1700, however after mixing in E30/E40 the rail pressure now tanks hard on 19psi. I have replaced the HPFP with a used unit (120k kms) and replaced all 4 O2 sensors, both with no effect. Really unsure what could be causing this sharp rail pressure drop. Could it be because I am ramping in the boost too quickly, drying out the HPFP?

I am self tuning the car, and have not touched the BRO table, and the fuel scalar was what was needed to keep my STFTs close to zero. I had leaned out the AFR target to 0.8ish lambda. AFAIK there aren't any other "fuel" tables that I could have screwed up?

Also, unsure what would be causing the different lambda between banks. I have replaced the O2 sensors hoping that was the problem, however have been unable to confirm if that fixed the issue as I have misfires when trying to log the car. I don't think I have a leaky injector as the cold starts are fine, and the AFRs return to 256 off throttle in tandem.

Any suggestions/advice would be appreciated, thanks!

Here is a log of 17 PSI on 98 RON and a log of 19 PSI on E40, both taken before I replaced the O2 and HPFP.


  • MHD_TD03_17PSI_Map_Rev5.bin
    2 MB · Views: 3
  • 21PSI_E40_V4_MHD_15T.bin
    2 MB · Views: 7
Last edited: