HPFP crashing?


New Member
Aug 23, 2023
Hey guys, having some trouble with my high side fuel pressure and was hoping for some help.

The car is a N54 335i, TD03-15T turbo, PR Stage 2 LPFP. 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. My BRO table is full stock, and the fuel scalar was what was needed to keep my STFTs close to zero. 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.

I have also attached my BINs for each of these logs.


  • MHD_TD03_17PSI_Map_Rev5.bin
    2 MB · Views: 6


New Member
Feb 25, 2024
Hello im new here! and to the n54 platform i am familiar with BMW'S as ive had many e46s, F30 n20,e90 n52's IM having the same issue IM MHD stage 2+ FBO no outlet/inlet i got the car stock in limp mode i bought at 132k now it as 134k once i added bolt ons and found out MY VSRF charge pipe was causing 30ff code switched to arm charge pipe it fixed issue but added more issues with fueling that's how i found out my injectors were bad/leaking replaced with new ones i changed most maintenance items(prone to fail components) ex( HPFP used unsure of miles, INDEX 12 i changed them between different sets to ensure that wasn't the issue, LPFP STAGE 2 precision race works & Also converted back to stock fuel pump as of now did not fix issue, step 1 colder sparks triple checked GAP there new, Coil packs, fuel regulator, VANOS solenoids, PCV) everything else i replaced shouldn't affect cyl 6 im getting 29D2 & 29D9 my good friend/mechanic says maybe my hpfp is capable of stock maybe stage 1 power not stage 2 plus power i have not tested this theory out as i just found this issue and have work, My car drives OK in drive maybe 30% throttle it may bog a little any more it will misfire it will stutter like im hitting the bumps on the side of the freeway only CYL 6 if i go in sport it will stutter even worse as of now driving in "D" it goes to moderate speeds i cannot do a quick overtake incase of bad drivers or merging onto freeway or i will misfire plz help! IM not sure how this relates to you but my rail pressure averages about 680-720 i went in my buddies car custom tune FBO upgraded turbos stock fueling other than index 12 his averages 720 minimum average it goes low but never like mine