E89 Z4 dual lpfp in-tank?

dwspen01

New Member
Mar 8, 2017
6
3
0
Ride
2009 BMW Z4 35i DCT
Ok...so I have a 2009 Z4 DCT with upgraded turbos and FBO and just added Port Injection, all fuel lines upgraded and Walbro 535 in tank, with goal of 600whp on E85. I am using the 335i metal fuel line to the HPFP and an AEM fuel pressure sensor to a digital gauge to meaure fuel pressure. I am running 93oct and my low pressure is 48 psi at idle and never gets to 72 psi. It fluctuates under boost but then falls into the 30s and causes my HPFP pressure to drop to 400 psi around 4,000rpm at only 15psi of boost. I am getting ready to swap out my EKP for another but wanted to see what idle pressure others are seeing with the walbro 535 and see if anyone had any other ideas.
 

dwspen01

New Member
Mar 8, 2017
6
3
0
Ride
2009 BMW Z4 35i DCT
Thanks everyone for the feedback. Mechanic verified pressure at idle with a mechanical pressure gauge to be 72 psi. We realized that he installed a 150 psi sensor and I had my gauge calibrated for a 100 psi sensor so 48 on the gauge was really 72psi. For some reason the high pressure is crashing at 3000 rpm and drops below 400 psi at 4000 rpm on 93 oct and 15-16 psi boost so more testing tomorrow to diagnose and I will update with findings this weekend. Log attached.
 

Attachments

  • 2021-01-09 16_58_38 INA0S FF David_Spencer_INA0S_FlexFuel_N20_600RR_PI_V1_WBALM73519E38162.csv
    19.8 KB · Views: 2

dwspen01

New Member
Mar 8, 2017
6
3
0
Ride
2009 BMW Z4 35i DCT
My problem was a weak hpfp. Replaced today and all is good. Logged with 93 oct and sent to my tuner. Also have the Motiv Flex Fuel module so looking forward to having 1 tune to handle 93, E85 and everything in between!

Thanks again!
 

JuniorB

Sergeant
May 9, 2017
343
111
0
Rhode Island
Ride
07 e60
The demons and the shelbys run twin 525lp pumps, with boost a pumps. You leave so much on the table not utilizing the voltage needed to run these pumps, expectedly on a stock ekp, they definitely need voltage to really wake up.Not sure on like the 2021 modules, but there were info on what they run, there not on facto wiring without a little help.