Updates and struggling with an issue (help needed)...
Earlier mods this year:
Walbro 535 with Radium Check Valve on the outlet
New genuine tank filter/regulator assembly
Last week:
Replaced all vacuum lines (no leaks now, one was leaking probably a bit causing a little off from the boost target)
AN6 PTFE fuel lines with Radium 6um fuel filter
Ethanol sensor & Flex Fuel
HPFP filter removed
HPFP has a new seal
PFS POD installed with rails etc
I have retrofitted the LPFP sensor (replaced the hardline with with one with the sensor) to this Z4 so I can monitor LPFP side
Intake has all new seals
After the modifications car is stuttering at WOT and gives misfires. Rail pressure is oscillating heavily, we believe this is causing also the LPFP pressure to follow the same behavior. AFR values are also oscillating and following rail pressure, sometimes bank 1 and sometimes bank 2. Misfires were happening in cylinders 1(+2) and 6 (not same time), which is also suggesting eventually fueling (as POD HPFP hose comes to middle of the rail between injectors 3 and 4). I've done the high pressure adaptations, it did not help.
We changed the tune so that the rail pressure was dropped a bit (from 200bar/2900psi what it is asking). This stabilized the behavior a bit, I have not had misfires since and the car pulls better. I've taken 10+ logs with 20psi map (E45), rail pressure behavior has stabilized a bit. With 25psi map this is much clearer that the car does not pull smoot especially in the higher revs (about 5500rpm onwards). So drop of the rail pressure asking value made the behavior a little better...for me it looks like the high pressure side is not in control.
Logs after rail pressure lowering (without misfires):
First pull 20psi E45
Pull 12 20psi E45 rail pressure stabilized a bit (adaptation?)
Last pull 25psi E45 you can clearly feel that up top the pull is not smooth, rail pressure also bouncing.
Some troubleshooting done:
- I have chased the misfires with new spark plugs and bought a new coil also to chase this (I have Eldor B58 coils). Note that I did not have issues before the last week mods, so likely this is not the root cause.
- I took the injectors to a test bench end of last week, all came out good. I have all index 12, 1 new and 5 has less than 20k kilometers.
- No leaks (vacuum or boost).
- HPFP is genuine with ~5k kilometers (replaced last year). Worked OK before last week modifications.
Has anyone had similar issues (with PFS POD or Helix) and what has been the root cause? Or is this just typical after installing overdrive and it needs time to adapt?
P.S. Other observation was that the rail pressure increases sometimes when stopping the car and the POD starts then to rattle. This is a bit annoying. Anyone know about this issue?
I will also install Walbro 535 + inline filter with upgraded fuel lines (remove HPFP filter) when I get the car in the spring (April I think, I'm from Finland). I currently have Walbro 450 which has so far been OK. And I have another ekpm3 with thermal pads, heatsinks and fan ready also.
