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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > MHD stage 2 causing low fuel pressure



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      05-14-2016, 01:45 PM   #1
turekaj
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MHD stage 2 causing low fuel pressure

Here is the log with MHD stage 2 91(IC + catless downpipes)

Low pressure fuel supply dropped to 43 PSI on a pull. I have recreated it since to prove its not a fluke. Now back on the stock MHD tune until I figure out the issues.

http://datazap.me/u/turekaj89/fuel-p...zoom=2657-3511

I also saw timing corrections on Stage2 93 previously and dropped down to 91 octane.

Previous stage 2 log 93 octane:
http://datazap.me/u/turekaj89/log4?log=0&data=13-22


Here is a log with the MHD stock map tune
Fuel pressure never drops below 60
http://datazap.me/u/turekaj89/stock-run?log=0&data=4-13

Does this simply mean that i have a weak LPFP ? going on a roadtrip to Las vegas from Texas soon, don't want to risk the FP going out on the trip.

What do you guys think?
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      05-14-2016, 03:42 PM   #2
bpdef29
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It's likely weak and can't sustain the additional fuel needed to complement the increase in boost pressure.

I've had similar problems when flashing new maps. Resetting air/fuel and lambda adaptations post-flash keeps me out of the 40's and keeps my HPFP from crashing. Every car is different though. I still plan on replacing my LPFP soon.
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      05-14-2016, 04:24 PM   #3
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WEAK lpfp, nothing to do with MHD
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      05-14-2016, 11:48 PM   #4
hellokitty
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Quote:
Originally Posted by turekaj View Post
Here is the log with MHD stage 2 91(IC + catless downpipes)

Low pressure fuel supply dropped to 43 PSI on a pull. I have recreated it since to prove its not a fluke. Now back on the stock MHD tune until I figure out the issues.

http://datazap.me/u/turekaj89/fuel-p...zoom=2657-3511

I also saw timing corrections on Stage2 93 previously and dropped down to 91 octane.

Previous stage 2 log 93 octane:
http://datazap.me/u/turekaj89/log4?log=0&data=13-22


Here is a log with the MHD stock map tune
Fuel pressure never drops below 60
http://datazap.me/u/turekaj89/stock-run?log=0&data=4-13

Does this simply mean that i have a weak LPFP ? going on a roadtrip to Las vegas from Texas soon, don't want to risk the FP going out on the trip.

What do you guys think?
Looks like LPFP but I would like to see some longer WOT logs... looks like you were flooring it for a couple of seconds and letting off. I'd like to see the entire rpm range at 100%.

Stage 2 LPFP next so you can run some E85??
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      05-15-2016, 08:35 PM   #5
turekaj
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Here are 3 CSVS uploaded to one datazap log.

I did full 2nd gear pulls, but only partial 3rd gear due to speed limits. I realize that the higher RPM the more rail pressure is removed.

Note, I was having odd idles and some shaking at 4K rpms, so removed my previous "free blow off valve mod" and all the options in MHD except for cold start noise reduction.

Here are logs on stock map, stage 2 91 OCT, and stage 2 ACN91 (all v6.1 beta maps this time around)

Looking at the logs, Rail pressure never drops below 1500 psi, even when LPFP pressure drops below 50 psi. More so, there are no timing corrections at WOT in the stage 2 91 octane log. There are a few in OCN91, which is interesting. Also, I am running Shell V-power 93 octane gas .

http://www.datazap.me/u/turekaj89/lp...2-24&mark=2093
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