Stage 3 fuel and still dropping pressures

shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
So I'm running the precision race works stage 3 LPFP setup with the CP-E PI (55# injectors) with N20 sensor on GC lite 2.0's, straight E85. Currently around 5000 or above RPM at 24 PSI of boost my LPFP pressures keep dropping into the 40's. It even does it if I run the pumps both straight at 100% output (wired straight to the battery). Full tank of gas as well.

The pressure always pops back up, but its annoying to see them drop like they do.

Here are a few logs:

https://datazap.me/u/shushikiary/gc...-no-boost-request-increase?log=0&data=3-13-23

https://datazap.me/u/shushikiary/1st-tune-change-gc-lite-20?log=0&data=3-13-23

https://datazap.me/u/shushikiary/gc-lites-20-3rd-gear-changed-recordings?log=0&data=3-13-23

I'm really thinking the restriction is somewhere else in the system, not the pumps, because they should be able to supply enough fuel. Is it in the fuel line from the tank to the engine bay? Is it in the stock FPR? (which PR sells an upgrade for): http://www.precisionraceworks.com/index.php?route=product/product&path=20_59&product_id=90

Anyone running these kinds of power levels who have experienced issues like this, I'd love to hear what you did to fix it. Thanks!
 
Last edited:

frontside0815

Corporal
Nov 9, 2016
126
48
0
Germany
Can´t really help with your Problem. Maybe your LPFP sensor is shot, because you seem to have enough fuel (if not your Rail pressure would dip).

But man they spool bad, why is that? Vargas advertises them as spool like oem... but your logs Show nothing like that.
 

shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
That is spooling like OEM. I think its the heat, look at the IAT temp, and the fact that I'm at altitude. They are spooling almost exactly like my stock turbos did in these conditions, welcome to low density air, lol.

The last few days have been 100 degree days, its rough.
 

shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
5280, ambient was 105 or so, 10% humidity. Which equates to a density altitude of 15373 feet 0_0 The tune isnt complete yet either, as you can see the WGDC should have stayed higher for longer as well, but fighting through these other issues has to be done first before trying to fix all that.


I'm using all the stock fuel lines
 
Last edited:

SlowE93

Lieutenant
Jul 2, 2017
644
226
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E93
Just a thought, maybe the fuel lines arent fully snapped in ? Bad O ring ? Seeping just a little pressure, or a tiny pinhole in fuel line that jumps the 2 lpfp together ?
 

R.G.

Lieutenant
Nov 17, 2016
669
325
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Henderson, NV
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E92 335, F10 M5
I can’t look at logs on this Zoolander phone but are you doing old school “gun it in 3rd gear pulls” or 1-2-3 pulls?

I ask because my lpfp dips hard when I do straight 3rd pulls (40s) with twin Walbros but stays in the 60s when it’s dig style logs
 
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buster84

Corporal
Mar 24, 2018
240
91
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335 bmw xdrive
So I'm running the precision race works stage 3 LPFP setup with the CP-E PI (55# injectors) with N20 sensor on GC lite 2.0's, straight E85. Currently around 5000 or above RPM at 24 PSI of boost my LPFP pressures keep dropping into the 40's. It even does it if I run the pumps both straight at 100% output (wired straight to the battery). Full tank of gas as well.

The pressure always pops back up, but its annoying to see them drop like they do.

Here are a few logs:

https://datazap.me/u/shushikiary/gc...-no-boost-request-increase?log=0&data=3-13-23

https://datazap.me/u/shushikiary/1st-tune-change-gc-lite-20?log=0&data=3-13-23

https://datazap.me/u/shushikiary/gc-lites-20-3rd-gear-changed-recordings?log=0&data=3-13-23

I'm really thinking the restriction is somewhere else in the system, not the pumps, because they should be able to supply enough fuel. Is it in the fuel line from the tank to the engine bay? Is it in the stock FPR? (which PR sells an upgrade for): http://www.precisionraceworks.com/index.php?route=product/product&path=20_59&product_id=90

Anyone running these kinds of power levels who have experienced issues like this, I'd love to hear what you did to fix it. Thanks!

I cant look at the logs since I'm on vacation and on my phone (annoying to use to look at) but I also have VTT GC 2.0s (yours are lites so even less cfm than mine) and I have pushed 30 psi (from overboost targeted 28) and my fuel pressure doesnt go below 60, there was a time it dipped to 58 but recovered right away later in the rpms.

I have the fuel it stage 3 setup with upgraded lines and fpr. I'm also running there pi setup and a race intercooler. I'd double check to make sure you dont have a clog anywhere in your lines, but as those power levels and running full e85 it's better to just upgrade them anyways because you might he tapping the maximum flow of the stock fuel line, fuel filter setup. Another possibility is your fuel pump bucket isnt getting enough fuel fast enough, maybe the venturi isnt working right?
 

shushikiary

Corporal
Jun 4, 2018
172
74
0
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335xi
This was on a full tank so the bucket couldnt go empty as the fuel level was above the top of the bucket.

I went ahead and ordered the fuel line upgrade from Fuel-It! and then got the precision race works FPR/fuel filter replacement setup. I'll also replace the walbro filters and the LPFP sensor while I'm at it just to be sure.
 
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Mar 14, 2017
418
346
0
Minot, ND
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2010 135i
The PR regulator and lines should remove any bottlenecks in the system for sure. I wouldn’t be surprised if its the fuel line size and OEM regulator causing your problem. Have you shorted out the trigger to make sure the pump is working?
 
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shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
Interestingly.... I dont have a trigger.

Originally I thought the issue was perhaps my PID algorithm, but I ruled that out when I tied them both straight to the battery to just run always on. When I did that testing I also tried each pump by its self to make sure both pumps were working right. Both got the same results running just 1 pump, so I know they are both good.

To explain, I have an arduino M0 that I wrote code for that uses its ADC to read the LPFP sensor voltage and then gives me a PWM output from a PID I wrote. The PWM output then goes to a dual half H bridge, one per pump, that can handle up to 30 amps continuous. So both pumps always run at the same time, there is no trigger.

The above resulted in the same as running both straight off the battery.
 

Lifestyler

Specialist
Nov 22, 2016
69
50
0
World
Ride
135i
Unless to Run Booth Pumps Same time everytime. They getting to hot also.

Run a hobbswitch 12~ psi or so
 

shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
They dont run full on 100% of the time, its a PWM controller with PID, so when you're at low load they run slow, but when you're at high load they they run faster. DC motors do very well with PWM control, usually their RPM is linearly related to PWM duty cycle, though pump flow and pressure are non linear to RPM.
 
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shushikiary

Corporal
Jun 4, 2018
172
74
0
Ride
335xi
Installed the new precision raceworks fuel filter an FPR setup.... much better:

https://datazap.me/u/shushikiary/pr-fuel-linefilter?log=0&data=3-13-23

Now I just need to get the check valve in the system figured out. Its not working for some reason so the fuel dumps to 0 psi immediately on ignition off. So I have to turn the ignition on the prime the lines, then quickly turn it off then start it from the off position (to avoid getting a 0x2ADC code because of the N20 sensor at altitude... joy). Built in theft deterrent?
 

roywillems

Private
May 18, 2017
43
40
0
Netherlands
Installed the new precision raceworks fuel filter an FPR setup.... much better:

https://datazap.me/u/shushikiary/pr-fuel-linefilter?log=0&data=3-13-23

Now I just need to get the check valve in the system figured out. Its not working for some reason so the fuel dumps to 0 psi immediately on ignition off. So I have to turn the ignition on the prime the lines, then quickly turn it off then start it from the off position (to avoid getting a 0x2ADC code because of the N20 sensor at altitude... joy). Built in theft deterrent?

I got the same problem with a external fpr, it is bleeding out the pressure, but not to 0 in a few sec. Also here is some info from aeromotive fpr:

6.) I’ve installed my new Aeromotive bypass regulator. Fuel pressure seems to adjust fine and holds great when the engine is running, but when I shut the engine off, pressure drops quickly to zero. Shouldn’t the pressure hold like it did with a stock regulator?
No, Aeromotive EFI bypass regulators may not seal perfectly when the pump is off. They are engineered for the highest possible performance when the engine is running. OEM regulators must hold pressure for 30-minutes after shut-down to pass EPA emissions standards. At Aeromotive we know our customers priority is to have the best possible flow and pressure control when the engine is running and we don’t compromise this standard to force the regulator to seal when the engine is off. If extended crank or hard-start becomes a concern, first allow the pump to run and prime as long as possible after turning the key to the run position, then start cranking the engine, just before the pump shuts off. If the priming cycle is too short to allow the engine to start easily with this approach, extend the priming cycle in the ECU if programmable, or ad a timer board or momentary button to the fuel pump run circuit.