Fuel system rework changed rail pressure

pysical

Sergeant
Jun 16, 2017
350
76
0
Ride
2009 335xi E90
Originally I had two 450's in a bucket going through both stock top hats. Then it was 6an line to the engine with the e85 sensor in line. Here is the latest log with this setup: https://datazap.me/u/pysical/312-1?log=0&data=3-22


Then I removed the stock FPR, added a PR return setup with external FPR. I have 1 450 going through normal plumbing to power the venturis and then the 2nd 450 comes right out the top hat. Both pumps merge to a 8an line up to the engine. Here is log https://datazap.me/u/pysical/314-new-fuel-line-setup?log=0&data=3-22

So it seems like my low pressure isn't a issue. But my HPFP struggles. It tanks at around the time PI kicks on. I am not sure what the issue would be? I didn't think changing the fuel lines would make this big of a difference.


Does anyone know of some things that could possibly be wrong or worth checking? Or is this expected?
 

rev210

Corporal
Feb 24, 2019
159
70
25
Ride
335i - 08 Coupe .
Whats the E level of the fuel and FPR set at or are you using rising boost reference?

I run a boost reference myself.

Im close to hitting the limits of the bucketed stage3 on E85 , as rail pressure and lpfp pressures are dropping lower(still within a safe range) than say E20 (lfp in the 80s or high 70s) on same boost. But, its a warning sign.
 
Last edited:

pysical

Sergeant
Jun 16, 2017
350
76
0
Ride
2009 335xi E90
FPR is set to 72. I am not using boost reference.

I could always go with bigger pumps. But the rail pressure was good before all of this. No changes to the tune were made. I figured if anything it would be better since the fuel system is less restrictive now.
 

rev210

Corporal
Feb 24, 2019
159
70
25
Ride
335i - 08 Coupe .
Second log does have 5% more E and a psi or so of extra boost. So with no tune revision , you still are having a tune change if you are on flex. But, still it's a decent change. Frustrating but, possibly you are making more power and sucking the requisite amount of fuel to suit now.

If you have stage2+ turbos like me, you are likely needing to do as Martymil suggests. I am in that boat too.
 

pysical

Sergeant
Jun 16, 2017
350
76
0
Ride
2009 335xi E90
Actually its a 6466. But my car takes a few pulls to wake up before it starts running some consistent numbers. Also the only revision to the tune between them was some code removals.
 

noorj

Corporal
Jul 12, 2017
138
102
25
Detroit, MI
Ride
'07 E90 335i
wTell your tuner to give it more PI fuel across the board, especially down low where pressure dips and you won't have an issue any more. What size PI injectors?
 

JuniorB

Sergeant
May 9, 2017
343
111
0
Rhode Island
Ride
07 e60
-8 is a big hose, try keeping - 6 all the way. Your going to loose pressure going up is size. If the pump outlet is 5/16, and you put a 3/8 hose to 1/2, pressure will tank. The hard line in these cars are 5/16. All the way to the high pump. -6 for 2 pumps should be able to keep pressure.
 
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