Fuel system rework changed rail pressure

[pysical]

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?

 

[martymil]

Upgrade to dual 535 pumps with the secondary pump running a one way inline valve will sort your pressure problem permanently.

Or get a bpm4 and run them simultaneously which is best but expensive.

 

[rev210]

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.

 

[pysical]

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]

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]

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]

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]

-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.