HPFP issue or restriction on low pressure side?

[bradsm87]

https://datazap.me/u/bradsm87/rev50?...0&zoom=231-300

I'm very disappointed to say the least that my rail pressure has fully crashed by 6500 at 17psi. I have some later logs where it even does it at 16psi. I'm only running E25. I've heard of plenty of people running 21+ psi on E40 without TBI or PI.

I've only ever heard of HPFPs failing with more noticeable issues such as long cranks and sudden fuel pressure drops. I don't have any such issues. Has anyone heard of HPFPs slowly wearing with the only symptom being a lower flow limit? I haven't.

LP fuel pressure on most of my logs is around 60psi at high RPM and load. If I go down the path of replacing the fuel filter in the hope to get the LP pressure higher, is that likely to help? I think of course it would but I hear time an time again that it's fine as long as it's over 50psi.

I'm at a point in my life where I truly, truly hate working on my cars. Nothing would be more frustrating to me than replacing things and finding out they did nothing to help.

Thoughts, findings or opinions?

[Payam@BMS]

No jb4 right? What is your lpfp setup? Never seen hpfp take a $#@! that bad unless it was already dying.

[iminhell1]

I'll go with problem on the low side.

I'm FBO + inlets and on a single 450. But I also have the upgraded feed line and new filter.
I'm pump E50 and I've been running a tune that will hit 29psi most of the Summer, hit or miss is pressure crashed. So long as my IATs where above about 90*f I was good. Any lower and i was making too much power and pressure crashed, flat out out of HPFP capacity.
My HPFP is factory stock far as I know and right now I'm sitting at just under 100k on the car.

So based on mine, I'd say you need to see about the low side before tackling anything else.

[bradsm87]

I'll go with problem on the low side.

I'm FBO + inlets and on a single 450. But I also have the upgraded feed line and new filter.
I'm pump E50 and I've been running a tune that will hit 29psi most of the Summer, hit or miss is pressure crashed. So long as my IATs where above about 90*f I was good. Any lower and i was making too much power and pressure crashed, flat out out of HPFP capacity.
My HPFP is factory stock far as I know and right now I'm sitting at just under 100k on the car.

So based on mine, I'd say you need to see about the low side before tackling anything else.

Have you got any logs that include low pressure fuel pressure?

[bradsm87]

No jb4 right? What is your lpfp setup? Never seen hpfp take a $#@! that bad unless it was already dying.

Flash only. Fuel-It Stage 2.

It's the exact same sympton as when the stock LPFP ran out of flow. LP fuel pressure drops then HP dies hard. That's what makes me think it might just need a bit more LP fuel pressure.

[NA55]

Rail pressure looks low for those boost levels.. I’m going to say it’s a failing HPFP..

[bradsm87]

Rail pressure looks low for those boost levels.. I’m going to say it’s a failing HPFP..

Yes very low rail pressure is the issue. Where it gets tricky is that low LPFP pressure leads to low HPFP rail pressure too (like when reaching the limit of the stock LPFP, HPFP rail pressure crashes).

[NA55]

Yes very low rail pressure is the issue. Where it gets tricky is that low LPFP pressure leads to low HPFP rail pressure too (like when reaching the limit of the stock LPFP, HPFP rail pressure crashes).

Your LPFP values are solid and shouldn’t be of any concern.. Everything else on the log look alright too so I don’t see any other reason why rail pressure would be so low..

[iminhell1]

Hopefully this is direct to the log, --> https://datazap.me/u/iminhell1/log-1...og=1&data=2-17

it should be 2017_08_27 23_39_58

I don't run out as much RPM as you're trying to push, no power to be made there. But as you can see on a tired HPFP but all up to snuff LP stuff you can push limits very far.
I never test E content, just fill from the pump and pray. I'm thinking these are on the low side of my target E50.
The LPFP in this is about a year old. Filter and line brand new.

In some later logs my HPFP really crashes and like normal I think it's the pump needing to be replaced. Then later on it's fine. Really hit or miss what it's going to do. I really feel it's something on the tuning side we don't have access to that's the problem.
I know for sure that if we had access to the LPFP tuning we'd do much better on worn HPFP's. All you have to do is look at the pressure traces and you know that the LPFP PID control is for $#@! on the stage 2+ pumps.

[Sticky]

So what's the verdict? Replace HPFP or a tuning issue?

[bradsm87]

Hopefully this is direct to the log, -->

https://datazap.me/u/iminhell1/log-1...og=1&data=2-17

it should be 2017_08_27 23_39_58

I don't run out as much RPM as you're trying to push, no power to be made there. But as you can see on a tired HPFP but all up to snuff LP stuff you can push limits very far.
I never test E content, just fill from the pump and pray. I'm thinking these are on the low side of my target E50.
The LPFP in this is about a year old. Filter and line brand new.

In some later logs my HPFP really crashes and like normal I think it's the pump needing to be replaced. Then later on it's fine. Really hit or miss what it's going to do. I really feel it's something on the tuning side we don't have access to that's the problem.
I know for sure that if we had access to the LPFP tuning we'd do much better on worn HPFP's. All you have to do is look at the pressure traces and you know that the LPFP PID control is for $#@! on the stage 2+ pumps.

I've also noticed some runs it doesn't go below 1700psi and others it crashes to 800. Your pressures look amazing in that log!

I doubt very much that it's a tuning issue as by that stage, both the LPFP and HPFP control is well and truly maxed at 100%.

So what's the verdict? Replace HPFP or a tuning issue?

Not tuning. Could be LPFP, Fuel filter, HPFP inlet filter or HPFP really.

I just lowered my boost. I don't have the time or money to replace expensive parts at the risk that it won't change anything.