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Fuel Pressure Dips at WOT (Not Meeting Requested)

OhioMK6

OhioMK6

Ready to race!
I've been protuning my K04 via Stratified and I've been having some fueling issues. Perhaps someone has experienced something similar and has found a solution or can point me in the right direction.

On full WOT pulls, usually in 4th gear for example, my car will fail to supply enough fuel some of the time. When this happens, actual rail pressure can be 300-500 PSI below requested. My injection times skyrocket, AFR's lean out, and my STFT rise to 1.25 (25%) My tune has been dialed back, but it still occurs, so it seems to now be a hardware issue. Has anyone experience this? If so, was it your HPFP, LPFP, injectors, or other? I've change the fuel filter and cleaned injectors to no avail.

I made 296WHP/320WTQ on a Mustang dyno, which shouldn't be the limits of stock fueling from what I've seen on here. I'd like to replace my weak link and get the car dialed in, but I'm not sure what to replace.
 
OhioMK6

OhioMK6

Ready to race!
Cadubya said:
LPFP controller faulty or LPFP dying.
Click to expand...

My LPFP controller doesn't seem to get hot. Can they fail intermittently without overheating? Also can the LPFP lose efficiency with time? Some pulls are perfect, while others lack fuel pressure.
 
OhioMK6

OhioMK6

Ready to race!
Anyone else have insight? I don't want to fire the parts cannon at it, but I want to order either a LPFP or HPFP.
 
OhioMK6

OhioMK6

Ready to race!
mraaf said:
LPFP
Click to expand...

Okay that's two votes for LPFP. It's weird that my LPFP Duty Cycle is only in the 70's during pulls. I figured if the pump was being asked for too much, the duty cycle would be higher.
 
DallasDub94

DallasDub94

Go Kart Newbie
My lpfp duty cycle reads in the 70s on my Stratified stage 2 tune with a ported ihi turbo on pump gas. I'm in agreement with everyone else that it's probably your lpfp. However, when was the last time you replaced your fuel filter... It could be clogged?? My lpfp was working! Before I changed my fuel filter... Low-mid 90s duty cycle, and that was running less boost than I am now.
 
OhioMK6

OhioMK6

Ready to race!
U-20T said:
Highly doubt lpfp, you need to look at injection time MS. And momentary fuel trims.
Click to expand...

Yeah I see +25% maxed out short term fuel trims and high injection times (I’ve seen up to 13ms) when this occurs.

It seems to happen when I do a pull starting completely off the throttle and then immediately going WOT. Fuel pressure seems to struggle going from 700PSI while coasting to 2000+ PSI so fast.
 
M

Mk6 Steve

Ready to race!
Do you get fuel cuts/misfires when this occurs?
 
OhioMK6

OhioMK6

Ready to race!
Mk6 Steve said:
Do you get fuel cuts/misfires when this occurs?
Click to expand...

No misfires, but the car slows acceleration because the tune pulls things back to save it from completely leaning out.
 
M

mraaf

Passed Driver's Ed
OhioMK6 said:
Okay that's two votes for LPFP. It's weird that my LPFP Duty Cycle is only in the 70's during pulls. I figured if the pump was being asked for too much, the duty cycle would be higher.
Click to expand...

I believe duty cycle varies depending on tune. Revo maxed out at 91.4%. Yours probably maxed out at 70% idk. A worn out LPFP won't be able to supply sufficient flowrate at 4-6.6 bars required for the HPFP.
 
OhioMK6

OhioMK6

Ready to race!
Update:

Nothing has fixed the issue.

I've replaced LPFP, LPFP controller, HPFP, Fuel Filter, O2 Sensor, and cleaned the MAF. Anyone else have any thoughts? If I roll into throttle it doesn't happen, but if I punch the throttle after being off throttle the rail pressure struggles to build pressure.
 
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