Roadrunner_GTI
Drag Racing Champion
You’d definitely benefit from auxiliary fueling. Injector times above 8 are approaching the max duty cycle of the injector.
6
GTI (K04) Fuelling Issue? Advice Wanted, Datalogs Inside.
- Thread starter davisharr
- Start date
davisharr
Go Kart Champion
Yeah I purposefully stopped where I did, I wanted the max power you can get outa stock fuel system, I don't want to dive any deeper, I know there's power to be gained but you gotta set a hard stop somewhere. The cars fast enough, when healthy it spins my PS4S's through 3rd. I'd way sooner spend money on a LSD then any more power.
Just gotta get it back to where it was before this issue. It was perfect to me.
brat_burner
Autocross Champion
Do you know what exactly that 's' measurement is?
davisharr
Go Kart Champion
I notice between the healthy, and not healthy runs, on the unhealthy ones, the Fuel Rail Pressure Request is notably lower than on healthy ones. So not only is it getting less fuel pressure, but thats actually what its asking for. I don't know if that means anything. But something I noticed...
I am really tempted to throw a LPFP at it and see what happens. Anyone know if there are any tests you can do of LPFP performance besides just replacing and see what happens?
Also, I thought of something today, this all began to happen after my area got some new gas available, Shell 93, which is about 8-10% ethanol. I ran a few tanks of it, began having this issue, and blamed the ethanol content and it's effect on fuel volume needed, and the fact that I am right at the limit of the fuel system as is. I switched back to Shell 91 0 Eth. which is what the car was originally tuned on, but the issue never went away... Is it possible I overstressed something trying to adjust and pump that increased volume, and when switching back to the known good fuel, it was too late as that component was already damaged a bit. Perhaps the LPFP? Not sure, but does the theory make sense to anyone?
I am really tempted to throw a LPFP at it and see what happens. Anyone know if there are any tests you can do of LPFP performance besides just replacing and see what happens?
Also, I thought of something today, this all began to happen after my area got some new gas available, Shell 93, which is about 8-10% ethanol. I ran a few tanks of it, began having this issue, and blamed the ethanol content and it's effect on fuel volume needed, and the fact that I am right at the limit of the fuel system as is. I switched back to Shell 91 0 Eth. which is what the car was originally tuned on, but the issue never went away... Is it possible I overstressed something trying to adjust and pump that increased volume, and when switching back to the known good fuel, it was too late as that component was already damaged a bit. Perhaps the LPFP? Not sure, but does the theory make sense to anyone?
Roadrunner_GTI
Drag Racing Champion
It’s milliseconds, meaning how long the injector is open during each pulse. It’s also known as injector window, or the window of time the injector has to open.
Roadrunner_GTI
Drag Racing Champion
Your LPFP duty cycle is much higher (~90%) than I’d expect it to be (mid-70s). Could be a plugged fuel filter, could also be the pump itself.
davisharr
Go Kart Champion
Did a filter 2 months ago as part of diagnosing this, no change. When I first got the tune and the car was healthy LPFP duty cycle at most was 88%. Now it often pegs at 92%, not that big of a difference, but it does seem 92% is the max it will ever go, and it is easy to get it there even at part throttle. I wish I had idle and part throttle from when it was healthy to compare. At warm idle its about 55%. The way I understand it is LPFP max varies by tunes, some tunes the most you ever see is in the 70's, others in the 90s, I think perhaps its scaled different by different tuners or suites. But you are Cobb and Stratified like me so if yours at most is ever in the 70s thats interesting.
Roadrunner_GTI
Drag Racing Champion
I would expect our LPFP to be similar in terms of duty cycle. I always hate throwing parts at a problem, but if it’s the original one it wouldn’t hurt to replace it. For reference, I replaced mine last year because the check valve went bad and caused intermittent long starting.
davisharr
Go Kart Champion
Thanks for your input. I really am leaning this way. It would kinda explain why it keeps up in a full pull but not when you shock it with dropping a gear, pump doesn't have time to build the pressure in lines and so the rest of the system starves. When you do a full cycle from low RPM up, its slow enough of a process for the pump to attempt to keep up and at least be close. I'm off on vacation out of town for a few weeks here so I have some time to think it over while the car sits, but I'm really leaning towards trying this...
