Hey Guys, I've been trying to diagnose a significant fuel cut under heavy load for 3 drift days now, and am finally at my point after failing miserably last weekend at summer bash that I need to try reach out for help.
I do apologize for boring anyone to death if they decide to read this post. I've pulled a 10minute log from the ecu and trawled through it to the best of my ability. From what I can see is the tps is all over the place. My foot couldn't even emulate how quick the massive fluctuations are on the tps. At some points I can see I'm on the limiter and can see really low tps %. The run starts at 7:40 and ends at 11.
Hopefully someone with a lot more know how with these logs can possibly tell me if the tps is one of the reasons why the cars dropping it's power that'd be a massive help. Otherwise I've outlined below what's been gone over in the fuel system to try eliminate a mechanical issue and or try put blame on the fuel system instead of the tps.
...........................................................................................................................................................................................................................
the easiest way I can describe what it's doing is as follows. I'll initiate and get into full boost and be able to hold the car on power while on the turn. Upon transition and firing off into the next corner the car will stutter like it's run out of fuel, if I mash my foot to the floor it won't pull through the stutter. In one case it was so bad even with my foot on the clutch and fully on the throttle the car wouldn't even rev up. Once I fully come off the throttle and back on I'll be able to accelerate again (Within a second) This issue has been getting worse and worse with each track day. (every time you transition it's like the high pressure fuel pump is turning on and off)
Fuel setup is bosch 1000cc inj, turbosmart fpr1200, aem 400LPH submerged in a Aeroflow 2.4L surge tank, walbro 335 lph low pressure lift pump in tank. The high pressure pump uses it's own power source / relay. The intank lift pump runs on the stock s15 wiring. Something I did repair before this event was the intank fuel pump wires heat shrink had slid down the wires, allowing those wires to potentially touch each other as they were solder joined. (no blown fuses presented or wiring damage) Bench tested the fuel pump to be sure and the flow seemed good, so repaired the wiring thinking I'd solved my issue. "not the case, in fact much much worse on the day"
Trying to include all details here so I can be singled out in the blame as well, so this is the bit where a finger can be pointed at a mechanical issue. I had recently dropped it off to the tuner to run it up again for the 3rd time trying to diagnose the issue, all 3 times there was no issues found on the dyno. All mixtures seemed perfectly fine. I noticed after the last dyno session the bung had fallen out of the fpr gauge and all of it's liquid had come out, admittedly i'd refilled it's fluid some years ago as the very same bung had popped out before. This time I replaced the gauge and fired the car up to find the fuel pressure to be at 26psi (vac plugged in). I could of sworn it should of been around 38psi with the vac on. so I was thinking maybe the fuel pressure was turned down by the tuner as the old gauge had no fluid maybe it was stuck reading high.
After attempting to drive the car on the weekend the fuel pressure gauge was now showing 18psi !! With me about to give up for the day I decided to try turning it up. It turned up to 42 psi with the vac unplugged and settled to 38psi when plugged in. Took it for a drive up the road and leaned on it holding the handbrake and foot brake and saw it did rise at 1.1 hitting a peak of 62 psi (22psi of boost), it held and didn't appear to drop off. So pushing my luck I jumped back on the track just to test one corner to see what it would do (same thing so ended the day way to early).
I know all of what I've said above presents like it's clearly a fuel pump issue, but to drain a 2.4L surge tank in 1 turn is pretty much impossible. The surge tank pump relay is triggered by the ecu, so should have uninterrupted power supply. All wires going to that pump had been thoroughly inspected and appear ok.
Where I'm at with it now is essentially replace both pumps & completely redo the wiring to both pumps. (get the injectors tested)
Removing the stock plug socket from the fuel pump cradle & put some bulk heads in so I know the fuel system can't possibly be the issue
heavy miss.llg
S15 RB25 tune file.pclr