The car isn’t misfiring or breaking up but i’m like 95% sure it should be higher even at idle. In one of the logs it did touch 55-57 psi during WOT and i feel like it’s causing the hpfp to work harder. I threw out the original one like a dummy man …
LPFP Psi Too low?
- Thread starter Bimmerny
- Start date
It may not be at the perfect factory specificed pressure but im sure even they have a range listed. As long as your low pressure is oscillating and not just taking a steep dive and staying low your ok. And obviously if your hpfp isn't crashing you've got enough fuel. The low pressure sensor on the n54 is in a difficult spot. Speculation says that because the low pressure sensor is so close to the pump that the vibration from everything and demand and pull changes from the hpfp cause it to oscillate that way. It really needs a pulsation dampener or to be relocated to smooth it out. Even with all of my work done i still have oscillations but, they are greatly reduced. The injectors also add to the oscillations from their own pulsing and being right next to the cylinders will add to it. From an engineering standpoint, it is accurate. It gives an unfiltered raw image of what's happening to the fuel at the pump. I wish we had a log on a completely stock car just for baseline comparison.
so the bucketed DIY needs a T fitting ; one side to the venturi and the other to the fuel line to the HPFP.
The T fitting and the 90° fitting got the same connection and can be connected to the n54 fuel line. When my venturi line poped out, Ive removed the T and plug the 90° directly to the n54 fuel line.
now im back to the T fitting so I can run low fuel level, and randomly this morning I was at 72psi even with the venturi....
Last edited:
Thanks a bunch, i may have to replicate this since i’m also bucketed. Looks very clean and seems to work well if you are hitting 72 psi
last picture not mine, but 2 first yes. I dont have clear pictures.
For now it works, and I can daily the car.
From my last hose faillure, Ive attached it with ziptie around the venturi a little bit like this DIY + a hose clamp : https://www.1addicts.com/forums/showthread.php?p=22273254
To report the limit of my fuel system. Not sure if it still the venturi valve that cause issues, or simply maxed out my setup.
- HPFP drop to 5 ( 5x 150psi = 750psi), normally we want around 1200psi minimum at high rpm and wot.
- LPFP went from 72psi to 54psi.
- Trims went up.
However, before this big drop, timing jumped to 6.7° to 7.5°.
AFR are good, probably because of the meth injection.
Still annoying, this is around 480whp, I was expecting a bit more from a 94oct fuel + meth 50/50 + 450walbro. On a 6262bb gen2 turbo.
I'll drill out 1/16'' the fuel rail to see if I can get a couple hundred psi.
- HPFP drop to 5 ( 5x 150psi = 750psi), normally we want around 1200psi minimum at high rpm and wot.
- LPFP went from 72psi to 54psi.
- Trims went up.
However, before this big drop, timing jumped to 6.7° to 7.5°.
AFR are good, probably because of the meth injection.
Still annoying, this is around 480whp, I was expecting a bit more from a 94oct fuel + meth 50/50 + 450walbro. On a 6262bb gen2 turbo.
I'll drill out 1/16'' the fuel rail to see if I can get a couple hundred psi.
Wow, you can run WOT at 750psi and not misfire? I thought misfires started occuring when rail pressure got down to around 1500psi, give or takeTo report the limit of my fuel system. Not sure if it still the venturi valve that cause issues, or simply maxed out my setup.
- HPFP drop to 5 ( 5x 150psi = 750psi), normally we want around 1200psi minimum at high rpm and wot.
- LPFP went from 72psi to 54psi.
- Trims went up.
However, before this big drop, timing jumped to 6.7° to 7.5°.
AFR are good, probably because of the meth injection.
Still annoying, this is around 480whp, I was expecting a bit more from a 94oct fuel + meth 50/50 + 450walbro. On a 6262bb gen2 turbo.
I'll drill out 1/16'' the fuel rail to see if I can get a couple hundred psi.
Have you considered a PFS POD, or the Hydra hpfp overdrive mod?
1/16" is small, but still huge compared to the injector orifice. I'm not sure how much extra capacity you'll get from drilling that out. But it doesn't cost anything to try.
might be a little off, JB4 using power draw to estimate the pressure.Wow, you can run WOT at 750psi and not misfire? I thought misfires started occuring when rail pressure got down to around 1500psi, give or take
Have you considered a PFS POD, or the Hydra hpfp overdrive mod?
1/16" is small, but still huge compared to the injector orifice. I'm not sure how much extra capacity you'll get from drilling that out. But it doesn't cost anything to try.
max pressure I saw is 1950psi (13 x150psi).
750psi is typical to idle, or light throttle.
So yeah quite low on high rpm. afr was still low, so seems the fuel delivery+meth was enough to avoid missfire.
