I show 67 psi fuel pressure at idle and 62-63 psi at 14 psi of boost, AFRs are lean at 12.6+ right now
E36 M3 TT st 2 with aeromotive 340 fuel pump and stock FPR
before throwing a new FPR at this , just wondering if this could be caused by something else?
http://www.bmwmregistry.com/detail.php?id=13792
* E39 M5 SterlingGray -RIP 11/2018
* E36 328 vert Schwarz - ~TurboProject underway
* E90 335i Sedan MonocoBlau - Daily ToddlerTaxi
Vacuum line is an obvious first step, but that fuel pressure reading, if correct, is sky high. I've pulled 5 FPR from junk yard cars and tested them with wildly different results (ranging from 2.5bar to 4.35bar)... so it is possible your FPR is bad.
That said... I could never get the stock 3/2 valve setup to work properly with a high flow fuel pump. It over powers it. When you go to replace the FPR, make sure you use a new Pierburg only. Do not bother with a Bosch unit, they come out of spec (two brand new ones read 4.0bar on my bench tester). Don't be surprised if fuel pressure is still an issue, even with new parts.
Sounds to me like your pump is just overrunning the regulator at idle, which is when nearly all the fuel needs to go through the regulator. The pressure in boost is about right.
It’s going to make idle and part throttle difficult to tune. Should get an aftermarket regulator and then get a tune revision.
interesting thing is that it idles fine but AFRs are a bit lean in boost
A 340 wont overpower the stock regulator. Not from my experience anyway....450 is a different matter.
I'm running the 340lph from rally road. It definitely overpowers the stock 3/2 valve causing idle issues and rich conditions in boost. Went to the aeromotive 13109 and haven't had any problems since. I also had a lean condition at some point and it was the vacuum line going to the fpr. Make sure it is still in tact.
From previous builds I've seen, it looks the stock 3/2 valve can only keep up with the 255 pump. Anything higher than that should really have an adjustable fpr to be safe.
I wouldn't say it overpowers the FPR (I've never tested a standalone FPR before), but 340lph+ most definitely overpower the 3/2 valve setup. If I recall correctly, even a 255lph pump can cause issues.
You can disconnect the 3/2 valve from the fuel system when you install an aftermarket FPR, just leave the electrical connector connected to the 3/2 valve.
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