Radium FPR Noise

[duracellttu]

Hey gang, a while back I installed the full Radium setup: rail, FPR, and filter. After driving the car for a bit I noticed that the FPR was making a groaning sound at idle and off throttle while cruising. Has anybody else experienced this, or know what is causes this? Radium seems to be aware of it but not sure if there is a fix to eliminate it.

Also, I noticed that there is a new FPR design that Radium recently released. Has anybody installed this? Wondering if this new design is a solution to the noise issue or if it will have the same problem.

I’m trying to figure out how to achieve 3bar of fuel pressure for the Bosch 550cc injectors I’m running with the OEM setup to avoid these weird noises, if possible too.

[BBRTuning]

I had the same issue, couldn’t really hear it with the engine running but definitely when running the pump. In the end I went back to the factory FPR but kept the rest of the Radium kit since the Radium regulator (actually an AEM regulator internally) just isn’t happy at 5Bar, it’s right at its maximum, the set screw is almost bottomed out. I datalog fuel pressure and it would vary quite a lot, if you turned the pump on 5 times in a row you’d get slightly different pressures each time and it would act like the diaphragm was sticking. Acted more normally at lower pressure. If you’re running stock fuel pump you also want to use the smallest orifice/restrictor insert.

For an NA engine you really want the high fuel pressure. I actually wanted to run a bit higher than 5 Bar as a test, maybe eventually I’ll look into a better high pressure FPR option. I’m also running the Bosch 550cc and they’re perfectly fine at 5Bar if tuned properly.

[duracellttu]

I had the same issue, couldn't really hear it with the engine running but definitely when running the pump. In the end I went back to the factory FPR but kept the rest of the Radium kit since the Radium regulator (actually an AEM regulator internally) just isn't happy at 5Bar, it's right at its maximum, the set screw is almost bottomed out. I datalog fuel pressure and it would vary quite a lot, if you turned the pump on 5 times in a row you'd get slightly different pressures each time and it would act like the diaphragm was sticking. Acted more normally at lower pressure. If you're running stock fuel pump you also want to use the smallest orifice/restrictor insert.

For an NA engine you really want the high fuel pressure. I actually wanted to run a bit higher than 5 Bar as a test, maybe eventually I'll look into a better high pressure FPR option. I'm also running the Bosch 550cc and they're perfectly fine at 5Bar if tuned properly.

Thanks for the input! I reached out to Radium and they know about the noise issue. They suggested changing the internal orifice to PN 14-0772 and attributed the issue to the restriction through the return lines. This supposedly smooths it out.

I'd much prefer to run a stock like setup. The specs on the Bosch 550cc injectors recommends 3 bar so I'm trying to stick with that. I am also running a stock fuel pump. I found a FPR from an older 318i PN 13-53-1-743-378 that shows a 3 bar spec and looks like a similar shaped design. Does anybody know if it will fit in our FPR housing? For $30 from FCP I might just buy one and see if it fits. My build is NA.

Can somebody refresh my memory, what is the stock FPR spec?

[BBRTuning]

I was actually recommended the smallest orifice by them, the smaller orifice should theoretically bring the pressure adjustment back into a more neutral range instead of the spring being almost fully compressed to achieve 5 bar, but it did only very little for me. If the restrictor was too small you'd have excessive fuel pressure and not be able to reduce it which I didn't find to be the case. Curious to see how the large orifice works which is what it looks like they're now recommending to you.

The Bosch 550cc are flow rated at industry standard 3bar like all injectors. There is no "recommended" fuel pressure for them, they can handle much higher than 5bar. There is a not insignificant power gain to be had running higher fuel pressure on highly tuned NA engines, which is likely why factory runs 5 bar. You can gain maybe 5-7HP on these engines by properly tuning the injection end angle which can only be achieved with larger injectors at high fuel pressure.

[duracellttu]

I was actually recommended the smallest orifice by them, the smaller orifice should theoretically bring the pressure adjustment back into a more neutral range instead of the spring being almost fully compressed to achieve 5 bar, but it did only very little for me. If the restrictor was too small you'd have excessive fuel pressure and not be able to reduce it which I didn't find to be the case. Curious to see how the large orifice works which is what it looks like they're now recommending to you.

The Bosch 550cc are flow rated at industry standard 3bar like all injectors. There is no "recommended" fuel pressure for them, they can handle much higher than 5bar. There is a not insignificant power gain to be had running higher fuel pressure on highly tuned NA engines, which is likely why factory runs 5 bar. You can gain maybe 5-7HP on these engines by properly tuning the injection end angle which can only be achieved with larger injectors at high fuel pressure.

If the Bosch 550cc injectors can handle a higher fuel pressures, is there any issue with just using the 3.5 bar stock e46 M3 FPR? I was under the impression impression this entire time that it needed to be 3 bar. Now I feel like it was a wasted effort to upgrade everything.

[BBRTuning]

If the Bosch 550cc injectors can handle a higher fuel pressures, is there any issue with just using the 3.5 bar stock e46 M3 FPR? I was under the impression impression this entire time that it needed to be 3 bar. Now I feel like it was a wasted effort to upgrade everything.

Stock E46M3 FPR is 5 bar. That's what I'm back to using now as I found it more consistent than the Radium/AEM FPR, but just kept the rest of the Radium kit (filter etc) as it makes it easier to run AN lines for a flex fuel sensor and fuel pressure sensor.

Typically fuel pressure is only lowered to 3-3.5 bar when running forced induction on these cars, but ask your tuner what they recommend as that's what matters in the end.