Any E46 Fuel Pressure Experts????

[thekubiaks]

I am trying to figure out where my top end horsepower is going on my ESS 330i. I have a boost gauge and know the Supercharger is putting out 8 PSI @ redline and the engine runs like a swiss watch. I'm still getting erratic dyno runs and my 1/4 mile times aren't much better than stock. Certainly no 110HP more than stock as claimed. I also watch the ignition timing in real time but no problems there. BMW specs call for a fuel pressure of ~50.75PSI. At idle I am getting about 42 psi but under WOT, I'm not able to measure it. Perhaps I should install a fuel pressure gauge??? Anyway, for the experts, the fuel pressure regulator is integrated into the fuel filter, I noticed what looked like a vacuum line running into the fuel filter. Does the ECU vary the fuel pressure or since I am measuring 42psi at idle, that is what I am getting at WOT. If that is the case, then my engine is starving for fuel at high RPM's because I'm not getting enough fuel pressure. Can I install a manual fuel pressure regulator or "tweak" the BMW FPR for more pressure????? THANKS :str8pimpi

[RENNsport]

Before you start playing with the fuel system/pressure, you should get the car on the dyno and measure the AFR...this way you'll know if the car is running lean on top-end.

[thekubiaks]

Before you start playing with the fuel system/pressure, you should get the car on the dyno and measure the AFR...this way you'll know if the car is running lean on top-end.

Thanks for the response, I agree. I watch the ignition timing and AFR in realtime during the runs and saw around 12.8 AFR during WOT. The ignition timing would occasionally roll back for unknown reasons. ESS supposedly had the DME firmware code too conservative (to prevent detonation). To clarify, as soon as the DME even thought about being on the lean side, it rolled back timing thus sapping horsepower ( very safe, but restricts the Superchargers contribution by rolling back the ignition) . In the current firmware revision I have now, the rollback is less conservative and I'm feeling more horsepower but the 1/4 mile times and 0 - 60 times are still very near stock numbers. My G-Tech Pro comp (not all that accurate in my opinion but a good indicator) is showing around 225HP to the rear wheels, which agrees with the 1/4 mile times. All I have left that can be the culprit to the loss of power is the fuel pressure, I can't think of anything else it could be. THANKS

[Mr Paddle.Shift]

Getting a fuel pressure gauge will definitely help. In any case, I am guessing as well about ESS's revised DME to deal with detonation. I don't suppose your setup has an intercooler? I am curious as to how high your IAT is under heat soak condition cos this is when detontation rules.

[thekubiaks]

Getting a fuel pressure gauge will definitely help. In any case, I am guessing as well about ESS's revised DME to deal with detonation. I don't suppose your setup has an intercooler? I am curious as to how high your IAT is under heat soak condition cos this is when detontation rules.


I'm definitely not buying an intercooler if the S/C isn't making the power. I've never had a detonation problem, even on hot days. As far as IAT, I don't have a gauge.

[Mr Paddle.Shift]

I think you misunderstood my post.

YES: ESS most likely tuned the DME to prevent detonation.

YES: Detonation can occur in your situation if ESS hasn't done so to the DME. Why? Because at 8psi without an intercooler, charged air is at the state of detonation. Again, ESS probably programmed the DME to deal with that.

YES: Last but not least, your 2001 330i has an IAT sensor. Use any OBD II s/w and you can read the numbers. In fact, I believe ESS's kit requires the IAT sensor to be relocated from the intake runners to the MAF area. Why again? In order to deal with detonation.

[thekubiaks]

I think you misunderstood my post.

YES: ESS most likely tuned the DME to prevent detonation.

YES: Detonation can occur in your situation if ESS hasn't done so to the DME. Why? Because at 8psi without an intercooler, charged air is at the state of detonation. Again, ESS probably programmed the DME to deal with that.

YES: Last but not least, your 2001 330i has an IAT sensor. Use any OBD II s/w and you can read the numbers. In fact, I believe ESS's kit requires the IAT sensor to be relocated from the intake runners to the MAF area. Why again? In order to deal with detonation.


Yep, I misunderstood you, I have a realtime OBD scanner and I'll get some IAT numbers for you. And yes, the IAT sensor was relocated to the outside air intake at the top of the hood right in front of the firewall right under the microfilter. By the way, if ESS programmed the DME to roll back timing to preemptively prevent detonation, then how could it ever develop 100 additional horsepower as clamed. For example, if everytime you got above 5000 rpm's under WOT and boost was increasing rapidly towards 8 psi but the DME started rolling back timing, no way your going to make horsepower. I can't believe that is what is happening. I've got to get back to the dyno for more data, I still suspect inadequate fuel delivery to the injectors at WOT and the DME is sensing that and rolling back timing. What are your thoughts about that?? Thanks for the reply. :)