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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Fuel Pressure Sensor Logic



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      01-30-2013, 03:54 PM   #1
TenshiWingusu
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Fuel Pressure Sensor Logic

Having some trouble wrapping my head around this one, need to bounce my logic off you guys.

My car:
Xi 6MT Procede 2.5SE DCIs with 80k and one HPFP at 42k

Transport3r's car:
i 6MT Procede 2.5 AFE box with 70k and one HPFP at 42k also

Now I fully understand that the two cars are different and that things will never be 100% similar, but this is a fundamental concept.

We both run the 9-10 aggressive maps with almost identical boost settings. He runs OL Fueling at the default 75% I run mine at 100% start boost both at 30% So here is the problem; at the same RPM and boost level with the same timing and similar HPF Voltages (4.5V vs 4.4V) my fuel trims are near maxed out. Not only that as the second gear pull goes on my fuel trims start to dive into the negatives at the end of the pull. One would think that for a similar fuel pressure, RPM, and boost that we would have at least remotely similar fuel trims right? Since a similar amount of fuel should be injected for the similar amount of air. I've concluded that something in my fuel system is messed up but I have no codes and no long start issues, I do have a nasty idle misfire that never throws a code....

All I have to work with is that:
-The LPFP is at 100% PWM
-My fuel trims almost max at boost onset (OLF=100%) and then taper negative throughout the pull
-No codes...
-Bad idle
-Another car that's near identical but OLF=75% does not have this issue

Search turned up nothing useful on HPF sensor failure and my symptoms pretty much overlap failure of any component in the fuel system... My logic points to HPFP or HPF sensor. Any other thoughts?
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      01-31-2013, 03:46 PM   #2
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It's your blowoff valve brah. It's venting so fast your fuel pressure drops..
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      01-31-2013, 04:07 PM   #3
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Bad Idle?
What do your spark plugs looks like?

I smell some injector replacements are needed perhaps or maybe the LPFP is dying. What's the vehicle history on the injectors?
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      01-31-2013, 04:16 PM   #4
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How are you measuring that the lpfp is at 100%? Just curious as I would like to log my lpfp as well.
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      02-06-2013, 10:42 PM   #5
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Quote:
Originally Posted by Jeff@TopGearSolutions View Post
Bad Idle?
What do your spark plugs looks like?

I smell some injector replacements are needed perhaps or maybe the LPFP is dying. What's the vehicle history on the injectors?
Sorry for the late response, have been traveling the past few days.
Brand new OEM plugs 2 weeks ago. Injector is a possibility (never replaced) but from the way it acts with fuel trims I'm leaning towards the LPFP like you said, its getting bad but not bad enough to trip a code and since the PROcede controls it it might not ever throw a code. Or it may be both, the annoying thing is I don't get any codes when the car idles so bad that it almost stalls...

Quote:
Originally Posted by Dmacc View Post
How are you measuring that the lpfp is at 100%? Just curious as I would like to log my lpfp as well.
In the Vishnu 5.34 software log the channel "CAN Fuel Pump PWM". It wont give you pressure but it will show you the duty cycle of the pump.
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      02-06-2013, 10:48 PM   #6
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Quote:
Originally Posted by TenshiWingusu
Quote:
Originally Posted by Jeff@TopGearSolutions View Post
Bad Idle?
What do your spark plugs looks like?

I smell some injector replacements are needed perhaps or maybe the LPFP is dying. What's the vehicle history on the injectors?
Sorry for the late response, have been traveling the past few days.
Brand new OEM plugs 2 weeks ago. Injector is a possibility (never replaced) but from the way it acts with fuel trims I'm leaning towards the LPFP like you said, its getting bad but not bad enough to trip a code and since the PROcede controls it it might not ever throw a code. Or it may be both, the annoying thing is I don't get any codes when the car idles so bad that it almost stalls...

Quote:
Originally Posted by Dmacc View Post
How are you measuring that the lpfp is at 100%? Just curious as I would like to log my lpfp as well.
In the Vishnu 5.34 software log the channel "CAN Fuel Pump PWM". It wont give you pressure but it will show you the duty cycle of the pump.
Awesome thanks man
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