N54 having LPFP spikes over 110psi!

[alvinhobh]

N54 having LPFP spikes over 110psi!

2007 335i e92
Fuel-it stage 3 LPFP
550 cc PI
AIC2
Motiv- FF sensor
Running e85

In the process of tuning my car, noticed the LPFP pressure was all over the place, dropping below 40 and spikes over 100psi, so I decided to replace the following:

HPFP ( FCP lifetime warranty so why not)
HPFP sensor
LPFP sensor
Both LPFP filters
Driver side tank filter/ regulator tank
Removed and blocked off the stock FPR
Install an external FPR
Replaced the EKP ( used on from Ebay, coded with protool)

Pressure doesnt drop as lowe as before but still like crazy spikes! Tuner is working with me on this, giving me above and beyond support. He lowered the boost target so we can how things behave and I don't need help on analyzing anything in the log, but I wanted to put it out here and see if anyone has ever experienced the same issue with the LPFP spikes.

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[Cruizinmax]

Your fuel pressure is significantly better on the log you did with the vacuum line disconnected. With that connected it is trying to increase your fuel pressure by the equivalent of your manifold pressure which we don't want in our platform. I'd say issue solved at this point.

The fluctuations you're seeing is simply the column of fuel in the line between the regulator and HPFP stopping and starting as the HPFP utilizes it. Not really hurting anything. If it bothered you, you could add a fuel pressure damper.

 

[alvinhobh]

Thanks for the feedback. If >100psi doesn't hurt the system, then it doesn't bother me lol just don't want run into issues. Is this type of fluctuation normal on stage 3 LPFP with PI?

 

[martymil]

It actually wont hurt anything mechanically but will make your ekp run real hot and possibly overheat due to it working real hard to control
the lpfp rail.

I actually turned the fuel pump fix off on my ekp with a 535lph pump and its not throwing the error.

 

[alvinhobh]

It actually wont hurt anything mechanically but will make your ekp run real hot and possibly overheat due to it working real hard to control
the lpfp rail.

I actually turned the fuel pump fix off on my ekp with a 535lph pump and its not throwing the error.

Got it. How do you go about turning off the fuel pump fix? Is that something I can do with Protool? I’ll try it out

 

[martymil]

I wouldn't turn it off unless you got the spikes under control and yes it can be turned of using protocols only if you turned it on.

Its the spikes that make it run hot trying to control the fuel pressure from spiking.

 

[JBacon335]

It actually wont hurt anything mechanically but will make your ekp run real hot and possibly overheat due to it working real hard to control
the lpfp rail.

I actually turned the fuel pump fix off on my ekp with a 535lph pump and its not throwing the error.

I'm going to be doing a stage 2 pump imminently and already bought a new ekpm3. the bigger pump isn't burning it out? I was worried about it with a 450 but if I can go bigger I'd rather do this job once and be good.

 

[alvinhobh]

I wouldn't turn it off unless you got the spikes under control and yes it can be turned of using protocols only if you turned it on.

Its the spikes that make it run hot trying to control the fuel pressure from spiking.

I believe I read in other thread that you got the BPM4 to replace the stock EKP, how did that work for you? Do you think it would help me here?

I am still running the EKPM2, I see some people “upgrading” to the EKPM3, not sure what is an upgrade

 

[martymil]

I dont run the bpm4 any more as I have no need for it , I replaced my stage 3 pump with a buckeless 535 with a 15x15 inch hydramat.

It has all the flow I need for my setup.

If your upgrading from an ekp2 don't waste your time and go directly to the bpm4 especially if your still chasing power or building your car.

The ekp3 can handle a single pump no issues and im no fan of the Hobbs switch.

Had the hobbs switch fail a number of times before I switched over to the bpm4.

A single buckless pump has far greater flow and will be more than adequate for 99% of peoples needs, bigger is not always better.

 

[alvinhobh]

Mount your lpfp sensor on the reg where you would normally run a fuel pressure gauge.

Got it!

Relocated the sensor to the FPR port, cleared up a lot. I still don't understand why most people don't have this issue.

The pressure is dropping some, but I assume its reasonable?Car is tuned down for troubleshooting so I will see how it goes now that I can more forward.

Thanks for everyone's help!

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[martymil]

Put the radium fuel pressure damper between the lpfp sensor and hpfp with no boost reference and it will halve the spikes again and almost eliminate them.

Then reset your adaptations.

 

[martymil]

Ekp3 will help some what too, but if your chasing big power and can afford it go for the BPM 4

 

[alvinhobh]

Put the radium fuel pressure damper between the lpfp sensor and hpfp with no boost reference and it will halve the spikes again and almost eliminate them.

Then reset your adaptations.

Is that really necessary? The point of smoothing out this signal, even more, is simply to help the EKP have a longer life, correct? Or are there other benefits that come along with that?

Thanks.

 

[martymil]

Well the damper helps the ekp2 not work as hard so it will not heat up as much, the ekp3 is a much better
controller but it doesnt offer that much extra head room.

Basically it will run cooler so you have less chance of being stranded if it overheats without running one.

 

[martymil]

I dont know why but the graph was showing real bad swings when I first looked at it now its different, yeah that graph
looks fine but the damper will help.

Dont worry about the ekp judging from the latest one.

 

[martymil]

So guys if you want to smooth out your lpfp rail you really need this type of setup for our dead head system, if you already have a fpr and return line
relocate your lpfp sensor on to the fpr fuel pressure reference port

 

[martymil]

Here is the inline damper you will need

FPD-XR base pressure requirement = 40 - 120psi (static) no boost reference needs to be connected.

Fuel Pulse Damper, Inline Kits

The Radium Fuel Pulse Damper Kit helps regulate and maintain safe and consistent fuel pressures. Erratic fuel pressure is commonly associated with random lean air fuel ratio spikes that are difficult to tune out.

www.radiumauto.com

 

[fmorelli]

So @martymil am I understanding this correctly? The sensor sits right up behind the HPFP, which causes spikes read by the sensor. The sensor, being in close loop system controlling the LPFP, causes the EKPM3 to go nuts. So one way to solve it is to move the sensor and dampen the line, that way the everything plays nice with the algorithm (that does not account for this spike activity). Hypothetically, software that knew how to deal with these spikes would "dampen" the EKPM3 spike reactions. Which then leads me to the question - Z4 has no LPFP sensor ... and as best I know, the LPFP just runs. So in the Z4 case is this one of those, "if a tree falls in teh forest and no one is there to hear it, does it make a sound?"

Filippo

 

[noorj]

Does anyone know the adapter fittings needed to get the stock LPFP sensor to a 1/8" NPT on the fuel pressure regulator?

 

[martymil]

yep the z4 you don't have to worry about it as the ecu cant see the spikes but the BIG BUT if you put a damper on it it will help smooth out HPFP spikes, as the hpfp spikes have a direct correlation to lpfp ones.

They basically help one another.

Does anyone know the adapter fittings needed to get the stock LPFP sensor to a 1/8" NPT on the fuel pressure regulator?

Older sensors were 1/8" npt the newer ones are metric straight with an oring, I just use a bit of gas plumbers tape on it.

I think this is the fitting if you want to be anal

Metric Female to NPT Male - Raceworks

 

[alvinhobh]

I used my old sensor and left the new one I bought in the original position.