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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[NoGuru]

My guess would be the EKP. It should have some form of PID controlling to stop it from shotting up and down. Here is a cheap way to cool down the EKP.
Try running with the seat cover off too just to see if maybe it is getting too hot. https://bmw.spoolstreet.com/threads/ekp-active-cooling.6329/#post-94488

 

[iminhell1]

How is the second pump triggered? powered?

The relief valve on the 274 is 112psi. The 267 is 85psi.


I'm running a 267 as my primary pump. A 274 as my secondary, triggered at 6psi. After it's triggered I hold right about 100psi. But I'm not sure the LPFP sensor can read any higher.

 

[alvinhobh]

2nd pump is triggered by a hobb switch, kicks on at about 12 psi, turning on a replay which pulls power straight from the battery.

So under load you are holding 100psi? I was under the impression anything about 80-90 was too much for the lowside fuel

 

[Cruizinmax]

What kind of external fpr are you running? If it can't keep the pressure below the set point that means it's unable to bypass enough fuel. Some regulators have different sized orfices for the return. You'll need to either allow the regulator to return more fuel or lower the volume of fuel you are sending to it.

Is it possible that the regulator just isn't set appropriately? Perhaps the base pressure is set too high?

 

[alvinhobh]

I have tried setting it from 45psi all the way to 70psi. Either end I see spikes over 100.

using the Racetronix FPR
REG-FI10106BS

Fuel Pressure Regulator, -10 / -6 AN E85, Black/Silver (REG-FI10106BS): Regulators - Fuel Injection

Purchase Fuel Pressure Regulator, -10 / -6 AN E85, Black/Silver or shop other Regulators - Fuel Injection and Racetronix products.

www.racetronix.biz

Here is a log when I set it to 72 psi idle

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[Cruizinmax]

That regulator should be able to bypass enough fuel. How is the regulator plumbed in? Regulator under the hood using factory feed, -6 return back to the tank? Do you have the vacuum reference on the regulator connected to anything?

 

[alvinhobh]

I’m using this FPS filter/FPR. The vacuum reference is connected to the manifold on the log above.


Upgraded fuel lines originally bought from fuel-it, and now the return line going to the top hat of the passenger side tank from FPS, ( I have to check the side of the hose, I believe it’s an -8an)

Plug, and Play E9X/E8X External Filter/FPR kit

PFS is proud to offer the most complete external filter/FPR kit on the market. With this kit utilizing our fuel line upgrades, you can simply bolt on the perfect fueling solution for high powered applications all in one compact unit. This kit includes our 10 micron Billet CNC filter, Fuel...

performancefuelingsolutions.com

 

[alvinhobh]

Here is a log before I replaced any of the components from the initial post, so stock FPR. I had spikes with the stock FPR

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[JBacon335]

the vacuum reference is making it bring pressure up as boost rises. For our fuel systems I would recommend running it without manifold reference and just set it to 75 and forget it.

 

[martymil]

the vacuum reference is making it bring pressure up as boost rises. For our fuel systems I would recommend running it without manifold reference and just set it to 75 and forget it.

100% you do not connect the boost reference line, set the base pressure when the motor is not running.

Easiest way to set base pressure is using the prime fuel pump feature using protools so the ekp is not adjusting your fuel pressures, prime the pump and it will do this for 2 min and adjust your FPR to 75psi.

You will never see a spike again over what you set.

 

[alvinhobh]

100% you do not connect the boost reference line, set the base pressure when the motor is not running.

Easiest way to set base pressure is using the prime fuel pump feature using protools so the ekp is not adjusting your fuel pressures, prime the pump and it will do this for 2 min and adjust your FPR to 75psi.

You will never see a spike again over what you set.

I did exactly what you described.. used protool to prime the pump with the car off, set it to 75 psi. Disconnected the vacuum reference from the manifold, but still spiking...

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[RNM]

Not to thread jack, but I am facing a similar problem. Hope we all get this resolved..

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2007 335i
Helix overdrive
Fuel it walbro 525 lpfp
EOSpeed bpm4 controller
Precision Raceworks Fuel regulator assembly with upgraded - 8an fuel line

 

[martymil]

I did exactly what you described.. used protool to prime the pump with the car off, set it to 75 psi. Disconnected the vacuum reference from the manifold, but still spiking...

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

 

[doublespaces]

Easiest way to set base pressure is using the prime fuel pump feature using protools so the ekp is not adjusting your fuel pressures, prime the pump and it will do this for 2 min and adjust your FPR to 75psi.

Does this send 100% DC to the EKP?

I did exactly what you described.. used protool to prime the pump with the car off, set it to 75 psi. Disconnected the vacuum reference from the manifold, but still spiking...

Can you take a photo of the tightening screw so we can see how far you have it cranked down? Have you tried loosening it a bit below 75 PSI at idle to see how that works?

 

[martymil]

yes 100% DC

 

[alvinhobh]

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

Not sure if I follow. I have the stock LPFP sensor on its stock location ( #6).

Where we would normally a fuel pressure gauge in most cars would be in the rail, but in our case, that is the High side.

 

[martymil]

yep remove it from stock location and move it to the LPFP FPR fuel pressure reference port.

 

[alvinhobh]

yep remove it from stock location and move it to the LPFP FPR fuel pressure reference port.

okay, is that common? Would that be for troubleshooting or for good?

 

[martymil]

for good, the hpfp is switching so fast causing spikes on the lpfp rail, you can also use the radium fuel pressure dampener to help with this too.