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      06-18-2015, 06:27 AM   #1
mightbaal
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What's your Lpfp pressure in your N54 at idle? Trying to figure this out

I am trying to figure out if 67 psi at idle is low for a stock pump? I'm looking to replace it with a stock one and upgrade later as this car has cost me way to much since I bought it a month ago. When running barely a 30% e85 mixture I get sudden dips of in the 40's for pressure WOT. I have found a 95 dollar oem pump assembly so that's not bad. Car handles 93 octane all day with DCI map 5 or map 1 no pressure problems. When I get 40's I loose tons of boost and sometimes get a misfire on cylinder 4 probably due to not enough fuel. I would be happy running 30% e85 because it hits hard for a good 5 seconds lol until pressure drops. I know this is somewhat simular to my last post but I'm just wondering what others get for pressure who knows maybe my LP sensor is going out as readings fluctuate a bit and the cylinder 4 misfire is from something else . It's all good on stock settings so no warranty coverage on this would be nice tho. Just gathering some more info before I pull the trigger on my options.
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      06-18-2015, 07:07 AM   #2
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~72 psi here on a new upgraded lpfp
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      06-18-2015, 08:02 AM   #3
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Might as well just get the upgraded walboro for like $100 more... You can run 100% E85 on it. The stock fuel system isn't made for E85 anyways.
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Last edited by Antetokounmpo; 06-18-2015 at 08:23 AM..
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      06-18-2015, 08:49 AM   #4
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Your LPFP cant handle e30. Idle pressure doesnt really matter since you are dropping below 50 at WOT.

Get the stage 2.

At idle my oem was at 67, and at wot with e40 it was between 60-70. My stage 2 is at 67 at idle and stays around 67 with E70
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      06-18-2015, 09:02 AM   #5
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Quote:
Originally Posted by csu87 View Post
Your LPFP cant handle e30. Idle pressure doesnt really matter since you are dropping below 50 at WOT.

Get the stage 2.

At idle my oem was at 67, and at wot with e40 it was between 60-70. My stage 2 is at 67 at idle and stays around 67 with E70
Every cars stock LPFP is slightly different. Some can handle E40, like mine does, and some go haywire over 20% E85, but in reality anything over E40 should be paired with an upgraded LPFP anyway, and a backend flash.
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      06-18-2015, 09:07 AM   #6
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Originally Posted by 335NJ View Post
Every cars stock LPFP is slightly different. Some can handle E40, like mine does, and some go haywire over 20% E85, but in reality anything over E40 should be paired with an upgraded LPFP anyway, and a backend flash.
Yeah I know, mine handled e40 fine.

Im saying his cant handle e30. He made another thread about this yesterday.
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      06-18-2015, 09:09 AM   #7
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DME targets 72.5PSI flat regardless of load applied.
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      08-02-2020, 05:27 PM   #8
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I know it's an old thread....but I've got a question about LPFP pressure at idle.

Just did a new stage 2 LPFP install. When I fire up the car....it's right at 72psi. But as soon as I start driving the car and put a load on it.......the LPFP bumps up to around 85psi...and stays there until I shut the car off and restart it again. Is that normal?

It's not causing any issues......just wondering if that's normal when running a Walbro 450 pump.
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      08-02-2020, 07:14 PM   #9
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82-83psi

Mines only a year old
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      08-02-2020, 08:25 PM   #10
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I heard that the DME targets 72psi at idle ...which mine does. Then when you put a load on the motor, the new target jumps up to around 85psi.

Sounds like yours does the same....guess it's normal.
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      08-02-2020, 09:21 PM   #11
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Not sure why it wouldn't go back down to about 72 when back at idle.
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      08-03-2020, 11:35 AM   #12
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Quote:
Originally Posted by Emilime75 View Post
Not sure why it wouldn't go back down to about 72 when back at idle.
Not sure....what's what I'm trying to figure out. Unless the DME goes into some sort of "safe mode" when it sees the higher amp draw from the bigger stage 2 pump?

It runs fine.....would just like to know why it's doing that.
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      08-04-2020, 01:54 PM   #13
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Mine likes to hang around 82 psi under no load and low load, but occasionally it's around 72 psi in the same conditions. I just went back and checked some logs from the stock LPFP and it did the same thing, so this discrepancy isn't unique to an upgraded pump.

So I don't know the reason, but it behaves the same as stock, so I'm not concerned.
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      08-04-2020, 02:12 PM   #14
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Quote:
Originally Posted by stewbets View Post
Mine likes to hang around 82 psi under no load and low load, but occasionally it's around 72 psi in the same conditions. I just went back and checked some logs from the stock LPFP and it did the same thing, so this discrepancy isn't unique to an upgraded pump.

So I don't know the reason, but it behaves the same as stock, so I'm not concerned.
Ok, sounds good. I did talk to a guy the other day that said I could reset the fueling/lambda adaptations....and that would let the DME "relearn" the correct pressure for the LPFP. Might give it a shot.....but like you said, at this point....it's not a big deal.

Also....I just checked an old log with my stock LPFP...... you're right, it did the same thing. Around 72psi before a pull.....And then would be up around 82psi after the pull.
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      09-01-2020, 07:13 AM   #15
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I am also trying to figure this out. My high pressure values seem good. But my low pressure is miserable. At idle or light throttle is at 50-54 psi. On WOT comes down to 40 psi.
This is on a new Walbro 450 pump + new Lp sensor + new Hp sensor + cleaned and checked injectors.

Any suggestions will immensely help me. I’m in the dark.
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      09-01-2020, 07:24 AM   #16
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What lead you to replacing all of those parts? Were you having fuel pressure problems before and decided to upgrade the pump?

Last edited by Emilime75; 09-01-2020 at 07:35 AM..
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      09-01-2020, 11:29 PM   #17
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Quote:
Originally Posted by Emilime75 View Post
What lead you to replacing all of those parts? Were you having fuel pressure problems before and decided to upgrade the pump?
Yes. On stock lpfp I also had 40-50 psi low pressure readings. So I decided to change everything I could think of. The only thing left is the EKPM3, which I wouldn’t know how to code.

Once everything was changed, I am still getting 40-50 psi. So at the moment, I don’t know what exactly should be changed.
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      09-02-2020, 12:15 AM   #18
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Yeah, could be a faulty EKPM, could possibly also be the FPR?
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      09-02-2020, 04:53 AM   #19
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Quote:
Originally Posted by Emilime75 View Post
Yeah, could be a faulty EKPM, could possibly also be the FPR?
I am a 2006 335i n54, would you know where the relay is located? And what it looks like?
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      09-02-2020, 06:48 AM   #20
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FPR = Fuel Pressure Regulator.
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      09-02-2020, 11:55 AM   #21
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Quote:
Originally Posted by Emilime75 View Post
FPR = Fuel Pressure Regulator.
Oops, my bad. Regarding the in tank regulator, is it possible to run an external regulator without the usage of port injection? I see only pot injected 54s having it. (As far as I have seen)
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      09-02-2020, 12:55 PM   #22
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Sorry, I don't know the answer to that.
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