N54 LPFP Pressure Target issues

nyt

Sergeant
Sep 15, 2019
331
1
289
0
Ride
2010 335xi
I'm having a bit of an issue, and I'm not sure if it's tune or mechanical.

I'm targeting 5525hpa (80psi) in the lpfp pressure table while under load. I have a regulator without pressure reference set to 80psi. Dual 450HPs in tank feeding to the stock filter with the factory regulator removed and blocked off.

The second pump is controlled by JB4, which turns it on around 11psi of boost. In the log, shortly after it's brought on, fuel pressure hits 80psi, then winds up down around 70psi at 7krpm. This pull isn't exactly running a heap of boost, so It's surprising it's dropping as it is. Is this the correct table to adjust the low pressure target, or are there others I'm missing? It started raining on me, or I'd just go hook up a portable scope to the factory pump and see what it's doing under load. I think I'm leaning towards a mechanical restriction at this point, but I didn't think the oem filter was this bad? 78k miles on the clock, don't think it's beenr eplaced.

Thoughts?

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Last edited:

KClemente

Sergeant
Nov 26, 2019
284
147
0
Ride
E90 335i
I know for rail pressure, the maps used by the dme are the external maps (BMW), meaning its the maps with all caps abbreviations. For example, KF_PRAIL_H is the external map for rail pressure target and ip_sup_hom is the internal (Continental) rail pressure target that isn't used.

Last time I went through the ols, I haven't found any external maps for low pressure, but that wasn't my focus back then

If you have INPA, you can directly view pump pwm in realtime and see what it's doing under load. The oscillations are interesting as they show the Proportional and Integral (no Derivate in the lpfp control loop) working.


Try adjusting c_fup_efp_sp_ext_req ("ext" the abbreviation for external)

and if that doesn't work, c_fup_efp_sp_man ("man" the abbreviation for manual) alongside the toggle lc_fup_efp_sp_man_act which is a manual setpoint that the dme will toggle 100% of the time no matter what
 

nyt

Sergeant
Sep 15, 2019
331
1
289
0
Ride
2010 335xi
I know for rail pressure, the maps used by the dme are the external maps (BMW), meaning its the maps with all caps abbreviations. For example, KF_PRAIL_H is the external map for rail pressure target and ip_sup_hom is the internal (Continental) rail pressure target that isn't used.

Last time I went through the ols, I haven't found any external maps for low pressure, but that wasn't my focus back then

If you have INPA, you can directly view pump pwm in realtime and see what it's doing under load. The oscillations are interesting as they show the Proportional and Integral (no Derivate in the lpfp control loop) working.


Try adjusting c_fup_efp_sp_ext_req ("ext" the abbreviation for external)

and if that doesn't work, c_fup_efp_sp_man ("man" the abbreviation for manual) alongside the toggle lc_fup_efp_sp_man_act which is a manual setpoint that the dme will toggle 100% of the time no matter what

So a couple issues, obviously INPA would be good to monitor, but it doesn't play nice while the JB4 is active, which is controlling my boost. I have a BPM4 coming, which I can monitor directly once I have it installed, and see what the DME is doing.

Strangely, after driving around and boosting a bit, my fuel pressure was around 78psi while idling, normally it's in the 60s. I restarted the engine and it was back in the 60s.

Still, though, I'd imagine even low duty cycle would be enough as I have a full second 450hp pump powered with a direct feed once it hits 11psi, and I've monitored that working.

Anyway, needs more investigating.

The other issue is that I don't have those maps defined for ije0s nor do I have the actual data sources to try mapping them for myself, so I'm stuck with what's in the public xdf using tunerpro. Do you have a link to the ols and any info on how to map from there to xdf?

The LPFP pressure target as defined in that xdf references ip_fup_efp_sp