Coding Higher Voltage Limit to Avoid 2AAE Fuel Pump Error Code

[Renzke]

Dear together,
I created a package for NCS Expert for the EKPM3 - Wert 50 (N55) and Wert 105 (N54) - those are used for E9x cars.

The N54 folder has different current limits inside (max. possible current "25.5A", 21A, 19.7A), see files (the factory fuse is 20A).
I changed the fault limits and updated the checksum + added the specific parameters to the *.C13 file.

(Cedits to Torr - N54tech forum, as I used his files for N55 max. current and to Verhicular DIY as I used his changes for the N54 max. current in the nettodat file).

Have fun with it. Use at your own risk ;-)

FYI: Going with an used EKPM3 needs coding because you may don't know where it's excactly coming from. I was using the "Wert 50 - N55" for testing for my N54 MSD81. This is the coding value you usually have by factory for an N55 equipped E9x car. Result: EKPM runnning all the time on a duty cycle of min. 77% and 86psi + current draw @ idle ~17Amps. Anyway the car was running fine without an error. Without additional cooling you may fry the EKPM3 on long term and destroy your fuel pressure regulator. (Correct coding: 72psi, ~60-65% duty cycle, current draw at idle ~7.6A for a single Walbro 450).

Idea: As the curve and bits in the Nettodat file for "l/hour vs. pump speed" are known (see N54tech forum) it's possible to create an own curve.
I see the pump speed (actual) vs. pump speed (current) doesn't fit for a Walbro450 according to INPA / Diagnosis SW (delta is getting bigger with higher fuel demand / WOT and high rpm). It could be possible to adopt the curve to a Walbro pump. Maybe the 2AAF code is set when the delta is to high (aka. ECU demands high fuel amount). This may avoid the 2AAF shadow code and the pressure of ~83psi after WOT (even at idle) that some people see until an engine restart. I may play around with this. Anyway I'm not sure about what causes the problems and this is just an idea and potencial solution. If somebody has more information, feel free to share it ;-).

 

[turbohugh]

Dear together,
I created a package for NCS Expert for the EKPM3 - Wert 50 (N55) and Wert 105 (N54) - those are used for E9x cars.

The N54 folder has different current limits inside (max. possible current "25.5A", 21A, 19.7A), see files (the factory fuse is 20A).
I changed the fault limits and updated the checksum + added the specific parameters to the *.C13 file.

(Cedits to Torr - N54tech forum, as I used his files for N55 max. current and to Verhicular DIY as I used his changes for the N54 max. current in the nettodat file).

Have fun with it. Use at your own risk ;-)

FYI: Going with an used EKPM3 needs coding because you may don't know where it's excactly coming from. I was using the "Wert 50 - N55" for testing for my N54 MSD81. This is the coding value you usually have by factory for an N55 equipped E9x car. Result: EKPM runnning all the time on a duty cycle of min. 77% and 86psi + current draw @ idle ~17Amps. Anyway the car was running fine without an error. Without additional cooling you may fry the EKPM3 on long term and destroy your fuel pressure regulator. (Correct coding: 72psi, ~60-65% duty cycle, current draw at idle ~7.6A for a single Walbro 450).

Idea: As the curve and bits in the Nettodat file for "l/hour vs. pump speed" are known (see N54tech forum) it's possible to create an own curve.
I see the pump speed (actual) vs. pump speed (current) doesn't fit for a Walbro450 according to INPA / Diagnosis SW (delta is getting bigger with higher fuel demand / WOT and high rpm). It could be possible to adopt the curve to a Walbro pump. Maybe the 2AAF code is set when the delta is to high (aka. ECU demands high fuel amount). This may avoid the 2AAF shadow code and the pressure of ~83psi after WOT (even at idle) that some people see until an engine restart. I may play around with this. Anyway I'm not sure about what causes the problems and this is just an idea and potencial solution. If somebody has more information, feel free to share it ;-).

Wow let's pursue this further. I've been pondering the same thing about the pump speed (actual) vs (requested). I'm seeing my requested speed higher than my actual and I was hoping someone had an understanding of the setpoints for the pump speed. I'd like to narrow the delta between pump speed (Actual) vs (requested/expected) as I think this is part of the problem.
Also I'm noticing with my hobbs actuated secondary pump I get weird oscillations ; I'm speculating the pressure increase causes the dme to pull PWM then it drops and then increases etc.. I will hopefully be able to track that thread [if you can Private message a link to it that would be great].

Thanks for your work !

 

[Renzke]

Wow let's pursue this further. I've been pondering the same thing about the pump speed (actual) vs (requested). I'm seeing my requested speed higher than my actual and I was hoping someone had an understanding of the setpoints for the pump speed. I'd like to narrow the delta between pump speed (Actual) vs (requested/expected) as I think this is part of the problem.
Also I'm noticing with my hobbs actuated secondary pump I get weird oscillations ; I'm speculating the pressure increase causes the dme to pull PWM then it drops and then increases etc.. I will hopefully be able to track that thread [if you can Private message a link to it that would be great].

Thanks for your work !

As the "problems" with the shadow code and the higher pressure after WOT are not really problems because everything is running fine even when all problems are "active" it's just something for people who like to have it perfect.
A new fuel pump curve: As the meaning of all hex values in the NETTODAT.MAN are NOT clear for me as well there is a risk. If there is a failure or the different curve results in a strange EKPM behaviour we create a potencial problem (Worst case: The EKPM shuts off the pump during WOT. This is most probably not that good for the engine at all) ;-). On the other hand the chance to have a solution by creating a different fuel-pump rpm curve is not that small in my opinion and testing / logs will tell if it's working or not. The creation of a pump curve is quite simple. If you want to start a test I can provide this. As I said I may do this by my own if I have time (not the next weeks). Good starting point is to investigate the pump speed (requested vs. expected) under WOT conditions (low to high rpm) by doing a log.
Regarding the Hobbs switch: If you have another fuel pump curve the regulation (PWM value by the DME) will still try to "solve" the situation by (most probably) oscillation BUT maybe the PWM change results in a smaller requested rpm change at your first pump due to a different fuel pump curve in the EKPM3 and the regulation circuit is working better to solve the problem with less or no oscillation at all. This is just a theory. Besides this I will send you a PM and some other ideas because I think the Hobbs switch is not the topic of this thread.

 

[Darke Peak]

Did anybody make any progress on adjusting the flow rate table for a higher flow pump (Walbro 450/525/535)? I used the fuel pump test function in Protools to check the theoretical flow rate (factory pump table) to the actual flow rate of my Walbro 535. Using the 60L/hr (=1L/min) test I found it was only 30 seconds to flow 1L (=2L/min). Therefore, the Walbro 535 LPH pump is flowing double the factory 255LPH pump. That makes sense: 2x255=510. So, if the table can be changed then the pump will draw less current and won’t work as hard?

 

[AzNdevil]

Did anybody make any progress on adjusting the flow rate table for a higher flow pump (Walbro 450/525/535)? I used the fuel pump test function in Protools to check the theoretical flow rate (factory pump table) to the actual flow rate of my Walbro 535. Using the 60L/hr (=1L/min) test I found it was only 30 seconds to flow 1L (=2L/min). Therefore, the Walbro 535 LPH pump is flowing double the factory 255LPH pump. That makes sense: 2x255=510. So, if the table can be changed then the pump will draw less current and won’t work as hard?

in theory yes, in reality, all these issues arise only when WOT and some people need to add extra fuel pumps for more fuel flow so... there isnt much point changing the table if it exists because a single pump isnt flowing enough in the first place

 

[carabuser]

Also DME is limited to 255l/h as the maximum fuel flow at the moment. It needs a program mod to go higher which is why you see rail pressure oscillating with overdrives setups.

 

[Darke Peak]

in theory yes, in reality, all these issues arise only when WOT and some people need to add extra fuel pumps for more fuel flow so... there isnt much point changing the table if it exists because a single pump isnt flowing enough in the first place

But you don’t have to add extra fuel pumps for more flow, you can replace the single OE 255L/Hr pump with an aftermarket 535L/hr pump and have more flow.

My question is more about what happens if the engine requirements exceeds the OE pump capacity of 255L/hr, even though a higher capacity pump is installed. For example, if the demand on the DME is to provide 300L/hr, beyond what the table says it can supply, does it reduce boost, or reduce throttle position or some other means to get the demand below 255L/hr? Or more simply, what happens when the demand exceeds 255L/hr?

 

[Darke Peak]

Also DME is limited to 255l/h as the maximum fuel flow at the moment. It needs a program mod to go higher which is why you see rail pressure oscillating with overdrives setups.

Yes, that’s why I’m asking if anyone had any luck changing the table(s) in the program. I’ve started seeing many more rail pressure oscillations ever since I fitted the Walbro 535, but I’m not running an overdrive. My original HPFP also failed less than 200 miles after I installed the Walbro 535 - too much of a coincidence to me. The car has less than 55,000km (32,000 miles) and I’m in Australia with high sulphur content fuel (good for lubricating high pressure fuel pumps).

I’m desperately trying to get the LPFS monitoring working on my car but I have a theory on the rail pressure oscillations:
> Imagine that while accelerating under WOT the engine needs 200L/hr.
> the DME looks up the table and sees that 200L/hr requires a PWM signal that equates to 15A (just a guess), and sends that to the EKPM3
> the EKPM3 carries out the DME request and sends a PWM signal of 15A to the LPFP
> the Walbro 535 spins up with the 15A PWM signal and delivers 400L/hr of fuel to the HPFP
> the HPFP doesn’t need that much so the excess flow causes pressure to rise on the low pressure side of the HPFP
> the pressure between LPFP and HPFP exceeds 80psi and the pressure regulator bursts open.
> with the pressure regulator open the supply pressure to the HPFP drops below 30psi
> the DME sees the rail pressure drop accordingly so it sends a higher PWM signal to the solenoid on the HPFP.
> the LPFP pressure regulator closes and the supply pressure goes back up
> the rail pressure spikes accordingly and the DME tries to resolve by reducing PWM signal to HPFP solenoid
> process repeats at high frequency and you see oscillations of the rail pressure.

It’s just a theory based on my limited understanding of the system.

 

[carabuser]

Yes, that’s why I’m asking if anyone had any luck changing the table(s) in the program. I’ve started seeing many more rail pressure oscillations ever since I fitted the Walbro 535, but I’m not running an overdrive. My original HPFP also failed less than 200 miles after I installed the Walbro 535 - too much of a coincidence to me. The car has less than 55,000km (32,000 miles) and I’m in Australia with high sulphur content fuel (good for lubricating high pressure fuel pumps).

I’m desperately trying to get the LPFS monitoring working on my car but I have a theory on the rail pressure oscillations:
> Imagine that while accelerating under WOT the engine needs 200L/hr.
> the DME looks up the table and sees that 200L/hr requires a PWM signal that equates to 15A (just a guess), and sends that to the EKPM3
> the EKPM3 carries out the DME request and sends a PWM signal of 15A to the LPFP
> the Walbro 535 spins up with the 15A PWM signal and delivers 400L/hr of fuel to the HPFP
> the HPFP doesn’t need that much so the excess flow causes pressure to rise on the low pressure side of the HPFP
> the pressure between LPFP and HPFP exceeds 80psi and the pressure regulator bursts open.
> with the pressure regulator open the supply pressure to the HPFP drops below 30psi
> the DME sees the rail pressure drop accordingly so it sends a higher PWM signal to the solenoid on the HPFP.
> the LPFP pressure regulator closes and the supply pressure goes back up
> the rail pressure spikes accordingly and the DME tries to resolve by reducing PWM signal to HPFP solenoid
> process repeats at high frequency and you see oscillations of the rail pressure.

It’s just a theory based on my limited understanding of the system.

That's actually close what happens but the low pressure side doesn't really cause the oscillation since the fuel pressure regulator keeps the low side pressure stable.

The cause of oscillation is the high pressure side. Because fuel demand is limited to 255 at the VCV control you have no fine control of the VCV above that flow request. So you essentially only get to send a single PWM value to the VCV abote 255l/h and if that generates too much pressure the loop presure controller will reduce the flow setpoint but that has no effect until it dips below 255 again and by that time the controller output is moving really fast.

 

[Darke Peak]

That's actually close what happens but the low pressure side doesn't really cause the oscillation since the fuel pressure regulator keeps the low side pressure stable.

The cause of oscillation is the high pressure side. Because fuel demand is limited to 255 at the VCV control you have no fine control of the VCV above that flow request. So you essentially only get to send a single PWM value to the VCV abote 255l/h and if that generates too much pressure the loop presure controller will reduce the flow setpoint but that has no effect until it dips below 255 again and by that time the controller output is moving really fast.

Ok. So I presume VCV (volume control valve) refers to the solenoid/valve on the HPFP? If so, is that also limited to 255L/hr via a table like the LPFP?

 

[carabuser]

Ok. So I presume VCV (volume control valve) refers to the solenoid/valve on the HPFP? If so, is that also limited to 255L/hr via a table like the LPFP?

Yes, volume control valve.

It's not limited to that, it's just that the control loop responsible for the rail pressure is has its output scaled maxed out at 255l/h. So it leaves the control range of the loop when going above that. It's not normally an issue since at those load levels the VCV is at maximum output trying to achieve target but when you upgrade the fuel system you get problems.

It's not a hard issue to solve, it's just not on the radar for MHD currently.