N54 HPFP VCV Tables

[mj6234]

Possibly a dumb question here, but looking at the PFS POD and want to understand what needs to be done to tune for the cold start and other situations. I have done my own tuning so far.

Is the only real issue the cold start? The fix to lower the coolant temp threshold to flip to the hot map doesn't seem great to me. It seems like the flow request->current request table would need to be changed to account for additional flow at lower loads (if the POD is spinning the HPFP at 3x the stock rate)? Or maybe it would be better to do it in the current request->PWM table if low currents cause an issue with HPFP?

Are there other known tables that are missing?

 

[V8bait]

Possibly a dumb question here, but looking at the PFS POD and want to understand what needs to be done to tune for the cold start and other situations. I have done my own tuning so far.

Is the only real issue the cold start? The fix to lower the coolant temp threshold to flip to the hot map doesn't seem great to me. It seems like the flow request->current request table would need to be changed to account for additional flow at lower loads (if the POD is spinning the HPFP at 3x the stock rate)? Or maybe it would be better to do it in the current request->PWM table if low currents cause an issue with HPFP?

Are there other known tables that are missing?

If you want to try and find the cold start flow req tables, test them, then define them for all the roms for a slightly more accurate hpfp control when everything is cold feel free. We have to work within the defined tables and it's 10x better on the components to just basically bypass the cold start hpfp controls for the minimal emissions benefit they may provide rather than let it flop around using the currently undefined and definitely uncalibrated cold ones. Just being real here.

 

[mj6234]

Appreciate the feedback, if the cold start stuff is emissions, that makes me feel better. Wondering if the LPFP target + HPFP target and associated PID tables are coming in the XDF update. Seems like those would be very useful as well for this.

 

[V8bait]

Appreciate the feedback, if the cold start stuff is emissions, that makes me feel better. Wondering if the LPFP target + HPFP target and associated PID tables are coming in the XDF update. Seems like those would be very useful as well for this.

It's not all emissions, but higher pressure helps atomize fuel when the motor is cold, so you don't need to burn as rich and it's cleaner etc. Using the warm pressure targets it's still superior to any port fuel car so I don't think it's a big concern.

 

[KClemente]

It's not all emissions, but higher pressure helps atomize fuel when the motor is cold, so you don't need to burn as rich and it's cleaner etc. Using the warm pressure targets it's still superior to any port fuel car so I don't think it's a big concern.

So I’ve been tuning my own Helix for some time now and defined a bunch of rail pressure target maps and adjusted the to suit the 3x. Before I removed my dual fuel pump setup (temporarily) I would still get oscillations of about +/-4 on my FP_H. Jake said he’d send me a custom userchannel.xml for MHD rail pressure target monitoring but I never got it.

All I have are the generic helix/shotgun calibration + my custom targets on the rest of the rail pressure maps.

What’s the direct cause of the hpfp oscillating during pulls?

 

[mj6234]

All I have are the generic helix/shotgun calibration + my custom targets on the rest of the rail pressure maps.

What are the generic changes?

 

[KClemente]

What are the generic changes?

The photo in the .zip file on the first post of this thread. Attached are the official instructions Spool sends you when you request for the tune changes. I'm not kidding.... Change the extension to .docx if you wanna view the document yourself.

 

[mj6234]

I found these in another thread as well. Seems to be close to what you are suggesting. ***Disclaimer*** I havent tested any of this so use at your own risk. Increasing the max current seems to be the most risky to me.

 

[langsbr]

I know this thread is all over the place but is the chatter fix merely targeting a lower temp than 40*c on the "Coolant temp threshold to switch to FP target"?

I have MHD Flex fuel which my understanding removes the cold start idle. Do I still need to modify the "cold" table or is it ignored and only the regular target is used?

 

[Amateur]

Hi, guys! Tell me please, will this callibrations affect my mhd firmware? Or Can I ask my tuner to put this stuff directly to my mhd soft?

 

[Stormshadow335]

It's pretty straightforward. Your tuner would change the settings in your bin and reflash your tune. Shouldn't affect your firmware.

 

[mj6234]

@carabuser not sure if you'd be willing to help with this or not, but hoping to get some custom channels logged for IJE0S around the VCV. I'd like to at least get the PWM DC but also if possible the L/H value in the 2nd table in the screenshot. After getting my Helix installed, I have noticed after driving on the highway for a while and then idling, rail pressure creeps down into the 600s, then shoots up into the 2000s. I assume some kind of adaptation issue is causing this as if I do a short drive (not highway) and idle, this behavior doesnt happen.

I assume there is some HPFP PID control that we dont have in the XDF. I dont know that I need those tables, just would be good to know the P-value relative to HPFP DC so I can know where it is off.

I am sure I can trial and error it and figure it out at some point, but data is better!

 

[KClemente]

@carabuser not sure if you'd be willing to help with this or not, but hoping to get some custom channels logged for IJE0S around the VCV. I'd like to at least get the PWM DC but also if possible the L/H value in the 2nd table in the screenshot. After getting my Helix installed, I have noticed after driving on the highway for a while and then idling, rail pressure creeps down into the 600s, then shoots up into the 2000s. I assume some kind of adaptation issue is causing this as if I do a short drive (not highway) and idle, this behavior doesnt happen.

I assume there is some HPFP PID control that we dont have in the XDF. I dont know that I need those tables, just would be good to know the P-value relative to HPFP DC so I can know where it is off.

I am sure I can trial and error it and figure it out at some point, but data is better!

It's been on my to figure out list but it's only happened to me one time throughout the course of my 2 year helix ownership and never happened again.

If you rev it out of idle, rail pressure goes down to normal, but about 5 seconds after entering idle state, rail pressure will go back up.

That's all I remember about it and it hasn't happened since. No matter how short or long I drive.

 

[mj6234]

It's been on my to figure out list but it's only happened to me one time throughout the course of my 2 year helix ownership and never happened again.

If you rev it out of idle, rail pressure goes down to normal, but about 5 seconds after entering idle state, rail pressure will go back up.

That's all I remember about it and it hasn't happened since. No matter how short or long I drive.

Ya, 100% that is the behavior. Mine is fairly reproduceable. My theory is at highway cruise speeds, the adaption value is pushing HPFP DC down (i.e. too many amps/DC at cruising speed). At idle, the adaption becomes negative enough to put things in the bad cycle (which I am assuming adaptions are global for the HPFP, meaning some universally applied % +/- for DC). I noticed that before rail pressure shoots up to 2000+, it slinks down into the low range 600 (where target is 5MPa or 725psi). Once it gets too far under target rail pressure, the DME overcompensates and has it shoot up.

I am going to test some things out this weekend and see if I make things better (or maybe I will just make them worse). I mean I just have no idea where on the L/H hour table I am at different loads/RPM, so makes it tough.

 

[carabuser]

I'm looking into this for a customer at the moment. I think most cars with upgraded HPFP systems have these kinds of spikes and I just think it's because the DME is calibrated to work with a stock system, when you put in more capable components then you just end up overshooting the fuel pressure target. It's like putting massive hybrids on the car without altering your PID and base WGDC control.

There are different control schemes for the VCV control. I'm not sure what are active currently, it'll take more reading to work out. What I do know for certain is that the VCV is responsible for the spikes.

 

[carabuser]

I think the adaptation you are struggling with is CUR_VCV_BAS_AD_VAR_2_ADD

The control of the VCV varies but during WOT it operates in "MFP" control. I assume that's mass fuel pressure, I know it looks at the fuel demand but also has a PID that control on the rail pressure I think.

EDIT:
MFP control is constructed of 2 stages of control. It has a component that looks at the target fuel pressure and the actual and generates a kind of precontrol value.
It also has a base component which looks at the calculated fuel mass. That calculation relies on the actual load and corrects based on the trim values.

 

[mj6234]

I think the adaptation you are struggling with is CUR_VCV_BAS_AD_VAR_2_ADD

The control of the VCV varies but during WOT it operates in "MFP" control. I assume that's mass fuel pressure, I know it looks at the fuel demand but also has a PID that control on the rail pressure I think.

EDIT:
MFP control is constructed of 2 stages of control. It has a component that looks at the target fuel pressure and the actual and generates a kind of precontrol value.
It also has a base component which looks at the calculated fuel mass. That calculation relies on the actual load and corrects based on the trim values.

Interesting. WOT seems fine for me, but I guess that makes sense on what you found.

A couple other updates from my end. I pursued my theory, make some educated guesses, and flashed a new set of the 2 VCV tables. After 2 long trips, no more cycles at idle post long drive (so far). I will continue to monitor, but the exact same drive cycle gave the behavior this morning before the change, and it happened pretty much 100% of the time after any highway drive. I was watching rail pressure at cruise, idle, in gear coast and more or less whenever I could and seems like it is more stable with operation in a tighter range. Just from looking at the supplied tables, they seem focused on providing more fuel on the top end versus a holistic redesign across all conditions.

A couple other cases that I observed with the tables provided by Spool that I found odd were:
(1) I have a MT. In gear with 0 throttle, the rail pressure would 'race' a little up from ~725psi to maybe 1000 and bounce around a little until throttle was reapplied. After my changes, it seems to only go up to ~875 or so and sticks there. I am giving it less DC at 0 L/H of flow, which has a value of 1.20A stock. I am going to drop the value in this cell at my next test to maybe to 1.1A. I am assuming that in gear but coasting would still target 5MPa/725psi on the high pressure side, but it seems like it does.

(2) After coming off cruise and applying low throttle, I would see dips in rail pressure down in the 300-450psi range. Eventually it would catch back up. In my last drive cycle, the behavior was still there, but was confined to more in the 575psi range and didnt go lower.

@carabuser how is the adaption you mentioned (CUR_VCV_BAS_AD_VAR_2_ADD) applied? Is it truly a 'globally applied' value, for example +/- some % DC adjustment to the VCV itself regardless if at idle, cruise, part throttle acceleration - basically anything other than at WOT (since that is MFP mode?).

 

[carabuser]

I'm sure the MFP mode is active in normal driving too. There's no real distinction between cruise and WOT. There's 2 adaptations, that adder one and another multiplication one that will both be active whenever in MFP mode.

There are different modes for pre-start, start, idle, "crash", "VCV closed" and a few others. I think in normal operation you'll always be in MFP.

 

[RSL]

Fuel trims are additive and multiplicative.

 

[mj6234]

Had a few more drive cycles this weekend and have had the idle rail pressure hunting happen at the end of the drive cycle 2 out of 8 drives. Based on what carabuser said above, I probably have no idea what I am doing.

That being said, I am going to keep tinkering with the 2 main tables. I am open to any guidance or to test new tables that have been discovered.