N54 and early N55 HPFP Volume Control Valve Tuning

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Sbrach

Corporal
Oct 2, 2017
224
As many of you who follow my tuning thread in the N55 section know, early last year when I installed a PS2 on my N55 running E55 I quickly met the limit of HPFP capacity. This didn't make sense, I've seen N54s hit high 500s even into the 600s on E40 w/ just the stock DI. So a lot of time in WinOLS and translating German documentation resulted in finding the tables that define the behavior of the Volume Control Valve. Adding some custom logging channels revealed that the VCV was limited to about 62% duty cycle. N54s run a bit more. Later, after testing and tuning on my car and some local test cars for a while, I shared these tables with MHD and they were incorporated into the N55 E series OTS tunes for higher ethanol content. Jake Yamona defined the same tables for his N54 test car and did some testing, he found there was not as much additional capacity due to the higher stock duty cycle. On N55 E series increasing the duty allows maxing a PS2 on E50 with no supplemental fueling.

Now with these OD pumps from Spool currently being tested by us at Wedge Performance along with others we have partnered again with Jake and MHD to define the necessary tables and logging channels to properly tune a HPFP that is turning faster than stock as well as maximize the flow at full demand. These tables are also useful for cars without an overdriven HPFP, especially early E series N55 (98G0B) which are limited so greatly on the stock calibration.

The DME takes the requested fuel flow variable and calculates the current required at the VCV to achieve the desired flow. The PWM value that will draw that desired current is calculated and applied, of course with PID and adaption on top of that.

We are currently working with Spool to test these tuning solutions with their new pumps and will release these tables soon. More to come. Thanks to Jake for all the help getting these tables and logging channels defined on the N54 ROMs.

VCV I8A0S.JPG
 

doublespaces

Administrator
Oct 18, 2016
7,471
AZ
Sorry for the lack of context but let me insert this mini-dialog as I think it is important:
V8bait said:
Excellent work, this might explain why overdriven pumps fall off up top, couldn't scope the output while driving lol
Sbrach said:
I think so. The valve becomes a restriction at high flow and I’m sure PID is maxed negative at low flow too with stock calibration and then it has to revert to positive up top
V8bait said:
Yep, it errors out eventually, especially on the twin pump setups if you don't target high enough to just let it tap the sensor. Single pump is actually trickier to keep it from erroring out the pid, like 30ff on the hpfp
V8bait said:
doublespaces said:
I would really like to see more on this. Is this shown as a sharp decline in pressure?
Yep, it errors out eventually, especially on the twin pump setups if you don't target high enough to just let it tap the sensor. Single pump is actually trickier to keep it from erroring out the pid, like 30ff on the hpfp
Here are a couple of logs from a previous setup, would you consider this the same thing as it falls to a pressure and just holds steady?
27718

27719

27720


At first you can see it recover in the gearshift and the next one it doesn't even try? At first, there is so much pressure it bounces off the mechanical relief at 3600 and then somehow pressure disappears and then doesn't change? It must be some sort of fall back?
 

Weehe

Lurker
May 21, 2019
14
So is there anyway an individual could get the xdf with these tables defined? I understand Sbrach is not in charge of the public xdf. I'm fine paying for it/a tune, but I want to keep an unlocked bin so I can tweak it as needed.
 

V8bait

Sergeant
Nov 2, 2016
366
Texas
@doublespaces yeah that's what I'm talking about. Can usually tune around it but sometimes it's really frustrating. Some cars don't hit it. It's holding back the single overdriven pump cars on the vtt setup from hitting even higher numbers so I'll be looking forward to more testing.
 

jyamona

Captain
Free Vendor
Nov 7, 2016
1,026
Philly
So is there anyway an individual could get the xdf with these tables defined? I understand Sbrach is not in charge of the public xdf. I'm fine paying for it/a tune, but I want to keep an unlocked bin so I can tweak it as needed.
Not at the moment, as there is a lot more work to be done. Right now it's very easy to make your rail pressure worse than it is with stock values :)
 

houtan

Corporal
Nov 2, 2017
127
Really awesome work.

So is there anyway an individual could get the xdf with these tables defined? I understand Sbrach is not in charge of the public xdf. I'm fine paying for it/a tune, but I want to keep an unlocked bin so I can tweak it as needed.
Since it was provided to MHD, I feel like we should be bugging them for the xdf and they should provide it. What you think?
 

Weehe

Lurker
May 21, 2019
14
Not at the moment, as there is a lot more work to be done. Right now it's very easy to make your rail pressure worse than it is with stock values :)
So what still needs to be done? All I (and probably every diy N55 tuner) am looking for is the xdf with the tables defined. Are there more tables that need to be defined? Sbrach was able to get it to work for himself. I'm not looking for OTS values, just something for me to work with and test on my car. You can also mess up boost pretty bad with the available wgdc/pid tables if you don't know what you are doing.

Since it was provided to MHD, I feel like we should be bugging them for the xdf and they should provide it. What you think?
I agree, didn't mean to keep bugging Sbrach.
 

Bnks334

Sergeant
Dec 1, 2016
308
New York
Since you brought up spool, I'd be interested to see how the tuning side of things is panning out... I've seen some rail pressure oscillations in logs since the release of the e-N55 tables. Might just be tuning needed but could point to some of the other hurdles that still need to be crossed. I am curious what the logs look like of the few people running around with Spool pumps pushing 3-4x volume. It's hard to capture the consequences of some of this stuff even with MHD having half-way decent logging resolution. I know some N55 guys have posted up logs capturing momentary losses of pressure and super lean points before rail pressure finally settles on target.
 
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Weehe

Lurker
May 21, 2019
14
Changes are being made guess-and-check style as is. It will need all PID tables added, more base logging params, and the PID logging params at a minimum.
I'm not going to pretend I know anything about table discovery, but, is there anyway to just compare differences between N54 and N55 bins to narrow down the tables? I'd just like to get up to N54 E85 levels. Should we start a table discovery fund for this as well?
 

houtan

Corporal
Nov 2, 2017
127
Since the pumps are in testing, can you share what type of lpfp or any other modifications that will be required to support the the OD? Will any stage two pump work? Will fuel lines need to be upgraded? Etc.
 
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