Increasing line pressure by increasing reported torque

Sbrach

Corporal
Oct 2, 2017
200
#1
Some of you probably saw on FB in the DCT group but I have been measuring DCT clutch and system pressure via INPA in an attempt to get some verified data regarding the differences between E and F series tq holding capacity.

My car is a 2011 E82 w/ PS2 running around 22psi. EGS is flashed with the 135is file via WinKFP.

Popular opinion is that the F series cars hit 18bar on the clutches and that E series was limited to something less. As you can see in the screenshots, I hit 16.76bar at around 800nm.

Increasing load to torque in an attempt to report the max 1024nm at the clutch resulted in a NMAX torque limiter (rev limit) that didn’t actually reduce load req, timing, or anything until 6200rpm where it dropped load req hard. Very weird.

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I’m back on stock load to torque now but if anyone with an F series or an e9x wants to try to grab the same data points I think the comparison would be interesting.
 

houtan

Specialist
Nov 2, 2017
79
#2
Could that nmax torque limiter at 6200 rpm be the reason why I hit limp mode around the same rpm (6000ish) when I have boost above 19psi, even though my log looks perfect?
 

jyamona

Lieutenant
Free Vendor
Nov 7, 2016
770
Philly
#3
Steve, what's the approx reported torque where the 2048 lim popped up?
 

Sbrach

Corporal
Oct 2, 2017
200
#4
I’ll post the L2T table I was running but 2048 popped up as soon as full throttle was applied. I think it was hitting a driver torque request limit. Not sure why it didn’t do anything to reduce tq until the limiter dropped off at 6200 but I have a lot of other things changed. Would be interesting to test just increasing the L2T on an otherwise stock car.
 

RSL

Sergeant
Aug 11, 2017
275
#6
Nice info. How well does log output line up with the actual INPA values? I'd go out and run mine, but laptop is dead and adapter is in storage :rage:

It may be rev limiter limiter at 6200rpm, but you can hit 2048 at barely any throttle/RPM (E N54) and not even in prep for/during a shift, so classifying 2048 strictly as a rev limiter limiter may be a bit of misnomer. It's obviously triggered during other scenarios as well.

I assume you have torque cap and limit offsets maxed. Not sure on N55, but N54 stock cap is 1000nm and will toss a limiter 1 (which is also DTC) when you reach it. 998.6nm is no limiter, 1000nm is limiter 1. Everything else goes as planned (boost, load, etc.) during the limiter. I was just messing around a year or 2 ago to see if I could reach the max without issue. I didn't try raising the cap or shifting closer to redline (let off at 5600 here), just called it done and flashed back to normal lol

tq_cap.png
 

Sbrach

Corporal
Oct 2, 2017
200
#7
I think 2048 is strictly rev limit but various things can cause a reduced rev limit. For example before I found some wheel speed plausibility tables the logged speed value would drop to zero past 171mph. This caused a revlimit tq limiter because at 0mph the rev limit is reduced.
 

jyamona

Lieutenant
Free Vendor
Nov 7, 2016
770
Philly
#8
but you can hit 2048 at barely any throttle/RPM (E N54) and not even in prep for/during a shift, so classifying 2048 strictly as a rev limiter limiter may be a bit of misnomer. It's obviously triggered during other scenarios as well.
What? lol. Tq Lim 2048 is definitely max rpm.
 

RSL

Sergeant
Aug 11, 2017
275
#9
I'll try to dig up logs, but they're years old. I could easily hit 2048 at part throttle and less than 3000rpm. Torque monitor adjustments averted it. In my case, seems like a monitor caused a limit reduction like Sbrach said, but it was actually a torque problem, despite a rev limit limiter being called. I could hit a 2048 pulling out of the driveway if I tried lol

When I think rev limit limiter, I think shifts and high RPM, that's just not always the case.
 

Sbrach

Corporal
Oct 2, 2017
200
#10
Lots of things can induce a lowered rev limit. Vehicle speed, oil temp, gear, EGS or DSC issues, etc.
 

Sbrach

Corporal
Oct 2, 2017
200
#12
Jake would be the guy to talk to about NLS, LC, Anti-lag, etc that needs custom logic.

I’m just working on getting stock calibration tables defined and understood so we can fix as much as possible via calibration rather than custom logic. The good news is based on the 1000whp S55 with MEVD17 I think we can get a lot done with just calibration compared to N54.
 

RSL

Sergeant
Aug 11, 2017
275
#13
Lots of things can induce a lowered rev limit. Vehicle speed, oil temp, gear, EGS or DSC issues, etc.
Thanks. The usual things I was aware of, but honestly hadn't given much thought to the limit being pulled down past that and mine revolved solely around torque changes, which made it difficult to think its response was actually a rev limit. Makes sense though and seems blanket solution for a lot of situations, where ever they actually stem from. I could hit it at will cold/warm, 5-70mph, any gear, etc. in varying states of testing, but found my notes for it (2015 lol) and they indicate a 2D59 set, so definitely a torque issue, and dropping the rev must be the go-to response.

Back to the actual line pressure testing...
 

jyamona

Lieutenant
Free Vendor
Nov 7, 2016
770
Philly
#14
@RSL yea it sounds like whatever monitor you were exceeding caused a limp style rpm limit to get set.

Could this be used for 2 step then ;P
No lol. Even regular DCT launch control as is doesn't keep the throttle fully open, which I've had to change.
 

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