DCT autoshifting early at mid RPM range

ganque

Specialist
Jan 22, 2018
53
9
0
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BMW 135i N55 DCT pure stage 2
Hi everyone,
I’ve been facing a recurrent issue lately on my 135is PS2 with DCT.
Every time I use the launch control it’s working perfectly fine, but when I shift it to 2nd it almost immediately shifts it to 3rd without any manual intervention.
I thought it was the clutches slipping or maybe too much torque and wheel spinning... I tried first lowering boost on 2nd gear without any success. Then I heard about the upcoming release of xHP which I decided to keep this issue for me until I had the chance to flash the xHP Stage 3 map, but it’s still doing the same thing.

car is putting down 544 whp and 470tq and using Toyo R888R tires.

any ideas on what might be affecting the DCT to auto shift? Is there any specific adjustment via the new xHP settings I could adjust to avoid this?
I have already installed and tested the xHP stage 3 map.

please see examples here (watch closely on the RPMs when shifting to 2nd gear):



 
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aus335iguy

Colonel
Nov 18, 2017
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335i DCT 2009
On 135/335 launch control is done with the DSC still partially active. I have long suspected it’s the DSC intervening; reason being that the M3s don’t do it and there’s nothing usually logged by the DME. My best advice (its a hunch) is to try flashing the M3 DSC calibration and see if that fixes it. Failing that its genuinely a TCU issue and a custom flash with a portion of or all of the m3 code will definitely fix it
 
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Olza

Corporal
Feb 2, 2020
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Minsk, Belarus
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BMW 135 2011
can you make a log for TCU GS40? interesting SCHALTUNGSART_AKTUELL - current logic program like XE, S or Manual and any of torque requests.
 
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RSL

Lieutenant
Aug 11, 2017
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I actually logged them yesterday testing shift maps. I need better pointers to which are which map by address in the bin though. I wasn't able to verify what I thought was XE by the changes I made yesterday, but it was a first test to see if it would even take a custom map more than anything.

Sport button off:
Normal D - XE / EGS switch 0
Normal S (shifter left) - S / EGS switch 2
Normal M - XE / EGS switch 0

Sport button on:
Drive D - E / EGS switch 1
Shifter left S - XS / EGS switch 3
Manual - XE / EGS switch 0

XE and EGS 0 for both manual modes seemed odd. I assume there is other data/flags that go with it.

I'm not sure shift maps are the answer for this problem, but could try pegging upshift shaft speeds for 2nd and 3rd to see if helps at all.
 

RSL

Lieutenant
Aug 11, 2017
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@Olza Scratch that, I was using DKG90 and a different param. Is there are GS40.prg that I haven't found? What file/job is SCHALTUNGSART_AKTUELL in?
 

aus335iguy

Colonel
Nov 18, 2017
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Really? Are you 100% sure it's because the JB4?
No I don’t have a real clue but you have an extra variable that could be affecting things. To figure out if it’s an issue or not you’d need to remove it from the equation per scientific method to be sure.
 

ganque

Specialist
Jan 22, 2018
53
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BMW 135i N55 DCT pure stage 2
No I don’t have a real clue but you have an extra variable that could be affecting things. To figure out if it’s an issue or not you’d need to remove it from the equation per scientific method to be sure.
Not trying to be one of those JB4 super fan guys.. but the issue literally started when I raised boost to 26 psi target, before that I didn't have any issues with the current setup.
Plus, when JB4 is in BEF mode, it's supposed to work just as a Boost controller / meth controller and PI Controller
 

aus335iguy

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Nov 18, 2017
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Not trying to be one of those JB4 super fan guys.. but the issue literally started when I raised boost to 26 psi target, before that I didn't have any issues with the current setup.
Plus, when JB4 is in BEF mode, it's supposed to work just as a Boost controller / meth controller and PI Controller
I’m not implying you are it’s just as I said another variable. If for example JB4 isn’t reporting torque actual accurately it could mean that the gearbox is sensing slip and as a result, short shifting. It might be that it’s doing nothing wrong as well.
 

Tzaks

Private
May 30, 2019
42
5
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35i e89
I have the same problem. FBO and stock turbos, on LC it spins the wheels up to around 40mph and then 2nd is shifted early at around 5200 rpm.

Out of 4-5 LC, only one went through the 2nd properly.

I tried running 8psi in 1st and 12 in 2nd. No difference..
Running XHP ST3 and adjusting the shift points in the flash settings to 6500, still didn't made a difference.

I'm not sure why is this happening.

I don't have JB4 and I'm running the MHD ST2+ OTS. Soon I replace the turbos and see if this is still happening.
 

ganque

Specialist
Jan 22, 2018
53
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BMW 135i N55 DCT pure stage 2
I have the same problem. FBO and stock turbos, on LC it spins the wheels up to around 40mph and then 2nd is shifted early at around 5200 rpm.

Out of 4-5 LC, only one went through the 2nd properly.

I tried running 8psi in 1st and 12 in 2nd. No difference..
Running XHP ST3 and adjusting the shift points in the flash settings to 6500, still didn't made a difference.

I'm not sure why is this happening.

I don't have JB4 and I'm running the MHD ST2+ OTS. Soon I replace the turbos and see if this is still happening.
Yeah... I've also tried to adjust settings via xHP. There's no difference on the issue.
I just tried with a different setup a few minutes ago. Same thing.
 

Mvaccarelli01

Specialist
Apr 18, 2020
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0
I have same issue.. Car will shift instantly to 3rd after 2nd like describe. same problem. when i had stock turbos it was fine went to doc kit and now it happens FULL MHD with g force boost controller. was hoping the XHP flash would fix it
 

aus335iguy

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Nov 18, 2017
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Just wanted to draw attention to this post from XHP in the xhp experience thread
Clemens here from xHP...




Short-Shifting: Thats more an opinion as really an actual error. Can be intended by us and is just not as the user wants it to be or is caused by changed throttle/load mapping in ECU Tune. Shiftpoints in BMW Software are based on raw Pedal-Value. If Tuner applies a more "aggressive" Throttle-Mapping in DME, it inevitably pulls down all Shift-Points. Possible solutions: Ask Tuner to leave that stuff alone, flash Stock DME Map, remove crappy "Throttle-Tuner" (Placebo-Box connected at Pedal), press Sport Button, use Shiftmap-Editor in xHP, check "Use Stock Shiftmaps" in xHP. For instance on our 335i the typical take-off 1-2 shiftpoint is down from 3000 to 2300, with the current FBO DME Map. The shiftmap in the TCU has not changed, but the throttle is adjusted to be more aggressive in the DME Tune, so you are only giving it 20% Throttle, instead of ~ 35% on a normal take-off, which pulls down the shiftpoint. Thats inherent and thats the reason the Shiftmap-Editor is there. There is no "optimal" mapping for all the throttle/load maps all the Tuners out there create. We map for stock Load/Throttle Mapping as that is the only base and consistently tell all Tuners to leave those maps alone. (they often just do not know what they are causing)
Seems to indicate that linear throttle settings or similar should get rid of this behaviour
 

houtan

Sergeant
Nov 2, 2017
363
95
0
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135i N55 DCT; PS2
yes, get the xhp flash and turn traction all the way off (hold button down) issue never happened to me again. XHP gives you full manual mode

the op already said xhp didn’t fix the issue. I am hoping to get feedback that a resolution was found.
 

Mvaccarelli01

Specialist
Apr 18, 2020
93
32
0
the op already said xhp didn’t fix the issue. I am hoping to get feedback that a resolution was found.
He is using LC... Launch control is used with traction partial on, not fully off. going off by the videos he posted. I been using the traction fully off function launch options of xhp (burnout mode and performance launch.... floor it and builds rpm and dumps clutch.. never happen again for me and i had same issue but going off my experience