XHP DCT - Experience Thread

aus335iguy

Major
Nov 18, 2017
1,789
Down under
Referring to people with little to no patience.. It takes time before things can be perfect. Just like any other product that releases to the public, you'll usually have a few issues on its first outing.. lol
I agree but at the same time the product is expensive, the company is experienced in this field and so expectations are understandably high.
 

v.i.335is

Private
Jan 12, 2017
37
I agree but at the same time the product is expensive, the company is experienced in this field and so expectations are understandably high.

Which is also true, but they did state that it's not a one size fits all type of application..

I do think they should have some kind of you tube tutorial on how to properly make adjustments to fit ones specific / similar setup.
 

JohnDaviz

Sergeant
Jan 6, 2019
254
i don´t understand why they silently changed the rev limit when ppl flash stock rpm limits?!

Makes ppls suddenly worry what happened that the car now shifts at 6.6k rpm instead like before at 7k. This is frustrating if company communication is not even there with the revision history of the software (which is usually a mandatory documentation for software. At least where i work).
 

Dagumpf

New Member
May 4, 2019
6
TQ Limit 4 is not normal during shift. There is a bug in the IJE0S and INA0S ROM that causes torque limit 4 on shift when you change the boost ceiling from 1.28 bar. For this reason all new MHD OTS maps remain 1.28 bar because it causes shift delay on the DCT cars. We can have @jyamona look into why, but I want to be clear that torque limit 4 is not normal. I'm personally running up to 30 psi with my Z4 35is, I do not have torque limit 4 on shift because I keep my boost ceiling at 1.28 bar and scale with a 5 bar sensor to achieve a 40 psi boost target (ceiling).
Well slap me thigh and bugger me senseless with a rubber crocodile!!!!! I have been trying to solve my xHP DCT / JB4 BEF (my own custom) issue for WEEKS, and not Terry (BMS) and not Clemens (@RayBan) or Semin (both from xHP), great peeps that they are, could solve it, and then, LO!, @WedgePerformance solves the problem in an off the cuff! Muchas gracias! I just pulled this back from 1.41 to 1.28 and my slow 0.6-0.9s gear shifts have gone!!!!!! Hallelujah brothers and sisters. Now I can go back to enjoying 360kW/700Nm without slow shifts!!
 
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carabuser

Corporal
Oct 2, 2019
142
Torque limiter 4 is normal during shifts but MHD logging doesn't give us the full picture so if you see "Tq Lim Active 4" on an MHD log then you have a problem.

There's two levels of torque limiter in the DME. Fast and slow. A fast torque intervention uses timing to correct the torque output of the engine to meet the request from the TCU. If the TCU request can't be satisfied with timing reduction alone it uses a slow intervention which uses the throttle (fuel restriction is also used at some point) .

The MHD torque lim parameter only shows the slow limiters which typically are used when the gearbox shifts at low loads, this limiter can open the throttle to raise torque during shift to get smooth engagement. Slow interventions can also come in to prevent stalling so normal during different operations. If you see a slow limiter active during a full load upshift then you'll feel it as a sluggish shift which is what you're seeing with the raised boost ceiling.

A raised boost ceiling is not the only cause of a slow limiter being active on upshifts and it's certainly something you want to look out for in logs even though you have it set back to stock ceiling. From my testing it seems that having low reported torque or overshooting boost target significantly during shift can cause slow limiters. The severity of the slow limiter varies depending on how much torque reduction the TCU is asking for, with the raised boost ceiling the torque reduction value the TCU passes is a lot lower than usual which is why you were getting horrible 1s shifts.

Would be great to get to the bottom of why the torque reduction requests are so low when using the MHD MBoost option, it's a problem that stems from within the DME, when using MBoost MHD makes logic changes to the DME that changes the data type of the boost ceiling register, this causes corruption in one of the signals that is sent to the TCU and used by the TCU to calculate the requested torque reduction during shift which is why the TCU sends back a request for a huge drop in torque. This could be fixed by either MHD or xHP, hopefully one party will have a crack at it!
 

Dagumpf

New Member
May 4, 2019
6
Torque limiter 4 is normal during shifts but MHD logging doesn't give us the full picture so if you see "Tq Lim Active 4" on an MHD log then you have a problem.

There's two levels of torque limiter in the DME. Fast and slow. A fast torque intervention uses timing to correct the torque output of the engine to meet the request from the TCU. If the TCU request can't be satisfied with timing reduction alone it uses a slow intervention which uses the throttle (fuel restriction is also used at some point) .

The MHD torque lim parameter only shows the slow limiters which typically are used when the gearbox shifts at low loads, this limiter can open the throttle to raise torque during shift to get smooth engagement. Slow interventions can also come in to prevent stalling so normal during different operations. If you see a slow limiter active during a full load upshift then you'll feel it as a sluggish shift which is what you're seeing with the raised boost ceiling.

A raised boost ceiling is not the only cause of a slow limiter being active on upshifts and it's certainly something you want to look out for in logs even though you have it set back to stock ceiling. From my testing it seems that having low reported torque or overshooting boost target significantly during shift can cause slow limiters. The severity of the slow limiter varies depending on how much torque reduction the TCU is asking for, with the raised boost ceiling the torque reduction value the TCU passes is a lot lower than usual which is why you were getting horrible 1s shifts.

Would be great to get to the bottom of why the torque reduction requests are so low when using the MHD MBoost option, it's a problem that stems from within the DME, when using MBoost MHD makes logic changes to the DME that changes the data type of the boost ceiling register, this causes corruption in one of the signals that is sent to the TCU and used by the TCU to calculate the requested torque reduction during shift which is why the TCU sends back a request for a huge drop in torque. This could be fixed by either MHD or xHP, hopefully one party will have a crack at it!
Yes, I still see both timing and throttle pulls on every gear change, but shifts are now much quicker. I can't monitor with MHD, though, because of the JB4, and thus only getting what the JB4 can log every 1/10th of a second.
 
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RayBan

Corporal
Oct 27, 2016
154
Apart from the creep and launch features it appears different mapping has been added but as you mentioned no ones talking about the documentation so no one really knows
Open App, Click on your Car, click on Map, read Changelog we post for EACH Map-Update.
 

Dagumpf

New Member
May 4, 2019
6
Open App, Click on your Car, click on Map, read Changelog we post for EACH Map-Update.
I can only find it (Android) by going to Support Check, looking up my vehicle, then clicking on the relevant map and scrolling to the bottom. Only change I can see from 1.0 to 1.1 is on map 3: DCT can blip on it's own in D & S as necessary, and, Much more sporty behaviour during braking and cornering
 

JohnDaviz

Sergeant
Jan 6, 2019
254
So my next Update:

Support at XHP seems not to know why i can´t change the rev limit. Even further there seems to be some kind of issue going on as the shifts are not smooth.
First shift at 6680rpm, second shift at 6613 but before that, rpm was at 6646 and declined a bit before shifting (felt strange) and hitting long tq limit 4 after the shift.. which is again..strange?

I may be the only one affected with this strange issue but also i never heard of anybody running stock turbos and shifting at 6.6k rpm. Everybody i know shifts around 5.8-6k..

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The recommendation now is to use stock shiftmap. Sounds like a workaround to me.
Flashing stock and everything is fine and also in the true manual mode i can hit 7k rpm. Only during automatic modes in D and S not.

What is your experience with V1.1?

I guess there will be ppl who like the new downshift behaviour but it is not my thing.
What i don´t like: When i drive towards a red light and being e.g. in 6th gear and i brake a bit harder the car hits 3rd and 2nd gear in so harsh that smooth braking is not possible anymore. Really uncomfortable.

Over all i don´t understand why XHP introduces a new Rev Limit and this downshift logic hard into the OTS maps. First one should be left for ppl to adjust in the Max RPM table and latter might be an on/off option. In the end my 335 is not a race car and i dislike this downshift logic as it makes the car less comfortable in D in different situations. Overall it still is not an M car and many ppl (who i know) use it as a daily and even family car. At least here in Germany.

Another thing is that my car is now shifting like 4 times as much as before that "upgrade" in daily city use.

I hope that XHP will change their policy of introducing/dictating "Features" that may be unwanted for some ppl and would be a great on/off option.
 
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Grunt

Lurker
Jul 30, 2019
14
Lancaster, P
Just had a weird experience. Currently running stage 3 (V1.1) for maybe 50 miles now. Was in D mode with nothing else selected. No sport button lit up green and I did not touch or deactivate the dsc. I was getting on the highway going up hill behind a semi and in 4 gear around 40 mph. I stomped the pedal, but not far enough to hit the switch. The car revved up to red line, but it did not change gears and the car did not accelerate at all. A new red warning lamp came up that I have never seen before and the idrive said that the transmission had overheated and pull over immediately and turn the car off. I switched MHD over to check fault codes and nothing. Reseting the one code I had eliminated the idrive message and the car drove fine after that. I also checked Protool and there was no code. I checked on XHP for codes and it says it has not codes. The car has never had an issue before and continues to drive fine. Anyone else have this experience?
 

carabuser

Corporal
Oct 2, 2019
142
Just had a weird experience. Currently running stage 3 (V1.1) for maybe 50 miles now. Was in D mode with nothing else selected. No sport button lit up green and I did not touch or deactivate the dsc. I was getting on the highway going up hill behind a semi and in 4 gear around 40 mph. I stomped the pedal, but not far enough to hit the switch. The car revved up to red line, but it did not change gears and the car did not accelerate at all. A new red warning lamp came up that I have never seen before and the idrive said that the transmission had overheated and pull over immediately and turn the car off. I switched MHD over to check fault codes and nothing. Reseting the one code I had eliminated the idrive message and the car drove fine after that. I also checked Protool and there was no code. I checked on XHP for codes and it says it has not codes. The car has never had an issue before and continues to drive fine. Anyone else have this experience?
You had clutch slip. Are you running a JB4?
 

aus335iguy

Major
Nov 18, 2017
1,789
Down under
Just MHD with custom tune by BQ and now the XHP for dct. No JB4. Horsepower is around 450 ish at wheels . Never had a sliip before. ???
Hmmm what mods? Miles on the car ? BQTunings tunes are know to be good at reporting torque. Is you gearbox leaking ? Have you serviced it and if so what fluid ?
 

Grunt

Lurker
Jul 30, 2019
14
Lancaster, P
Hmmm what mods? Miles on the car ? BQTunings tunes are know to be good at reporting torque. Is you gearbox leaking ? Have you serviced it and if so what fluid ?
2011 335is, just broke 88,000, stock twins, mmp down pipes, vibrant resonators (replace 2nd cats), BQ tune, vrsf cp, tial bov, csf intercooler, stage 2 fuel it lpfp, flex fuel kit but only running e40 due lack of pressure from hpfp (still debating Helix or PI), and all the other little things in between those modes to make them work. I've had the car now for the last 20,000 miles and I've been relentless with the maintance. Can't speak for the former owner though, but the car was unmolested when I bought it. The transmission is wet on the bottom towards the front of the car, but I'm not really sure if it is leaking or not as the oil pan gasket is definitely leaking and that will be a weekend in Sept./Oct. to get corrected. As for slipping, I've never experienced any slipping until I switched off the creep mode in xhp. When putting the car in reverse or even taking off in 1st, there have been times where I'm wondering when the car is going to start moving as I keep giving it more gas and nothing is happening. But in normal driving, I can't recall any slippage at any time. As life long manual transmission driver though (30+ years), I will say that I do not like driving in any of the auto modes and then stomping on the gas pedal as it seems the car will downshift, and then downshift again and then take off. That delay is annoying. Which is why I'm in manual sport mode 99% of the time. As for servicing the dct, I did buy a new filter (smaller one) and fluid, but I was having an issue with ISTA loading up correctly on my laptop so I did not do that project yet as I would need to cycle the fluid level.
 

JohnDaviz

Sergeant
Jan 6, 2019
254
When putting the car in reverse or even taking off in 1st, there have been times where I'm wondering when the car is going to start moving as I keep giving it more gas and nothing is happening.
Interesting. I observed that with their latest uncommunicated and v1.1 documented updates also yesterday.
Sometimes at a traffic light i hit 1.5k rpm without clutch engaging nor the car moving.
Some take offs felt like the gearbox was unsure what to do now.
At the very beginning when creep off was released and v1.0 maps i didn´t have these issues.

Going to v1.0 again and i hope that it solves this take off slipping from hell.
 

Grunt

Lurker
Jul 30, 2019
14
Lancaster, P
Interesting. I observed that with their latest uncommunicated and v1.1 documented updates also yesterday.
Sometimes at a traffic light i hit 1.5k rpm without clutch engaging nor the car moving.
Some take offs felt like the gearbox was unsure what to do now.
At the very beginning when creep off was released and v1.0 maps i didn´t have these issues.

Going to v1.0 again and i hope that it solves this take off slipping from hell.
When I get out to garage, I will be undoing the creep off and see how it behaves. I'll leave v1.1 on for now. If problem persists, then I'll drop back down to v1.0.
 

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