Discussion about issues encountered whilst converting to M3 Flash and GWS

[aus335iguy]

It's more likely that there could be different tables in the TCU used, if it even sees the sport mode variable. I'll have to double check if it gets sent.

If we assume this to be correct that it affects throttle and is sent to the TCU and we have talked about this previously then it stands to reason that because we haven’t addressed this it could be the cause. The sport button in a 335i goes to the TCU, not the DME. In an M its the other way around. That means we need to make the DME now send the ‘Power’ command to the TCU OR use a can shield that simulates it

The 1M flash has it and we would need to wire up the button.

 

[Jake@MHD]

Even still, I don't think it will magically fix the shifting in the higher gears.

 

[aus335iguy]

Even still, I don't think it will magically fix the shifting in the higher gears.

What else do you think it could be ?

 

[Jake@MHD]

N54 reported torque being drastically different than S65 reported torque, different final drive than expected, etc.

 

[aus335iguy]

I think you’re right but we’re struggling to test both of these theories in a conclusive way.
For the reported torque scenario we need to know how n54s and M3s report torque differently. How can we find that out?

For the final drive ratio it’s simple, we just need someone to change it.

 

[Jake@MHD]

You can already log torque output on N54. It isn't the exact val sent to the TCU, but it is very close. If for whatever reason it needs to be exact, I can track that down. But what's available should suffice for now.

S65, I am not sure if they even have logging available lol.

 

[aus335iguy]

Which of the n54 tuners here do s65’s as well ?

 

[RSL]

I tried reading through much of this, but I think I got blind sided by the N55 introduction into this while Im trying to stay focus on the N54 DCT specifically. I need to see a log of the gear the shifting issue is occurring, please use MHD default logging parameters.

Thanks

Welcome BQ, glad you're here! Right now, 1 N54 that could get to a stock (unlocked) bin for testing (TireDeathRacing) and 1 N55 DCT that I've been dabbling with for days (Strokes). N55 is an entirely different can of worms, be prepared if you open it.

 

[dyezak]

So I kind of just had an idea after looking at my log https://datazap.me/u/dyezak/log-1524081908?log=0&data=2-18-19&mark=20-21-28

Some foundational data:

1st 4.780
2nd 2.933
3rd 2.153
4th 1.678
5th 1.390
6th 1.203
7th 1.000
FD 2.56

I have 3 marks set up on this log link for you guys. Let me walk you through it:

Mark 1 - Time Stamp 70:15, shift from 1-2 initiated. RPM was 6784rpm and speed is 40mph. If we do our calculations on gear ratios and speed we can see that with the factory 335is 2.56 gearset all is well.

Mark 2 - Time Stamp 70:28, shift into 2nd done (0.13ms shift time), RPM drops to 5748rpm exactly and flat lines. But for some reason RPM's aren't climbing. The transmission is slipping the clutch. Throttle is still WOT, speed is still climbing (showing continuous acceleration), but the RPM is flat lined.

Why would the CAN request be for a drop in RPM to 5748rpm? That's not right. For 40mph, shifting to 2nd gear we should see a drop down to 4000rpm! But instead of going to 4000rpm and then starting a full acceleration up through the RPM range we are seeing a drop to 5748rpm. And at 5748rpm in 2nd gear the speed would be 55mph.

Mark 3 - Time Stamp 71:05, we hit 55mph (what the speed should be for this rpm) and BAM! RPM starts climbing.

WTF?!?!

Well, lets change our FD down to 3.15 and re-do our calculations. Oh my mother fucking jesus christ son of a bitch, the CAN requested shift RPM matches up directly with the damn car expecting a 3.15 rear diff!!!

How many fucking curse words can I say in my head right now?!

Guess what my next change is going to be? That's right, my diff that's been sitting in my garage for 6 weeks is going the fuck in finally.

(sorry for all the fucks...but not sorry for all the fucks)

 

[LMB335is]

A "eureka" moment hopefully.

 

[dyezak]

A "eureka" moment hopefully.

If I am correct, then take this and apply it in the reverse. Use the stock 335is logic expecting a 2.56 rear diff ratio and now put in a 3.15 ratio. The 1-2 shift will drop RPM down to 4000rpm, but it should be at 5800, the clutch will engage and the engine will go into seizures and herky jerky shit will start happening. It would be like you going 40mph down the road in a 6mt, pushing in the clutch and letting the rpm drop 2000rpm, then dropping the clutch. You'll get engine braking (deceleration) instead of acceleration.

If we did that on a 6mt we would just push the clutch in because we did stupid things. But how the hell is the TCU supposed to know that? So it goes into seizures and just throws a fault.

Hence why a factory 335is putting in a 3.15 diff will cause the car to be undrivable. That is also why @Bimaxtremeretro never saw this issue. Because he went to the correct diff immediately and never ran the 2.56 diff.

(This is all theory, but I feel that it is sound. To test this we would need to directly log the PT-CAN bus before the JBB. The JBB does manipulation to the PT-CAN messages and not all of them are available at the OBD port. We should then see a CAN message with the originator being the TCU at the time of a shift, and that destination should be the DME. The payload should be requested RPM, Throttle, Torque, etc.)

 

[aus335iguy]

Well then...
That’s me out. There’s no way I’m changing mine to a 3.15 which is a shame

 

[doublespaces]

Well then...
That’s me out. There’s no way I’m changing mine to a 3.15 which is a shame

Same. Can't see myself driving a 3.15.

 

[dyezak]

Well then...
That’s me out. There’s no way I’m changing mine to a 3.15 which is a shame

Think about this another way guys. It's the reported speed not matching the actual RPM+gear....

You don't have to change the rear diff...I am just doing it because I have the option right now since it's in my garage. But just put one of these on each of your wheels speed sensors:

https://yellr.com/

Well look-y look-y. With (4) of those and a little math you can run any rear diff you want. Your speedo would be off and require custom coding or something to correct that, but you just need to make the speed match the calculated RPM+Gear expected speed

 

[LMB335is]

Makes perfect sense. Same reason Terry had all kinds of issues when he dropped a M3 drivetrain into his 335is. Changed to a higher ratio and it was all good. I'm hoping the 2.81 gear will be close enough to work without issue. Not the cheapest solution but far more liveable on a daily basis than a 3.15

 

[RSL]

Is the car maintaining speed during the flat line or is it actually accelerating?

I haven’t seen anything remotely close to RPM flat lined like that on other logs, so tempted to think this particular issue may be related to the M3 DSC. Post-shift seems to be where issues are for everyone regardless, so obviously there is a miscalculated, misreported or mismatched data for everyone to some extent somewhere, but this seems different.

Curious what your shifts/RPMs look like shifting manually rather than letting the modules make the determination. Even on stock 335is, there can a be a significant difference in shifts between auto and manual shifting, even at the same throttle speeds.

I don't think these impact AT/DCT at all and have never tested, but would be great if they did

 

[dyezak]

Is the car maintaining speed during the flat line or is it actually accelerating?

I haven’t seen anything remotely close to RPM flat lined like that on other logs, so tempted to think this particular issue may be related to the M3 DSC. Post-shift seems to be where issues are for everyone regardless, so obviously there is a miscalculated, misreported or mismatched data for everyone to some extent somewhere, but this seems different.

Curious what your shifts/RPMs look like shifting manually rather than letting the modules make the determination. Even on stock 335is, there can a be a significant difference in shifts between auto and manual shifting, even at the same throttle speeds.

I don't think these impact AT/DCT at all and have never tested, but would be great if they did

View attachment 10752

The log was a manual shift. Speed is in the log provided so you can see the acceleration. You can also see the speed spike immediately after the shift (wheel spin) due to the trans engaging the clutch at an RPM that was too high. Then the speed spike (wheel spin) comes back as the trans starts slipping the clutch.

And yes, the DME tables you show are only used for the 6mt. Reason being (presumably), is the 6at and DCT use can to tell the DME what it needs. While the 6mt is dumb.

 

[Hpaula]

https://datazap.me/u/hpaula335is/lo...13-21&solo=13&mark=37-45-40-38-36-39-15-16-18

My car does the same as yours Darrick, rpms don’t climb when I shift, check 2-3 shift

 

[RSL]

Ok, just wasn't sure which actually matched what was really occuring, speed or RPM. Interesting.

 

[RSL]

Don't know where @TireDeathRacing went too, he's stock turbos and TMAP, was just on an E85 OTS map. Maybe he's waiting for the IKM0S.