Discussion about issues encountered whilst converting to M3 Flash and GWS

[dyezak]

@BQTuning I may take you up on your offer, but we haven't touched anything DME side and everything was flawless before we started down the DCT journey. After applying a little math and logic to the logs I'm fairly confident now that the axle ratio is the missing piece. If that hardware change doesn't do it then I'll start digging into DME side stuff.

On a related note...factory diff is out. Need to get a 36mm socket for my axles and I'll slip my M3 diff in place tomorrow morning. I will have to wait for the driveshaft to be fixed up for me though, and I fly out to California on Monday. That means I won't be able to test the diff theory until Thurs/Fri of next week.

 

[TireDeathRacing]

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.

Sorry been busy at work running a 2nd shift.
My gas light just came on so I should be good to try a stock map with whatever changes. Just email it to me and I'll flash it tomorrow. [email protected]

 

[RSL]

@BQTuning I may take you up on your offer, but we haven't touched anything DME side and everything was flawless before we started down the DCT journey.

I missed that, everything was fine on yours? What happened to change that?

Sorry been busy at work running a 2nd shift.
My gas light just came on so I should be good to try a stock map with whatever changes. Just email it to me and I'll flash it tomorrow. [email protected]

No sweat, was just pointing you out as a potential tester that could go to stock a map. IKM0S isn't in the works yet, so if you want to mess with INA0S in the meantime, flash it back to stock, run some logs on it with standard MHD parameters and post up. If BQ is willing test changes for the M3 DCT conversions, I'd HIGHLY recommend letting him

 

[BMWJunkie]

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)

My car does this currently with the 2.81 installed. You can watch it happen on the tach. When I shift the tach needle goes to the anticipated shift point (for 2.56) and then corrects itself to actual vehicle rpm when it doesn't match that rpm prediction.

During part throttle I can shift at lets say 4k and it drops to 3k and bumps up 300rpm a half second later. I 100% believe you are on the right track and shifts should be perfect with the 3.15 m3 diff.

 

[BMWJunkie]

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

We can thank AD-E for this idea

 

[RSL]

My car does this currently with the 2.81 installed. You can watch it happen on the tach. When I shift the tach needle goes to the anticipated shift point (for 2.56) and then corrects itself to actual vehicle rpm when it doesn't match that rpm prediction.

During part throttle I can shift at lets say 4k and it drops to 3k and bumps up 300rpm a half second later. I 100% believe you are on the right track and shifts should be perfect with the 3.15 m3 diff.

Half the systems have been told it's an M3 (with a 3.15 FD and an 8400rpm tach) and we thought 3.15 might be needed early on to make it work properly unless someone can crack the TCU bin or alter the necessary signals. Seems we might be back to that.

We've seen floaty RPM for post-shift problems, like it's waiting for a match to allow full torque, but in dyezak's case here, reported RPM just sits flat until something catches up to expected speed. Both scenarios are a probably a result of the same discrepancies, but a noticeable difference in what's reported/logged. I'm assuming that stems from the M3 DSC. Does your car have the M3 DSC also @BMWJunkie? Are your 4th gear+ WOT shifts clean and solid (other than initial potential post-shift RPM)?

 

[BMWJunkie]

Half the systems have been told it's an M3 (with a 3.15 FD and an 8400rpm tach) and we thought 3.15 might be needed early on to make it work properly unless someone can crack the TCU bin or alter the necessary signals. Seems we might be back to that.

We've seen floaty RPM for post-shift problems, like it's waiting for a match to allow full torque, but in dyezak's case here, reported RPM just sits flat until something catches up to expected speed. Both scenarios are a probably a result of the same discrepancies, but a noticeable difference in what's reported/logged. I'm assuming that stems from the M3 DSC. Does your car have the M3 DSC also @BMWJunkie? Are your 4th gear+ WOT shifts clean and solid (other than initial potential post-shift RPM)?

I have the stock dsc unit.

My shifts are solid but when I had a 2.93 it felt very sloppy. I also run a taller tire to somewhat offset the 2.81

 

[aus335iguy]

We can thank AD-E for this idea

Yep. I disagreed at the time but it might work.

I see an issue with it - Effectively, we have to trick the car into thinking it’s going faster so that the revs will match. The DSC needs this for stability management and traction control. It will likely have other undesirable effects on the car

 

[aus335iguy]

On the other hand, we can run a shorter FD now. M3 guys can also run taller.

What’s the longest FDin a DCT m3?

 

[aus335iguy]

The other thing is we might not need all the other m3 modules to do it all Just the hardware to make this work.

 

[Stokes]

On the other hand, we can run a shorter FD now. M3 guys can also run taller.

What’s the longest FDin a DCT m3?

Research say 3.62 is the shortest.. 3.85 causes transmission errors. Not sure how the tallest gear. They don't tend to go that direction.

 

[Stokes]

Just curious if anyone has access to a 3.08 manual transmission differential? That should swap in quickly and be pretty damn close for a test run. I was looking around for short tire/wheel combo, but need something like a 22" diameter setup to emulate the 3.15 gearing. Nothing in that size will fit over the brakes.

 

[TireDeathRacing]

I've got a Bin from BQ i will flash it and do some logging and report back in the next couple days.

 

[dyezak]

So I had a bugger of a stuck axle. Penetrating lube, 5lb sledge, double sledge, dead blow, heat....nothing would get it to move. So I bought a cool new toy:

Needless to say the Diff saw is WELL underway!

 

[RSL]

Damn. Not sure I'd be kneeling in front of that setup while hitting it with hammer, but at least it's loose

 

[NoQuarter]

So I had a bugger of a stuck axle. Penetrating lube, 5lb sledge, double sledge, dead blow, heat....nothing would get it to move. So I bought a cool new toy:

Needless to say the Diff saw is WELL underway!

I was just looking at one of those in the Harbor freight ad the other day.

What brand is yours? Certainly did the job!

 

[dyezak]

It's the $99 harbor freight one.

 

[dyezak]

Diff swap is done. I will take the driveshaft down to the shaft shop and have the rabbi circumcise it tomorrow. But I fly out to California on Tuesday and get home Wednesday only to fly out to San Antonio on Friday and get home late Sunday night. So I have one day this week to wrench on the car. I don't think I'll get this accomplished this week with my tight schedule. Sorry for the delay guys.

 

[aus335iguy]

Im fairly certain it will resolve the issue so don't feel pressure to rush and get it done - Its your car man!
Appreciate all the work you've done to get it to this point - essentially you now have an M3 with an N54!

It would be nice to have a way to get drive logic without all of this having to be done but it looks increasingly unlikely.
Until someone cracks the TCU we're stuck. Should we group buy a Mag2Pro and be done with it ?

 

[doublespaces]

Im fairly certain it will resolve the issue so don't feel pressure to rush and get it done - Its your car man!
Appreciate all the work you've done to get it to this point - essentially you now have an M3 with an N54!

It would be nice to have a way to get drive logic without all of this having to be done but it looks increasingly unlikely.
Until someone cracks the TCU we're stuck. Should we group buy a Mag2Pro and be done with it ?

What's the price? That should be too tough.