I can get the info to anyone that wants to swap a 2.81 into their M3 diff. Just ask Terry what driving around on a 3.15 is like.
Discussion about issues encountered whilst converting to M3 Flash and GWS
- Thread starter aus335iguy
- Start date
+1000. Waiting/praying for confirmed clean operation on a stock 335is FD. 2.81 would be a damn sight better than 3.15 for a daily if it comes to that, but hoping the last bits Derek has left will clean up the 3-4 shifts before he swaps the rear.
Guys what problems are you having exactly when you have changed the diffs.
Please be as technical as possible.
Please be as technical as possible.
I jumped back into this thread to check on progress as last time I had the GWS in my car the shifts were bad/floaty/indeterminate.
At this point, @dyezak has:
Now, the shifts are good? The M3 DSC didn't have an affect? Did it come down to NCS Expert 'tricking' to make the modules update correctly?
At this point, @dyezak has:
- Swapped DSC for the M3 DSC
- 'Tricked' NCS Expert into thinking a different VO was active in car (but didn't flash VO to NFRM/CAS)
- Flashed M3 DSC modules
- Calibrated car/DSC
- Swapped KOMBI for M3 KOMBI (after virginizing)
Now, the shifts are good? The M3 DSC didn't have an affect? Did it come down to NCS Expert 'tricking' to make the modules update correctly?
When shifting, gears above 2nd/3rd felt 'floaty' and the car struggled to land on an RPM when these shifts occur. It is reminiscent of a new manual car driver that feathers the clutch far too much. This 'floating' would take 2-3 seconds sometimes with engine speed going up and down to try to 'achieve' desired RPM. Once the transmission finally shifted, the car was able to apply power. No codes were thrown and reverse/neutral/drivelogic all performed perfectly.
Just to be clear, no one has changed the diff ratio to an m3 one yet. @dyezak and @LMB335is both have parts with @LMB335is putting an extra layer of complexity with a 2.81 final drive.
If @dyezak has an error free car that still doesnt shift properly its either the SZL or the final drive or we’ve missed something in the coding.
The concern was with using the factory 2.56 ratio, verses the assumed expected 3.15 of the DCT M3 when coding the trans with the M3 DCT programming. We made the assumption that "something" is watching wheel speeds and calculating a result outside expected parameters (aka faster wheels speeds with 2.56 vs 3.15). As I typed that, I started thinking, wheel speed shouldn't matter at all, since the rear speed would need to be out of sync with the front to cause an issue. Rumor has always been that final rear drive ratio can only been off from 10-15% of what the factory final drive was in the M3 (3.15). Therefore, based on the rumor we think the speed of the rear wheels needs to be within some expected parameter, but are not sure how to adjust so that we can run factory gearing and not have to swap ratios to something less ideal for our engine rpm/power range.
Ok guys,
Now I'm confused. As far as I'm aware,
Darricks car is now working as intended.
He simply needs to test the cruise and fit the mdm szl and test it.
Then, we can move onto diffs. I see no reason why we can't make any diff ratios work.
The other derik, are you saying the spungy shift feel on your car was the result of diff swap?
Do we have any conclusive reference at all where stock diff swaps beyond this 10-15% have been an issue ? Rumour is ok but really not enough for us to go on. I've never had a known issue with any ratios.
Now I'm confused. As far as I'm aware,
Darricks car is now working as intended.
He simply needs to test the cruise and fit the mdm szl and test it.
Then, we can move onto diffs. I see no reason why we can't make any diff ratios work.
The other derik, are you saying the spungy shift feel on your car was the result of diff swap?
Do we have any conclusive reference at all where stock diff swaps beyond this 10-15% have been an issue ? Rumour is ok but really not enough for us to go on. I've never had a known issue with any ratios.
Very nice.
Remember the m3 unit only has dsc not dtc. It's actually allot less sophisticated in terms of functions that the 335 unit.
No coding that into the cic removes all the mdrive menus and they still didn't work before I changed that. Also upon driving it it still feels like it has the funky shifts. But I will confirm that tomorrow.
I believe that the settings that @TireDeathRacing uncovered in the CIC for DSC activation/deactivation are the ones for a z4is. Can you confirm @NoQuarter ?
Gear ratios and diff really isn't my thing. Can you provide a brief
I have not seen those settings in the iDrive but I will look again when I get the car back. Still in the body shop.
It functions as intended if I shift at or near readline under WOT. If I'm not at WOT I get spongy shifts like the clutches are being slipped excessively. I've got some videos but put some family time in yesterday. I'll post a video or two along with some MHD logs so we can see what's going on.
Oh I see my bad.
So this is different behaviour to what you had originally before we spoke right ?
I'm sure we can get to the bottom of it.
Correct, before I always had spongy shifts after 3rd gear no matter what.
To recap:
- Swapped DSC for the M3 DSC
- 'Tricked' NCS Expert into thinking a different VO was active in car (but didn't flash VO to NFRM/CAS)
- Flashed M3 DSC modules
- Calibrated car/DSC
- Swapped KOMBI for M3 KOMBI (after virginizing)
This differs from before where shifts were only correct when <4th gear (1-3rd).
Just need to figure out why car can only shift near WOT?
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