If you can hold off one / two more days I should have a definitive answer and video.
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- Thread starter dyezak
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If you can hold off one / two more days I should have a definitive answer and video.
So... upshifts do not use the "set RPM" routine that launch control and downshifts use, which makes sense. However, I am trying to think through why shifts would be sloppy when using the wrong FD. Best I can come up with is the TCU keeps clutch pack open and sending the "I'm performing an upshift" message to the DME until RPM is where it expects it to be. I've verified that the TCU knows exactly where RPM should be for the next gear (assuming correct FD), as during a downshift the "set RPM" routine is updated every 10ms until the downshift completes.
So can we trick the TCU with a fake RPM message and then send the correct one once the clutchpack is closed back up?
It doesn't take in RPM as a message, I believe it gets it from it's own input shaft speed sensor or something. Someone mentioned it in this thread I know.
The shafts have Hall effect sensors from what I've seen, but spoofing them would be internal to the TCU, in which case, would still need access to TCU bin or comms. That, assuming we can confirm there is positively no RPM CAN communication to/from the TCU. For some reason, I thought there was.
Yeah there’s an RPM sensor on the input shaft according to the documentation I read.
Edit There’s 3 sensors. one on the input shaft, one on input shaft 1 post clutch and input shaft 2 post clutch.
It was discussed here https://bmw.spoolstreet.com/threads/bmw-dct-information.2950/
I think the reason the call routine for RPM during launch can be altered and this cant is because when launch is initiated the box is still waiting for the correct RPM and you can launch in that period. The shift behaviour requires RPM in a narrow band.
Sadly I dont think that DME logic is likely to fix this TBH but @jyamona youd know more what do you think ?
Edit There’s 3 sensors. one on the input shaft, one on input shaft 1 post clutch and input shaft 2 post clutch.
It was discussed here https://bmw.spoolstreet.com/threads/bmw-dct-information.2950/
I think the reason the call routine for RPM during launch can be altered and this cant is because when launch is initiated the box is still waiting for the correct RPM and you can launch in that period. The shift behaviour requires RPM in a narrow band.
Sadly I dont think that DME logic is likely to fix this TBH but @jyamona youd know more what do you think ?
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+1 ...*Aus335iguy looks @ @Bimaxtremeretro, *looks in wallet...
Depending on things such as power levels and how your car is set up to deliver this, differences in gear change characteristics following the 'M3 swop' and whether changing the final drive could add addition strain, you may want to consider upgraded options - I've already had one OEM driveshaft break!
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OEM E8x driveshaft or a modified M3 driveshaft? The M shaft makes the E8x/E9x look like a toothpick.
I get it, it's hard to argue with 0 quid. I have my modified M3 shaft going in this week along with the rest of the drivetrain. It was about $500 US for the driveshaft and modification which was pretty reasonable I think. M3 shifter and programming is going on right now.
Sounds good. I looked into something similar but couldn't get close to that price.
Have seen it done a few times and appears to be a good route to go.
Interestingly, I believe there was a recall on pre 04/11 E82 N55 for a weakness identified in I think a driveshaft joint. Mine's a 07/11 build but it does get you thinking.
Might try to dig up the recall details to see exactly what it was.
Seems the right way to go.
Maybe expand more on other ratios that may work? (based on the percentage differences)?
Maybe expand more on other ratios that may work? (based on the percentage differences)?
No other ratio will upshift properly. And the 3.15 comes with quite the low mph ceiling for anyone trying to 1/2mi
I take it That’s tested and proven that your logic fix doesn’t work now ?
Thanks for trying man!
Yea, a built head with Ferra valvetrain and setting up the redline at 8000rpm will be the final piece of the puzzle. That will give you the same exact rpm/speed as the M3.
I take it That’s tested and proven that your logic fix doesn’t work now ?
Thanks for trying man!
Yea, the TCU only sends the RPM request for launch control and downshifts. So I don't think there's anything I could do on dme side. Its too bad it doesn't seem to gets rpm signal from dme either. You could yellow box all the wheel speed signals going to the TCU but that might have some negative side effects.
Isn't M3 redline 8300? What would the max mph be at 8k with a taller tire vs. 8300?
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