Running a 3.62 diff with a DCT

[peter de la mare]

Well, I've just driven the car home in both auto and manual modes, up to 5k, and all seems good so far. Will drive it more tomorrow.

[Redd]

I think the problems occur at downshifts.

[dmk08]

Originally Posted by peter de la mare

Well, I've just driven the car home in both auto and manual modes, up to 5k, and all seems good so far. Will drive it more tomorrow.

Cant wait to hear more! Very interested to do this to my car.

[C-los]

Originally Posted by peter de la mare

Were you able to have a look?

Sorry, no i haven't. I haven't even had time to drive the M in two weeks

Been working on a house construction project. I plan to hook up this weekend and check it for you guys. I'll Keep in touch on it.

[peter de la mare]

It’s not a problem. I’ve driven it to Germany and completed a track day at the Nordschleife and driven it back. No problems whatsoever.

[nycplumber]

Originally Posted by peter de la mare

It’s not a problem. I’ve driven it to Germany and completed a track day at the Nordschleife and driven it back. No problems whatsoever.

Were you able to compare times? How would you the describe the change in performance?

[peter de la mare]

Originally Posted by nycplumber

Were you able to compare times? How would you the describe the change in performance?

Not really able to compare times sadly, as I'm still dialling myself into the track, but the eagerness out of the corners and especially Bergwerk up to Kesselchen is noticeable. I was also to close up fairly easily on a near identical E92 here.

[bigjae1976]

Originally Posted by peter de la mare

Not really able to compare times sadly, as I'm still dialling myself into the track, but the eagerness out of the corners and especially Bergwerk up to Kesselchen is noticeable. I was also to close up fairly easily on a near identical E92 here.

Good to hear. I think gears on a DCT will be a massive advantage.

The problem with the E46 is most people put manuals on track and the SMG is too rough. A 4.10 results in extra shifts which gives back some, all or more than the advantage gained from gearing. The DCT is so much better. I think you can run short gears on a DCT car with no time penalty from extra shifts.

[SYT_Shadow]

Originally Posted by bigjae1976

Good to hear. I think gears on a DCT will be a massive advantage.

The problem with the E46 is most people put manuals on track and the SMG is too rough. A 4.10 results in extra shifts which gives back some, all or more than the advantage gained from gearing. The DCT is so much better. I think you can run short gears on a DCT car with no time penalty from extra shifts.

Yes, I concur.

My question is whether this is for your MCB car or if you're buying another E9X to be dedicated to the track?

[bigjae1976]

Originally Posted by SYT_Shadow

Yes, I concur.

My question is whether this is for your MCB car or if you're buying another E9X to be dedicated to the track?

I occasionally think about an E90/2 track car in the future. Kind of leaning towards an E90.

Need to get the E46 M3 setup, run TT, hopefully win my region and then sell.

[SYT_Shadow]

Originally Posted by bigjae1976

I occasionally think about an E90/2 track car in the future. Kind of leaning towards an E90.

Need to get the E46 M3 setup, run TT, hopefully win my region and then sell.

Best of luck!

[peter de la mare]

I need to update this. The downshift blips are all messed up. I finally got some good track day time last night and with the shift speed set at 6, the downshifts were mistimed and way too low.

Luckily my car is getting a Syvevs ECU installed and mapped in a couple of weeks' time which will resolve this.

[jcolley]

Originally Posted by peter de la mare

I need to update this. The downshift blips are all messed up. I finally got some good track day time last night and with the shift speed set at 6, the downshifts were mistimed and way too low.

Luckily my car is getting a Syvevs ECU installed and mapped in a couple of weeks' time which will resolve this.

Who is your stock DME tuned by? It might be worth asking them to change the final drive ratio in it to see if that helps. If I recall looking through the disassembly, the code for rev matching is within the DME, not the DCT firmware. I'd have to go back and look again to confirm that.

[M3SQRD]

Originally Posted by peter de la mare

I need to update this. The downshift blips are all messed up. I finally got some good track day time last night and with the shift speed set at 6, the downshifts were mistimed and way too low.

Luckily my car is getting a Syvevs ECU installed and mapped in a couple of weeks' time which will resolve this.

What do you mean by "mistimed and way too low"? I've been running a diffsonline 3.62 diff for nine years combined on my '09 (sold) and '12 e92 M3s and I've had zero downshifting issues. However, I always use the shift paddles (manual mode) so I have control over when/where a downshift occurs.

[peter de la mare]

On track I only ever use manual mode and in setting 6. The downshifts do not rev match at all, and it’ll drop into gear and match revs once the gear is engaged. I’ll upload a video of my trackday on Monday and you’ll see.

[M3SQRD]

Originally Posted by peter de la mare

On track I only ever use manual mode and in setting 6. The downshifts do not rev match at all, and it’ll drop into gear and match revs once the gear is engaged. I’ll upload a video of my trackday on Monday and you’ll see.

Are you running stock DCT or GTS DCT software? I've used both and the only difference is the GTS software is slightly quicker shifting and rev matching. However, I didn't encounter any rev match issues with stock software. Also, I haven't had the FD changed in the software.

[peter de la mare]

GTS software

Compare these videos, after first, and before 2nd.

After.

Before

[C-los]

Originally Posted by C-los

I think you can just program and tell the DME what Final Drive you have and it'll auto compensate. My autel when i hook it up lets me retrofit different differential ratios?

at least i remember seeing it there. I'd have to double check again.

Ok, I finally got off of my ass and double checked. I SWEAR I saw it there... But, could not find it. I know BMW has removed features throughout it's updates.. like the emergency blinking taillights under heavy braking.... I'll keep digging into it. It's bugging the crap out of me... Lol.

[MSY]

I'd be very surprised this offered at benefit on track. I can't think of a single cali track that I'd want a shorter 3rd gear on other than a few corners like Andretti hairpin but I wouldn't want the trade off of having to shift into 4th earlier given the total track consideration.

[driftflo]

a 3.62 is a no brainer for a track car. 15% more torque on the wheels compared to no time you loose while shifting in a dct car...
i do not know anybody regreting to have switched to 3.62... including myself!

[MSY]

It's more than time lost shifting! You have to shift sooner in each gear therefore anytime you now need to sgmhift earlier to 4th, you lose the benefit of being in 3rd. It really all comes down to individual tracks

[bigjae1976]

Originally Posted by MSY

It's more than time lost shifting! You have to shift sooner in each gear therefore anytime you now need to sgmhift earlier to 4th, you lose the benefit of being in 3rd. It really all comes down to individual tracks

The point is the DCT shifts fast enough to have a negligible effect on acceleration.