BMW DCT swap gear ratio best option

[Nbjeeptj]

I have been researching DCT options to swap into my 6 speed S550, I’m coming across 2 different options on the gear ratios for these. One where 1 to 1 is on 5th which is where my current 1 to 1 is and the other with closer ratio between gears with 1 to 1 on 7th. I never use over drive on the track and rarely even use 1 to 1. So would it make sense to do the closer ratio unit to get more options, or is that going to cause too much shifting up and down?

Currently I run NASA SE and we are on CMP, Robeling road, and Road Atlanta as the main tracks. At CMP and Road Atlanta I end up shifting 3rd to 4th a lot and at CMP will even shift to 2nd for turn 14 some. Robeling road I have found staying in 4th for the whole track is faster but would like to get into 3rd but the time to shift does not seam worth it and on a lap timer I am quicker staying in 4th.

 

[Mad Hatter]

What DCT are you looking at? And what its your rear end gear ratio? Ahh, I see you have the auto 10spd (you mentioned 7th gear... but say you have a 6spd??). How's the overheating going?

 

[Nbjeeptj]

I currently have a 6 speed manual (mt82). Rear end is 3:73.

Looking at the BMW DCT from either a M4 (long ratio) or the one from a Z4 (short ratio)

 

[Mad Hatter]

From what I found out before, the swap to the bimmer DCT is not that simple... Need some good computer skills to get the brains from the DCT to talk to rest of the car . If you went DCT, I would get the short ratio unit so to take advantage of the fast gear changes, had a race prepped Z4 for competition and his gear ratios were bang on. My car is with the Calimer stage 3 MT82 and use the 5th (1:1 with 3.73) all the time at speeds over 120mph.

 

[cholmes1]

Do you have a shop or knowledge source you are pulling from for this swap? Are you thinking some group like https://www.seemslegitgarage.com/DCT

 

[Nbjeeptj]

Seams ligit was where I was thinking of getting most of the parts probably eBay for the transmission itself.

 

[Mad Hatter]

Seams ligit was where I was thinking of getting most of the parts probably eBay for the transmission itself.

The parts will be the easy part... Getting them to talk to each other is way beyond anything I could get done locally, so hats off to you if you get it to work. You need some pretty cool electrical/computer skills to get it done.

 

[FilxNZ]

Slightly off topic, however these days it might be better to look at a ZF 8HPxx transmission to swap instead of the DCT. There is a lot of information and support from the 8HP swap community and some interesting products to help make it achievable like TurboLamik

 

[Mad Hatter]

I think that would be simpler. But truthfully, shifting your own gears is part of the excitement of the stang.

 

[Nbjeeptj]

I think that would be simpler. But truthfully, shifting your own gears is part of the excitement of the stang.

While I do agree that changing gears is fun, there are a few other issues for my situation that are making the paddle shift option attractive. I have said before in other threads that I started tracking cars back in 2018 and bought my mustang in 2019. The 19 mustang has rev match so I never learned to heal toe the car. So here I am running TT3 events with NASA some 80 track days worth of experience and I can’t heal toe a manual trans. My car has a issue now where with no warning it will just not rev match, so I am likely doing 140+ at the end of a long straight and need to down shift for a turn and it gets real exciting when the rev match does not work when I let the clutch out. I have tried to solve the issue with that but I just can’t seem to find what is causing it. I have had the opportunity to drive both a GT3 with PDK and several BMW’s that have the DCT and I fell in love with the paddle shift while holding the gas pedal to the floor option. I do however have a huge investment in both money and time to build my mustang into the track toy it is now so I don’t want to give up on it, I just want a paddle shift option, that is quick and strong enough to live in this environment. So for me the pros / cons goes like this:

Pros
Technically faster than a manual

Don’t have to relearn how to drive manual with heal toe in the middle of a TT3 points race

Less expensive than a Porsche, or BMW.

Cons
Not super cheap

Can’t seam to find a wealth of knowledge of what it takes to carve one into a mustang

Probably more expensive to maintain and repair / replace as needed.

 

[Mad Hatter]

Just thinking, you could plumb in a alternative revmatch kit like Autoblip? Its a very cheap option. I think a new make came out with one as well, forgot the name. Remembering now that most DCT bimmers I raced with had a lot of heat issues and frequently went into limp mode when pushed hard.

 

[67GTA]

Just thinking, you could plumb in an alternative revmatch kit like Autoblip? It’s a very cheap option. I think a new make came out with one as well, forgot the name. Remembering now that most DCT bimmers I raced with had a lot of heat issues and frequently went into limp mode when pushed hard.

Xineering - plug & play harnesses with digital programming. Highly recommend.