Gathering information on the M-DCT transmission

[IND-Distribution]

While the S65 engine of the E9x M3 has been the subject of fairly extensive study by many tuners and BMW enthusiasts since the car’s development, we feel that the knowledge base for the car’s incredible DCT transmission has remained quite limited, especially when compared to the wealth of information available about the car’s many drivetrain, suspension, and control systems.

With this in mind, we began to take a closer look at the DCT to understand what limitations the transmission had, and where those limitations would stop us and our fellow enthusiasts in enjoying our M3s. Over time it became abundantly clear that the transmission hardware was overall incredibly robust. Even after installing multitudes of ESS VT2 supercharger kits on our client’s cars and seeing those same cars log hundreds of track miles for several years, we’ve seen no hardware failures to date.

Clearly, then, the physical hardware seems to be robust enough for the most demanding M3 driver in even very stressful situations. From what we’ve seen, if the M-DCT transmission has any one weak point, it is temperature control. Damage to the clutches and other internal components can occur if the transmission temperatures climb above a safe level. Fortunately for all of us BMW M has protected us by forcing the M3 to enter a safe mode when the transmission temperatures rise above acceptable levels.

It is possible to achieve high enough operating temperatures to engage limp mode if operating in very high ambient temperatures while simultaneously making very high power levels. Although we’ve heard of very few instances where this has occurred, two of our clients with very high output engine setups operating in extremely harsh have encountered BMW’s DCT safe mode. Although both have only seen limp mode a couple of times, this prompted us to investigate further. Oddly, even basic information regarding the transmission’s operating temperature ranges was largely unknown by the BMW enthusiast community. After repeated queries, even our best contacts at BMW were not able to say exactly where the M3 chooses to enter safe mode to protect the DCT transmission, or what criteria are used to calculate this critical temperature!

I wanted to share the information we do know with the M3Post community, in hopes of expanding the community’s knowledge of the M-DCT transmission.

The DCT transmission uses two coolers to control temperature: a coolant to oil heat exchanger and a oil to air heat exchanger.



The coolant to oil heat exchanger facilitates a faster transmission warm up by circulating transmission oil through a bypass valve in the transmission thermostat (the thermostat is part number 9 in the above diagram). The transmission oil exits the thermostat and travels to the top of the transmission via a soft line (part number 12 in the above diagram) where it enters a heat exchanger. This heat exchanger uses warm coolant from the engine to help the transmission oil get to operating temperature more quickly during a cold start. The oil then returns to the thermostat block through pipe number 13 in our diagram, and re-enters the transmission. The coolant is circulated to the heat exchanger via an auxiliary coolant pump which is electronically controlled via the M-DCT computer and can be turned on or off when needed. This system will first bring the transmission oil up to operating temperature more quickly for better cold starts, and then use the engine cooling to maintain a stable transmission oil temperature once operating temperature has been reached.



At 203 degrees Fahrenheit, the thermostat opens oil flow to the front mounted oil to air cooler, positioned in the passenger side bumper opening. This oil to air cooler will work to maintain a stable oil temperature from that point forward. Part number 1 in the diagram above is the supply line to the oil cooler, and part number 2 returns the cooled oil to the transmission.

This covers the transmission cooling system during normal operation, but what about when the oil temperature exceeds BMW’s acceptable parameters? This is what we set out to explore. To help our clients better understand how their DCT transmission is operating, we created an adapter that can interface with a temperature sending unit to give an accurate reading of the DCT oil temperature.



We are still waiting for our friends at BMW to give us the maximum allowed temperature value, but in the mean time we will communicate with our clients who have already installed our DCT oil temp adapter and gauge set to monitor their experiences as they use their cars both on the street and the track.

I apologize for the long post, but I do hope that we can begin an open discussion about the DCT trans and educate the BMW community!

[tha_good_life]

good info! Glad I have a 6 speed. No need to worry about this when I get my SC

[IND-Distribution]

Thanks.

Just to be clear- the DCT transmission is a very tough cookie. Through all that us and our clients have put the transmissions through, we've never had a problem.

I wouldn't say there's something to worry about, as much as there is something to be curious about.

[cipher5]

Good info Ilia! Keep it coming.

[klammer]

Was waiting for this am also wondering as am planning on testing the limits of this car as a dual performer (track/DD) Either I put this car in the ground or drive it forever, and Ilia and the guys at IND will be with me for the ride This is what makes IND great, not just slapping a diffuser on the car and sending you on your way, but trying to innovate and improve upon our already "ultimate" driving experience, thx guys

[Crazy Bimmer]

Excellent info.

As someone who doesn't own a supercharger but wants to keep his DCT M3 for a long time this has perked my interest. I may install this just to monitor the temperature as it would give me a better understanding on when its warmed up enough for a beating.

[jmflukeiii]

Hey thank you so much for posting this all. Its actually why I originally joined this forum... to learn more about the car I drive. Very good stuff.

[aajami]

It's great that IND (and you, Ilia) do so much R&D on your own in addition to the day-to-day work that pays your bills. It's an excellent example of long-term strategic thinking that keeps companies like yours at the top of your industry. Too many other shops are just content installing air filters and taking your money.

[swamp2]

Good effort. Although the coupled engine/transmission thermal management system was announced and described long ago by BMW. Not in quite the detail you have offered, but nothing really new here in this regard.

Here is what I would really like to know. How can you do a FULL fluid drain and swap. I don't want to replace 1/3rd of the fluid 3-5 times to arrive at a fluid condition that is not even fully clean/new fluid.

Coming up with some instructions on how to accomplish this would be a huge service to those that do not drink the "life time DCT fluid" BS from BMW.

[Brosef]

awesome info! these are the kind of threads that make this forum worthwhile.

[Gearhead999s]

Good info!Considering that I got my new M-DCT last week I will be following this thread with lots of interest.

[flipm3]

great thread Ilia! when I first saw the pic of the "adapter" i had a good feeling it was a DCT temp sensor! this is great news and opens up some doors to see the needs of an oil cooler.

like klammer and Crazy Bimmer mentioned, this is great for DCT drivers who plan on keeping their vehicles for the long haul and putting it through it's tough paces.

its stuff like this that proves that iND is more than just a top installer, more than having the best taste in style, but they are true enthusiasts and automotive tuners.

i can't wait for more info!

[bigjae1976]

Originally Posted by swamp2

Here is what I would really like to know. How can you do a FULL fluid drain and swap. I don't want to replace 1/3rd of the fluid 3-5 times to arrive at a fluid condition that is not even fully clean/new fluid.

Coming up with some instructions on how to accomplish this would be a huge service to those that do not drink the "life time DCT fluid" BS from BMW.

+1

[bobbyd1961]

great thanks for the info its unfortunate i dont know what your talking about

[SchnellM3]

Originally Posted by Brosef

awesome info! these are the kind of threads that make this forum worthwhile.

+1000000

DCT + S65 = I cannot wait to see what the future holds for them

[hl0m4n]

to expand the knowledge check out the m3 dct build thread, has many pictures, explanations, ssp developed products, etc; good read too. http://www.***********.com/showthrea...-BMW-DCT-Build

[biglare]

Great stuff Ilia. I'm glad that you guys are thinking along these lines for our DCT cars. I'll be at the track this weekend, but I don't expect to get any DCT limp mode issues. Lets touch base next week.

[stega]

very cool.

[stega]

Originally Posted by hl0m4n

to expand the knowledge check out the m3 dct build thread, has many pictures, explanations, ssp developed products, etc; good read too. http://www.***********.com/showthrea...-BMW-DCT-Build

LOL so I guess they dont like beemer boost here??? lolz.. would not even let me put the name in this thread..

I do understand there is some beef between some people on the two sites. But there really is some good info there.

[swamp2]

I referenced that thread in another post and it got the same treatment. My (vague) understanding is that forum was started by the king of being banned here at m3post.com, member "Sticky". In all fairness he was a real piece of work. He got so mad about being banned he said he would start up his own message board and did. It is a bit uptight to edit this severely IMHO...

[lve2xlr8]

Great info guys. Definitely subscribed

[bigjae1976]

Not sure what I expected but that DCT unit looks like a normal MT gear box except you'd be in for a nice 173lb surprise when you remove it!

[IMG]http://www.***********.com/attachment.php?attachmentid=569&d=1270084254[/IMG]

So I guess the clutch packs are behind that metal plate? Its looks so easy to service!