BimmerBoost: Tell me about SSP's experience with dual clutch transmissions and why SSP got into this market?
SSP: To make a long story short, we found a niche that no one else was doing. We researched and researched and surrounded ourselves with knowledgeable people who really know this area. We have a desire to do it as the manufacturers won't give owners the information and the parts. Dealerships will just tell you to get a whole new tranny for about $15k. It should be a crime to sell the whole transmission instead of the parts. Basically, we provide something no one else does for a much better price. There are no parts available and no information on fixing these transmissions so that the Manufacturers can keep the profit for themselves but this is going to change soon.
BimmerBoost: What torque capacity are you able to take the GTR to?
SSP: Right now, the GTR is often seeing over 750 pound feet of torque. This is limited due to the tuning. We have 1000 hp clutch packs right now. Those are for cars making almost 800 pound-feet. The problem with the GTR is it just makes so much damn torque, stupid torque. Everything we have thrown at the GTR our clutch packs have held. We had one guy burn a set up but his car was not tuned correctly. It all came down to tuning. I got him a new set, paid for shipping overnight, he got a new tune, and he was tickled pink.
BimmerBoost: What instantly struck you when you opened up the BMW Getrag unit vs. the Nissan GTR GR6 Borg Warner unit?
SSP: There was a lot of similarity between the Borg Warner and Getrag clutch packs and the clutch discs were similar. The technology is all really close, someone has to be sharing something between the two companies. The BMW unit more resembles the DSG units used in Audi cars. It is very similar to that along with the Porsche PDK.
BimmerBoost: Do you believe the power holding potential of both is about the same?
SSP: It is tough to say. Everything is VERY heavy duty in the BMW Getrag unit. The BMW unit is way stronger than the DSG for example. The BMW will get to around the same point as the GTR unit. It is very hard to say as the GTR was supposed to handle half of what it is handling and it is handling 860+ whp right now. The BMW Getrag clutch discs are a little larger than the Nissan GTR discs.
BimmerBoost: You mentioned the GR6 is set up better for upshifts than the M3 DCT but the M3 DCT is set up better for downshifts, is this correct and why?
SSP: I'm going off what has been said about the DCT lag. The GTR is instantly in the next gear. The Borg Warner has better response. We are talking milliseconds here though. The GTR engagement is like night and day though, no hesitation at all. I think the reason for this is partially software and partially hardware as the BMW hesitates. Now, with the GTR we fixed the clutch play in it. The BMW has more clutch play and we need to shim it at 3 mm. Once we shim it, we hope it will fix the DCT lag. So it is 50-50 software and hardware.
BimmerBoost: There has been a big issue with shift lag in the DCT M3's. It has been largely assumed this was software but it seems you have discovered some reasons for why this is a hardware problem.
SSP: You don't build an expensive car without having some control. The software recall can only do so much. They upped the line pressure, changed the shift points, and other minor parameters. It comes down to it being cheaper to simply change the software and up the line pressure to increase clamping force as much as possible instead of doing a hardware recall. The software can really only basically raise the line pressure a bit and that is it. The rest is in the hardware.
I learned a few things from this interview. Namely, the BMW DCT is stronger than most people give it credit for and it is really built well with SSP considering it heavier duty on the inside than the Borg Warner unit in the GTR. The clutch discs are also slightly larger so it should be able to handle just as much torque as the GTR.
The DCT's trans fluid is not exactly the best as mine was in bad shape when they drained it being basically burnt. This is obviously partially my fault due to pushing the DCT so hard but I would be concerned about BMW's claim that the fluid is for the life of the tranny. My feeling is that BMW just wants to keep their costs down like they do with oil changes keeping the interval as far apart as possible. Fortunately, aftermarket fluid is already available.
Another thing, the factory DCT oil filter is pretty bad. SSP is working on a replacement for this as well which can replaced fairly easily with the transmission still in the car. This will be something those that do track days or race will want.
The DCT lag is the other interesting thing discussed. Everyone assumed it was just software but the play in the clutch basket seems to be a factor in the response as well. Just as SSP stated, software changes can only do so much. They can up the pressure in the line forcing the clutches to clamp harder/earlier but there is a limitation here. BMW just saw this as their most cost effective solution rather than having to open up every DCT transmission and shim the clutch basket. Also, this would have been embarrassing for Getrag so they probably got together and discussed the cheapest and easiest way to handle it.
The most important thing to gather from all of this is that we won't be dependent on dealers for our DCT needs and will be able to work on these transmissions and change the parts without the blessing of BMW and without a huge bill from the dealer.
Here are a couple other things SSP is working on that are interesting for those with big power going through a DCT. What leads to failure often is parts twisting due to the torque. SSP is currently working on a 6061 aluminum billet case for the GTR transmission which will prevent it from twisting under the stress. It will weigh about double, but will be worth it.