Swapping an automatic transmission to a good ol’ fashioned, three-pedal manual transmission has been a thing for a long time. Whether due to maximizing one’s enjoyment behind the wheel, upgrading to a sturdier drivetrain, or any other benefit, it’s a staple of aftermarket fiddling. But imagine going from a conventional auto or manual to a dual-clutch automatic transmission.
A dual clutch transmission is, simply put, a transmission with two clutches. One clutch engages the odd gears, the other the even gears. It utilizes a complex system of synchronizers and input shafts to get the job done, this video demonstrates it all perfectly.
Motorsport Enterprises Racing (MER) recently announced that it swapped a BMW dual-clutch gearbox into its NC Miata endurance racing car. The benefits of a dual-clutch are significant: Lightning fast shift times, less attention required for performing flawless, manual-transmission shifts, very little upsetting of the drivetrain from shifting gears, less fatigue during endurance racing, and more.
Plus, MER can accommodate a wider variety of drivers with this setup. Doing arrive and drive with MER for a race weekend, and aren’t a heel-toe pro? No worries, the shifts will always be lightning fast and allow you concentrate on everything else. The benefits are really quite apparent. So will it become a more common transmission swap?
It Appears To Be Easier Than You’d Think
A DCT swap appears to be easier than one would think, albeit if someone has the resources. Mechanically, there’s a bit to do as far as making an adapter to mate the transmission housing mate to the engine.
Then, there’s the matter of making the transmission communicate with the car’s non-BMW inputs. Seems Legit Garage (SLG) does a great job at explaining this:
“So if these are so great, why don’t people use them more often? Well, they have required OEM electronic controller architecture which is very hard and expensive to implement in a vehicle it wasn’t designed for. From the factory the DCT relies heavily on CAN messages to learn about what’s going on from other vehicle modules such as the Engine Controller, Brake Pedal, Shift Paddles, and more. It then takes into account all of the external factors and makes shift and clutch pressure strategy decisions based on a computer inside the transmission. If missing any CAN signals, the transmission can easily not act as it should and can even go into limp mode.”
Essentially, the transmission has its own brain, the transmission control module (TCM), which needs to pull data from various inputs and sensors to work properly. It’s just below the ECU in terms of car-go-forward hierarchy, and both need to be able to talk to each other. SLG’s solution is actually pretty simple, all things considered:
“All is well in this world though, the aftermarket has come up with a solution to bypass this overbearing and overcomplicated OEM system. We can take the onboard controller out of the equation and essentially hotwire directly to a few sensors and the shift solenoids inside the transmission. From there, the aftermarket transmission control module (TCM), which is mounted in the car like any normal ECU, can control the shifting based on just a few easily inputted signals such as accelerator pedal position (0-5V), brake pedal status, and RPM. Fun fact, we can even implement a 0-5V electronic clutch pedal or steering lever (Like on a F1 steering wheel) to override the DCT clutches and perform conventional standing starts, clutch kicks and burnouts!”
Porsche’s dual clutch gearbox, the PDK (Porsche-Doppelkupplungsgetriebe, say that funf times fast!), can do clutch kicks – so can aftermarket tuning now!
Don’t Forget: More Power
Another important point that SLG brings up, is the DCT’s potential to hold more power, especially wet-clutch type systems. Wet clutch systems have clutch packs that have fluid in them to help with heat, whereas dry clutch systems do not.
SLG states that from the factory, BMW DCTs can hold as much as 450 pound-feet of torque. That’s a lot, and far more than almost any Miata track/race car would need. However, re-tuning the TCU can yield as much as 740 pound-feet, upgrading to stronger clutch packs can transmit as much as 1,000 pound-feet.
That’s pretty damn impressive, and further begs the question: why haven’t more people mounted these up and hacked into them to work on their non-BMW drivetrains?