Dual-Clutch Transmission Swaps Are a Thing, And I’m Here For It

It’s not as complicated as you might think.

byPeter Nelson| PUBLISHED Sep 23, 2022 9:30 AM
Dual-Clutch Transmission Swaps Are a Thing, And I’m Here For It
BMW / Peter Nelson
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Swapping an automatic transmission for a three-pedal manual transmission has been a modification for a long time. Whether it's for maximizing enjoyment behind the wheel, upgrading to a sturdier drivetrain, or chasing another benefit, it’s a staple of aftermarket fiddling. But imagine going from a conventional auto or manual to a dual-clutch automatic transmission—it's happening, and it's a welcome addition to the world of customization.

A perfect example is Motorsport Enterprises Racing's NC Miata endurance race car with a swapped BMW dual-clutch gearbox. The benefits of this type of swap are significant: Lightning-fast shift times, less attention required for 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. If somebody wants to do arrive-and-drive with MER for a race weekend but can't heel-toe, no worries, the shifts will always be super quick and allow you concentrate on everything else.

It Appears To Be Easier Than You’d Think

A DCT swap appears to be easier than one would think, albeit with all the right resources. Mechanically, it's an involved job creating an adapter to mate the transmission housing 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, noting that the DCT relies heavily on CAN messages to learn what's going on between the engine controller, brake pedal, shaft paddles, and other inputs. The transmission's computer, the transmission control module (TCM), takes all of this into account to strategize the ideal shift and clutch pressure, so if any one input is missing, it won't work right.

The TCM is 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 (and service) 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 PDK gearbox 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 lb-ft 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 lb-ft, upgrading to stronger clutch packs can transmit as much as 1,000 pound-feet. That’s impressive and makes the increasing commonality of DCT swaps something to look forward to.

One Very Cool Example

GridLife time attack racer Jackie Ding did a video about SuperK Adventures’ awesome DCT-and-turbo-K-swapped S2000 time attack car. It’s a neat setup; this S2K uses a stock Acura TSX engine, basic turbo setup, standalone engine management, and a BMW dual-clutch transmission. There’s quite a bit more to it than that, but it’s not like the engine is thoroughly built or has any unobtanium parts thrown in. This is purpose-built to be a reliable time attack racer.

According to SuperK, "The acceleration rate on it at Gingerman Raceway from Turn 10 to Turn 11, until the drag takes over, is identical at 400 wheel-horse as 500 wheel-horse with an h-pattern." That’s pretty darn impressive that just being able to shift much faster means acceleration is like having 100 more horsepower sent to the rear wheels.

There seems to be zero delay in acceleration, and equally important is that you don’t fall out of boost. All of this is done via installing a GCU, or Gearbox Control Unit, which joins in with the car’s standalone engine management to make everything work. The reason for making a DCT work over going with a fully sequential gearbox is to skirt the bit in GridLife’s rulebook that bans sequentials. Intuitive, to say the least.

This post originally published on CarBibles.com.