20 Bar Clutch-Pressure on DCT

20 Bar Clutch-Pressure on DCT

This is why you need it!

The DCT (Dual Clutch Transmission) was introduced in 2008 with the M3 E92 as the successor of the mediocre SMG transmission. It was promised to combine the best of both worlds, being very comfortable during cruising and at the same time being able to deliver very fast and punchy shifts in the higher drive logic settings. For nearly 10 years the DCT (delivered by Getrag) was BMW's transmission of choice for their M-Models (except for the X5M/X6M) and it also made a short appearance in the 135i E8x, 335i E9x, and Z4 35i. It utilizes 2 separate clutches and gear sets to seemingly switch between gears. Shifts are "overlapped", which means one clutch closes, while the other one opens simultaneously to deliver seamless shifts.

BMW Clutch Temperature

Rated at 700 Nm (520 ft-lb) the DCT offered plenty of reserve when entering the market for the M3 E92 and 335i in 2008. However, times have changed and 700 Nm often gets exceeded by far in the aftermarket/tuning world nowadays. Even the stock BMW M5/M6 F1x touches that limit with their competition variants delivering 700 Nm from the factory. Unlike the ZF-Automatic Transmissions, the DCT does not employ torque limiters per gear to protect its internals. Slipping clutches in the ZF 6HP/8HP will trigger torque limiters sent to the Engine Controller, to quickly get everything in check again during driving. Often this happens completely unnoticed by the driver. The DCT however, won't do that. It will try to raise pressure until it hits the 17/18 bar limit, but then clutches will just slip. In case of a minor slip, this might go unnoticed by the driver. Most people do not feel a few 100 RPM slips, when being overwhelmed by the sensation of 700+ Nm put down to the road. In this case, the slip will just continue until one of the clutch temperature monitors starts to trigger and you are left with an "Overheat" Message in the iDrive and Limp-Mode. Of course, your clutches have taken a substantial beating already at this point.