miami_car_flipsJul 2, 02:50 PM

Transmission Mechanical Efficiency: Dual-Clutch (DCT) vs Manual Gearbox fluid temps.

Running track days in a BMW M4 (F82). My friend has the manual, I have the DCT. During a 20-minute hot session in 90°F ambient, my DCT fluid temperature spiked to 245°F, while his manual transmission temp barely hit 190°F. Since DCTs are mechanically similar to manuals, why is the thermal dissipation requirement so much higher? Is it just the hydraulic pump heat generation?

Discussion

5 comments

luke_vtecJul 2, 04:49 PM

Manual transmissions have no pump, no clutches bathing in oil, and only experience splash lubrication. They are much simpler and reject very little heat to the oil.

cody_whippedJul 4, 04:35 AM

Also, wet clutch packs in the DCT are constantly slipping slightly during engagement and disengagement. That shear friction in the fluid is a huge thermal load compared to a single dry clutch manual.

tx_diesel_powerJul 5, 08:31 PM

You need an upgraded DCT oil cooler. The stock heat exchanger is tied to the engine coolant loop, so when your engine gets hot, it stops cooling the DCT effectively.

cali_built_brzJul 6, 10:21 PM

Yes, the hydraulic actuator pump runs constantly at high pressure (up to 700 PSI) to handle the lightning-fast shifts and keep the wet clutch packs clamped. That pump generates massive heat.

philly_stanceJul 8, 05:12 PM

Make sure you service the DCT fluid. 245F is starting to degrade the Pentosin DCTF-1. Upgrade to a larger aftermarket cooler core from CSF.