DCT vs. 6MT

[SteveC]

Hi all,

Was on another BMW forum where I came across an amateur test video of the pre and post LCI versions of the M135i. The guy's pre LCI was an 8speed auto and the newer version a 6 speed manual.

He made some interesting observations.......

The 8 speed, felt quite a lot faster, due to having closer ratios.
When cruising, the 8 speed was geared higher, so returned better MPG and was less noisy and more relaxing.

And most important...when shifting on the MT you couldn't fully lift off the gas without getting a slight hesitation afterwards. This hesitation is not present on the auto as there's no lift-off requirement. Lifting off obviously momentarily drops the pressure in the inlet tract, which takes time to build once open throttle is restored, resulting in an interruption in power, so called turbo lag. I wondered why perceived turbo lag should be worse with the 6MT....I never twigged it had to do with shifting. Obviously the same thing is happening with the M5 DCT vs 6MT