Merv the Derv

Anyone notice on the old E39 model the 0-60 figures were quite a bit different in terms of the auto being about a second slower than the manual. Now on the E60, which I thought used the same gearboxes, the difference is only 0.2 sec. Has BMW increased the efficiency of their gearboxes or is just wishful thinking?

ipp

Maybe one reason is the sixth gear?

znod

On the 545i, the differences between manual and auto definitely are small--maybe attributable to changed rear-end ratio(s) (don't know though). One 545i auto posted 5.2 to 60 is an R&T or C&D test, and I have never seen a manual beat that in an "official' test--which is interesting in its own right.

gwf545

The way I understand it is that there are two features at work in the ZF 6 speed Steptronic that make it more competetive with SMG or manual transmissions. First, the torque convertor is much more efficient and less lossy. Second, the torque convertor can be locked up in all six gears, which means that you can potentially remove all its loss once the lock-up occurs. Most auto transmissions do this today, but only their top gear. It's primarily for fuel economy.

Under what conditions the Step locks up in lower gears is unclear, but the PDF elsewhere on this site says it does. I have also experienced it lock up in 2nd and higher gears. It's much more diffcult to detect this in 1st, since it is such a low ratio. You can tell it locks up because a slight depression of the throttle will not run the RPMs up without accelerating the car as you might see in a conventional automatic. The engine in this case is clearly "connected" to the rear wheels and it feels like it. However, it also unlocks if you goose it hard enough and afterward I can't detect when it locks up again.

I am not sure how big a factor this is, but I suspect it has some bearing on the similar performance.

cobradav

545 Rear end ratio:

Auto = 3.23 Tranny - 1st = 4.17; 2nd = 2.34; 3rd = 1.52

Manual = 2.93 Tranny - 1st = 4.04; 2nd = 2.4 ; 3rd = 1.58

Enough to get you to 60 MPH easily. Definitely going to be quicker in 1st gear in auto then things start to even out so any loses in torque converter are made up somewhat. They can afford this higher numerical gearing in the auto because there are two overdrive gears in 5th and 6th.

alexnyc

i think the difference in 0-60 for E39 540i sport was 0.1 sec(6.1 against 6.0),not 1 sec-that would be too slow.As to why it is now 0.2 sec-i would not know,i also saw results posted in some mags as manual being slower...