Thread: M3 vs 335i
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      01-25-2008, 06:02 PM   #94
sdiver68
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Quote:
Originally Posted by footie View Post
I would like to explain why Audi chose not to fit the R8v12TDI with a DSG, is quite simple really, it can't take the torque levels (738ft/lbs) and the only gearbox available at the time was the ZF 6sp manual (before you say it, the Veyron gearbox cost £160K, it's a bit expensive don't you think). As for the RS6 well again the DSG box soon to be seen in the A4 and all models after this also can't take the torque levels (this includes the M-DCT) and the ZF 6sp auto can it's as simple as that. Also the RS6 is using the old quattro technology with the front diff mounted behind the gearbox so why develop a DSG box for a car which is to be discontinued in a couple of years or so.

You are right that the GTR is quoting slower shift times than Audi do but then again Audi also say that their box can take 200ms to change gear but this occurs only when you choose a gear out of sequence like say going up the gearbox from 1st to 2nd then 3rd but instead of choosing 4th you pick 2nd, the gearbox has chosen 4th and has to change it for 2nd gear which can take 200ms, do you follow me. The difference between Audi and Nissan is the Japanese are quoting it's worst time and not it's best.
Well I guess when you are only putting out 295 TQ the M-DCT is fine

I know the specific reasons and differences, and thanks for taking the time to reiterate for the benefit of others. However, what is the hold-up with developing high TQ DCT's? Is it because high TQ DCT's are required to be built from unobtainium to the tune of $300,000 per box?

You still have not explained why ZF has both DCT gearboxes and an improved 3rd generation '8HP' high performance speed version of their 2nd gen 6HP boxes in development. Could it be that neither technology hold a definitive edge over the other for road cars and trucks?

In your 2 gear change scenario, the ZF 6HP box can go direct, while DCT still has to go sequentially. Do we know the shift change speed comparison there? Of course, most 2 gear changes on a track would be during braking going into a corner where a few hundred ms don't mean squat.

Finally, we know the extremely fast lock-up TQ converter of the ZF box eliminates the pumping losses associated with the hydraulic TQ converters, giving a direct mechanical linkage between the pump and turbine.

Again, I'll reiterate, for the track DCT right now hold an advantage in most situations, as it should for 3x the cost of the ZF.
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