[jimmuller]

I'm asking only because I'm curious. I've seen comments how the 2.0L has a different torque curve for PDK vs. MT. (Should that be 6MT or MT6? I can never remember.) Supposedly the MT has 10 fewer lb-ft but holds the flat curve out to 6500 rpm. For the PDK the curve is flat 2000-4500, with peak power at 6500. To put the numbers into perspective, that means the torque will have dropped to 194 lb-ft at 6500. Both engines are listed as 300ph and AFAIK both at 6500rpm. So the MT isn't giving up much and presumably makes up much of the lost acceleration between 4500 and 6500.


So I'm curious what Porsches's thinking was. Seemingly they expect MT drivers to rev higher before upshifting. But why the lower torque overall? Is it because of some other limit imposed by, say, the clutch? Or is that the preferred limit for engineering reasons and they went over-target for the PDK because of its likely lower shift points? Or what?

 

[alf_17]

That seems weird, from other cars in the VW family it is normally the DSG (DirektSchaltGetriebe VW's name for the double clutch gearbox) which is the torque limiting factor.
But I guess that the specially developed PDK has very little in common with the VW DSG.

 

[jimmuller]

Supposedly the MT has 10 fewer lb-ft but holds the flat curve out to 6500 rpm. For the PDK the curve is flat 2000-4500, with peak power at 6500. To put the numbers into perspective, that means the torque will have dropped to 194 lb-ft at 6500. Both engines are listed as 300ph and AFAIK both at 6500rpm.

After looking at the these number again I think they make no sense. Peak power occurs where, as rpm increases, the torque drops faster than the rpm is rising. (In math terms dT/dR < -1. That's how you can calculate the torque at 6500; it's the torque at plateau level times the ratio of rpms when it drops off to the rpm when peak power occurs.)

Anyway, if the 270lb-ft flat torque curve really holds flat out to 6500 then its power at that rpm would 417hp, i.e. 300 * (270 / 194).

It could well be that the torque plateau is lower and falls off at a higher rpm, but that fall-off point can't be 6500. In fact, it can't be any higher than 4667rpm. It sure can't be higher than 6500 or the peak power would be even higher than 417. I'm thinkin' the people doing those videos or writing those online articles saying those specs aren't playing with a full gas tank.

 

[aeronca65tl]

Good question! Does the PDK "cushion" more?

Does the fact that PDK has 7 gears (as opposed to 6 gears on the manual trans), allow the load to be spread out over a greater amount of steps? Interesting.

 

[jimmuller]

Good question! Does the PDK "cushion" more?

Does the fact that PDK has 7 gears (as opposed to 6 gears on the manual trans), allow the load to be spread out over a greater amount of steps? Interesting.

I dunno'. But I'm starting to question my own logic.