chuckbdc

I am trying, and trying, and ....

simsgw

Now count the edges.

Gary

speed21

No flywheel as such but the rotating mass appears to be still there in the clutch assembly. This would effectively take the place of a conventional flywheel. There would still be a specific weight component which would suit the requirements of the engine. The main difference appears to be that the PDK's clutch pack assembly is now incorporated as part of the drive unit, connected to the engine by a splined shaft entering into the rear of the crank instead of being attached by a drive plate on the crank....as was the case with a fluid flywheel which represented the main mass of the flywheel weight in an auto arrangement .

This new PDK clutch system looks neat in the way it is removed from the engine being part and parcel of the drive unit assembly. Looks far less complicated than having to remove the drive unit and then remove the clutch assembly from a drive plate off the rear of the crank.I suspect it has more to do with the gearbox's assembly and operational requirements rather than for the simple sake of doing away with a conventional drive plate though. It would be interesting to see how they have catered for the vibrational wear between the male spline and the female spline within the crank. There surely must be a damping arrangement somewhere to cater for the effect of the vibrations transmitted through the crank or the spline/s would be subject to wear. It sure is a magnificent piece of engineering though.....you've got to hand it to those Porsche engineers lol.

simsgw

It's brilliant. I asked that and a couple of other questions of the Cayman project manager who gave a presentation at the West Coast Tech Tactics. His first reply was ... well, an embarrassed look: "Uh... that's a subsystem issue I never looked into. I'd have to ask." I sympathize. You can't keep track of all the subsystems, and especially the ones being done best. And of course the PDK wasn't developed for the Cayman, just adapted from a successful application in the other models and in race models before that.

Twenty minutes later, he found me and said he had made a phone call and had the answer. [Stuttgart, I suppose.] Now from here on, remember it is two experienced engineers conversing, but one of them speaks English as a second language, the other one's German is thirty years out of use, and he was relaying to me what he learned from a presumably international phone call. During the cocktail hour in Germany? I didn't check my watch.

My synopsis, with those caveats, is that the rotating mass is greatly reduced to deal with the problem I had asked about [more if anyone really cares] and the clutch pack is hydraulic to help with torsional vibration. Or perhaps he was saying that the clutch pack is hydraulic for many reasons and as one effect, that deals with the torsional vibration. In any case, as you surmise, it provides the minimum rotating mass required by the engine, which I infer is not a lot. I'd have loved to pursue the discussion, but the thirty other people waiting for his attention dissuaded me.

On consideration, we used hefty flywheels in ye olden days because a highly tuned V-8 engine at idle is almost intolerable without something to smooth the lumpiness. Especially a carbureted one. But the more rotating mass, the slower the engine responds to throttle changes, and the more kinetic energy the clutch must absorb during gear changes. So the aftermarket offered lightweight flywheels for hot rodders and later for enthusiasts in general. In race cars, we don't give a hoot about comfort of course, so the flywheel is no heavier than it absolutely must be, which essentially means the clutch assembly itself is all we need.

Porsche are just moving the racing approach into a road transmission, and they can do that because the shifts are being controlled by a computer that I freely admit is better at that job than I am. Not to mention the engine is inherently smoother being a boxer configuration.

Really an impressive bit of kit, that PDK. I love the clean integration of analog and digital elements.

Gary

speed21

Makes sense that they accommodated the damping in the oil bathed plate assembly. It'd be interesting to see one dismantled to have a proper understanding. I'm sure there would be very few parts involved.

Very much so. It left me with the same impression. The advances made since 997's pdk are very significant. There is no way any man could change gears so efficiently... There is no loss of power and it's all "go".