The Physics of Tiptronic vs. R tronic?

[cmxi]

I understand that a Tiptronic transmission makes use of a torque converter, while the R tronic makes use of a clutch. Is that really all I need to know? Is there anything more than a simple clutch vs lockup torque converter difference? From a physics standpoint, what then makes the assisted manual better than a true Tiptronic?

I know this a loaded question. I've looked up both, but haven't gotten a reasonably easy to understand answer than explains how the use of an automated clutch results in more power and faster acceleration vs the use of an automatic Tiptronic system.

Apologies ahead of time.

[desperado]

http://en.wikipedia.org/wiki/Tiptronic
http://en.wikipedia.org/wiki/Semi-au...c_transmission
http://en.wikipedia.org/wiki/Dual_cl...lkswagen_Group

[cmxi]

First, I should say that this probably should have said 'Mechanics' and not 'Physics'.

I read all of those before asking my question. The only thing it says aside from a torque converter replacing the clutch in the manumatic system, is that an assisted manual system "can react much faster and more precisely than a human, and takes advantage of the precision of electronic signals to allow a complete clutch operation without the intervention of the driver." But it doesn't say why a clutch is better than a torque converter, which is the key, since both the Tiptronic and R tronic use electronic systems. I definitely understand that an automated dual clutch transmission is better than both of these systems simply because it shifts faster by anticipating the load for the next gear, but I don't understand why the Tiptronic is better than the R tronic.

The only thing I can think of is a difference in torque distribution. But how or why?

I guess the easy question becomes, how is a clutch better than a torque converter? How does the former result in better performance, from a mechanical standpoint?

[desperado]

I'll throw out a few random thoughts in response to your excellent question. I'm hoping Alex at Europrice or WillyJP will chime in here, as I believe they have more technical competence in this area than I do.

Weight. I suspect a clutch/manual trans might weigh less than a torque converter/auto trans.

Efficiency. Even a lockup torque converter will have quite a bit of slip during high torque conditions since lockup mainly occurs during cruise, while the dry clutch will have little or no slip under heavy acceleration.

Shifting technology. I assume the tiptronic uses automatic trans type band clutches to shift planetary gear packs. This is another place where oil-lubricated slipping is programmed in, during the band clutch engagement. On the other hand the automated manual uses shifting forks to engage dog clutches using conventional syncros. No slipping at all. Plus no oil pumps and complicated valving necessary (inside the trans that is; hydraulics are used in the compact external actuators).

Certainly modern automatic transmissions are extremely efficient, so these are perhaps more theoretical arguments than major performance penalties. Since most automatic transmissions are tuned for smooth shifts, one assumes they slip quite a bit. Certainly they wouldn't have to do so, if designed from the outset for high performance. Those highly modified Turbo Hydramatic 400s of my youth come to mind!

Availability. An appropriate automated manual transaxle was already available from the Gallardo which met the R8's layout requirements: longitudinal crankshaft, mid-engine, quattro, with adequate torque capacity. At the time the R8 was designed (and maybe still) I don't think that was the case for tiptronics, and certainly not for DSGs. The R8 is too limited in production numbers to build a dedicated trans, compared for example to the 911 platform which sells in much higher numbers.
However, eventually the transmission manufacturers will provide an appropriate gear box, probably a DSG, suitable for this layout and capable of taking the power.

[Geo3]

+1

A very intelligently written response, Desperado.