Quote:
Originally Posted by kyrix1st
The thing is ZF torque converters rarely let you go over 7000 rpm (hates it over 6500rpm redline) and you will definitely feel the lack of high rev in corners similar to Hatzenbach or even Pflanzgarten.
Depends on the setup and number of gears. You use SMF+sprung pressure plate in a 5 speed it would make little to no noise because it is damped. In a 6 speed (particularly getrag) it makes a pretty loud rattle even with sprung pressure plate, so we dampen it a little bit using the thicker oil. When the tranny gets hot, the rattle comes back because the oil thins out, but after some cool down, it doesn't make the rattling noise.
All those cars you mentioned are "hot hatch" segments and people who opt for DSG for its performance. You seem to be trying to divert attention to DCT overheating, but would a transmission(unless it is faulty) regardless of being DCT or torque converter overheat under normal use? Likely not. Where would it overheat? Fast mountain roads or track, and usually so when the driver doesn't quite know how to manage cooling cycles. You live in Europe so you should have been to nurburgring nordschleife. Ask a guy there whether he would drive an automatic over MT or DCT. Here there's a lot of E92 DCTs at the track but I haven't heard a single one complaining about transmission overheating.
I still stand on my two reasons I mentioned previously on why a transmission would overheat, and torque converter up until very recently has been the lesser being. I see that bumper aeros are also slightly different for M235i racing, and I assume that air duct path is also different. I wish I had the actual data to clarify the superiority of high end DCT vs high end torque converter other than the shifting speed and weight but I haven't digged in yet.
Never said ZF isn't a great transmission. My father happens to own '13 XFR(8 speed) and shifts are generally fast but you don't have that mechanical clunking feel of DCT. ZF is a very good transmission for comfort. Since your brought up journalism I would also comment on how Chris Harris (the current Top Gear host) thinks about these cars:
Where he mentions this about F12 M6.
"Difference here is the powertrain. The powertrain is just absolutely extraordinary, because it is aggressive and you have to get up and use all of it; then this car comes alive, and it comes alive in a way that the others I'm afraid can't match."
Which sums up the characteristics of DCT: sustainable at high rpm, rev happy, fast and aggressive. |
Just want to clarify that I also consider the DCT/PDK versions of double clutch transmissions to be the current gold standard. My point here is that the more aggressive ZF8HP transmissions are getting closer to the DCT and that automatic transmission, as proven by the latest GM/Ford auto, can offer just as quick shifts as the PDK. In my opinion it's just as irrelevant to talk about the old ZF6HP in this context as it is to use the GM TH350 from a 1978 Chevrolet Suburban as a reference to explain how a modern automatic transmission can perform.
I don't think that we have yet seen a ZF8HP that is as good as the DCT, even though the Alfa Romeo Giulia Quadrifoglio version seem to come pretty close, with fast and hard upshifts as well as aggressive rev matching on downshifting.
I have just tried to clear up some of the obvious misconceptions about how shifting, the torque converter and lock up works in a modern automatic trans.
I'm also worried about the apparent rpm limit in the ZF8HP. And if the rev counter video I shared is accurate, then it seems shift points have changed from roughly 7200rpm to between 6300-6700 rpm. That is a further deviation from the "high rpm M engine" philosophy if proven to be the case...
BTW, you do know that VAG offer the DSG in Polo, Touran, Tiguan, Sharan, Transporter/Multivan cars and that the models I referred to was just a random selection of models. Also, I wouldn't consider a 1,6l diesel Golf a "hot hatch" just because it's a Golf... (even though it seems you do
).
I have been to the Nürburgring quite a few times (once so far this year) and since no M-cars have had a automatic transmission it's not really a realistic proposition you make. However, a lot of AMG's, M235i's, Audi RS models, Jaguar F-type R's etc run around the Nürburgring with their 7- or 8-speed automatic transmissions without any problems. As well as a lot of ordinary BMW Gmbh models for instance.
The last M-car I drove was the F80 M3 CP with DCT and I also love how hard it shifts and the near instant gear changes, that makes the driving experience that bit more "special". AFAIK there isn't any technical reasons they can't achieve the same with an automatic transmission, especially with the HCC wet start clutch system instead of the torque converter. And it seems that the ZF8HP in the Alfa allready comes pretty close to the DCT.
Fingers crossed that the M5 will have a transmission that delivers!