[Video]:CarWow drags BMW M3 vs Audi RS4 vs Tesla Model 3 Performance

[CanAutM3]

Originally Posted by Arcades

That engineering part I didn't know about.

The RS5 I did hear the blips on the upshifts, but it was extremely subtle unlike the F90 M5 where it's generally in your face. I read that, the reason Audi didn't put the DSG in the RS5 is due to torque. The Audi DSG can't handle the torque but DSG is in the R8 for some reason but not the RS5. I could have read that wrong of course but who knows.

I think I mentioned in the thread I put up, there was some little "issues" with the ZF8 in the RS5 but I can generally forgive it because I was expecting it not to blow my mind. So, my expectation on the car wasn't great other than (I like the outside looks and Virtual Cockpit) bit. Did end up liking the RS5 more than I thought, which is surprising in itself.

I really want to avoid my next car having a Torq Auto, no matter how good the ZF8 is in the BMWs generally. Really do want to drive the RS3 though.

DKM3 don't you think though, the reason the ZF8 is taking over as it is, is due to just general factors? Lower in weight, and it is easier to drive for the general public? I mean, how many M-DCT whining threads have you seen as of late about people not knowing the little small details regarding the M-DCT tranny?

There is no technical reason to have a blip on upshift since the engine revs don't need to be raised, they need to fall to match the wheel speed.

While a DCT has "two clutches", it relies on hard splined dogs to lock the gears, just like a standard MT. A planetary AT relies on friction clutches to lock the gears, so in fact it has many more clutches than a DCT. It is using the slip between these clutches to shift power between gears without having to disengage the engine from the transmission through the main torque converter clutch. This allows the planetary AT to shift gears without interrupting power to the drive wheels similarly to what the DCT can do. However, those individual gear clutches are not as stout as the DCT main clutches and cannot handle an all out power shift, hence the engine power needs to be briefly reduced during the shift. This is what you are hearing on upshift, through clever engineering and engine management, they make it sound cool. But it is not as efficient as an all out DCT power shift.

As for the RS3 DSG, as I said, it is a transaxle, meaning that the diff is imbedded in the transmission. This transmission configuration is simply not applicable to a longitudinally mounted front engine driving the rear wheel, unless the transmission is rear mounted. The R8 also uses a transaxle since it has a mid mounted engine.

The ZF 8AT is in fact heavier and less efficient than the M-7DCT. The maindownside is not only the fact it has a torque converter, but rather that it uses planetary gears which leads the AT to have much more rotating inertia and hydraulic windage than a DCT, which makes the entire drivetrain more sluggish. This later fact combined with the shift action described above make the 8AT a less performance oriented option than a DCT. There's a reason why high end supercars still use DCT. And they can handle the torque if designed for it, just think of the Bugattis that use DCT!

I think there are multiple factors that are leading to the demise of DCT in performance sedans. The main one being cost optimization for the manufacturers, another being the general public wanting more comfort and also the fact that planetary AT have significantly closed the performance gap with DCT, so it might not be worth the investment for the small incremental gain in that market segment.

[Arcades]

Originally Posted by CanAutM3

There is no technical reason to have a blip on upshift since the engine revs don't need to be raised, they need to fall to match the wheel speed.

While a DCT has "two clutches", it relies on hard splined dogs to lock the gears, just like a standard MT. A planetary AT relies on friction clutches to lock the gears, so in fact it has many more clutches than a DCT. It is using the slip between these clutches to shift power between gears without having to disengage the engine from the transmission through the main torque converter clutch. This allows the planetary AT to shift gears without interrupting power to the drive wheels similarly to what the DCT can do. However, those individual gear clutches are not as stout as the DCT main clutches and cannot handle an all out power shift, hence the engine power needs to be briefly reduced during the shift. This is what you are hearing on upshift, through clever engineering and engine management, they make it sound cool. But it is not as efficient as an all out DCT power shift.

As for the RS3 DSG, as I said, it is a transaxle, meaning that the diff is imbedded in the transmission. This transmission configuration is simply not applicable to a longitudinally mounted front engine driving the rear wheel, unless the transmission is rear mounted. The R8 also uses a transaxle since it has a mid mounted engine.

The ZF 8AT is in fact heavier and less efficient than the M-7DCT. The maindownside is not only the fact it has a torque converter, but rather that it uses planetary gears which leads the AT to have much more rotating inertia and hydraulic windage than a DCT, which makes the entire drivetrain more sluggish. This later fact combined with the shift action described above make the 8AT a less performance oriented option than a DCT. There's a reason why high end supercars still use DCT. And they can handle the torque if designed for it, just think of the Bugattis that use DCT!

I think there are multiple factors that are leading to the demise of DCT in performance sedans. The main one being cost optimization for the manufacturers, another being the general public wanting more comfort and also the fact that planetary AT have significantly closed the performance gap with DCT, so it might not be worth the investment for the small incremental gain in that market segment.

Always nice to learn more

I honestly just go by feel for a lot of things then slowly learn about them on my own the side and by reading. Too bad didn't choose my major differently... (cough)

[ZCD1]

Originally Posted by CanAutM3

The VW/Audi DSG is a transaxle and therefore only used on their transverse mounted engine platforms. The longitudinal ones get the 8AT.

The 2012-2018 S6 and S7 used a DSG as well, with their longitudinally-mounted 4.0L TT V-8s...

[CanAutM3]

Originally Posted by ZCD1

The 2012-2018 S6 and S7 used a DSG as well, with their longitudinally-mounted 4.0L TT V-8s...

True, but that's not the same DSG unit as found in the current RS3 or R8. I don't know what the torque rating was for that DSG in the 2013-2018 RS6/7, but it was likely not used on the new RS5 due the torque limitations of that specific gearbox. The RS6 and RS7 of that era also had an 8AT for that exact reason.

DCT are being replaced with planetary AT for the reasons I stated in an earlier post.

[ZCD1]

Originally Posted by CanAutM3

True, but that's not the same DSG unit as found in the current RS3 or R8. I don't know what the torque rating was for that DSG in the 2013-2018 RS6/7, but it was likely not used on the new RS5 due the torque limitations of that specific gearbox. The RS6 and RS7 of that era also had an 8AT for that exact reason.

Mever said it was the same unit - just commenting that there was also a DSG for longitudinal applications.

Torque rating was 406 lb. ft., which, not coincidentally was the same as the 4.0TT's rating in that application (S6/S7).

The DSG would handle a fair amount more torque and power without modifications, but eventually people reached a breaking point, so tuners began offering software that clamped the clutches quicker, which helped.

The most recent RS6/RS7 never used a DSG.

[CanAutM3]

Originally Posted by ZCD1

Mever said it was the same unit - just commenting that there was also a DSG for longitudinal applications.

Torque rating was 406 lb. ft., which, not coincidentally was the same as the 4.0TT's rating in that application (S6/S7).

The DSG would handle a fair amount more torque and power without modifications, but eventually people reached a breaking point, so tuners began offering software that clamped the clutches quicker, which helped.

The most recent RS6/RS7 never used a DSG.

I am not quite sure what your point is