[lemetier]

Originally Posted by kyrix1st

6ms in a roughly 1cm travel distance of clutch engagement is very possible. Do the math and you get the horizontal velocity of 1.67 meters per second, which is 1/455th of a bullet travel speed (760m/s.) And electric transfer switch what? Speed of light is 3.72E5 times the speed of bullet.

By this transmission, do you mean ZF8HP? I've never owned one with it, but I've driven 120d, M135i, Audi RS7 (pre-facelift). I didn't say I dislike it, I just think it doesn't quite fit the M character. ZF could be fast, but you can't argue you don't feel as connected as that of SMG or DCT. Downshifts never feel as firm.

Other ones I've driven (haven't owned them all except E60 for brief period) E60 M5, F82 M4, F10 M5, Cayenne (tiptronic) and Panamera S. PDK feels faster than the current Getrag DCT in the M.

Thinking of getting a low mileage E63 coupe/F87 (two very different cars I know) in the coming months but torque converter is unlikely to be on my priority list for the enthusiastic driving. Overheats way too quickly and goes into limp mode; sucks for prolonged high rpm (>7000) driving. Ever noticed how ZF doesn't like you shifting at the redline? Their limit is 7500rpm before shit starts breaking down

I don't need to calculate the order of magnitude (the maths). The 6ms figure you keep mentioning is simply incorrect. ZF do not even quote such a time in their restricted technical papers. The electrical portion of the mechatronics takes time to process and travel to the mechanical interfaces. Additionally a multi-transmission gearbox does not perform a normal gear change in sequential order (PDK 7DT, and DCT are 2 transmissions, not 1). A 1-2 change is considered a Transmission A to Transmission B shift. Only when a shift on the same Transmission occurs is it possible to be considered a normal gear change (i.e. On DCT, 5th to 7th would qualify as they are on the same input clutch, same input shaft, same sub-transmission, same dog clutch, and same output shaft). I do know of a VAG DSG Transmission that used the 7ms number in publications, however it is misleading and only represents the duration when ZERO torque is transmitted during an overlapping shift process on a transverse DSG with TWO output shafts.

There are multiple versions of the ZF 8HP, and I asked specifically to see if you've driven the 2nd Generation (ZF 8HPTU) which incorporates many significant design and operating characteristic improvements. None of the cars you've listed have it. For BMW AG Products only certain vehicles with Sport Automatic Option have the GA8HP50, GA8HP75, GM8HP75 and GA8HP95 (one exception is Rolls Royce Ghost V Specification with the GA8HP90 which is a TU variant). That 3rd one is unique (note the M designation for M GmbH). It utilizes a different torque converter that does not unlock except when stationary, though comfort shifts have some slip included. The G12 Alpina B7 and G30 M550i share the same GA8HP75 with modified torque converter rated at 800nm but with RPM limitations on peak torque from below 3000rpm and above 5000rpm on the B7 and below 1800rpm on the M550ix. The M760LiX and Rolls Royce Ghost based Black Badge Variants use the GA8HP95 rated for the full 1000nm from 1200rpm to 6500rpm. Unfortunately with up to 900nm currently available at 1500rpm (this will be increased soon to 1000nm), launch control must occur with 2nd gear active to prevent damage to the Axle to body mounting points.

The Max Speed on torque converters is an "issue" if a very high redline is needed. At 7200rpm input speed, the impeller vanes are near supersonic, causing bubbles to form in the fluid. At 7400rpm, these bubbles implode and vaporize at 7500rpm causing complete TC Stall and physical damage. I've personally gone head to head with engineers from ZF and multiple Auto Manufacturers over this issue (coined the term ZF Honk which earned me the nickname Keyser Söze of the Automotive World). My F90 will mark the 45th BMW Group vehicle I've acquired via personal means and additionally, it, along with equipment and features the F90 introduces, will be incorporated into BMW Security Vehicles and the Security Driver Training Program which I have been an instructor at for 2 decades.

When the rumors first began about the F90 switching to the 8HP75, I answered a post in this forum that a TC was no-go unless the powerband was "neutered". Although this is one way of looking at it, compared to DCT, there is no calibrated torque reduction for the sake of the transmission or driving dynamics above 7km/h. It was the best choice for the F90. M DCT was a Getrag Manual Gearbox (it was to be the 7 Speed Manual that was patented) with Borg Warner Mechatronics and Clutch Pack just as ZF 7DT is also the basis of the ZF 7MT.

Engine redline will be 7000rpm with fuel cutoff at 7200rpm to prevent possible TC Vane overspeed. Unlike the M550i, in certain operating modes it does not shift early. Overheating won't be an issue for the vast majority of track venues.

ZF 8DT would be a handicap IMO (a DCT F90 Prototype I drove wasn't quite as good overall). In the ICE only version, Max torque is 750nm in AWD mode, Switchable 100% rear 2wd is not possible (and would have further torque restrictions), and it wastes space. Without the Electric Assist, the bell housing is essentially empty.

Originally Posted by kyrix1st

It's funny because I mentioned VLN on my previous thread; they are likely using upgraded transmission cooler with bigger fans. Also, the car can't really be compared since it is less powered and much lighter than M5 so there is less strain.

I think it would depend on which ZF tranny they are running; the one with 1000Nm torque limit should have much higher threshold whereas 750Nm one will run very close.

If you like the floating carpet feel, ZF is the right choice. I don't think it's right for M, it should be more dynamic. There will never be half the aggressiveness of mechanical "banging" in torque converters since it absorbs all that shock by tranny fluid.

The M235iR (2015 version with HCC) is the basis for the most aggressive Manual Mode Shift Setting. It performs them in 40ms and the "bang" has been tuned in on the F90. The torque limit will be 850-900nm across the full powerband. That said, with Drivelogic in Automatic Sport+ (D3) and MDM 4wd Sport+ Active, the shifts are the fastest and most pronounced (this is internally referred to at ZF as Supersport Mode). In more relaxed modes it does behave like a sporty TC Auto, but that's where DCT fell short. I also feel that it's better than DCT at 8/10 and up.

Originally Posted by Boss330

Did you bother to read the ZF document on double clutch, torque converter and the new HCC?

Again, the lock up in a torque converter is a mechanical coupling just like the clutch on a DCT or single clutch manual transmission! The "fluid coupling" part of the torque converter is only used for start and stop. After that the lock up clutches mechanically locks the connection between the crank and the input shaft of the transmission.

Again, if you had read the ZF document you would have seen that the lock up system also employs a "twin torsional damper", to create the same effect a dual mass flywheel does, since gearshifts are done with the torque converter locked up! So to repeat once again, the fluid coupling is only used for takeoff, after that lock up is employed and vibrations are taken up by the torsional damping system (since the torque converter now is in a mechanically locked state).

A 270mm dual clutch pack weighs 13kg
A 270mm torque converter weighs between 17,4 and 18,8kg

So, yes a torque converter is roughly 5kg heavier than a DCT clutch pack

I'm not sure if you don't want to understand how the lock up system works or if you just want to argue

Look at these drawings that explains how the torque converter and lock up clutch works. Notice that the torsional damper is connected to the lock up clutch, not the torque converter. That is because the power transfer during driving goes through the lock up clutch and the damper takes up vibrations during shifting and on/off throttle situations etc.

The MW250's are installed in the 8HP75 (which is what the F90 transmission is based on). It will have a TC which doesn't appear in that brochure.

Originally Posted by mundo74

dont care how sophisticated the ZF is, it just sounds bad to say your m5 has an automatic transmission. doesn't sounds special one bit. after all buying these types of cars are mostly emotional and not rational.

Automated = Automatic legally from now on. FWIW, the F06/10/12/13/80/82/83/87 with DCT have S205A - Automatic Transmission hidden in the VCDS Data. The F90 has a new CIP module that incorporates all vehicle dynamics, drivetrain, connecteddrive, Radar, Nav, and Camera Systems. It's quite emotional and sophisticated.

Originally Posted by kyrix1st

Not the case with the ZF6HP on 3.0si z4 (e85). It has a lock up clutch and overheat like shit on track. It would be more time efficient for you to run both smg and zf versions of e85 on track than to give you shaky statistics behind my desk.
As for the article, if you can direct me the mechanical difference between zf 6 speed and 8 speed other than the obvious I will bother to read that.

I was not implying that lock up clutch does not act similar or identical to clutch packed manuals or dct; anything with centripetal acceleration will have centrifugal force outwards the rotating mass, in this case damped flywheel by dampers and turbine (as it seems to be in alignment with shaft rotation from your picture) in torque converter which will also be damped by tranny fluids inside the turbine. I do admit the way I said it is solely thanks to tranny fluid, which obviously isn't. In MT cars however, we do adjust gear rattle in SM flywheel with heavier oil so you can't say drivetrain vibration has nothing to do with fluid; it lubricates the rotating components afterall.

I have to point out the fallacy in your google logic of DCT vs torque converter is that people who drive sports cars with DCT tend to be more sensitive and caring while people with traditional automatics just go to service shop rather than discuss online because forum chatting is more time consuming so google doesn't do justice in showing demographics. People with automatics don't drive like complete idiots as sports car owners do. Thats why they buy an automatic! Launch control in addition is peformed from standstill, and while thermal capacity may favor zf torque convs, you launch once off the start line and sustain the momentum at high speeds both to cool the car and drive fast. Why would you launch the car several times except for drag race? This car isn't built for that. Buy a challenger for that stuff.

I have said repeatedly that primary disappointment is lack of connection between the car and the driver in torque converters, not just the creep(which can be adjusted seen in X6M) but each gear change which lacks the "bang."

Comparing the worst of the BMW Spec ZF6HP to a significantly modernized drivetrain system you've never experienced....

Originally Posted by mundo74

You need to send this to those poor idiots at Porsche, Lamborghini And Ferrari. They need to read this memo.

Porsche had no choice. The 8HP won't fit in the new MSP platform with Electric Assist. No other transmission will be offered on that platform due to these manufacturing constraints. Lamborghini and Ferrari will have the 8HP in at least 2 models.

Originally Posted by Boss330

I didn't think AMG used the ZF HCC since AMG/MB makes their own transmissions, but that what they use is similar to the ZF HCC...

And thanks for the info on the newer M235i Racing using the HCC instead of the torque converter.

Do you have a source that verifies that the F90 M5 won't use the HCC?

Daimler assemble their own transmissions in-house from components they make as well as source from ZF, Getrag, GKN, and Aisin. HCC is the MCT Startup Clutch. It isn't a torque converter. It is lighter and in its own way more "sporty". In more relaxed driving though, it sacrifices abrasive wear, builds up significant heat, and is overall more prone to faults and maintenance.

Van Meel already confirmed the TC in the F90 (and GM8HP75) transmission. The TC is a combination between the ZF Active Launch Torque converter and HCC. My time behind the wheel recently has not produced any complaints worth mentioning. I go way back with him and the promises have been kept with the F90.

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.

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.

Tech finally allows the TC to show its capabilities. As far as overheating, just because a TC locks, doesn't mean they all operate the same way. The E85 isn't always fully locked, as it has to follow fairly rigid programming logic. More often than not it's slipping to protect the more costly bits. Without a cooler, yes it heated up.

The Range Rover I'm using for DD is a test vehicle and has Drivetrain (except for the diesel power plant) more similar to the F90 than most current BMW's, but feels 100% Range Rover, easily copes with the daily torture tests, and only has shown one issue that can only be solved by the driver. It's about the programming now. It's what makes the F90 more special than its predecessors.

Originally Posted by Bowser330

Boss330 thanks for the detailed information about the ZF, it's going to be an amazing transmission to experience.

The CAR will be an amazing experience. There's still much to be revealed including a couple of features and functions I'm quite proud of.

Originally Posted by Boss330

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!

The Giulia Quadrifoglio didn't skip on tradition and go with the 8HPTU instead of a DCT Transaxle for costs

There will be complaints, praises, and then those who actually get it. They'll be the ones out driving an amazing feat of engineering full of soul rather than googling DCT vs Slushbox and being internet experts.