Disappointed with the F8X DCT specs

[e46e92love]

Originally Posted by Tacoma

What does shifting automatically quicker have anything to do with your "bottom line" of enjoyment? A manual is even slower to shift, so not understanding your logic.

nicknaz's view makes more sense to me. For all intents and purposes, while the mechanicals may be different, the DSC isn't going to be more fun or enjoyable than the 8-sp auto which is reportedly one of the best.

Also, I don't really buy the "too much traffic" excuse for not getting the manual. I've been driving manuals for 20 years in heavy Toronto traffic which is worst than Miami, and have never said to myself... geez, I wish I had an auto in this traffic. Never.

Really, really beg to differ. There are a lot of us 6MT guys converted to M-DCT who never did before even with the GREAT and FAST ZF trans in the 335is.....

Never heard ANYONE EVER get out of M-DCT and say it was no more involving or fun then a normal auto, no matter how good.

But your entitled to your opinion.

Cheers,
e46e92

[Tonymiabmw]

Automatics are slush boxes, try downshifting a Automatic into a corner see how much fun it is. No rev matching = no fun

[elitex]

Originally Posted by Tonymiabmw

Automatics are slush boxes, try downshifting a Automatic into a corner see how much fun it is. No rev matching = no fun

most sporty modern auto transmissions rev match.

[Tonymiabmw]

Originally Posted by elitex

most sporty modern auto transmissions rev match.

Its impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.

[elitex]

Originally Posted by Tonymiabmw

Its impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.

My old G37 did it, My BMW 550I did it, Lexus ISF on and on and on. Lot of these transmissions are directly connected after 2nd gear.

[CanAutM3]

Originally Posted by elitex

M5's DCT is simply awesome, much better than the E92 M3. Are you saying that it's going to cost significantly more money to change ratios? I don't think so but IDK enough about manufacturing costs.

^ This. Commonality goes a long way in terms of manufacturing costs. But you do also save on NRE by doing a simple carry over. I believe the ///M division had a limited budget and decided to invest on the 6MT development rather than the DCT on the F8X.

I am pretty sure that the DCT on the M5 is better than the one on the E9X M3. It has seen 7 years of evolution and development. It is just that the DCT on the E9X was specifically developed for the S65. I think that the latest DCT is better suited to the F1X and S63tu than the S55.

[czarmar]

Originally Posted by Tonymiabmw

Its impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.

As far as I know, the ZF-8 speed does rev matching between gears. The way an automatic shifts is still with clutches. brakes, and/or bands - these can all be programmed to be left open for the 50-100ms that the ECU is accelerating the engine or letting revs fall in between shifts. In a normal non-rev matching slush box, a downshift in a corner without throttle would upset the chassis as the engine braking force would decelerate the wheels. The rev match feature allows very smooth downshifts.

The ZF autobox is one of the best out there. It's still an auto, but I have trouble criticizing it, and for 90% of drivers, including those who want an engaging sporty feeling, it is perfect.

I'll take my F80 in 6MT please. I'l spend the $2900 on other options, and save myself the weight. If the weight and/or cost penalty had been less, I'd be interested in trying it out. I'm not likely to track my car much, and don't care about 0-60. I'd get it to try something different and enable my wife to enjoy the car.

[elitex]

Originally Posted by czarmar

As far as I know, the ZF-8 speed does rev matching between gears. The way an automatic shifts is still with clutches. brakes, and/or bands - these can all be programmed to be left open for the 50-100ms that the ECU is accelerating the engine or letting revs fall in between shifts. In a normal non-rev matching slush box, a downshift in a corner without throttle would upset the chassis as the engine braking force would decelerate the wheels. The rev match feature allows very smooth downshifts.

The ZF autobox is one of the best out there. It's still an auto, but I have trouble criticizing it, and for 90% of drivers, including those who want an engaging sporty feeling, it is perfect.

I'll take my F80 in 6MT please. I'l spend the $2900 on other options, and save myself the weight. If the weight and/or cost penalty had been less, I'd be interested in trying it out. I'm not likely to track my car much, and don't care about 0-60. I'd get it to try something different and enable my wife to enjoy the car.

yep, and ZF 8 speed is not the only one. Impossible?

[/// M sa]

Let's all drive the car first, then we all can bitch and moan. On paper things can look great or worse until you apply them in real life.

[CanAutM3]

Originally Posted by Racer20

On the DCT, 1st gear is 17% shorter, 2nd is 12% shorter, and 3rd is 10% shorter.

I would guess that the wider spacing is less of an issue for the DCT due to less rpm drop between shifts, and the shorter gears of allow greater torque multiplication. The powerband of this car doesn't really require tighter spaced gearing, and given the cost of developing a new gearbox and fuel economy sacrifice, I'd guess it was an easy decision to use the M5 DCT.

Being an engineer, you should have some understanding of the trade-offs that go into designing and developing something as complex as a modern car, and to say that BMW "went cheap" because they didn't build the car exactly to your liking is a bit ridiculous.

I can appreciate the desire to analyze and optimize these kinds of things, but at the same time, you need to be realistic.

I am realistic. The ///M division did design (at least provide the design specs of) the DCT on the E9X specifically for the S65, and thus resulted in a great powertrain combo. Yes, I do understand the costs involved in development and this is why I am saying they went cheap with the DCT. As posted earlier, I believe they had limited budget to work with on the F8X and decided to invest on the 6MT this time around.

Shifting at redline from 1st to 2nd brings the revs down to 4100RPM, well below the start of the power plateau at 5500RPM. Same for the 2nd to 3rd shift that brings the revs down to 5000RPM. This is not optimal for max acceleration performance.

Now, short shifting at the end of the power plateau at 7300RPM, the 4th to 5th shift brings the revs to 5700RPM (above the start of the power plateau). With a delimited car, the 5th to 6th shift would bring the revs to 6200RPM (700RPM above the start of the power plateau). Further, why do I need 3 gears that cannot reach top speed on a performance oriented car?

There was plenty of room to better optimize the ratios for the S55. It is my opinion that BMW decided that the DCT developed for the S63Tu was "good enough" for the F8X.

[/// M sa]

Originally Posted by CanAutM3

I am realistic. The ///M division did design (at least provide the design specs of) the DCT on the E9X specifically for the S65, and thus resulted in a great powertrain combo. Yes, I do understand the costs involved in development and this is why I am saying they went cheap with the DCT. As posted earlier, I believe they had limited budget to work with on the F8X and decided to invest on the 6MT this time around.

Shifting at redline from 1st to 2nd brings the revs down to 4100RPM, well below the start of the power plateau at 5500RPM. Same for the 2nd to 3rd shift that brings the revs down to 5000RPM. This is not optimal for max acceleration performance.

Now, short shifting at the end of the power plateau at 7300RPM, the 4th to 5th shift brings the revs to 5700RPM (above the start of the power plateau). With a delimited car, the 5th to 6th shift would bring the revs to 6200RPM (700RPM above the start of the power plateau). Further, why do I need 3 gears that cannot reach top speed on a performance oriented car?

There was plenty of room to better optimize the ratios for the S55. It is my opinion that BMW decided that the DCT developed for the S63Tu was "good enough" for the F8X.

Don't you think the turbos makes up for it? I rather get max power at low rpm than shifting at 8000 rpm to achieve optimal power.

[CanAutM3]

Originally Posted by Kadema

The 89lbs penalty mainly derives from the improved MT, the DCT has improved over E9x as well, but not that much, at least concerning its weight.

The 6MT weight goes down by 26lb. The DCT weight goes up by 18lb.

The 6MT/DCT weight difference on the E9X was 45lb. For the F8X: 45+26+18=89lb

Originally Posted by Kadema

I can't quite understand the very short 1st and short 2nd gear. I don't believe this is due to responsiveness, though. I think this has got to do with daily use practicality like slow maneuvering on a parking area. You can't play with the clutch like in a MT M3/4, so 1st gear got to be shorter.

I think we may be partly saying the same thing when I mentioned "responsiveness". The S55 shows very strong torque relatively low in the RPM range. But that is at WOT. My guess is that at part throttle, there will not be that much torque to be had and the engine may seem sluggish. This is why a short 1st gear is used. I think 1st gear on the 6MT is better suited for the S55, the DCT just has whatever the M5/6 has.

Originally Posted by Kadema

Since I go about 55000km/35000miles a year on the german autobahn, a long 7th gear is really great for me. I guess they also must have had customers like me in mind, not just those who primarily care for maximum track performance. Life's a bitch!

I would not have minded a long 7th gear with gears 1 to 6 optimized for acceleration. It would have been the best of both worlds.

Originally Posted by Kadema

I think the main advantage of the DCT over the MT with s55 is that you don't lose much turbo spin regardless of how you drive. The difference on the track seems to be a little less compared to E9X MT/DCT.

Agreed about the benefits of maintaining boost during shifts. Also the near instantaneous shifts times are a huge advantage. What concerns me, is that BMW does not quote a performance advantage above 100km/h for the DCT; are the weight and loss penalties offsetting the benefits? I rarely go below 100km/h at the track. I guess we'll have to wait for independent tests to get a better idea, but the BMW numbers is the only thing I can go with before I need to finalize my choice .

Originally Posted by Kadema

And no, I don't think they went cheap on us, it's all just about compromise in many respects.

I think they did, because they compromised in favour of cost. But hey, that is only my opinion

[CanAutM3]

Originally Posted by gee-m-w

You should be able to drive an entire track in 4th gear this car. Drop to 3rd if you're being ridiculous but there's so much torque you don't technically have to.

To stay in the power plateau, the lowest speed you can go in 4th in about 100mph. If you need to drop below 100mph, it is preferable to downshift from 4th. I know a lot of tracks that require speeds below 100mph.

[CanAutM3]

Originally Posted by //M sa

Don't you think the turbos makes up for it?

Yes they do, as long as you keep the revs above 5500RPM (in the power plateau).

[Needsdecaf]

Originally Posted by Tonymiabmw

Its impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.

The ZF8 in the F3x and F1x 100% without a doubt rev match on downshifts.

It's been published in many places, plus I can tell you that I've now owned two cars with the gearbox, and they both rev match.

[Tonymiabmw]

Originally Posted by CanAutM3

I am realistic. The ///M division did design (at least provide the design specs of) the DCT on the E9X specifically for the S65, and thus resulted in a great powertrain combo. Yes, I do understand the costs involved in development and this is why I am saying they went cheap with the DCT. As posted earlier, I believe they had limited budget to work with on the F8X and decided to invest on the 6MT this time around.

Shifting at redline from 1st to 2nd brings the revs down to 4100RPM, well below the start of the power plateau at 5500RPM. Same for the 2nd to 3rd shift that brings the revs down to 5000RPM. This is not optimal for max acceleration performance.

Now, short shifting at the end of the power plateau at 7300RPM, the 4th to 5th shift brings the revs to 5700RPM (above the start of the power plateau). With a delimited car, the 5th to 6th shift would bring the revs to 6200RPM (700RPM above the start of the power plateau). Further, why do I need 3 gears that cannot reach top speed on a performance oriented car?

There was plenty of room to better optimize the ratios for the S55. It is my opinion that BMW decided that the DCT developed for the S63Tu was "good enough" for the F8X.

Yeah but what's interesting is the figures says it's making max torque @ 1500-5000rpm and max HP from 5500-7500rpm so doesn't this ratio make sense

[bmwluvr24]

Originally Posted by Needsdecaf

The ZF8 in the F3x and F1x 100% without a doubt rev match on downshifts.

It's been published in many places, plus I can tell you that I've now owned two cars with the gearbox, and they both rev match.

+1 I constantly play around with the transmission and mode combos just to see what happens. I know for a fact that it rev matches every time.

[CanAutM3]

Originally Posted by Tonymiabmw

Yeah but what's interesting is the figures says it's making max torque @ 1500-5000rpm and max HP from 5500-7500rpm so doesn't this ratio make sense

To maximize acceleration, you want to maximize the average power produced over the acceleration run. Ratios that bring the RPM bellow 5500RPM are therefore not optimal. You also need to factor in transmission losses and engine inertial factors, but the concept remains.

[ss134]

Originally Posted by Tonymiabmw

Yeah but DCT doesn't feel even close to as sterile as a Automatic.

+1 - you cannot compare DCT to the 8 AT. I hate automatics and had only owned MT cars (for 20 years) until I tried DCT .....it is an incredible transmission and just as much fun for me as MT in different ways.

[Tonymiabmw]

Originally Posted by ss134

+1 - you cannot compare DCT to the 8 AT. I hate automatics and had only owned MT cars (for 20 years) until I tried DCT .....it is an incredible transmission and just as much fun for me as MT in different ways.

Thanks, everyone else that disagrees seem to drive a Auto F30 or manual E9x so of course they are bias. I also drove manuals before DCT. God I remember test driving a E46 DCT. It was horrible and ended up with a manual E46. Then I got a e60 and from there I was in love with DCT.

[CanAutM3]

Originally Posted by Tonymiabmw

Thanks, everyone else that disagrees seem to drive a Auto F30 or manual E9x so of course they are bias. I also drove manuals before DCT. God I remember test driving a E46 DCT. It was horrible and ended up with a manual E46. Then I got a e60 and from there I was in love with DCT.

Not sure I follow you. E46 and E60 both had SMG (single clutch automated manual). DCT was first introduced on the E9X.

But I agree. I also was a year 20 MT driver before I got my DCT E92 and totally love the DCT. This is a big reason for my disappointment with the DCT specs on F8X.

[Tonymiabmw]

Originally Posted by CanAutM3

Not sure I follow you. E46 and E60 both had SMG (single clutch automated manual). DCT was first introduced on the E9X.

But I agree. I also was a 20 MT driver before I got my DCT E92 and totally love the DCT. This is a big reason for my disappointment with the DCT specs on F8X.

Meant SMG forgot thats what they used to call it, been 4 years. But E60 SMG was a huge improvement over E46