Disappointed with the F8X DCT specs

[nicknaz]

Originally Posted by Tonymiabmw

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

I have the dct in my z4 (same unit as e9x m3) and 8spd sport auto in f30 335 and they feel pretty close when I use the "manual" mode

OP I understand where you are coming from. I am on the fence about DCT for the F80 also.

My key concern is which one has better cooling and which can handle more torque if I decide to modify. Haven't been able to find any tech on this front.

[swamp2]

Somewhat ill informed and highly speculative (as pointed out by a prior reply)...

Originally Posted by CanAutM3

I am hugely disappointed with the DCT specs on the F8X so far

That 89lb penalty is the first blow.

I also find that the gear ratios have been poorly selected for optimal acceleration performance.

Speculation without simulation. As noted prior, gear ratios don't matter that much what matters is average power, I think you know this. I'd be happy to run some comparisons vs. what you feel are improved gear ratios, just provide the ratios. However, I can also predict the results in advance - very little change. Probably some improvement and some things hurt. Hopefully, you have some better ideas than the last totally oddball gear ratios you had in mind in one of our prior discussions.

Also, as pointed out prior, with the power curve in this engine, the ratios are even less important.

Originally Posted by CanAutM3

1st gear is so highly de-multiplied, that it will be impossible to put the power down. I think it was selected mostly to make the engine feel responsive in off boost puttering around.

And one can avoid substantial wheel spin under agressive acceleration with exactly which sports cars?

Originally Posted by CanAutM3

7th is only an additional overdrive for fuel economy; having 7 gears is no longer used as an advantage for acceleration (tighter overall gear ratio spacing).

I like this choice, 6 gears is more than enough and an overdrive makes sense.

Originally Posted by CanAutM3

Looking at BMW published acceleration numbers (http://www.bmw.de/dam/brandBM/market...2975025706.pdf), the DCT has a 0.2s advantage over the 6MT from 0-100km/h. However, that 0.2s gap is maintained from 0-200km/h. I would have thought that the DCT quick shifts (2 more shifts needed to go from 100-200km/h) would have widened the gap. It seems that the lighter weight and/or gear ratios of the 6MT allow it too keep up with the DCT in that speed range.

BMW often makes up numbers, you know this. They are very conservative on 0-60 but often much less conservative on standing 1km, etc. Also, wait for some real world test with less effective MT drivers who can bang off perfect shifts every time.

Originally Posted by CanAutM3

Further, looking at the 80-120km/h pick-up numbers in 5th gear, the DCT is slower by 0.1s. Both cars have the same 5th gear overall ratio.

Noise, not meaningful.

Originally Posted by CanAutM3

that the additional weight and losses of the DCT are the culprit.

Reasonable. More weight doesn't help.

Originally Posted by CanAutM3

We will have to wait for independent tests to confirm any of this. In the meantime, going with the numbers available to us, my feeling is that BMW went cheap on us for the DCT on the F8X .

They certainly should have focused more on achieving the same weight difference as in the last generation.

[Tonymiabmw]

Originally Posted by nicknaz

I have the dct in my z4 (same unit as e9x m3) and 8spd sport auto in f30 335 and they feel pretty close when I use the "manual" mode

OP I understand where you are coming from. I am on the fence about DCT for the F80 also.

My key concern is which one has better cooling and which can handle more torque if I decide to modify. Haven't been able to find any tech on this front.

Come on, I've driven 3s with 8 speed auto and my x5m has one.
Shifting manually on the autos sucks period. I drive my e90 DCT manual most of the time( except rush hour traffic).

[mdss6]

Originally Posted by e46e92love

+10000.

These cars are NOTHING alike, and I don't want BMW trying to earn the customer who does, because that leads down the path to the dark side when these cars BECOME like those.

They are all great performance cars that are NOTHING alike. That is like saying all humans that weigh the same have the same BMI....

Cheers,
e46e92

"Nothing" is a bit strong, but I agree the cars are distinctly different. And now the M3/M4 are going to be different too. With changes that concern many E90/2 buyers, as reflected in forum threads and comments too numerous for me to count. But I'm very glad to see the improved fuel economy. If a relatively low-torque high-RPM motor (and all the inherent track friendly characteristics) could have been retained while achieving the improved fuel economy, that would have been great. But the M engineers went in a different direction, with more torque at lower RPM. Without any test drives or independent reviews, the degree of change in character is anyone's speculation. But while I thought the E90 was a wonderful dynamic experience, its fuel consumption was a deal breaker. And I think BMW has made the right changes...while eager awaiting reviews and the ability to make my own evaluation. Regards

[dmk08]

Im thinking of unchecking DCT and using that money on full leather.

[Needsdecaf]

Originally Posted by Tonymiabmw

Come on, I've driven 3s with 8 speed auto and my x5m has one.
Shifting manually on the autos sucks period. I drive my e90 DCT manual most of the time( except rush hour traffic).

Your X5M has a 6 speed auto.

[Tonymiabmw]

Originally Posted by Needsdecaf

Your X5M has a 6 speed auto.

yup was wrong

[Tonymiabmw]

[ybbiz34]

Originally Posted by Tonymiabmw

Come on, I've driven 3s with 8 speed auto and my x5m has one.
Shifting manually on the autos sucks period. I drive my e90 DCT manual most of the time( except rush hour traffic).

Interesting. The ZF 8-speed "Sport Auto." in the F30 335i is one of the best automatic transmissions I have ever tested and used.

Praise for its quickness is nearly universal. And I don't/didn't find the shifts in M mode to be slow either. Upshifts were virtually instantaneous in the F30 335i and there was a thunderous "fart" or crack every time I ripped one off with the paddle.

That transmission was the perfect pairing for the N55.

[Tonymiabmw]

Originally Posted by ybbiz34

Interesting. The ZF 8-speed "Sport Auto." in the F30 335i is one of the best automatic transmissions I have ever tested and used.

Praise for its quickness is nearly universal. And I don't/didn't find the shifts in M mode to be slow either. Upshifts were virtually instantaneous in the F30 335i and there was a thunderous "fart" or crack every time I ripped one off with the paddle.

That transmission was the perfect pairing for the N55.

Most DCTs are outsourced to Getrag BMW,Ferrari and Mercedes. It's all software IMO

[Kadema]

Originally Posted by CanAutM3

I am hugely disappointed with the DCT specs on the F8X so far

That 89lb penalty is the first blow.

I also find that the gear ratios have been poorly selected for optimal acceleration performance. The DCT essentially has similar ratios as the 6MT from 1st to 6th, I even find that the ratios on the DCT are worse than on the 6MT . The lower gears have too much spacing while the higher gears are too tightly spaced to properly leverage the S55 power curve. 1st gear is so highly de-multiplied, that it will be impossible to put the power down. I think it was selected mostly to make the engine feel responsive in off boost puttering around. 7th is only an additional overdrive for fuel economy; having 7 gears is no longer used as an advantage for acceleration (tighter overall gear ratio spacing).

Looking at BMW published acceleration numbers (http://www.bmw.de/dam/brandBM/market...2975025706.pdf), the DCT has a 0.2s advantage over the 6MT from 0-100km/h. However, that 0.2s gap is maintained from 0-200km/h. I would have thought that the DCT quick shifts (2 more shifts needed to go from 100-200km/h) would have widened the gap. It seems that the lighter weight and/or gear ratios of the 6MT allow it too keep up with the DCT in that speed range.

Further, looking at the 80-120km/h pick-up numbers in 5th gear, the DCT is slower by 0.1s. Both cars have the same 5th gear overall ratio. Further, the 6MT matches the DCT 4th gear 80-120km/h despite the DCT having a slight gear ratio advantage in 4th. So I can only assume that the additional weight and losses of the DCT are the culprit.

We will have to wait for independent tests to confirm any of this. In the meantime, going with the numbers available to us, my feeling is that BMW went cheap on us for the DCT on the F8X .

A view thoughts:

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.

I checked up the DCT gear spacing. It allows the F8x to stay (almost) exactly in the power band shifting III-IV and IV-V, the higher gears are tighter, so that should be ok. 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.

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 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.

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

[Tonymiabmw]

Bottom line any one who enjoys manual, will always enjoy DCT more that Automatic. I would get manual but Miami traffic is horrible and don't like to sit in traffic with a manual.

[paddy335]

Why would you care how fast your car went from 80-120 in 5th? If you're in 5th you're not in a hurry

[ybbiz34]

Originally Posted by Tonymiabmw

Most DCTs are outsourced to Getrag BMW,Ferrari and Mercedes. It's all software IMO

Software does play a role. For example, the ZF 8-speed in the F30 335i has been described as sharper than the one in some of the new Jags.

[hwelvaar]

Originally Posted by Tonymiabmw

Bottom line any one who enjoys manual, will always enjoy DCT more that Automatic.

How is that?

[Tonymiabmw]

Originally Posted by hwelvaar

How is that?

Steptronic on automatic is pretty clunky in manual mode, especially on downshifts. It doesn't change gear as quickly as DCT either. So basically you have a transmission that is both smoother and has better response. Plus less loss of power through the torque converter.

[CanAutM3]

Originally Posted by Tonymiabmw

Ratios are also based off power band of the car so I don't understand how you can say the ratios disappointing without driving the car or knowing characteristic of the cars engine.

The power and torque graphs of the S55 have been published by BMW. Combined with the gear ratios, it possible to get a very good understanding of the powertrain characteristics under acceleration.

[Tonymiabmw]

Originally Posted by CanAutM3

The power and torque graphs of the S55 have been published by BMW. Combined with the gear ratios, it possible to get a very good understanding of the powertrain characteristics under acceleration.

You have a link haven't seen the chart only one with a line no numbers.

[Boss330]

Originally Posted by Tonymiabmw

You have a link haven't seen the chart only one with a line no numbers.

It's been on the main threads "for ages":



http://f80.bimmerpost.com/forums/sho...d.php?t=923444

[CanAutM3]

Originally Posted by Jonas

In reference to the stated "very significant performance advantage on the E9X".

The following is from a Car & Driver test of the E92 M3 DCT.

"But Is It Quicker?

After scouring the test results for some useful conclusion, the answer is “not really.” The M DCT car hit 60 mph in 4.3 seconds, cleared the quarter-mile in 12.7 at 113 mph, and achieved 150 mph in 26 seconds flat. Compare that to the six-speed manual’s numbers of 4.3, 12.8 at 113, and 24.3, respectively. If you zoom in even closer and look at each 10-mph increment, the two cars trade off which is quicker until 120 mph, when the manual starts pulling away."

http://www.caranddriver.com/reviews/...quicker-page-2

One of my track buddies has '11 ZCP 6MT M3. We are both running the same wheels and tires at the track. On more than one occasion, while playing around together, I was able to pull a clean pass on him on the back straight at LCMT (90-135mph), that is significant. When he is behind me, I just pull away and he can't keep up despite the draft. I've had similar experiences playing with other 6MT M3s. As much as I would like to say that I am the better driver , I attribute this advantage to the transmission .

[CanAutM3]

Originally Posted by mdss6

But engineering decisions involve a series of tradeoffs.

I believe the tradeoff was more one of cost in this case.

Originally Posted by mdss6

By using the more heavily built gearbox from the M5 I have every confidence it will never be a weak point in the M3/M4, almost no matter how much the engine is tuned up. I will be surprised if the M3/M4 can't reliably and durably launch off the line, as well as provide high end acceleration.

Robustness is a good point. It is however pertinent to point out that some folks have been reliably running stock DCTs on SC S65s at very high power levels.

[Tacoma]

Originally Posted by Tonymiabmw

Bottom line any one who enjoys manual, will always enjoy DCT more that Automatic. I would get manual but Miami traffic is horrible and don't like to sit in traffic with a manual.

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.