DCT shift speed Question

[shchow]

I also believe that there comes a point in time when it is no longer clinically relevant.
If I may draw on some extremes...if a shift were to take place 0.0001ms vs 0.001ms, would it make any difference in actual performance times?
On the other extreme, if a shift were to take place in 5 seconds, there is no doubt performance will be affected.
So there must be some threshold at which there is no further actual improvement in performance, and that may have already been achieved? I don't know...
And the bottom line for 99% of us is driving pleasure, of which shift speed is probably a miniscule component. I'll take the Ferrari F430 single clutched system anyday.

[waremark]

Originally Posted by shchow

I'll take the Ferrari F430 single clutched system anyday.

Ferrari won't. The 458, like the California, uses a Getrag sourced DCT like our M3's.

Our transmissions are far more pleasant to use than any SMG.

[waremark]

Originally Posted by !Xoible

If you're on the happy path and it knows which gear then the shifts are fast, if something happens on the way and it prepares the wrong gear then the shifts will be considerably slower. in VW's DSG that can take up to .5-.6 of a second.

The relevant shift time is torque to torque on full throttle upshifts, for which the appropriate next gear is always ready to go. Other shifts are not so time critical.

[waremark]

Originally Posted by -=Hot|Ice=-

But VW's have perfected their DSG's. They are absolutely amazing.

In what way is VW's implementation better than the DCT in the Z4 35i?

Have VW made a version which can cope with the power output and revs of the BMW V8? (I will be interested to see if they put one in the RS5; they didn't in the RS4 or the R8).

[shchow]

Originally Posted by waremark

Ferrari won't. The 458, like the California, uses a Getrag sourced DCT like our M3's.

Our transmissions are far more pleasant to use than any SMG.

I understand that Ferrari has upgraded to a dual clutched system.
But my point is that I will take the F430 over whatever dual clutched system you might suggest (besides another Ferrari). That the driving experience is much more than shift speed; such as steering feel, exhaust note, etc.
I would liken it to the appeal of an actual three peddle clutched manual. There is full agreement that the automated clutch provides shift speeds that are not humanly possible, but some of us actually like to row the gears, despite the fact that it is becoming more and more archaic...

[footie]

Originally Posted by waremark

In what way is VW's implementation better than the DCT in the Z4 35i?

Have VW made a version which can cope with the power output and revs of the BMW V8? (I will be interested to see if they put one in the RS5; they didn't in the RS4 or the R8).

The RS5 will receive the DQ550 which is basically the same rev limit and torque capabilities as the M-DCT. The R8 at the time of development was considered too small of numbers to justify the tooling and R&D costs. But as the R8 has proved to be a roaring success I would imagine the Mk2 version will get it, as will the next RS4.

[footie]

Originally Posted by shchow

I understand that Ferrari has upgraded to a dual clutched system.
But my point is that I will take the F430 over whatever dual clutched system you might suggest (besides another Ferrari). That the driving experience is much more than shift speed; such as steering feel, exhaust note, etc.
I would liken it to the appeal of an actual three peddle clutched manual. There is full agreement that the automated clutch provides shift speeds that are not humanly possible, but some of us actually like to row the gears, despite the fact that it is becoming more and more archaic...

The SMG in F360 was plain awful, it was jerky and painfully slow at shifting, though much better the F430 (non Scuderia) was still an awful jerky experience. Given the choice of one of these or rowing myself I would pick the manual every time.

If you like the jerk that your M5 has then you will feel perfectly at home with an M3 M-DCT set to either S5 or S6, only you marvel at the speed of them in comparison.

[Sleeper519]

Originally Posted by footie

...If you like the jerk that your M5 has then you will feel perfectly at home with an M3 M-DCT set to either S5 or S6, only you marvel at the speed of them in comparison.

The SMG in the M5 and M6 should not even be comapred to the DCT in the same sentence. I had the opportunity to drive all 3 back-to-back at the M-school last week. The SMG is total crap (with apologies to those who already own one). Very disappointing. WOT shifts at 8k took about 1000 msec, er, 1 full sec (at least). The M3 DCT on the other hand was lightnig quick and butter smooth. That jerk you feel on S5 or S6 is not from any mechanical roughness in the tranny, it's the torque coming back on so fast and strong that it justs snaps your head back! THAT'S what makes it fun! Night and day difference between the two technologies, that you actually feel while driving hard. JMHO.

[footie]

Originally Posted by Sleeper519

The SMG in the M5 and M6 should not even be comapred to the DCT in the same sentence. I had the opportunity to drive all 3 back-to-back at the M-school last week. The SMG is total crap (with apologies to those who already own one). Very disappointing. WOT shifts at 8k took about 1000 msec, er, 1 full sec (at least). The M3 DCT on the other hand was lightnig quick and butter smooth. That jerk you feel on S5 or S6 is not from any mechanical roughness in the tranny, it's the torque coming back on so fast and strong that it justs snaps your head back! THAT'S what makes it fun! Night and day difference between the two technologies, that you actually feel while driving hard. JMHO.

My point was that those coming from the SMG still look for that mechanical connection between shifts, the jerk/surge give that connection though it's far superior but the end result is the same.

I just find it surprising that anyone would actually prefer the old fashioned SMG over DCT but there you go.

[Petlizard]

So, still no general agreement on this question. Aside from the DCT is a step forward from SMG.

[footie]

Originally Posted by Petlizard

So, still no general agreement on this question. Aside from the DCT is a step forward from SMG.

Is the answer really that important to you?

What would really be the difference if one did it in 8ms and the next took 20ms, the effect on acceleration is barely noticeable, even with the best of timing equipment.

[Petlizard]

Originally Posted by footie

Is the answer really that important to you?

What would really be the difference if one did it in 8ms and the next took 20ms, the effect on acceleration is barely noticeable, even with the best of timing equipment.

The importance of the answer is no longer as intriguing as the fact that we don't have an clear answer. I loved the DCT (that's why it was chosen over a c63) enough that it doesn't really matter how fast or slow it is.
Just noticed that many other manufactures list their gear shift times as selling points to their cars, but not bmw. Either they have a slower box, or like most other stated here, it really doesn't matter since the driving experience speaks for itself.
It's like have a fast modem but don't know how fast it is in numbers.

[swamp2]

The 8ms figure has been discussed here on the forum extensively. It was given on some article on some website (again exact references are here in the forum) for the DSG unit. The vast majority of those that have either thought about, measured and or compared this figure to other units and other information realize this number is absurd.

Furthermore the SMG figures that have been floated of both 80 and 65 ms are deceptive. IIRC those figures are from BMW directly. They likely only cover the shift and conveniently leave out the clutching. SMG shift times were at best about 0.2 seconds (200 ms) which about the same as a good but fast human can shift. Again the article that shows the actual testing that concludes this figure of about 200 ms for a good typical upshit it referenced in prior posts on the forum. If you are really interested use google to search this forum rather than the forums built in search function. Just append a good boolean search with "site:m3post.com".

I've seen test data for a human in a MT at 0.25 s (250 ms). Shift time really vary for all DCTs and many of the good current units are in the range of tens of ms for ideal upshifts to tenths of seconds for non ideal multiple downshifts (maybe even 0.5 s or longer).

[mvagusta]

what is the claim that bmw is stating for a mt and a dct in a 0 to 60mph? Or the 1/4 mile?

[RichB]

I just timed myself in a 6MT....6ms.

Of course I am just kidding. Could not pass up the opp.