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      07-11-2008, 08:40 PM   #1
EscortKing
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Question Any videos for confirming/refuting M-DCT upshift lag?

I mean, it wouldn't be so difficult to take a video that shows the moment when your hand presses the paddle and the revs fall because of the gear change. We could then measure the time difference, leaving the subjective part out of the equation.

Any other ideas for finding out if this is a general issue or just a defective batch of M-DCT boxes?

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      07-12-2008, 01:33 AM   #2
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What lag? DCT is instantaneous.
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      07-12-2008, 05:50 AM   #3
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I'm sure you know what I mean. In auto mode it is nearly instantaneous as any other double clutch system. But in manual mode, many people claim that there is a lag from the moment the driver presses the paddle till the software/hardware "decides" to execute the upshift. Once the upshift begins, it is nearly instantaneous. Many other people claim that there is no lag at all, that it is as fast in manual as in auto. It is not clear if this is an issue related to the driver... maybe the drivers that feel the lag are very sensitive, maybe they do something wrong, maybe the drivers that don't feel the lag are not sensitive at all... OR maybe this "problem" is not present in all cars.
That's why i think that some videos could solve the debate.

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      07-12-2008, 07:50 AM   #4
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Originally Posted by MDCTFTW View Post
What lag? DCT is instantaneous.
Not that instantaneous.
It takes a couple of miliseconds to change gear.
IMHO i think that the gear changes are more quick in the stick. In think that the paddles are a little bit slower.
Could be just me.

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      07-12-2008, 08:08 AM   #5
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There is no lag. I click the paddle and it shifts. What's so hard to believe?
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      07-12-2008, 09:00 AM   #6
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Watch this video from fifthgear on the DSG, at 2:11approx watch Jason's fingers flick the paddle and listen to the revs drop. You could'n't click your fingers any quicker and that a system which is slower than the M-DCT.


Lag..............what lag?
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      07-12-2008, 09:56 AM   #7
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There can be a delay depending on the conditions under which you request the shift. You can measure it when it happens. I felt it. It's been reported in press reviews. But it is pretty short and a somewhat subjective thing to consider so it would take some work to instrument things properly to be able to measure it under different conditions. This has nothing to do with the actual shift time. The lag must predominantly arise from the fact that the second clutch cannot be simultaneously pointing at the higher and the lower gear, and the system has to pick one. If you end up doing what the system has not anticipated, it will need to change the gear the second clutch is pointing at, which will cause a slight delay. No way around that unless you have a third clutch and both possibilities are always covered (2nd clutch pointing at the lower gear, 3rd clutch pointing at the higher gear). In the dual clutch system, the chance of requesting a gear the computer has not anticipated probably depends on how well the computer can predict what you want to do next depending on throttle input and engine speed and maybe some other variables. It makes sense for the computer to be conservative and pick the lower gear in normal driving conditions in low-mid range rpms since the lower gear is where the power is in case you want to accelerate quickly (for peak acceleration, the sensible thing to do would be to downshift and floor it rather than floor it in the current gear). So, the delay seems to be absent for a downshift when you are cruising around calmly. I don't see this being an issue when you are driving aggressively at high revs as what you want to do should be much more transparent to the computer in that case. That said, in objective terms, I don’t know that this is a major issue overall.

However, even if you experience a delay under certain conditions, I'm pretty sure:

the delay + DCT shift time < human MT shift time.
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      07-14-2008, 01:44 PM   #8
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What is LAG?....I have 2 lags, and two arms
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      07-15-2008, 11:20 PM   #9
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Exactly Lucid, only two clutches, one works odd gears, one even gears, if you shift in a manner its not expecting, the clutch needs to move and engage. If you shift two gears in either direction(odd gear to odd gear or even gear to even gear), delay expected. Most likely the shift is still occuring faster than most can pull it off on a MT. More to come in a month, ordered a cruisecam and eventually the car will arrive.

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      07-16-2008, 12:03 AM   #10
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Quote:
Originally Posted by lucid View Post
There can be a delay depending on the conditions under which you request the shift. You can measure it when it happens. I felt it. It's been reported in press reviews. But it is pretty short and a somewhat subjective thing to consider so it would take some work to instrument things properly to be able to measure it under different conditions. This has nothing to do with the actual shift time. The lag must predominantly arise from the fact that the second clutch cannot be simultaneously pointing at the higher and the lower gear, and the system has to pick one. If you end up doing what the system has not anticipated, it will need to change the gear the second clutch is pointing at, which will cause a slight delay. No way around that unless you have a third clutch and both possibilities are always covered (2nd clutch pointing at the lower gear, 3rd clutch pointing at the higher gear). In the dual clutch system, the chance of requesting a gear the computer has not anticipated probably depends on how well the computer can predict what you want to do next depending on throttle input and engine speed and maybe some other variables. It makes sense for the computer to be conservative and pick the lower gear in normal driving conditions in low-mid range rpms since the lower gear is where the power is in case you want to accelerate quickly (for peak acceleration, the sensible thing to do would be to downshift and floor it rather than floor it in the current gear). So, the delay seems to be absent for a downshift when you are cruising around calmly. I don't see this being an issue when you are driving aggressively at high revs as what you want to do should be much more transparent to the computer in that case. That said, in objective terms, I donít know that this is a major issue overall.

However, even if you experience a delay under certain conditions, I'm pretty sure:

the delay + DCT shift time < human MT shift time.
that makes a lot of sense. i am a MT guy, but I know I won't be beating DCT anyday when it comes to shift times.
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      07-16-2008, 12:09 AM   #11
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New DCT review by Edmunds.

Very positive, they loved it.

http://www.edmunds.com/insideline/do...hotopanel..1.*
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      07-16-2008, 04:09 AM   #12
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Quote:
Originally Posted by JetBlack5OC View Post
New DCT review by Edmunds.

Very positive, they loved it.

http://www.edmunds.com/insideline/do...hotopanel..1.*
From this article:

Edmunds.com Editor in Chief Karl Brauer says:

[...]

"At over 2 tons this is by far the heaviest M3 ever, even outweighing its sibling coupe and sedan by several hundred pounds.
The extra strain is seen in the performance numbers, while acceleration and shifting action left me unimpressed. Using the most aggressive throttle (Sport Plus) and transmission settings had the car lurching when I drove out of corners and banging through gears like an old Torqueflite in need of a rebuild. Dialing things back to the midlevel throttle (Sport) position and halfway up the transmission settings (three bars out of six) solved most of these issues, but delays between paddle pull and shift action were still too long."
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      07-17-2008, 10:20 PM   #13
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Quote:
Originally Posted by EscortKing View Post
From this article:

Edmunds.com Editor in Chief Karl Brauer says:

[...]

"At over 2 tons this is by far the heaviest M3 ever, even outweighing its sibling coupe and sedan by several hundred pounds.
The extra strain is seen in the performance numbers, while acceleration and shifting action left me unimpressed. Using the most aggressive throttle (Sport Plus) and transmission settings had the car lurching when I drove out of corners and banging through gears like an old Torqueflite in need of a rebuild. Dialing things back to the midlevel throttle (Sport) position and halfway up the transmission settings (three bars out of six) solved most of these issues, but delays between paddle pull and shift action were still too long."

Sometimes changing have a little delay, but not everytime. Anyway, this delay is not so much noticable.
The most bigger problem for me what I have noticied is what sometimes you pull the paddle for kick-down and nothing... pull second time and then its kicks-down... This had happened with me 2-3 times only at over 11.000kms.
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