DCT question

[mstevens]

Originally Posted by Memphis1

by the way, DCT is smoother than any auto tranny and smoother than a manual

It's certainly not my experience that the DCT is smoother than a manual.

[rmorin49]

Originally Posted by mstevens

It's certainly not my experience that the DCT is smoother than a manual.

+1, "Smoother than a manual" would clearly depend on who is doing the shifting of the manual.

[Memphis1]

^^ you don't even have a DCT

[BlueZ4AZ]

The DCT is smoother shifting than any manual. It's human vs computer.

Someone with a manual would have to concentrate on shifting as smoothly as possible just to be close the the smoothness of the DCT.

If someone is TRYING to shift as smooth as possible with their manual, or like mstevens who says the manual is smoother, then it seems they are defeating the purpose of having a manual in the first place. I drove a manual for 12 years prior to getting the 35i, ('97 Prelude, '00 Eclipse, '02 s2000, '05 350Z and '07 Corvette, all manuals) and the last thing I thought about was how smooth I could shift.

Why would anyone leaning strongly towards the manual over the DCT or who already decided on the manual over the DCT even care about whether it is as smooth as the DCT?

[Wraith.]

I just think ppl have a hard time letting go of the concept of the traditional manual, I know I did.

[ManiacGT]

My only comment on the DCT is that I feel a little less at one with the car.. But there's no denying it's super smooth and super quick.

[mstevens]

Originally Posted by BlueZ4AZ

The DCT is smoother shifting than any manual. It's human vs computer.

Someone with a manual would have to concentrate on shifting as smoothly as possible just to be close the the smoothness of the DCT.

If someone is TRYING to shift as smooth as possible with their manual, or like mstevens who says the manual is smoother, then it seems they are defeating the purpose of having a manual in the first place. I drove a manual for 12 years prior to getting the 35i, ('97 Prelude, '00 Eclipse, '02 s2000, '05 350Z and '07 Corvette, all manuals) and the last thing I thought about was how smooth I could shift.

Why would anyone leaning strongly towards the manual over the DCT or who already decided on the manual over the DCT even care about whether it is as smooth as the DCT?

I'm pretty sure I said it hasn't been my experience that the DCT is smoother than the manual, not that the manual is smoother than the DCT.

Before we go much farther with this, it's important to acknowledge that nobody in the US is going to be able to do an apples-to-apples comparison of DCT vs. manual in a 35is. Perhaps we also have to define what "smooth" means, since there are different ways of using that term. That said, I can compare a 3.0 e85 Z4 manual to an e89 35is Z4 with DCT.

To me, "smooth" shifting means quick gear transitions with minimal effect on the car's suspension and with minimal unpredictability. I'm probably also unavoidably including the idea that these transitions happen exactly when I want them to. With the DCT, shifts are not instantaneous by any means. Under some conditions, there's significant lag between when I send the shift signal and when it occurs. This never happens with a manual. If a shift does not happen precisely when I order it, that's not "smooth" to me. DCT shifting is all or nothing - you can't feather the clutch, which is sometimes preferable to using the brakes.

If my "smooth" one means "barely perceptible most of the time," then in my opinion this is true of both the DCT and of skillful manual shifting.

Why would anyone think of smoothness of shifting? When driving competitively, smoothness (of steering, shifting, and braking) is almost always what makes the difference between winning and losing, not horsepower or torque. If the last thing you thought of was how smoothly you were shifting, you weren't getting the most performance from your car.

As to why anyone would care which is smoother, that really seems to be more the concern of those who love the DCT, not those who like manuals.

Human vs. computer, btw, is a total red herring. Computers usually suck at things humans are good at. Smooth, fluid movements are an excellent example of this. Human surgeons, artists, etc. have nothing to fear from computers for a very long time.

[richard in NC]

My experience with the DCT is it shifts smoother than I ever could with a manual and I've had plenty over 25 years.

The DCT in normal mode does have a slight lag but it still is probably quicker than the whole manual shift action (clutch in, shift, clutch out) around town. Even with this slight lag, power delivery is scarcely interrupted. In manual sport modes, shifting occurs more quickly than any human could ever shift, and smoother than most.
The KEY to a smooth manual shift is rev matching so that the RPM and power delivery of the new gear is correct, more important on a downshift than an upshift. There are track experts that do this quite well but none do it quicker than DCT.

The only issues I ever have with the DCT are with a rolling stop and a reverse to drive shift. In the rolling stop, the DCT seems to drop into first just as you want to go and you get a delayed clutch re-engageent, especially when cold.. I also note a delay shifting from reverse to drive, after backing out a parking spot.

[Z_Victor1]

Originally Posted by BlueZ4AZ

The DCT is smoother shifting than any manual. It's human vs computer.

Someone with a manual would have to concentrate on shifting as smoothly as possible just to be close the the smoothness of the DCT.

If someone is TRYING to shift as smooth as possible with their manual, or like mstevens who says the manual is smoother, then it seems they are defeating the purpose of having a manual in the first place. I drove a manual for 12 years prior to getting the 35i, ('97 Prelude, '00 Eclipse, '02 s2000, '05 350Z and '07 Corvette, all manuals) and the last thing I thought about was how smooth I could shift.

Why would anyone leaning strongly towards the manual over the DCT or who already decided on the manual over the DCT even care about whether it is as smooth as the DCT?

Second that............

[flpnout]

Originally Posted by BlueZ4AZ

The DCT is smoother shifting than any manual. It's human vs computer.

Someone with a manual would have to concentrate on shifting as smoothly as possible just to be close the the smoothness of the DCT.

If someone is TRYING to shift as smooth as possible with their manual, or like mstevens who says the manual is smoother, then it seems they are defeating the purpose of having a manual in the first place. I drove a manual for 12 years prior to getting the 35i, ('97 Prelude, '00 Eclipse, '02 s2000, '05 350Z and '07 Corvette, all manuals) and the last thing I thought about was how smooth I could shift.

Why would anyone leaning strongly towards the manual over the DCT or who already decided on the manual over the DCT even care about whether it is as smooth as the DCT?

My thoughts exactly....if I cared about smoothness and whatever the seconds difference is, I would have opted for DCT. I just like the feel of being able to run through the gears and my left foot pressing a clutch. And not everyone could drive my car....lol "Oh, it's a stick" reaction.

[BlueZ4AZ]

Originally Posted by mstevens

Human vs. computer, btw, is a total red herring. Computers usually suck at things humans are good at. Smooth, fluid movements are an excellent example of this. Human surgeons, artists, etc. have nothing to fear from computers for a very long time.

Wow, I better cancel that computerized laser eye surgery I have scheduled for next Tuesday. I knew that price was just too good to be true.

[mstevens]

Originally Posted by BlueZ4AZ

Wow, I better cancel that computerized laser eye surgery I have scheduled for next Tuesday.

There's still a surgeon involved, who does the parts requiring judgment and skill (such as operating the keratotome). All the computer does is basically sand away the subepithelial corneal tissue with a laser. This doesn't have to be particularly smooth since the epithelial layer will be glued back down on top of it.

[Memphis1]

^^ pointless argument... you hold something to be true, even though it is not, and you're just being stubborn to accept that technology saves us everyday from human error.

[BlueZ4AZ]

Originally Posted by mstevens

There's still a surgeon involved, who does the parts requiring judgment and skill (such as operating the keratotome). All the computer does is basically sand away the subepithelial corneal tissue with a laser. This doesn't have to be particularly smooth since the epithelial layer will be glued back down on top of it.

Joke






Your head

[mstevens]

Originally Posted by Memphis1

^^ pointless argument... you hold something to be true, even though it is not, and you're just being stubborn to accept that technology saves us everyday from human error.

Ah, the use of bold-face as evidence has finally convinced me.

Or were you responding to BlueZ4AZ's pointless argument?

[mstevens]

Originally Posted by BlueZ4AZ

Joke






Your head

Does that actually mean anything?

If so, what?

[BlueZ4AZ]

You understood I was making a joke and you know Memphis1 was calling your argument pointless, not mine.

????????

[Alext]

Eh I drive a manual and a DCT everyday when I get the chance. No comparison, DCT is miles smoother in normal usage. I have to really try hard and imagine I am driving around the Queen to get the manual even close....

[Dr Stig 2]

Agree with AlexT

While the clutch is depressed in any manual car, there is no forward force so the car is decelerating. So as you transfer up through the gears you will always have a certain amount of surge on the new gear engagement. Ie accelerate-deccelerate-accelerate-etc... This causes the heads of the driver and passenger to go back and forth, impacting the "smoothness" of the driving. It gets more pronounced the faster you accelerate and the longer it takes you to change gears. Ie everyone will get a different amount of jerk in their manual gearchange.

DCT minimizes the deceleration period to an unnoticeable time (they call it instantaneous) so you merely have a small change in the forward acceleration rate. This will minimise the amount of force your body feels for the same net acceleration of the car.
So I would say that for the same acceleration rate, the DCT will always be smoother.

If you want to split hairs and try to say that at crawling pace the DCT is a bit jerky compared to a skilled manual driver who rides the clutch, then give your car to your grandmother and see if she can drive it like it's supposed to be driven. Ie like a sports car.

[Alext]

This is the most understandable and comprehensive explanation I have read on this topic Stig ...

[HerrK]

Originally Posted by Dr Stig 2

DCT minimizes the deceleration period to an unnoticeable time (they call it instantaneous) so you merely have a small change in the forward acceleration rate. This will minimise the amount of force your body feels for the same net acceleration of the car.
So I would say that for the same acceleration rate, the DCT will always be smoother.

DCT's, just like other automatics, are always transfering torque to the drive wheels - there is never a complete power transfer disconnect from the engine as in a manual. Jawohl -the crossover from one clutch set to the other is minimized, and as you state produces a smoother gear transition. Here is a nice explanation (with a great cutaway and CAD graphics) of the Porsche PDK. The Getrag DCT used in the BMW's is similar.

http://www.roadfly.com/features/2009...nsmission.html

[skier219]

Smooth, huh? What is this, a Buick forum? ;-)