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How do DCTs work?

Old 11-30-2018, 05:28 PM
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Tom73
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Default How do DCTs work?

Can someone help me out here. With all the talk about a DCT in the new C8, I am courious as to how they work. I have never been around one let alone driven one. Sounds to me that they are like a manual shifting automatic but I am sure there is much more to then than that.

Do do they use a torque converter or an automatic clutch of some type? Do you have to shift to neutral when you stop, Do you have to go through each gear when going up/down or can you skip gears?

Is there any advantage other than shifting speed? Any everyday street driving advantage?
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Old 11-30-2018, 05:36 PM
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They drive just like autos but shift quicker. No manual intervention is required but you can play with paddles if that is your thing. Most do not use torque converters but some do.
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Old 11-30-2018, 05:47 PM
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Originally Posted by Tom73 View Post
Can someone help me out here. With all the talk about a DCT in the new C8, I am courious as to how they work. I have never been around one let alone driven one. Sounds to me that they are like a manual shifting automatic but I am sure there is much more to then than that.

Do do they use a torque converter or an automatic clutch of some type? Do you have to shift to neutral when you stop, Do you have to go through each gear when going up/down or can you skip gears?

Is there any advantage other than shifting speed? Any everyday street driving advantage?
Why wouldn't you just google this or watch a video on YouTube? You would get a much quicker and more comprehensive answer.
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Old 11-30-2018, 06:11 PM
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Originally Posted by Sub Driver View Post
Why wouldn't you just google this or watch a video on YouTube? You would get a much quicker and more comprehensive answer.
I can find things on how they work mechanically but not on how the drive and work in the real world. When reading about the dual clutches, one for even gears and one for odd gears, i can imagine two clutch pedals, one for the even gears and one for the odd gears

I am basicly looking for real world input from those that have and use a DCT on a daily basis.
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Old 11-30-2018, 06:17 PM
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There are no clutch peddles. The computer engages the clutches as needed. Just like an auto.
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Old 11-30-2018, 06:25 PM
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It's an automatic shifting manual.

"Engineering explained" has an excellent video. I suggest you watch.
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Old 11-30-2018, 06:33 PM
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Tom73,

I sent you a PM with lots of links and info.

Last edited by elegant; 11-30-2018 at 06:34 PM.
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Old 11-30-2018, 06:37 PM
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It shifts like an automatic with an intelligent shift kit in it. At low throttle, it feels like a good automatic. At WOT it shifts hard, like if you put a shift kit in an automatic. Or you can put it in manual mode and play with the paddles. I do that when I'm autocrossing. This is in a 2010 Audi A5.
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Old 11-30-2018, 06:58 PM
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Originally Posted by Tom73 View Post
Can someone help me out here. With all the talk about a DCT in the new C8, I am courious as to how they work. I have never been around one let alone driven one. Sounds to me that they are like a manual shifting automatic but I am sure there is much more to then than that.

Do do they use a torque converter or an automatic clutch of some type? Do you have to shift to neutral when you stop, Do you have to go through each gear when going up/down or can you skip gears?

Is there any advantage other than shifting speed? Any everyday street driving advantage?
@stonebreaker's answer is pretty good from the point of view of the driving experience.

MY DCT car is a 2018 Golf R. VW/Audi have been in the DCT business for about 15 years.

To answer your questions:

No TC. Two electronically controlled clutches, each connected to a geartrain.

Nothing needed when stopping. Trans will disengage.

When paddle shifting, it's sequential, just like an F1 car. Nothing to stop you hitting a paddle several times quickly to downshift.

Fuel economy is the advantage (other than shift speed).

A DCT trans will have "auto" and "manual" modes. You pick. The modes may also have sub-modes "economy" "sport" "race" etc.

One purpose of the testing we have seen will be to fine tune the software that controls the trans.
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Old 11-30-2018, 08:57 PM
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Originally Posted by Tom73 View Post
I am courious as to how they work.
In a manual tranny (or a single clutch automatic), when you want to switch up or down, the following sequence of events takes place:
a) the clutch disengages the drive
b) the old gear is deselected by a fork
c) the new gear is selected with a fork and the synchronizer spins the new gear up to road speed.
d) the clutch reengages the drive.

In a Dual Clutch Tranny, the following sequence of events:
a) the new gear is selected on the shaft not being used to drive the vehicle
b) both clutches move, one disengaging the current shaft the other engaging the other shaft; at the same time

So there is no dead time between gears, and the clutches do much of the work of the synchronizers.
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Old 11-30-2018, 10:16 PM
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The FORD GT500 is rumored to be shown at the same auto show that the ME will be shown and it will have 700 hp and a DCT. v e r y interesting
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Old 11-30-2018, 10:42 PM
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Most cars today I would worry of expensive repairs once passed the warranty, which is probably good for used car buyers.
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Old 11-30-2018, 11:23 PM
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The best way to think of it is as an automated manual transmission. I prefer to think of them as automated direct drive transmissions. The familiar automatic that has been around since 1940 is an indirect drive since the power has to flow through the torque converter which doesn't have a direct 1:1 connection between its input and output.

Bill
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Old 12-01-2018, 12:30 AM
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Originally Posted by Tom73 View Post
Can someone help me out here. With all the talk about a DCT in the new C8, I am courious as to how they work. I have never been around one let alone driven one. Sounds to me that they are like a manual shifting automatic but I am sure there is much more to then than that.

Do do they use a torque converter or an automatic clutch of some type? Do you have to shift to neutral when you stop, Do you have to go through each gear when going up/down or can you skip gears?

Is there any advantage other than shifting speed? Any everyday street driving advantage?
Just ignore anyone who says it's a manual transmission in any regard. It is not. A DCT is an automatic transmission that is able to shift gears very quickly and precisely because it contains a second clutch that is already engaged to shift the transmission to the next gear.

There is no such thing as a "manual automatic" or other such nonsense being mentioned here. A DCT is simply a different type of automatic transmission.

Put it this way: You know the A8 automatic transmission in the C7? Well, there is absolutely no difference in how you would operate the DCT transmission in a C8. You can either paddle-shift it (like the current A8) or you can allow the transmission to shift itself without using the paddles (like the current A8). NO DIFFERENCE other than the speed and precision in which the shifting is accomplished by the automatic transmission.
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Old 12-01-2018, 01:01 AM
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So if you are paddle shifting you have to go through all the gears when shifting up or down? In other words you cannot downshift from 8th to 4th without going through 7th and 6th. Or the other, skip from 2nd to 8th without going through the in between gears.
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Old 12-01-2018, 01:19 AM
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Originally Posted by elegant View Post
Tom73,

I sent you a PM with lots of links and info.
Thank you for the link.
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Old 12-01-2018, 01:21 AM
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Originally Posted by Speednet View Post
Just ignore anyone who says it's a manual transmission in any regard. It is not. A DCT is an automatic transmission that is able to shift gears very quickly and precisely because it contains a second clutch that is already engaged to shift the transmission to the next gear.

There is no such thing as a "manual automatic" or other such nonsense being mentioned here. A DCT is simply a different type of automatic transmission.

Put it this way: You know the A8 automatic transmission in the C7? Well, there is absolutely no difference in how you would operate the DCT transmission in a C8. You can either paddle-shift it (like the current A8) or you can allow the transmission to shift itself without using the paddles (like the current A8). NO DIFFERENCE other than the speed and precision in which the shifting is accomplished by the automatic transmission.
The DCT is MUCH closer to a manual gearbox than an automatic transmission with planetary gears and torque converter. What is automated in a DCT is the clutch engagement and preselection of gears.
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Old 12-01-2018, 01:23 AM
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Originally Posted by Tom73 View Post

I can find things on how they work mechanically but not on how the drive and work in the real world. When reading about the dual clutches, one for even gears and one for odd gears, i can imagine two clutch pedals, one for the even gears and one for the odd gears

I am basicly looking for real world input from those that have and use a DCT on a daily basis.
And you're asking on a forum where virtually NO ONE has a DCT set-up?
Try P, F or Audi. They have thousands of DCT owners.
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Old 12-01-2018, 01:33 AM
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Originally Posted by NORTY View Post
And you're asking on a forum where virtually NO ONE has a DCT set-up?
Try P, F or Audi. They have thousands of DCT owners.
Sorry but not a part of any of those forums.
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Old 12-01-2018, 01:43 AM
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Like a turbo.... But it is magic lite.
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