Quote:
Originally Posted by doug_999
Yep, I was thinking about you when I posted this. You need to go thank those dealers for being complete A$$es 
I also find it interesting that so many people consider DCT such a huge benefit. Yes, it snaps off the shifts faster, but stop and go performance suffers -or at least it has in all of those that I have driven. |
doug, DCT has different configurations and based on those configurations has different characters. The most aggressive setting is S3/D3 while throttle is set in sport+ while the softest (D1/S1 with efficient throttle) is really soft and comfort, but not as smooth as ZF8 because of clutch instead of torque converter... To me DCT is a huge benefit and reminds me over 20 years manual tranny experience with the advantage of fast shifting, but as you know I'm biased to "love M6"
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I think this post has explained the difference very well...
Quote:
Originally Posted by Needsdecaf
A few things that are different.
Some of the posters above are steering you off track. I mentioned the torque converter not because it's the only way to get smooth take offs, but because of HOW IT WORKS. A torque converter uses two "fans" essentially, spinning in fluid (ATF). Very simply put, the "fan" on the engine side spins as the engine speeds up. At first, nothing happens. But as the "fan" spins faster, the fluid's shear eventually starts to transmit force to the other "fan" and the wheels receive power. This is very gradual and soft, hence "smooth starts". At some point, the two sides will lock together using a clutch, and you will have no loss due to the heat in the fluid.
Because the DCT has no torque converter, it uses a clutch to engage the drive side (engine) to the driven side (wheels) (two actually, one for odd gears, the other for even). So it's engagement behaves the same way that a manual transmission would. Here is the difference.
In a traditional manual transmission, the driver is in charge of two things, throttle and clutch. You choose how many revs to add, and how quickly or gradually to engage the clutch. You control the smoothness of the engagement.
In the DCT, you still control the throttle, but the computer controls the clutch. It needs to guess your intentions based on throttle input. So, if it senses you rolling into the throttle, it'll engage the clutch slowly. Jam into the throttle, and it'll slam the clutches shut, expecting that you'll want a fast takeoff.
So the trick is that you need to work simpatico with the computer that's engaging the clutch. Since there is no fluid filled torque converter damping out any differences, you're going to feel when you and the computer are at odds with one another.
I won't get into shifting underway, as that's usually not as much of an issue.
Hope this helps.
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