[arunphilip]

Originally Posted by Sutripta

In the figure below, how is the torque being transmitted in the sloping section of the blue line?

At each point of the slope, one clutch is being progressively disengaged while the other is being engaged, resulting in continuous torque output. In reality, the sloped portion should be more vertical, since the entire shift is completed faster than a manual (i.e. the red line).

Originally Posted by Sutripta

What are the thought processes behind choosing a dry clutch vs a wet clutch?

Historically, manufacturers opted for dry clutches for low torques (typically <300 Nm), and wet for higher, since the higher torque required better heat dissipation. Further, those higher torque engines could afford some power loss in driving the plumbing required for a wet clutch.

However, while that was the theory, in practice they found that dry clutches were installed in small cars having compact engine bays, that tended not to dissipate heat well. When combined with high ambient weather (e.g. tropical areas) and severe stop-and-go traffic, this resulted in high heat soak in the dry clutch, affecting its life.

As a result, manufacturers are directing their efforts towards wet clutches. Getrag, for one, have stated that all their PowerShift transmissions will have wet clutches henceforth.

[Sutripta]

Originally Posted by arunphilip

At each point of the slope, one clutch is being progressively disengaged while the other is being engaged, resulting in continuous torque output. In reality, the sloped portion should be more vertical, since the entire shift is completed faster than a manual (i.e. the red line).

You mean in a DCT, there are operating modes when both clutches transmit power simultaneously to the output shaft?

Historically, manufacturers opted for dry clutches for low torques (typically <300 Nm), and wet for higher, since the higher torque required better heat dissipation. Further, those higher torque engines could afford some power loss in driving the plumbing required for a wet clutch.

What sort of clutches did the American muscle cars and Italian exotics have? (talking wrt cars with MT, not AT obviously). And what sort of clutches on out commuter motorcycles?

Regards
Sutripta

[arunphilip]

Originally Posted by Sutripta

You mean in a DCT, there are operating modes when both clutches transmit power simultaneously to the output shaft?

No - that can't happen, since the gear ratio's are different. During the sloped part, one clutch is slipping/disengaging and one is driving. However, both shafts are already running at the right speed, so there's no delay in getting the 'new' clutch or shafts up to the right speed, all that's needed is an engine rpm change to match the new gear.

I sense you're leading onto something via the Socratic method, care to share it?

Originally Posted by Sutripta

What sort of clutches did the American muscle cars and Italian exotics have? (talking wrt cars with MT, not AT obviously). And what sort of clutches on out commuter motorcycles?

I'd not made it explicit, but the part from my previous that you've quoted ("Historically, manufacturers opted...") is relevant purely to dual-clutch automated transmissions (DSG/DCTs), and has no bearing on manual transmissions in cars or motorcycles. Just to set the record straight, here's a verbatim quote from the Getag CEO:

"So for very sporty cars with high torque you need a wet clutch, and for undersized engines in oversized vehicles you also need a wet clutch. There’s an area in the middle which works very well with dry clutch, and we have very effective ones in production today."
"I cannot speak for our competitors, but our new generation of DCTs at Getrag will be 100 percent wet clutch."

Sources:
1: http://drivelinenews.com/transmissio...ys-getrag-cto/ [Feb 2014]
2: http://drivelinenews.com/transmissio...or-dry-clutch/ [2010]

[Sutripta]

More easily visualised in a electrical system: Multiple sources/ single load - If one has to shift from source to source. then Break before Make. If important, engineer the break time to be as low as possible.

Re: wet/ dry clutches, the opinions were expressed as truths about clutches in general, not as Getrags opinion on clutches for DCTs. Hence the confusion.

BTW, in my example,

What sort of clutches did the American muscle cars and Italian exotics have? (talking wrt cars with MT, not AT obviously). And what sort of clutches on out commuter motorcycles?

what could be the reason for this?

Regards
Sutripta

[an_and]

How does a dual clutch - dry system compare to a cvt in performance and longetivity?

[ampere]

Not wanting throw a negative aspect to this brilliant article by Arun. But here is another angle which is building up

http://www.team-bhp.com/forum/intern...opularity.html

Would be great to put this in perspective.

[reignofchaos]

A question for all Ford Powershift owners: Do you folks shift to neutral on stop lights?

I have the Volvo version of the Getrag gearbox (MPS6 or 6DCT450) which has a wet clutch and higher torque capability and apparently much better reliability.

I have been diligently following a regime of shifting to neutral at long stop lights. Wondering what the others do?

[sk7671]

Thanks a lot for this awesome technical write up. My Ecosport AT was shuddering rather a lot these days and have dropped it off for its second free service. Gave this feedback to the service center folks. The car literally shudders when its shifting from 1 to 2 and 2 to 3. The shuddering is more when we slow down on a speed breaker and are trying to pick speed.

It even happens when am in the manual mode.

Seems like the service guys know about this issue and have to keep the vehicle for 2-3 days as they have to send diagnostics data to ford and get back next steps. AT least thats what they told me.

Kinda concerned on the overall purchase now. Love the car but worried.

[sk7671]

Team - This is an update on my AT Ecosport. When dropped off for 2nd service, service folks sent all the diags to Ford and seems like Ford has requested to change the clutch in the AT unit. It now has been replaced. I read on the internet about these problems and extended warranty given away by Ford just on the transmission. I have not yet picked up the car, but how do I go about it with Ford?

Originally Posted by sk7671

Thanks a lot for this awesome technical write up. My Ecosport AT was shuddering rather a lot these days and have dropped it off for its second free service. Gave this feedback to the service center folks. The car literally shudders when its shifting from 1 to 2 and 2 to 3. The shuddering is more when we slow down on a speed breaker and are trying to pick speed.

It even happens when am in the manual mode.

Seems like the service guys know about this issue and have to keep the vehicle for 2-3 days as they have to send diagnostics data to ford and get back next steps. AT least thats what they told me.

Kinda concerned on the overall purchase now. Love the car but worried.

[arunphilip]

Originally Posted by reignofchaos

A question for all Ford Powershift owners: Do you folks shift to neutral on stop lights? I have the Volvo version of the Getrag gearbox (MPS6 or 6DCT450) which has a wet clutch and higher torque capability and apparently much better reliability.

According to Jason Fenske of the Engineering Explained channel, shifting to neutral is not required, since both clutches are disengaged upon stopping. I covered the same point on page 1 of this thread: "The clutches will disengage when the brakes are applied."

There's no harm done by shifting to neutral, but its not required either.

5 Things You Should Never Do In A Dual Clutch Transmission Vehicle

Sorry about the delayed reply, and hope you're having fun with your Volvo V40.

[komalthecoolk]

Originally Posted by arunphilip

There's no harm done by shifting to neutral, but its not required either.

After reading your post multiple times and after test driving the Figo AT I was very impressed with the technology. But after watching related videos, reading about the possibilities of one of the clutch wearing out with slow moving traffic and reading global grievances and issues with the DCT, I've decided not to go for it :(

For a technology that's relatively new and seeing Ford silently replace many problematic transmissions all across the globe, it did not give me enough confidence to have this as my vehicle for the next 5-6 years. May be in the near future, if budget permits, I'd like to have the Figo AT as my secondary car though

[Jeroen]

We have just taken delivery of a Ford Focus 1.5L Ecoboost with this Ford Powershift dual clutch.

I have had earlier experiences many years ago with the VW DSG box. At the time I was driving ridiculous amounts of mileage and I was having all sort of problems with my arm/shoulders/neck. In essence RSI related problem and our company doctor ördered me to change my manual Audi A6 to a VW Touran with auto-box and a special orhopedic chair. I must admit at first I wasnt that pleased to have to go auto, considered myself a true petrol head and auto-boxes just dont cut it. But I really loved the VW DSG box, hated the Touran. Long story short, ever since I have been driving auto-boxes for all my daily drives in Europe and the USA. Manual shifting is for (some) of my hobby/classic cars.

I must say I do like the Ford Powershift. I've only done about 1500 km in the Focus, but for day to day driving it is just so convenient. It's also very smooth. Although I have yet to give if the beans fully, my initial impression is that it might be a tad slower to downshift than I seem to recall from the VW DSG box when you floor the accelerator.

This Focus also comes with the auto-stop system. I usually shift to N when stopped and I know/anticipate it's going to be a little wait. Actually for most autobox, unless at very high ambient temperatures and very long waiting times, keeping your auto-box in D is not a problem. However, with the auto-stop system I put it in N and the engine still remains stopped when I lift my foot of the brake. As soon as I shift into D, it will start.

All in all, I'm very happy with this new DCT. Excellent write up on how it works at the beginning of this thread. Thanks

Here is what I would consider one of the best car adds ever and it sums up a DGS or DCT for that matter.

https://www.youtube.com/watch?v=SJL15n5P9BU

Jeroen

[Sutripta]

^^^
VW has nice ads. Remember the kid/ Darth Vader one?

Regards
Sutripta

[Jeroen]

Originally Posted by Sutripta

Remember the kid/ Darth Vader one?

At the risk of going of topic, but these adds are very good!

https://youtu.be/lhzwmYRXPp4