Honda DCT technology explained by HondaProKevin

[dduelin]

A lot of the information presented here has been available on the World.Honda.com website over the last 6 years but this site pulls it together nicely in text and videos.

http://www.hondaprokevin.com/automa...pecs-auto-clutch-bikes-model-lineup-overview/

 

[drdubb]

This is great! I am going to spend a lot of time going through this, but even a quick glance was helpful.

 

[misterk]

Excellent


Sent from my iPad using Tapatalk

 

[670cc]

Regarding the article:

What's so bad about a glorified scooter? I like glorified scooters.

The article also mentions that the Honda "high-end, performance orientated DCT setup" is not like the paddle shift transmissions in the average econobox car. Umm, that's generalizing a little bit. My econobox car does actually have a DCT. But, maybe it's "low-end".

One thing I've not figured out. The article says the next gear is preselected on the unused clutch. I've never understood that logic. Does this really happen or is it just something that gets repeated over and over (like half a Fit engine)? Why do that if the chance that the next gear is down instead of up, or up instead of down. Say I have just shifted up to fourth gear. How does the computer know if I will shift up or down next? And if it's the wrong choice, time is lost having to shift the drum in the opposite direction. In addition, the diagram shows only one shift motor and shift drum. To be able to preselect the next gear (with a 50-50 chance of being right) would require a different drum layout than in a manual transmission. The present gear still needs to stay engaged, so to preselect the next gear would require a shift drum where two gear sets are engaged at the same time. Is this how it works? 1 and 2 together, step the drum to 2 and 3 together, step the drum to 3 and 4 together?

 

[fiah]

the gear selection and shifting always happens at the same time IME. With my bike, the first 3 gears are pretty loud when the oil is cold so you can easily hear and feel it happening immediately before it clutches

 

[lootzyan]

...One thing I've not figured out. The article says the next gear is preselected on the unused clutch. I've never understood that logic. Does this really happen or is it just something that gets repeated over and over (like half a Fit engine)? Why do that if the chance that the next gear is down instead of up, or up instead of down. Say I have just shifted up to fourth gear. How does the computer know if I will shift up or down next? And if it's the wrong choice, time is lost having to shift the drum in the opposite direction. In addition, the diagram shows only one shift motor and shift drum. To be able to preselect the next gear (with a 50-50 chance of being right) would require a different drum layout than in a manual transmission. The present gear still needs to stay engaged, so to preselect the next gear would require a shift drum where two gear sets are engaged at the same time. Is this how it works? 1 and 2 together, step the drum to 2 and 3 together, step the drum to 3 and 4 together?

Yes, this is happening. No learning or special AI required. PCM needs two parameters for it: speed sensor or throttle position and time. Actually two values from sensor are needed: just "before-now" and "now". Those values are stored in memory and constantly overwritten. Let's say position value "now" is 4 and previous value was 3, simple subtraction result is positive number - bike is accelerating "now". If DCT was on 3rd gear, 4th gear is engaged and ready. If bike is slowing down result is negative ("now" is 3 and "before" was 4) DCT would engage 2nd gear. At any moment, except neutral, two gears are always engaged.

 

[670cc]

Yes, this is happening. No learning or special AI required. PCI needs two parameters for it: speed sensor or throttle position and time. Actually two values from sensor are needed: just "before-now" and "now". Those values are stored in memory and constantly overwritten. Let's say position value "now" is 4 and previous value was 3, simple subtraction result is positive number - bike is accelerating "now". If DCT was on 3rd gear, 4th gear is engaged and ready. If bike is slowing down result is negative ("now" is 3 and "before" was 4) DCT would engage 2nd gear. At any moment, except neutral, two gears are always engaged.

Is "bike is accelerating" enough info? What if I am in D mode and accelerating gently. Bike sees I am accelerating leisurely so it predicts and preselects next gear up. But I decide I need to pass a car quickly, so instead I crank the throttle open wide and need a downshift. The wrong gear was predicted, and the shift drum has to turn the opposite way first before the clutches can swap.

In DCT manual mode, does the drum keep flipping back and forth whether I am on the throttle or off the throttle, trying to guess which shift is next?

 

[bamamate]

My understanding of “pre-selecting” the next gear……in a manual it goes disengage clutch, change gear up or down, engage clutch. With DCT the odd gears are on one shaft and even gears are on another so it doesn’t matter if you go up or down a gear the clutch for that shaft is ready. So as the clutch for the currently used gear, call it an even gear, is disengaged the next gear on the odd shaft, either up or down, is selected and the clutch for it engages. Basically you don’t have the pause to select the next gear that you do on a manual. The DCT has the next gear ready and the clutch engaging as soon as the other clutch finishes disengaging.

I understand his comment on the average econobox. They have been putting flappy paddles in everything but most of those are tied to regular torque converter automatics and/or CVTs. There are a few cars, including econoboxes, with DCT but they are the exception and not what is common hence his use of the word “average”.

 

[lootzyan]

Is "bike is accelerating" enough info? What if I am in D mode and accelerating gently. Bike sees I am accelerating leisurely so it predicts and preselects next gear up. But I decide I need to pass a car quickly, so instead I crank the throttle open wide and need a downshift. The wrong gear was predicted, and the shift drum has to turn the opposite way first before the clutches can swap.

In DCT manual mode, does the drum keep flipping back and forth whether I am on the throttle or off the throttle, trying to guess which shift is next?

In this case different functions are executed (if-then-else). From collected information (VS, TP , MAP sensors) PCM calculates acceleration ratio. From this the right gear is selected. You may notice slightly delay in execution. Manual downshifting is much faster and smoother.
Of course this is oversimplified explanation. Honda doesn't share programming information.

 

[dduelin]

Regarding the article:

What's so bad about a glorified scooter? I like glorified scooters.

The article also mentions that the Honda "high-end, performance orientated DCT setup" is not like the paddle shift transmissions in the average econobox car. Umm, that's generalizing a little bit. My econobox car does actually have a DCT. But, maybe it's "low-end".

One thing I've not figured out. The article says the next gear is preselected on the unused clutch. I've never understood that logic. Does this really happen or is it just something that gets repeated over and over (like half a Fit engine)? Why do that if the chance that the next gear is down instead of up, or up instead of down. Say I have just shifted up to fourth gear. How does the computer know if I will shift up or down next? And if it's the wrong choice, time is lost having to shift the drum in the opposite direction. In addition, the diagram shows only one shift motor and shift drum. To be able to preselect the next gear (with a 50-50 chance of being right) would require a different drum layout than in a manual transmission. The present gear still needs to stay engaged, so to preselect the next gear would require a shift drum where two gear sets are engaged at the same time. Is this how it works? 1 and 2 together, step the drum to 2 and 3 together, step the drum to 3 and 4 together?

DCT is rare in an economy car, the norm is a torque converter automatic box, but many automatics like this have paddle shifters. It's marketing talk to some degree but to many people torque converter automatics are all they know and Honda wants to highlight the fact that some high end performance cars are using this technology and its not just a set of paddle buttons on an old fashioned automatic.

As far as preselecting goes - The next gear, up or down, is on the other shaft with it's disengaged clutch. The next gear, up or down, is selected based on the Auto mode programming or rider preference in Manual mode or by overriding the Auto programming with the paddle buttons. The disengaged clutch allows the next gear to be engaged prior to disengaging the present one. This saves time and reduces loss of drive during that period. That is all "preselecting" means and that's accomplished with one shift drum.

 

[670cc]

As far as preselecting goes - The next gear, up or down, is on the other shaft with it's disengaged clutch. The next gear, up or down, is selected based on the Auto mode programming or rider preference in Manual mode or by overriding the Auto programming with the paddle buttons. The disengaged clutch allows the next gear to be engaged prior to disengaging the present one. This saves time and reduces loss of drive during that period. That is all "preselecting" means and that's accomplished with one shift drum.

Ok, it's a bit of marketing buzz, then. Obviously you would want the gear pre-selected on the shaft before you engage the clutch. That's how it has to work or it wouldn't work.

 

[dduelin]

snipped.........Manual downshifting is much faster......

I am going to ask for support on this. There is no way that one can say a single clutch downshift is faster than than a dual clutch one. The factory racers in MotoGp are using variations on clutchless transmissions. If it was faster and smoother to do it manually they wouldn't be spending so much R & D on it.

In terms of smoothness the Honda current motorcycle DCTs do leave something to be desired on the downshift side. Until they integrate throttle by wire and are able to electronically blip throttle for perfect rev matching a good rider can downshift smoother than a DCT does OTOH it isn't that bad and there are lots of riders that can't downshift even as well as the second gen DCT does. The third gen software in the AT and 2016 700/750s with adaptive clutch control is supposed to be even better.

 

[lootzyan]

...There is no way that one can say a single clutch downshift is faster than than a dual clutch one. ...

By "manual downshifting" I meant use of forced paddle gear shift in D/S mode. (I don't use M mode).

 

[DCTFAN]

DCT is rare in an economy car, the norm is a torque converter automatic box, but many automatics like this have paddle shifters. It's marketing talk to some degree but to many people torque converter automatics are all they know and Honda wants to highlight the fact that some high end performance cars are using this technology and its not just a set of paddle buttons on an old fashioned automatic.

As far as preselecting goes - The next gear, up or down, is on the other shaft with it's disengaged clutch. The next gear, up or down, is selected based on the Auto mode programming or rider preference in Manual mode or by overriding the Auto programming with the paddle buttons. The disengaged clutch allows the next gear to be engaged prior to disengaging the present one. This saves time and reduces loss of drive during that period. That is all "preselecting" means and that's accomplished with one shift drum.

I agree. Very simple and no complicated predictive logic required.
The ECU has already sorted out which is the next gear, based on past events,
like lootzyfan posted.
"auto mode programming" also described as "shift mapping" is referred to by the ECM at all times, since it's only a few lines of code
and happens in no time at all.
Also, I read that the shift motor can shift, clutch and de-clutch in less than 200 ms (not seconds).
Understandable, since it only requires turning the gear shift spindle less than half a turn for any gear change up or down.
Honda is justified in claiming that the next gear is "pre-selected" since ...
it simply is.

[FONT=&quot]...the Dual Clutch Transmission system’s ECU is programmed to minimize unnecessary gear changes by monitoring riding conditions on curvy roads like mountain passes. [/FONT]

 

[meteficha]

Does this really happen or is it just something that gets repeated over and over (like half a Fit engine)?

By the way, this isn't folklore. Obviously it's not exactly half of a Fit engine. But Honda engineers themselves have stated that they've started the design of NC700X's engine by cutting the Fit engine in half.

 

[dduelin]

By the way, this isn't folklore. Obviously it's not exactly half of a Fit engine. But Honda engineers themselves have stated that they've started the design of NC700X's engine by cutting the Fit engine in half.

Actually that is not true but who's paying any mind.

 

[lootzyan]

By the way, this isn't folklore. Obviously it's not exactly half of a Fit engine. But Honda engineers themselves have stated that they've started the design of NC700X's engine by cutting the Fit engine in half.

Read this....

Honda NC700X | Ash On Bikes

http://nc700-forum.com/forum/the-bar/4261-nc700-vs-honda-jazz.html

And welcome to the forum.