| nerdydorkus | 11-13-2006 01:58 AM |
Double Clutch-Heel Toe Downshifts...
�
�
at the same time.... (in movie baritone voice) :devil:
[url]http://www.youtube.com/watch?v=0j-3xIZK-Bk&mode=related&search=[/url]
although he does it throughout the whole video, it is very apparent when he downshifts 2 gears at 1:33. and i do not think he has a synchroless dogbox.
discuss... thanks!
[url]http://www.youtube.com/watch?v=0j-3xIZK-Bk&mode=related&search=[/url]
although he does it throughout the whole video, it is very apparent when he downshifts 2 gears at 1:33. and i do not think he has a synchroless dogbox.
discuss... thanks!
| psg | 11-13-2006 02:20 AM |
[QUOTE=nerdydorkus;15966630]at the same time.... (in movie baritone voice) :devil:
[url]http://www.youtube.com/watch?v=0j-3xIZK-Bk&mode=related&search=[/url]
although he does it throughout the whole video, it is very apparent when he downshifts 2 gears at 1:33. and i do not think he has a synchroless dogbox.
discuss... thanks![/QUOTE]
PM GarySheehan for details.
[url]http://www.youtube.com/watch?v=0j-3xIZK-Bk&mode=related&search=[/url]
although he does it throughout the whole video, it is very apparent when he downshifts 2 gears at 1:33. and i do not think he has a synchroless dogbox.
discuss... thanks![/QUOTE]
PM GarySheehan for details.
| PC tuner | 11-13-2006 02:35 AM |
Yep, this is the video that got me to start double clutching my downshifts. I find that it really helps me keep things timed correctly while downshifting. It's also quite a bit smoother than standard rev matching.
At first it can be pretty intimidating but after a little while it'll be second nature.
At first it can be pretty intimidating but after a little while it'll be second nature.
| Mykl | 11-13-2006 08:43 AM |
Practice makes perfect.
| jweiss | 11-13-2006 10:58 AM |
Ah yes, "double clutching":
[QUOTE](...) For six years, these naturalists tried various approaches to bring the number of Condors to a healthy status, and they did finally succeed. One of the important tricks they used was whenever Mama Condor would lay two eggs, one of these naturalists would sneak in through a trapdoor, remove an egg, and put it in an incubator. The Mama would look down and decide to lay another egg, since the number of eggs didn't look like a very large number. (Apparently Condors aren't as smart as crows, which can count up to 5 or 6 fairly consistently.) Anyhow, by this procedure, the Condor families were tricked into raising two clutches of eggs�one that the family would raise, and another that would be hatched and raised by the naturalists, behind the scenes. This trick was called, "Double-clutching. [URL="http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=6137"](linky)[/URL]
[/QUOTE]
:p
[QUOTE](...) For six years, these naturalists tried various approaches to bring the number of Condors to a healthy status, and they did finally succeed. One of the important tricks they used was whenever Mama Condor would lay two eggs, one of these naturalists would sneak in through a trapdoor, remove an egg, and put it in an incubator. The Mama would look down and decide to lay another egg, since the number of eggs didn't look like a very large number. (Apparently Condors aren't as smart as crows, which can count up to 5 or 6 fairly consistently.) Anyhow, by this procedure, the Condor families were tricked into raising two clutches of eggs�one that the family would raise, and another that would be hatched and raised by the naturalists, behind the scenes. This trick was called, "Double-clutching. [URL="http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=6137"](linky)[/URL]
[/QUOTE]
:p
| LastResort | 11-13-2006 11:01 AM |
Huh...I though double clutching was unnecessary on upshift's because the snychros natural slow down during the shift.
| gte123v | 11-13-2006 11:16 AM |
[QUOTE=LastResort;15969320]Huh...I though double clutching was unnecessary on upshift's because the snychros natural slow down during the shift.[/QUOTE]
it is unnecessary and pointless, unless you are vin diesel in FnF.:lol:
it is unnecessary and pointless, unless you are vin diesel in FnF.:lol:
| PC tuner | 11-13-2006 11:21 AM |
Double clutching is for downshifts. Syncros aren't even nessecary for upshifts.
| LastResort | 11-13-2006 11:56 AM |
[QUOTE=gte123v;15969553]it is unnecessary and pointless, unless you are vin diesel in FnF.:lol:[/QUOTE]That's what I thought.....the comment on the video starts with:
[QUOTE]almost everybody thinks that you can only double clutch on upshifts. the fact is that you can do it on both up and downshifts but more people only use it for upshifts so they think you can't do it on downshifts. [/QUOTE]I was very much :huh: .
[QUOTE]almost everybody thinks that you can only double clutch on upshifts. the fact is that you can do it on both up and downshifts but more people only use it for upshifts so they think you can't do it on downshifts. [/QUOTE]I was very much :huh: .
| PC tuner | 11-13-2006 12:12 PM |
Yeah, that's wrong. :lol:
Transmission bits don't need any help slowing down. They do need a little assistance to speed up though. Hence the reason for double clutching. :)
Transmission bits don't need any help slowing down. They do need a little assistance to speed up though. Hence the reason for double clutching. :)
| LastResort | 11-13-2006 12:13 PM |
Yeah. I've been working on my double clutch for neigh on 6 months now. I still stuck. I'm not race car driver. :(
| Scooby921 | 11-13-2006 12:17 PM |
[QUOTE=jweiss;15969245]Ah yes, "double clutching":
:p[/QUOTE]
:lol: :lol: :lol:
This belongs in OT where it'll get proper credit. Well done sir.
:p[/QUOTE]
:lol: :lol: :lol:
This belongs in OT where it'll get proper credit. Well done sir.
| SCRAPPYDO | 11-13-2006 12:56 PM |
I know when I race to put bread on the table for my family I always double clutch as precious tenths matter...wait, I am an engineer, its only in my pretend life that I race for a living where anything like that actually matters...
| PA04STI | 11-13-2006 01:06 PM |
Ok so instead of rev matching...Double clutching is literally just pushing the clutch once then doing it again and shifting....correct from what I saw in the vid
How does this do the same as rev matching....explain someone...
How does this do the same as rev matching....explain someone...
| waktasz | 11-13-2006 01:12 PM |
[QUOTE=PA04STI;15971077]Ok so instead of rev matching...Double clutching is literally just pushing the clutch once then doing it again and shifting....correct from what I saw in the vid
How does this do the same as rev matching....explain someone...[/QUOTE]
You rev match with the clutch out and car in neutral to speed up the input shaft, so the speeds of the input and output shafts are matched and you can slide right into gear. Helps with smoother shifts on our transmissions and is a requirement on non-syncronized transmissions.
How does this do the same as rev matching....explain someone...[/QUOTE]
You rev match with the clutch out and car in neutral to speed up the input shaft, so the speeds of the input and output shafts are matched and you can slide right into gear. Helps with smoother shifts on our transmissions and is a requirement on non-syncronized transmissions.
| LastResort | 11-13-2006 01:25 PM |
[QUOTE=SCRAPPYDO;15970947]I know when I race to put bread on the table for my family I always double clutch as precious tenths matter...wait, I am an engineer, its only in my pretend life that I race for a living where anything like that actually matters...[/QUOTE]:rolleyes: I can get into first at a roll while double clutching, but not without. I consider that a feature, rather than getting bogged down at a light trying to do 10mph in second.
| Mykl | 11-13-2006 01:46 PM |
[QUOTE=PC tuner;15969622]Syncros aren't even nessecary for upshifts.[/QUOTE]
That's wrong. Your syncros are still used while upshifting.
That's wrong. Your syncros are still used while upshifting.
| shemoves | 11-13-2006 01:54 PM |
I've been working on it for a while now. I never thought I'd get it, but I kept at it, and I can do it with fair success. Though I am not quick/natural enough to do it in a fast-paced/high-stress environment yet. Something I have noticed though, is that the shape of the shoes makes a big difference. There are certain shoes that it just don't work in, and some it does. Strange as it is, my rainbow sandals are actually pretty good for it :rolleyes:
| SubaruCO | 11-13-2006 01:59 PM |
[QUOTE=Mykl;15971611]That's wrong. Your syncros are still used while upshifting.[/QUOTE]
Not used if you are upshifting correctly. Otherwise all those poor suckers with dogboxes wouldn't get use anything higher than 1st.
Not used if you are upshifting correctly. Otherwise all those poor suckers with dogboxes wouldn't get use anything higher than 1st.
| Mykl | 11-13-2006 02:23 PM |
[QUOTE=SubaruCO;15971825]Not used if you are upshifting correctly. Otherwise all those poor suckers with dogboxes wouldn't get use anything higher than 1st.[/QUOTE]
The only ways you can bypass the syncros on upshifting is if you double clutch or if you shift slowly enough for the gears to decrease in rotational speed to the point where the collar can engage them. When I'm trying to go fast at an autocross or at a drag strip or around a track, I'm not shifting this slowly.
Dog boxes work differently. Collar->gear speeds are syncronized differently.
The only ways you can bypass the syncros on upshifting is if you double clutch or if you shift slowly enough for the gears to decrease in rotational speed to the point where the collar can engage them. When I'm trying to go fast at an autocross or at a drag strip or around a track, I'm not shifting this slowly.
Dog boxes work differently. Collar->gear speeds are syncronized differently.
| SubaruCO | 11-13-2006 04:43 PM |
[QUOTE=Mykl;15972177]The only ways you can bypass the syncros on upshifting is if you double clutch or if you shift slowly enough for the gears to decrease in rotational speed to the point where the collar can engage them. When I'm trying to go fast at an autocross or at a drag strip or around a track, I'm not shifting this slowly.
Dog boxes work differently. Collar->gear speeds are syncronized differently.[/QUOTE]
Sorry to burst your bubble, but I think you need to brush up on your concepts. Double clutching is ONLY for downshifting, and dogboxes are exactly like a synchronized transmission just without the synchronizer cones.
Dog boxes work differently. Collar->gear speeds are syncronized differently.[/QUOTE]
Sorry to burst your bubble, but I think you need to brush up on your concepts. Double clutching is ONLY for downshifting, and dogboxes are exactly like a synchronized transmission just without the synchronizer cones.
| DrBiggly | 11-13-2006 04:53 PM |
Isn't that Gary Sheehan's video from some time back as I swear it looks really familiar (and is the interior of a race prepped Subaru, big hint.) The guy who posted it on YouTube should absolutely either give proper credit or Gary should ask that it be taken down. :)
-Biggly
-Biggly
| SCRAPPYDO | 11-13-2006 04:54 PM |
I have no issues getting my car into first while it rolling without double clutching. Push clutch in, rev engine to about where the revs would be in first, and it always just slips in. No drama. No fuss. When on an autocross course, I have never felt the need to go back to first, and if I did, I am not sure I would have time to do a double clutch.
| LastResort | 11-13-2006 05:21 PM |
Revving the engine does nothing in that situation to assist gear engagement. Some people have problems, others don't.
| PC tuner | 11-13-2006 05:31 PM |
Double clutching doesn't take significantly longer to do than regular rev matching. I always double clutch my downshifts, be it auto-x, track, rally, or street.
| Impreza01 | 11-13-2006 05:34 PM |
[QUOTE=DrBiggly;15974529]Isn't that Gary Sheehan's video from some time back as I swear it looks really familiar (and is the interior of a race prepped Subaru, big hint.) The guy who posted it on YouTube should absolutely either give proper credit or Gary should ask that it be taken down. :)
-Biggly[/QUOTE]
Yes, it's Sheehan's video.
-Biggly[/QUOTE]
Yes, it's Sheehan's video.
| Mykl | 11-13-2006 06:04 PM |
[QUOTE=SubaruCO;15974364]Sorry to burst your bubble, but I think you need to brush up on your concepts. Double clutching is ONLY for downshifting, and dogboxes are exactly like a synchronized transmission just without the synchronizer cones.[/QUOTE]
I don't mean to be a dick, but I think you need to brush up on your knowledge of how manual gearboxes work. Double clutching is not ONLY for downshifting. It just isn't worth double clutching upshifts if your gearbox is healthy because it takes entirely too long to do. But if you've got a worn out syncro double clutching may be the only way to get the car into the specific gear that's hosed, going up or down into it.
But that's not my point. It may not be worth double clutching upshifts, but the fact is that the syncros are also utilized for upshifting. The degree to which the syncro is used on upshifting or downshifting depends on the gap in ratios from one gear to the next. If you're constantly shifting hard between gears that are widely spaced, like fourth to fifth on a '04-'06 STi, you're definitely using the syncros and if you don't slow your arm down it's experiencing accelerated wear.
Dog boxes are similar in operation, but they're built to handle the increased shock that comes from slamming the collars into place.
I don't mean to be a dick, but I think you need to brush up on your knowledge of how manual gearboxes work. Double clutching is not ONLY for downshifting. It just isn't worth double clutching upshifts if your gearbox is healthy because it takes entirely too long to do. But if you've got a worn out syncro double clutching may be the only way to get the car into the specific gear that's hosed, going up or down into it.
But that's not my point. It may not be worth double clutching upshifts, but the fact is that the syncros are also utilized for upshifting. The degree to which the syncro is used on upshifting or downshifting depends on the gap in ratios from one gear to the next. If you're constantly shifting hard between gears that are widely spaced, like fourth to fifth on a '04-'06 STi, you're definitely using the syncros and if you don't slow your arm down it's experiencing accelerated wear.
Dog boxes are similar in operation, but they're built to handle the increased shock that comes from slamming the collars into place.
| shemoves | 11-13-2006 06:12 PM |
[QUOTE=DrBiggly;15974529]Isn't that Gary Sheehan's video from some time back as I swear it looks really familiar (and is the interior of a race prepped Subaru, big hint.) The guy who posted it on YouTube should absolutely either give proper credit or Gary should ask that it be taken down. :)
-Biggly[/QUOTE]
It is his vid (i did not post it). It is a wrx IIRK (with stock brakes).
-Biggly[/QUOTE]
It is his vid (i did not post it). It is a wrx IIRK (with stock brakes).
| PC tuner | 11-13-2006 06:14 PM |
A very easy way to see that syncros aren't needed is to shift without pushing in the clutch. I picked this up for rally and auto-x when you are left foot braking. If you are at the proper throttle position the transmission will smoothly fall out of gear. From here you rev the motor to the exact revs required for the lower gear and smoothly engage that gear. Syncros weren't used at all in this process. You can also do this on an up shift with simmilar results. Again, without use of the syncros.
| Mykl | 11-13-2006 06:26 PM |
[QUOTE=PC tuner;15975538]A very easy way to see that syncros aren't needed is to shift without pushing in the clutch. I picked this up for rally and auto-x when you are left foot braking. If you are at the proper throttle position the transmission will smoothly fall out of gear. From here you rev the motor to the exact revs required for the lower gear and smoothly engage that gear. Syncros weren't used at all in this process. You can also do this on an up shift with simmilar results. Again, without use of the syncros.[/QUOTE]
That's because the clutch is engaged and the gearbox and the engine are still tied together. That means you can manually set the transmission speed to where it needs to be for the collar to engage the next gear. You're basically doing the same thing as if you'd double clutched.... which is bypass the syncros.
You can do this for upshifting too, but it's painfully slow and if you're not perfect every time you can easily bend/break a shift fork.
I don't left foot brake so I don't use this technique. I double clutch downshifts because I'm more comfortable with it.
That's because the clutch is engaged and the gearbox and the engine are still tied together. That means you can manually set the transmission speed to where it needs to be for the collar to engage the next gear. You're basically doing the same thing as if you'd double clutched.... which is bypass the syncros.
You can do this for upshifting too, but it's painfully slow and if you're not perfect every time you can easily bend/break a shift fork.
I don't left foot brake so I don't use this technique. I double clutch downshifts because I'm more comfortable with it.
| SubaruCO | 11-13-2006 07:40 PM |
[QUOTE=Mykl;15975416]I don't mean to be a dick, but I think you need to brush up on your knowledge of how manual gearboxes work. Double clutching is not ONLY for downshifting. It just isn't worth double clutching upshifts if your gearbox is healthy because it takes entirely too long to do. But if you've got a worn out syncro double clutching may be the only way to get the car into the specific gear that's hosed, going up or down into it.
But that's not my point. It may not be worth double clutching upshifts, but the fact is that the syncros are also utilized for upshifting. The degree to which the syncro is used on upshifting or downshifting depends on the gap in ratios from one gear to the next. If you're constantly shifting hard between gears that are widely spaced, like fourth to fifth on a '04-'06 STi, you're definitely using the syncros and if you don't slow your arm down it's experiencing accelerated wear.
Dog boxes are similar in operation, but they're built to handle the increased shock that comes from slamming the collars into place.[/QUOTE]
Hey, I don't think you're a dick, you're just wrong. The point of the double (de)clutch on the downshift is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs on the chassis when on the limit of adhesion. (It also happens to be necessary in a synchro-less H-pattern shifter in order to engage the "dogs" smoothly)
Double clutching is unnecessary on upshifts because once the clutch is depressed and the throttle closed the engine naturally looses RPM matching the next gear's required input rotation. The engine is decoupled from the transmission via the clutch but as the internals of the transmission slow with friction the slower rotational speed of the next higher gear (at a given road speed) will come naturally into play allowing smooth selection even without synchros. Ideally the engine will be slowing as well and when the clutch is re-engaged it will find the engine RPM and the required input RPM of the transmission very close. Of course it helps when the engine loses RPM fast enough to make the shifts faster but double clutching is unnecessary on upshifts. (It's frustrating on most stock manual cars because the heavy flywheels and DBW throttle conspire to hold onto revs too long for well matched upshifts)
Think about Ferrari's excellent paddle shift manual. The transmission double clutches (with precisely matched rpm blip) on downshifts but does not do it on upshifts. It's just not necessary.
The point is illustrated in the above clip of Sheehan. Also here's a good link to the ideas on a PPG dogbox: [url]http://www.ppgearbox.com.au/images/content/SCDOG.wmv[/url]
While this isn't exactly the same concept it illustrates the idea that double clutching on upshifts is unnecessary as the natural friction and pumping loss of RPM allow synchronicity of transmission upshifts. Of course it helps that presumably this car is powered by rotationally very light engine that loses RPMs fast enough to make the clutchless upshifts possible.
Don't worry, this confuses a lot of people.
But that's not my point. It may not be worth double clutching upshifts, but the fact is that the syncros are also utilized for upshifting. The degree to which the syncro is used on upshifting or downshifting depends on the gap in ratios from one gear to the next. If you're constantly shifting hard between gears that are widely spaced, like fourth to fifth on a '04-'06 STi, you're definitely using the syncros and if you don't slow your arm down it's experiencing accelerated wear.
Dog boxes are similar in operation, but they're built to handle the increased shock that comes from slamming the collars into place.[/QUOTE]
Hey, I don't think you're a dick, you're just wrong. The point of the double (de)clutch on the downshift is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs on the chassis when on the limit of adhesion. (It also happens to be necessary in a synchro-less H-pattern shifter in order to engage the "dogs" smoothly)
Double clutching is unnecessary on upshifts because once the clutch is depressed and the throttle closed the engine naturally looses RPM matching the next gear's required input rotation. The engine is decoupled from the transmission via the clutch but as the internals of the transmission slow with friction the slower rotational speed of the next higher gear (at a given road speed) will come naturally into play allowing smooth selection even without synchros. Ideally the engine will be slowing as well and when the clutch is re-engaged it will find the engine RPM and the required input RPM of the transmission very close. Of course it helps when the engine loses RPM fast enough to make the shifts faster but double clutching is unnecessary on upshifts. (It's frustrating on most stock manual cars because the heavy flywheels and DBW throttle conspire to hold onto revs too long for well matched upshifts)
Think about Ferrari's excellent paddle shift manual. The transmission double clutches (with precisely matched rpm blip) on downshifts but does not do it on upshifts. It's just not necessary.
The point is illustrated in the above clip of Sheehan. Also here's a good link to the ideas on a PPG dogbox: [url]http://www.ppgearbox.com.au/images/content/SCDOG.wmv[/url]
While this isn't exactly the same concept it illustrates the idea that double clutching on upshifts is unnecessary as the natural friction and pumping loss of RPM allow synchronicity of transmission upshifts. Of course it helps that presumably this car is powered by rotationally very light engine that loses RPMs fast enough to make the clutchless upshifts possible.
Don't worry, this confuses a lot of people.
| SubaruCO | 11-13-2006 08:14 PM |
[QUOTE=PC tuner;15975538]A very easy way to see that syncros aren't needed is to shift without pushing in the clutch. I picked this up for rally and auto-x when you are left foot braking. If you are at the proper throttle position the transmission will smoothly fall out of gear. From here you rev the motor to the exact revs required for the lower gear and smoothly engage that gear. Syncros weren't used at all in this process. You can also do this on an up shift with simmilar results. Again, without use of the syncros.[/QUOTE]
You're absolutely right, except that I'd say if you were not exactly right in your RPM blip the synchros were ABUSED in the process. :) Congrats, you are a better driver than me. I do do clutchless upshifts on my race car, but downshifts are scaryier(sp?). Although, I've done basically the same thing on my friends Yamaha R6, as have many sportbike riders I'm sure.
You're absolutely right, except that I'd say if you were not exactly right in your RPM blip the synchros were ABUSED in the process. :) Congrats, you are a better driver than me. I do do clutchless upshifts on my race car, but downshifts are scaryier(sp?). Although, I've done basically the same thing on my friends Yamaha R6, as have many sportbike riders I'm sure.
| electricpork | 11-13-2006 08:18 PM |
[QUOTE=SubaruCO;15976440]Hey, I don't think you're a dick, you're just wrong. The point of the double (de)clutch on the downshift is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs on the chassis when on the limit of adhesion. (It also happens to be necessary in a synchro-less H-pattern shifter in order to engage the "dogs" smoothly)
Don't worry, this confuses a lot of people.[/QUOTE]
SubaruCO, I believe you are victim of this confusion as well. :) You are talking about rev matching, which can be done with or without [i]double-clutching[/i]. Most people single-clutch just fine and rev match so as to not upset the chassis or shock the driveline. Rev matching is required regardless of whether you have chosen to bypass your synchros.
Regards,
Ben
Don't worry, this confuses a lot of people.[/QUOTE]
SubaruCO, I believe you are victim of this confusion as well. :) You are talking about rev matching, which can be done with or without [i]double-clutching[/i]. Most people single-clutch just fine and rev match so as to not upset the chassis or shock the driveline. Rev matching is required regardless of whether you have chosen to bypass your synchros.
Regards,
Ben
| waktasz | 11-13-2006 08:20 PM |
[QUOTE=electricpork;15976802]SubaruCO, I believe you are victim of this confusion as well. :) You are talking about rev matching, which can be done with or without [i]double-clutching[/i]. Most people single-clutch just fine and rev match so as to not upset the chassis or shock the driveline. Rev matching is required regardless of whether you have chosen to bypass your synchros.
Regards,
Ben[/QUOTE]
+1000.
Regards,
Ben[/QUOTE]
+1000.
| PC tuner | 11-13-2006 08:23 PM |
Here is a very good/long thread on the subject. This is the thread that introduced me to double clutching about a year ago.
[url]http://www.cobbforums.com/forums/showthread.php?t=30759[/url]
[url]http://www.cobbforums.com/forums/showthread.php?t=30759[/url]
| nhluhr | 11-13-2006 08:48 PM |
[QUOTE=Mykl;15975416]It may not be worth double clutching upshifts, but the fact is that the syncros are also utilized for upshifting. [/QUOTE]The other guy said the syncros are not necessary... as in not required... for upshifts. This is true. You can upshift perfectly well without syncros. You are absolutely right though when you say the syncros are utilized on upshifts, because cars have had syncros long enough that most drivers don't have any concept of timing their shifts (this includes most autocrossers as well). They are spoiled by the syncros and thus they end up using them quite heavily on upshifts.
| Mykl | 11-13-2006 08:55 PM |
[QUOTE=SubaruCO;15976440]Hey, I don't think you're a dick, you're just wrong. The point of the double (de)clutch on the downshift is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs on the chassis when on the limit of adhesion. (It also happens to be necessary in a synchro-less H-pattern shifter in order to engage the "dogs" smoothly)[/quote]
No, the point of *rev matching* is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs. You can rev match with a single kick of the clutch.
The point of *DOUBLE CLUTCHING* is to both match the engine speed (taking gear multiplication into account) to the *driveshaft* speed *and* match the speed of the gears with the collar that is meshing with it to ease the job of the syncros. Look this up on howstuffworks.com , it's all there.
[QUOTE=SubaruCO;15976440]Double clutching is unnecessary on upshifts because once the clutch is depressed and the throttle closed the engine naturally looses RPM matching the next gear's required input rotation. The engine is decoupled from the transmission via the clutch but as the internals of the transmission slow with friction the slower rotational speed of the next higher gear (at a given road speed) will come naturally into play allowing smooth selection even without synchros. Ideally the engine will be slowing as well and when the clutch is re-engaged it will find the engine RPM and the required input RPM of the transmission very close. Of course it helps when the engine loses RPM fast enough to make the shifts faster but double clutching is unnecessary on upshifts. (It's frustrating on most stock manual cars because the heavy flywheels and DBW throttle conspire to hold onto revs too long for well matched upshifts)[/quote]
Yes, they will naturally decrease in speed, and they'll decrease to the point that they need to to engage the next gear if you're patient enough.
Go for a drive and do an experiment. Without using the clutch, shift from 3rd to 4th gear. Be gentle so you don't break anything, just put delicate, even pressure on fourth gear. It will slip into gear, but the shift will be very slow.
The reason the syncros are used on upshifting is because most people move the shifter so fast that it doesn't give the gearbox enough time to spin down for the next gear, so the syncros help match speeds. You know that pause you feel when you go from one gear to another? That's the syncros doing their job. My gearbox pauses on upshifts, I'm sure yours does too.
[QUOTE=SubaruCO;15976440]
Think about Ferrari's excellent paddle shift manual. The transmission double clutches (with precisely matched rpm blip) on downshifts but does not do it on upshifts. It's just not necessary.
The point is illustrated in the above clip of Sheehan. Also here's a good link to the ideas on a PPG dogbox: [url]http://www.ppgearbox.com.au/images/content/SCDOG.wmv[/url]
While this isn't exactly the same concept it illustrates the idea that double clutching on upshifts is unnecessary as the natural friction and pumping loss of RPM allow synchronicity of transmission upshifts. Of course it helps that presumably this car is powered by rotationally very light engine that loses RPMs fast enough to make the clutchless upshifts possible.
Don't worry, this confuses a lot of people.[/QUOTE]
We're talking about syncro boxes, not dog boxes. You can get away with slamming through the gears on upshifting with a dog box, they're built for that type of shock. Most of the time when I ride around on a motorcycle I don't use the clutch on upshifts. But syncro boxes can't engage that quickly. So if you've got a trashed syncro you either have to double clutch up and down, or keep the clutch engaged and wait for the engine revs to drop on upshifts.
No, the point of *rev matching* is to match the engine speed to the transmission speed in order to significantly reduce engine braking inputs. You can rev match with a single kick of the clutch.
The point of *DOUBLE CLUTCHING* is to both match the engine speed (taking gear multiplication into account) to the *driveshaft* speed *and* match the speed of the gears with the collar that is meshing with it to ease the job of the syncros. Look this up on howstuffworks.com , it's all there.
[QUOTE=SubaruCO;15976440]Double clutching is unnecessary on upshifts because once the clutch is depressed and the throttle closed the engine naturally looses RPM matching the next gear's required input rotation. The engine is decoupled from the transmission via the clutch but as the internals of the transmission slow with friction the slower rotational speed of the next higher gear (at a given road speed) will come naturally into play allowing smooth selection even without synchros. Ideally the engine will be slowing as well and when the clutch is re-engaged it will find the engine RPM and the required input RPM of the transmission very close. Of course it helps when the engine loses RPM fast enough to make the shifts faster but double clutching is unnecessary on upshifts. (It's frustrating on most stock manual cars because the heavy flywheels and DBW throttle conspire to hold onto revs too long for well matched upshifts)[/quote]
Yes, they will naturally decrease in speed, and they'll decrease to the point that they need to to engage the next gear if you're patient enough.
Go for a drive and do an experiment. Without using the clutch, shift from 3rd to 4th gear. Be gentle so you don't break anything, just put delicate, even pressure on fourth gear. It will slip into gear, but the shift will be very slow.
The reason the syncros are used on upshifting is because most people move the shifter so fast that it doesn't give the gearbox enough time to spin down for the next gear, so the syncros help match speeds. You know that pause you feel when you go from one gear to another? That's the syncros doing their job. My gearbox pauses on upshifts, I'm sure yours does too.
[QUOTE=SubaruCO;15976440]
Think about Ferrari's excellent paddle shift manual. The transmission double clutches (with precisely matched rpm blip) on downshifts but does not do it on upshifts. It's just not necessary.
The point is illustrated in the above clip of Sheehan. Also here's a good link to the ideas on a PPG dogbox: [url]http://www.ppgearbox.com.au/images/content/SCDOG.wmv[/url]
While this isn't exactly the same concept it illustrates the idea that double clutching on upshifts is unnecessary as the natural friction and pumping loss of RPM allow synchronicity of transmission upshifts. Of course it helps that presumably this car is powered by rotationally very light engine that loses RPMs fast enough to make the clutchless upshifts possible.
Don't worry, this confuses a lot of people.[/QUOTE]
We're talking about syncro boxes, not dog boxes. You can get away with slamming through the gears on upshifting with a dog box, they're built for that type of shock. Most of the time when I ride around on a motorcycle I don't use the clutch on upshifts. But syncro boxes can't engage that quickly. So if you've got a trashed syncro you either have to double clutch up and down, or keep the clutch engaged and wait for the engine revs to drop on upshifts.
| Mykl | 11-13-2006 09:04 PM |
[QUOTE=nhluhr;15977128]The other guy said the syncros are not necessary... as in not required... for upshifts. This is true. You can upshift perfectly well without syncros. You are absolutely right though when you say the syncros are utilized on upshifts, because cars have had syncros long enough that most drivers don't have any concept of timing their shifts (this includes most autocrossers as well). They are spoiled by the syncros and thus they end up using them quite heavily on upshifts.[/QUOTE]
I see that now. The point that crossed me up is the way he said it. He insists that you don't need to use the clutch for upshifts, which is 100% true. However, using the same exact technique you can downshift without the clutch. Except instead of waiting for the revs to drop, you blip the throttle to bring the revs up.
It would be more accurate to him to say "the clutch isn't necessary for shifting."
I see that now. The point that crossed me up is the way he said it. He insists that you don't need to use the clutch for upshifts, which is 100% true. However, using the same exact technique you can downshift without the clutch. Except instead of waiting for the revs to drop, you blip the throttle to bring the revs up.
It would be more accurate to him to say "the clutch isn't necessary for shifting."
| nhluhr | 11-13-2006 09:06 PM |
I would prefer to have a clutch and syncros and also double-clutch my downshifts. :)
| Mykl | 11-13-2006 09:15 PM |
SubaruCO, I'm sorry if I misinterpretted your post. But the way you worded it was fairly confusing.
You can apply all three shifting techniques (single clutch, double clutch, clutchless) to both upshifting and downshifting. Syncros are a luxury, we don't *need* them, and it's easy to drive without them... but it's nice to have them.
...and I double clutch my downshifts, but single clutch my upshifts. Although I upshift with mechanical sympathy to go easy on the syncros because I want them to last. I don't do clutchless shifts because the engine revs don't fall fast enough and I don't trust my accuracy so much when I'm at the edge of sliding while braking and trying to turn in at an autocross. I'd rather use the clutch.
You can apply all three shifting techniques (single clutch, double clutch, clutchless) to both upshifting and downshifting. Syncros are a luxury, we don't *need* them, and it's easy to drive without them... but it's nice to have them.
...and I double clutch my downshifts, but single clutch my upshifts. Although I upshift with mechanical sympathy to go easy on the syncros because I want them to last. I don't do clutchless shifts because the engine revs don't fall fast enough and I don't trust my accuracy so much when I'm at the edge of sliding while braking and trying to turn in at an autocross. I'd rather use the clutch.
| nhluhr | 11-13-2006 09:32 PM |
[QUOTE=Mykl;15977507]...and I double clutch my downshifts, but single clutch my upshifts. Although I upshift with mechanical sympathy to go easy on the syncros because I want them to last. I don't do clutchless shifts because the engine revs don't fall fast enough and I don't trust my accuracy so much when I'm at the edge of sliding while braking and trying to turn in at an autocross. I'd rather use the clutch.[/QUOTE]This is exactly how I drive as well.
| Mykl | 11-13-2006 09:40 PM |
[QUOTE=nhluhr;15977708]This is exactly how I drive as well.[/QUOTE]
I wish I would have learned how to treat a gearbox before I killed a couple of them years ago learning how to drive my old FC RX-7's. :lol: At least those were cheap to fix.
I wish I would have learned how to treat a gearbox before I killed a couple of them years ago learning how to drive my old FC RX-7's. :lol: At least those were cheap to fix.
| nerdydorkus | 11-14-2006 12:10 AM |
hey guys, (im the OP) i just wanna say thanks for discussing this. ive learned a lot!
| MaxSTi05 | 11-14-2006 12:23 AM |
[QUOTE=nhluhr;15977708]This is exactly how I drive as well.[/QUOTE]
+1
But when I do downshift, on a race course or street, I brake/slow enough to the point of allowing just a SINGLE double-clutch downshift to the gear desired, e.g. 5th to 2nd, w/o over-revving at that low gear when all is matched up. I'm not sure with modern synchros you do need to downshift and double-clutch through each gear. Any negatives on this please chime in :)
+1
But when I do downshift, on a race course or street, I brake/slow enough to the point of allowing just a SINGLE double-clutch downshift to the gear desired, e.g. 5th to 2nd, w/o over-revving at that low gear when all is matched up. I'm not sure with modern synchros you do need to downshift and double-clutch through each gear. Any negatives on this please chime in :)
| nerdydorkus | 11-14-2006 01:35 AM |
ok sorry noob question.
double clutch downshifts. on the 1st clutch depression put the shifter into neutral, at this step do you hit the gas or not. or do you just hit the gas/rev match at the 2nd clutch depression.
double clutch downshifts. on the 1st clutch depression put the shifter into neutral, at this step do you hit the gas or not. or do you just hit the gas/rev match at the 2nd clutch depression.
| PC tuner | 11-14-2006 02:11 AM |
I usually end up blipping the throttle as I'm releasing the clutch on the first depression. You want the revs to be where they need to be when the clutch is out and your transmission is in neutral.
| davis10 | 11-14-2006 02:57 AM |
[QUOTE=PC tuner;15969622]Double clutching is for downshifts. Syncros aren't even nessecary for upshifts.[/QUOTE]
You also don;t need a clutch on upshifts ;) if you have a dogbox, this guy does, and you can see him clutchless upshift a few times.
You also don;t need a clutch on upshifts ;) if you have a dogbox, this guy does, and you can see him clutchless upshift a few times.
| davis10 | 11-14-2006 03:01 AM |
[QUOTE=nerdydorkus;15980198]ok sorry noob question.
double clutch downshifts. on the 1st clutch depression put the shifter into neutral, at this step do you hit the gas or not. or do you just hit the gas/rev match at the 2nd clutch depression.[/QUOTE]
When double clutching you revmatch after/during releasing the clutch for the first time, this way everything is spinning the required speed;) Therefore after the revs hit the speed you want you must perform the second clutch quickly so that no driveline parts, like the intermediate shaft, have time to slow down with respect to each other.
once you go heel toe you dont go back;)
double clutch downshifts. on the 1st clutch depression put the shifter into neutral, at this step do you hit the gas or not. or do you just hit the gas/rev match at the 2nd clutch depression.[/QUOTE]
When double clutching you revmatch after/during releasing the clutch for the first time, this way everything is spinning the required speed;) Therefore after the revs hit the speed you want you must perform the second clutch quickly so that no driveline parts, like the intermediate shaft, have time to slow down with respect to each other.
once you go heel toe you dont go back;)
| PC tuner | 11-14-2006 03:05 AM |
[QUOTE=davis10;15980673]You also don;t need a clutch on upshifts ;) if you have a dogbox, this guy does, and you can see him clutchless upshift a few times.[/QUOTE]
A dogbox isn't required for clutchless shifting.
A dogbox isn't required for clutchless shifting.
| Wylan | 11-14-2006 06:13 AM |
A dogbox definitely isn't needed for clutchless shifting, I had a mazda a long while back, and I could Up shift from 3rd all the way to 5th w/o the clutch
| davis10 | 11-14-2006 11:57 AM |
[QUOTE=Wylan;15981218]A dogbox definitely isn't needed for clutchless shifting, I had a mazda a long while back, and I could Up shift from 3rd all the way to 5th w/o the clutch[/QUOTE]
Yes I have shifted clutchlessly up and down on syncros, but it is definitly not going to help the life of you gearbox especially in race conditions. So, in a race evironment you essentially need to have a dogbox to clutchless shift, since the gears are designed to be slammed in.
Yes I have shifted clutchlessly up and down on syncros, but it is definitly not going to help the life of you gearbox especially in race conditions. So, in a race evironment you essentially need to have a dogbox to clutchless shift, since the gears are designed to be slammed in.
| PA04STI | 11-14-2006 11:47 PM |
ok so double clutch ='s rev matching....then why call it double clutching never heard of that terminology....:confused:
Matt
Matt
| PC tuner | 11-14-2006 11:53 PM |
Double clutching is not the same thing as rev matching.
| Mykl | 11-14-2006 11:56 PM |
You can rev match without double clutching... but rev matching automatically occurs when you double clutch. :)
| PA04STI | 11-15-2006 12:08 AM |
Ok give me the sequence for double clutching....
I know rev matching is clutch - neutral - rev - next lower gear
So is double clutching clutch - neutrl - clutch - lower gear????
I know rev matching is clutch - neutral - rev - next lower gear
So is double clutching clutch - neutrl - clutch - lower gear????
| LastResort | 11-15-2006 12:16 AM |
Clutch in->shift to neutral->clutch out->blip throttle->clutch in->shift to lower gear->clutch out
The key is to be on the brake the whole time. That's where heel toe comes in.
The key is to be on the brake the whole time. That's where heel toe comes in.
| PA04STI | 11-15-2006 02:35 AM |
that takes some damn impressive foot work to get all that done, brake, get setup for your turn...
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt
| Calamity Jesus | 11-15-2006 08:17 AM |
[QUOTE=PA04STI;15994734]that takes some damn impressive foot work to get all that done, brake, get setup for your turn...
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt[/QUOTE]Beginning ballroom dancers don't start with the Foxtrot. When your passengers start asking you what you're doing, and you have to get them to explain what it is you're talking about (and they describe rev matching), it's time to start working on the double-clutch.
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt[/QUOTE]Beginning ballroom dancers don't start with the Foxtrot. When your passengers start asking you what you're doing, and you have to get them to explain what it is you're talking about (and they describe rev matching), it's time to start working on the double-clutch.
| Mykl | 11-15-2006 08:54 AM |
[QUOTE=PA04STI;15994734]that takes some damn impressive foot work to get all that done, brake, get setup for your turn...
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt[/QUOTE]
For me the footwork is the easy part. The hard part is finding the damn gear I'm trying to downshift into when I'm driving around an autocross course. :D I swear, at least 25% of the time when I downshift at an autocross I miss the damn gear.
Double clutching isn't really required, so don't lose any sleep over it. You've got a really good gearbox with good syncros. The only reason I continue to do it is because I've been doing it for so long that I'm comfortable with it.
I'll stick to just the rev matching which I have trouble with enough doing properly
Matt[/QUOTE]
For me the footwork is the easy part. The hard part is finding the damn gear I'm trying to downshift into when I'm driving around an autocross course. :D I swear, at least 25% of the time when I downshift at an autocross I miss the damn gear.
Double clutching isn't really required, so don't lose any sleep over it. You've got a really good gearbox with good syncros. The only reason I continue to do it is because I've been doing it for so long that I'm comfortable with it.
| GarySheehan | 11-15-2006 09:17 AM |
I've posted this info elsewhere in the forum, but it looks like it might be helpful here.
When you guys are discussing double-clutching, you are walking through the steps serially, like this...
1. brake
2. clutch in
3. shift to neutral
4. clutch out
5. blip throttle
6. clutch back in
7. select next lower gear
8. clutch back out
9. off brakes
This serial processing is accurate when you are thinking about an action consciously. But when you process unconciously, your body can parallel process and do quite complicated things. Take walking for instance. Try and figure out all the steps required to walk down a hallway. There are so many it would be overwhelming and we'd decide to just stay on the couch.
So, when you consider how double-clutching works when your body processes in parallel, it isn't any slower. The reason is, you are not actually going through the 9 steps listed above. Things are going in that order, but actions are happening in parallel.
There are three ballistic actions that occur during a double-clutch. A ballistic action is an action that your brain starts, but doesn't have to finish because your body is programmed to complete the series of actions. Here are the three actions my body performs when I double-clutch. These are not in order, they are parallel processes that are synchronized appropriately.
1. Right foot depresses brake, throws in a throttle blip at some point and comes off the brakes later.
2. Right hand moves shift lever to neutral, then to next lower gear.
3. Left foot pumps clutch twice quickly
So, when you think about the body's ability to parallel process, it becomes a much simpler task of perfoming three synchronized actions simultaneously rather than performing nine seperate actions serially.
To show how a double-clutch is no slower than a single-clutch, let's look at what happens during a single-clutch:
1. Right foot depresses brake, throws in a throttle blip at some point and comes off the brake later.
2. Right hand moves shift lever to neutral, then to next lower gear.
3. Left foot pushes clutch down for the duration of (2) above.
So the only difference between the two is the left foot pumps the clutch twice quickly instead of holding the clutch down for a longer single cycle. The KEY here is that there is no pause while the shift lever is in neutral. As the shift lever is passing through neutral, the clutch is already out and the throttle has been blipped. No extra time was used.
Consider these three parallel processes (rather than nine individual steps) and watch the video again. It's clear that there are three processes taking place that are just tightly synchronized.
[ame="http://www.youtube.com/watch?v=2SXPHwe3swI"]Footbox Camera - YouTube[/ame]
Does that help explain it?
Gary
Sheehan Motor Racing
[url]www.garysheehan.com[/url]
When you guys are discussing double-clutching, you are walking through the steps serially, like this...
1. brake
2. clutch in
3. shift to neutral
4. clutch out
5. blip throttle
6. clutch back in
7. select next lower gear
8. clutch back out
9. off brakes
This serial processing is accurate when you are thinking about an action consciously. But when you process unconciously, your body can parallel process and do quite complicated things. Take walking for instance. Try and figure out all the steps required to walk down a hallway. There are so many it would be overwhelming and we'd decide to just stay on the couch.
So, when you consider how double-clutching works when your body processes in parallel, it isn't any slower. The reason is, you are not actually going through the 9 steps listed above. Things are going in that order, but actions are happening in parallel.
There are three ballistic actions that occur during a double-clutch. A ballistic action is an action that your brain starts, but doesn't have to finish because your body is programmed to complete the series of actions. Here are the three actions my body performs when I double-clutch. These are not in order, they are parallel processes that are synchronized appropriately.
1. Right foot depresses brake, throws in a throttle blip at some point and comes off the brakes later.
2. Right hand moves shift lever to neutral, then to next lower gear.
3. Left foot pumps clutch twice quickly
So, when you think about the body's ability to parallel process, it becomes a much simpler task of perfoming three synchronized actions simultaneously rather than performing nine seperate actions serially.
To show how a double-clutch is no slower than a single-clutch, let's look at what happens during a single-clutch:
1. Right foot depresses brake, throws in a throttle blip at some point and comes off the brake later.
2. Right hand moves shift lever to neutral, then to next lower gear.
3. Left foot pushes clutch down for the duration of (2) above.
So the only difference between the two is the left foot pumps the clutch twice quickly instead of holding the clutch down for a longer single cycle. The KEY here is that there is no pause while the shift lever is in neutral. As the shift lever is passing through neutral, the clutch is already out and the throttle has been blipped. No extra time was used.
Consider these three parallel processes (rather than nine individual steps) and watch the video again. It's clear that there are three processes taking place that are just tightly synchronized.
[ame="http://www.youtube.com/watch?v=2SXPHwe3swI"]Footbox Camera - YouTube[/ame]
Does that help explain it?
Gary
Sheehan Motor Racing
[url]www.garysheehan.com[/url]
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