what exactly is double cluthing?
05-17-2003, 09:20 PM
#3
Three Wheelin'
It's done for vehicles without synchros primarily to ensure that you can get a lower gear without playing a musical tune with your gearbox. You can do it with the clutch in a regular car with synchros as well, if you do it quick enough. The trick is when the clutch is out to rev the engine enough so that you can let off the gas, put the clutch in and select your gear and right at that point in time, the revs on the engine should be at or just slightly faster than the revs on the drivetrain/wheels and the gear will mesh perfectly. Of course during the whole process you have your foot on the brake slowing your car rapidly. It takes a lot of practice to do it well. Learning it at Skip Barber at Mid Ohio, once I had it down you go down two gears from 4th to 2nd at the end of the back straight from about 130mph to about 60mph and you do all of that in just a very small number of seconds...3-4 roughly. Sound complex and hard to do? It is until you get the hang of it. Much easier to do when you are braking hard and fast to me than when slowing more gently.
There is another topic on it right now where it is being discussed as well on heel and toeing.
Cheers!
There is another topic on it right now where it is being discussed as well on heel and toeing.
Cheers!
05-17-2003, 10:43 PM
#4
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by turbo944:
<strong>It's done for vehicles without synchros primarily to ensure that you can get a lower gear without playing a musical tune with your gearbox. You can do it with the clutch in a regular car with synchros as well, if you do it quick enough. The trick is when the clutch is out to rev the engine enough so that you can let off the gas, put the clutch in and select your gear and right at that point in time, the revs on the engine should be at or just slightly faster than the revs on the drivetrain/wheels and the gear will mesh perfectly. Of course during the whole process you have your foot on the brake slowing your car rapidly. It takes a lot of practice to do it well. Learning it at Skip Barber at Mid Ohio, once I had it down you go down two gears from 4th to 2nd at the end of the back straight from about 130mph to about 60mph and you do all of that in just a very small number of seconds...3-4 roughly. Sound complex and hard to do? It is until you get the hang of it. Much easier to do when you are braking hard and fast to me than when slowing more gently.
There is another topic on it right now where it is being discussed as well on heel and toeing.
Cheers!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You're describing a double-clutched downshift combined with heel-and-toe technique (heel-and-toe to blip the throttle while braking). Double clutching can also be used while upshifting, and it can be done while downshifting without simultaneous braking. One can also double-clutch without rev-matching on a downshift, though rev-matching is almost always done to smooth out the final re-engagement of the clutch.
Aaron
<strong>It's done for vehicles without synchros primarily to ensure that you can get a lower gear without playing a musical tune with your gearbox. You can do it with the clutch in a regular car with synchros as well, if you do it quick enough. The trick is when the clutch is out to rev the engine enough so that you can let off the gas, put the clutch in and select your gear and right at that point in time, the revs on the engine should be at or just slightly faster than the revs on the drivetrain/wheels and the gear will mesh perfectly. Of course during the whole process you have your foot on the brake slowing your car rapidly. It takes a lot of practice to do it well. Learning it at Skip Barber at Mid Ohio, once I had it down you go down two gears from 4th to 2nd at the end of the back straight from about 130mph to about 60mph and you do all of that in just a very small number of seconds...3-4 roughly. Sound complex and hard to do? It is until you get the hang of it. Much easier to do when you are braking hard and fast to me than when slowing more gently.
There is another topic on it right now where it is being discussed as well on heel and toeing.
Cheers!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You're describing a double-clutched downshift combined with heel-and-toe technique (heel-and-toe to blip the throttle while braking). Double clutching can also be used while upshifting, and it can be done while downshifting without simultaneous braking. One can also double-clutch without rev-matching on a downshift, though rev-matching is almost always done to smooth out the final re-engagement of the clutch.
Aaron
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05-18-2003, 01:39 PM
#8
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by 944S2NUT:
<strong>yes I heard that term on fast and the furious. Wonder what they meant by it on their newer cars.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
<strong>yes I heard that term on fast and the furious. Wonder what they meant by it on their newer cars.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
05-18-2003, 08:32 PM
#9
Three Wheelin'
Wait wait wait, what's this? If you have more power than your clutch can hold...You're car ain't set up right!
If the clutch is slipping from straight power, you want to push the clutch in, then reengage it so it catches? That is a really crappy way to drag race. You'd do better just shifting early, or am I reading your post wrong??
If the clutch is slipping from straight power, you want to push the clutch in, then reengage it so it catches? That is a really crappy way to drag race. You'd do better just shifting early, or am I reading your post wrong??
05-18-2003, 10:20 PM
#11
Race Director
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Doug&Julie:
[QBSounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
[/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Yep <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
[QBSounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
[/QB]</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Yep <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
05-19-2003, 01:19 AM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Doug&Julie:
<strong> </font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by 944S2NUT:
<strong>yes I heard that term on fast and the furious. Wonder what they meant by it on their newer cars.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">In vintage racing, however...
On the street, I have only ever found double-clutching to be helpful when nursing a car with bad synchros. Of course, I love the feeling from a good double-clutch and I do it often, but that's only for personal preference and not for performance.
Street cars with good synchros don't require it (just slows you down) and race cars with straight-cut gears and/or sequential transmissions don't really even need a clutch except for when taking off from the pits after a stop.
Aaron
<strong> </font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by 944S2NUT:
<strong>yes I heard that term on fast and the furious. Wonder what they meant by it on their newer cars.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Sounds like a "fancy racing lingo term" to use in movies for the uninitiated. One of those things where a real racer would stand up and say "that's not right!". Double clutching is rarely used today. Hell, in higher level racing, single clutching is rarely used today!
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">In vintage racing, however... On the street, I have only ever found double-clutching to be helpful when nursing a car with bad synchros. Of course, I love the feeling from a good double-clutch and I do it often, but that's only for personal preference and not for performance.
Street cars with good synchros don't require it (just slows you down) and race cars with straight-cut gears and/or sequential transmissions don't really even need a clutch except for when taking off from the pits after a stop.
Aaron
05-19-2003, 02:32 AM
#13
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I'm not 100% sure double clutching slows anybody down. At least in the cars I usually drive there's a significant delay before the syncros manage to match shaft speeds, you can't just slam the gears in when downshifting... so while that extra clutch engagement takes a small fraction of time, I think it more than makes up for it with the fact that you get to by-pass those slow syncros and your downshift just falls in with no resistance.
If I really try, I can drive around switching gears without anybody in the car noticing it (except of course the stick movements and rpm changes). I'm sure I couldn't do that with plain rev-matching... but hey, if it works for you, good!
And of course, I can't see any benefit in double-clutching when shifting up, since you actually want to slow the gearbox shafts down, not speed them up.
If I really try, I can drive around switching gears without anybody in the car noticing it (except of course the stick movements and rpm changes). I'm sure I couldn't do that with plain rev-matching... but hey, if it works for you, good!
And of course, I can't see any benefit in double-clutching when shifting up, since you actually want to slow the gearbox shafts down, not speed them up.
05-19-2003, 08:24 AM
#14
Race Director
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Sami951:
<strong>I'm not 100% sure double clutching slows anybody down.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">It most certainly does. I switched from double clutching to single clutching at racing school and it was a whole lot faster single clutching. I'm also certain that during a race (I do compete in SCCA racing) that double clutching would be significantly slower.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Sami951:
<strong>And of course, I can't see any benefit in double-clutching when shifting up, since you actually want to slow the gearbox shafts down, not speed them up.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The benefit for upshifting is the same as downshifting - you want to match the speed of the input shaft of the gearbox with the speed of the crankshaft.
<strong>I'm not 100% sure double clutching slows anybody down.
</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">It most certainly does. I switched from double clutching to single clutching at racing school and it was a whole lot faster single clutching. I'm also certain that during a race (I do compete in SCCA racing) that double clutching would be significantly slower.
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Sami951:
<strong>And of course, I can't see any benefit in double-clutching when shifting up, since you actually want to slow the gearbox shafts down, not speed them up.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">The benefit for upshifting is the same as downshifting - you want to match the speed of the input shaft of the gearbox with the speed of the crankshaft.
