double clutching
Evolving Member
Joined: Apr 2005
Posts: 110
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From: Alabama, Guntersville
I could be wrong but I think it is when you are in a gear you press the clutch in once put the car in neutral. Let the clutch out. Then press the clutch in again and put the car in gear.
This is correct but I haven't figured out a use for it in a car. In a 18 wheeler it's different.
The only thing I could see it for is keeping good pressure on the fly wheel I guess.
This is correct but I haven't figured out a use for it in a car. In a 18 wheeler it's different.
The only thing I could see it for is keeping good pressure on the fly wheel I guess.
Newbie
Joined: Nov 2004
Posts: 46
Likes: 0
This is a nice explanation from the Car Forums
Double Clutching (the easy way)
In another thread, several people expressed a desire to learn how to double clutch. I found this article which gives a good account on how to do it properly. The main thing to remember is you car is always talking to you, so learn to listen. You need to learn what rpm generates what speed in each gear. Tach's are great for this, but engine sound is a much better method. You don't always have time look at the tack. This procedure needs to be done quickly and SMOOTHLY. So turn off the boom-box and go have some fun.
I was afraid to post the link, so this is a C&P. I have included the authors name for credit.
John
The following is a beginner's approach to learning how to double - clutch. This technique allows downshifts from higher speeds without any synchroniser wear. This is VERY important if you ever want to drive really quickly and keep your transmission intact for extended periods!
The Easy Way to Double-Clutch
By Jeff Krause.
Double-clutching is the proper way to downshift at speed without placing excessive wear on the transmission's synchronizers. This allows you to select a much lower gear without the tell-tale lurch you normally get when the clutch is let out after downshifting.
When downshifting my BMW M5 from 4th gear to 2nd at 50 mph, I need to raise the engine speed from 2200 rpm to 5000. To prevent excessive synchroniser wear, the clutch is depressed and the shifter is moved to neutral. The clutch is then released, and the gas is depressed to bring the engine speed up to where it needs to be for the lower gear. The clutch is then depressed again and the shift lever moved into the lower gear. When the clutch is released the second time, the engine is already turning the proper speed . While this sounds complicated, it's easier done than said, and only takes about a second.
To better understand how the process works, a little background on transmission fundamentals will help.
A typical transmisson has two shafts, one connected to the engine through the clutch, and one connected to the rear wheels. There are usually four to six sets of gears on these shafts and they are selected with the gearshift lever inside the car. When changing gears, the clutch is depressed to disconnect the engine from the transmission so there isn't any stress on the moving parts. Since the output shaft is permanently connected to the rear wheels, the only way to match the speed of the two shafts is to use the throttle to adjust engine speed.
Once the engine is turning the right rpm, both shafts will be turning the same speed, and the gear lever will fall into gear WITHOUT using the clutch! (Although most of the time you are shifting too fast to be that accurate)
EXCERCISES
1) With the car idling in neutral, slowly step on the gas until the engine is turning 3500 rpm. Do it again bringing the rpm's up more and more quickly until you can give the pedal a quick stab and have the revs stop where you want . As you shorten the time allowed to match revs, you will notice it takes more throttle. In fast driving, you will be shifting so fast 4 will take full thottle! Now try matching revs at 4000 rpm.
2) Find a deserted road, and maintain 40 mph in 4th gear. Now shift into 3rd, and see how many rpm's the engine speed increased. At this speed, the difference won't be very much - maybe only a few hundred rpm. Go back into 4th gear. This time put the clutch in, push the lever to neutral and let the clutch back out. You are now coasting with the clutch out. Raise the engine speed to where it will be in third gear. Quickly push the clutch in, select 3rd gear, and let the clutch out. There should be no perceptible lurch if you accurately matched revs. Try the same thing at higher and higher speeds. As the road speed goes up, the speed difference between gears will go up as well. When going from 5th to 3rd a highway speeds, you may end up within 1000 rpm of redline. The easiest way of determining your maximum downshift speed is to watch the tach and speedo as you are shifting up at redline. If you shift at redline from 2nd to 3rd at 60 mph, subtract 10 mph, and that becomes your effective maximum downshift point for 2nd gear. If are within 10 mph, you are better off staying in the higher gear.
HEEL-AND-TOE DOWNSHIFTS
This combines double-clutching and braking into one event. Place your foot on the brake as far to the right as you comfortably can. While braking, roll your ankle so you can catch the left edge of the gas pedal with the right edge of your foot. If the pedals are too wide, try placing the ball of your foot on the brake, and the heel on the gas (This is where the term heel-and-toe originally came from). Now try gently slowing down and downshifting. With practice, you can brake hard and downshift in one smooth motion. This will prevent the wheels from locking when the clutch is let out in the lower gear, and you will be ready for a burst of acceleration coming out of your favorite corner!
Copyright The Driver's Edge 1997
__________________
John
Robert Benchley (1889-1945) noted, "no matter how well-intended, any reply to a dumba$$ question will inevitably appear smarta$$ed"
Double Clutching (the easy way)
In another thread, several people expressed a desire to learn how to double clutch. I found this article which gives a good account on how to do it properly. The main thing to remember is you car is always talking to you, so learn to listen. You need to learn what rpm generates what speed in each gear. Tach's are great for this, but engine sound is a much better method. You don't always have time look at the tack. This procedure needs to be done quickly and SMOOTHLY. So turn off the boom-box and go have some fun.
I was afraid to post the link, so this is a C&P. I have included the authors name for credit.
John
The following is a beginner's approach to learning how to double - clutch. This technique allows downshifts from higher speeds without any synchroniser wear. This is VERY important if you ever want to drive really quickly and keep your transmission intact for extended periods!
The Easy Way to Double-Clutch
By Jeff Krause.
Double-clutching is the proper way to downshift at speed without placing excessive wear on the transmission's synchronizers. This allows you to select a much lower gear without the tell-tale lurch you normally get when the clutch is let out after downshifting.
When downshifting my BMW M5 from 4th gear to 2nd at 50 mph, I need to raise the engine speed from 2200 rpm to 5000. To prevent excessive synchroniser wear, the clutch is depressed and the shifter is moved to neutral. The clutch is then released, and the gas is depressed to bring the engine speed up to where it needs to be for the lower gear. The clutch is then depressed again and the shift lever moved into the lower gear. When the clutch is released the second time, the engine is already turning the proper speed . While this sounds complicated, it's easier done than said, and only takes about a second.
To better understand how the process works, a little background on transmission fundamentals will help.
A typical transmisson has two shafts, one connected to the engine through the clutch, and one connected to the rear wheels. There are usually four to six sets of gears on these shafts and they are selected with the gearshift lever inside the car. When changing gears, the clutch is depressed to disconnect the engine from the transmission so there isn't any stress on the moving parts. Since the output shaft is permanently connected to the rear wheels, the only way to match the speed of the two shafts is to use the throttle to adjust engine speed.
Once the engine is turning the right rpm, both shafts will be turning the same speed, and the gear lever will fall into gear WITHOUT using the clutch! (Although most of the time you are shifting too fast to be that accurate)
EXCERCISES
1) With the car idling in neutral, slowly step on the gas until the engine is turning 3500 rpm. Do it again bringing the rpm's up more and more quickly until you can give the pedal a quick stab and have the revs stop where you want . As you shorten the time allowed to match revs, you will notice it takes more throttle. In fast driving, you will be shifting so fast 4 will take full thottle! Now try matching revs at 4000 rpm.
2) Find a deserted road, and maintain 40 mph in 4th gear. Now shift into 3rd, and see how many rpm's the engine speed increased. At this speed, the difference won't be very much - maybe only a few hundred rpm. Go back into 4th gear. This time put the clutch in, push the lever to neutral and let the clutch back out. You are now coasting with the clutch out. Raise the engine speed to where it will be in third gear. Quickly push the clutch in, select 3rd gear, and let the clutch out. There should be no perceptible lurch if you accurately matched revs. Try the same thing at higher and higher speeds. As the road speed goes up, the speed difference between gears will go up as well. When going from 5th to 3rd a highway speeds, you may end up within 1000 rpm of redline. The easiest way of determining your maximum downshift speed is to watch the tach and speedo as you are shifting up at redline. If you shift at redline from 2nd to 3rd at 60 mph, subtract 10 mph, and that becomes your effective maximum downshift point for 2nd gear. If are within 10 mph, you are better off staying in the higher gear.
HEEL-AND-TOE DOWNSHIFTS
This combines double-clutching and braking into one event. Place your foot on the brake as far to the right as you comfortably can. While braking, roll your ankle so you can catch the left edge of the gas pedal with the right edge of your foot. If the pedals are too wide, try placing the ball of your foot on the brake, and the heel on the gas (This is where the term heel-and-toe originally came from). Now try gently slowing down and downshifting. With practice, you can brake hard and downshift in one smooth motion. This will prevent the wheels from locking when the clutch is let out in the lower gear, and you will be ready for a burst of acceleration coming out of your favorite corner!
Copyright The Driver's Edge 1997
__________________
John
Robert Benchley (1889-1945) noted, "no matter how well-intended, any reply to a dumba$$ question will inevitably appear smarta$$ed"
I know this kinda an old thread but I think of double clutching differently than how everyone explained it.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
Regardless of your technique, I think the bottom line is to rev match. I experience very smooth shifting as long as let the needle drop a bit for upshifting, and then I rev a little higher when I downshift. I have more problems shifting into 1st at a red light. 
Originally Posted by slow_evo
I know this kinda an old thread but I think of double clutching differently than how everyone explained it.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
Originally Posted by tomcox58
This is a nice explanation from the Car Forums
Double Clutching (the easy way)
In another thread, several people expressed a desire to learn how to double clutch. I found this article which gives a good account on how to do it properly. The main thing to remember is you car is always talking to you, so learn to listen. You need to learn what rpm generates what speed in each gear. Tach's are great for this, but engine sound is a much better method. You don't always have time look at the tack. This procedure needs to be done quickly and SMOOTHLY. So turn off the boom-box and go have some fun.
I was afraid to post the link, so this is a C&P. I have included the authors name for credit.
John
The following is a beginner's approach to learning how to double - clutch. This technique allows downshifts from higher speeds without any synchroniser wear. This is VERY important if you ever want to drive really quickly and keep your transmission intact for extended periods!
The Easy Way to Double-Clutch
By Jeff Krause.
Double-clutching is the proper way to downshift at speed without placing excessive wear on the transmission's synchronizers. This allows you to select a much lower gear without the tell-tale lurch you normally get when the clutch is let out after downshifting.
When downshifting my BMW M5 from 4th gear to 2nd at 50 mph, I need to raise the engine speed from 2200 rpm to 5000. To prevent excessive synchroniser wear, the clutch is depressed and the shifter is moved to neutral. The clutch is then released, and the gas is depressed to bring the engine speed up to where it needs to be for the lower gear. The clutch is then depressed again and the shift lever moved into the lower gear. When the clutch is released the second time, the engine is already turning the proper speed . While this sounds complicated, it's easier done than said, and only takes about a second.
To better understand how the process works, a little background on transmission fundamentals will help.
A typical transmisson has two shafts, one connected to the engine through the clutch, and one connected to the rear wheels. There are usually four to six sets of gears on these shafts and they are selected with the gearshift lever inside the car. When changing gears, the clutch is depressed to disconnect the engine from the transmission so there isn't any stress on the moving parts. Since the output shaft is permanently connected to the rear wheels, the only way to match the speed of the two shafts is to use the throttle to adjust engine speed.
Once the engine is turning the right rpm, both shafts will be turning the same speed, and the gear lever will fall into gear WITHOUT using the clutch! (Although most of the time you are shifting too fast to be that accurate)
EXCERCISES
1) With the car idling in neutral, slowly step on the gas until the engine is turning 3500 rpm. Do it again bringing the rpm's up more and more quickly until you can give the pedal a quick stab and have the revs stop where you want . As you shorten the time allowed to match revs, you will notice it takes more throttle. In fast driving, you will be shifting so fast 4 will take full thottle! Now try matching revs at 4000 rpm.
2) Find a deserted road, and maintain 40 mph in 4th gear. Now shift into 3rd, and see how many rpm's the engine speed increased. At this speed, the difference won't be very much - maybe only a few hundred rpm. Go back into 4th gear. This time put the clutch in, push the lever to neutral and let the clutch back out. You are now coasting with the clutch out. Raise the engine speed to where it will be in third gear. Quickly push the clutch in, select 3rd gear, and let the clutch out. There should be no perceptible lurch if you accurately matched revs. Try the same thing at higher and higher speeds. As the road speed goes up, the speed difference between gears will go up as well. When going from 5th to 3rd a highway speeds, you may end up within 1000 rpm of redline. The easiest way of determining your maximum downshift speed is to watch the tach and speedo as you are shifting up at redline. If you shift at redline from 2nd to 3rd at 60 mph, subtract 10 mph, and that becomes your effective maximum downshift point for 2nd gear. If are within 10 mph, you are better off staying in the higher gear.
HEEL-AND-TOE DOWNSHIFTS
This combines double-clutching and braking into one event. Place your foot on the brake as far to the right as you comfortably can. While braking, roll your ankle so you can catch the left edge of the gas pedal with the right edge of your foot. If the pedals are too wide, try placing the ball of your foot on the brake, and the heel on the gas (This is where the term heel-and-toe originally came from). Now try gently slowing down and downshifting. With practice, you can brake hard and downshift in one smooth motion. This will prevent the wheels from locking when the clutch is let out in the lower gear, and you will be ready for a burst of acceleration coming out of your favorite corner!
Copyright The Driver's Edge 1997
__________________
John
Robert Benchley (1889-1945) noted, "no matter how well-intended, any reply to a dumba$$ question will inevitably appear smarta$$ed"
Double Clutching (the easy way)
In another thread, several people expressed a desire to learn how to double clutch. I found this article which gives a good account on how to do it properly. The main thing to remember is you car is always talking to you, so learn to listen. You need to learn what rpm generates what speed in each gear. Tach's are great for this, but engine sound is a much better method. You don't always have time look at the tack. This procedure needs to be done quickly and SMOOTHLY. So turn off the boom-box and go have some fun.
I was afraid to post the link, so this is a C&P. I have included the authors name for credit.
John
The following is a beginner's approach to learning how to double - clutch. This technique allows downshifts from higher speeds without any synchroniser wear. This is VERY important if you ever want to drive really quickly and keep your transmission intact for extended periods!
The Easy Way to Double-Clutch
By Jeff Krause.
Double-clutching is the proper way to downshift at speed without placing excessive wear on the transmission's synchronizers. This allows you to select a much lower gear without the tell-tale lurch you normally get when the clutch is let out after downshifting.
When downshifting my BMW M5 from 4th gear to 2nd at 50 mph, I need to raise the engine speed from 2200 rpm to 5000. To prevent excessive synchroniser wear, the clutch is depressed and the shifter is moved to neutral. The clutch is then released, and the gas is depressed to bring the engine speed up to where it needs to be for the lower gear. The clutch is then depressed again and the shift lever moved into the lower gear. When the clutch is released the second time, the engine is already turning the proper speed . While this sounds complicated, it's easier done than said, and only takes about a second.
To better understand how the process works, a little background on transmission fundamentals will help.
A typical transmisson has two shafts, one connected to the engine through the clutch, and one connected to the rear wheels. There are usually four to six sets of gears on these shafts and they are selected with the gearshift lever inside the car. When changing gears, the clutch is depressed to disconnect the engine from the transmission so there isn't any stress on the moving parts. Since the output shaft is permanently connected to the rear wheels, the only way to match the speed of the two shafts is to use the throttle to adjust engine speed.
Once the engine is turning the right rpm, both shafts will be turning the same speed, and the gear lever will fall into gear WITHOUT using the clutch! (Although most of the time you are shifting too fast to be that accurate)
EXCERCISES
1) With the car idling in neutral, slowly step on the gas until the engine is turning 3500 rpm. Do it again bringing the rpm's up more and more quickly until you can give the pedal a quick stab and have the revs stop where you want . As you shorten the time allowed to match revs, you will notice it takes more throttle. In fast driving, you will be shifting so fast 4 will take full thottle! Now try matching revs at 4000 rpm.
2) Find a deserted road, and maintain 40 mph in 4th gear. Now shift into 3rd, and see how many rpm's the engine speed increased. At this speed, the difference won't be very much - maybe only a few hundred rpm. Go back into 4th gear. This time put the clutch in, push the lever to neutral and let the clutch back out. You are now coasting with the clutch out. Raise the engine speed to where it will be in third gear. Quickly push the clutch in, select 3rd gear, and let the clutch out. There should be no perceptible lurch if you accurately matched revs. Try the same thing at higher and higher speeds. As the road speed goes up, the speed difference between gears will go up as well. When going from 5th to 3rd a highway speeds, you may end up within 1000 rpm of redline. The easiest way of determining your maximum downshift speed is to watch the tach and speedo as you are shifting up at redline. If you shift at redline from 2nd to 3rd at 60 mph, subtract 10 mph, and that becomes your effective maximum downshift point for 2nd gear. If are within 10 mph, you are better off staying in the higher gear.
HEEL-AND-TOE DOWNSHIFTS
This combines double-clutching and braking into one event. Place your foot on the brake as far to the right as you comfortably can. While braking, roll your ankle so you can catch the left edge of the gas pedal with the right edge of your foot. If the pedals are too wide, try placing the ball of your foot on the brake, and the heel on the gas (This is where the term heel-and-toe originally came from). Now try gently slowing down and downshifting. With practice, you can brake hard and downshift in one smooth motion. This will prevent the wheels from locking when the clutch is let out in the lower gear, and you will be ready for a burst of acceleration coming out of your favorite corner!
Copyright The Driver's Edge 1997
__________________
John
Robert Benchley (1889-1945) noted, "no matter how well-intended, any reply to a dumba$$ question will inevitably appear smarta$$ed"
Well said..........
Originally Posted by slow_evo
No....cuz you would already be rolling.
Originally Posted by JTB
Close..
- apply brake
- depress clutch pedal
- shift into neutral
- release clutch pedal
- blip gas
- depress clutch pedal
- shift from 3rd to 2nd
- release clutch pedal
- release brake and accelerate out of turn
The difference is you are rev-matching while in neutral with the clutch engaged. This brings the transmission up to speed so the syncros don't have to do it.
- apply brake
- depress clutch pedal
- shift into neutral
- release clutch pedal
- blip gas
- depress clutch pedal
- shift from 3rd to 2nd
- release clutch pedal
- release brake and accelerate out of turn
The difference is you are rev-matching while in neutral with the clutch engaged. This brings the transmission up to speed so the syncros don't have to do it.
someone had it right earlier
heel toe is used to down shift
double clutching is used while upshifting. used on old trannies with out synchros
Evolved Member
Joined: Nov 2003
Posts: 1,496
Likes: 0
From: Bangkok
^umm.... WHY is anyone double clutching when up shifting? And by that I mean like going from 2nd -> 3rd (increasing number).
The correct definition has been given a number of pages back and as far as I am aware, you only need to do it when you're downshifting. Why would you want to speed up the layshaft when going up gears?
I also don't see a lot of sense in the 'double clutch for drag racing' thing. I'd like more explanation if possible - i'm genuinely interested and not trying to be a smart ****. It just seems that hte net gain would be pretty minimal. The car will jerk forward, but since you've coasted for a bit (with the clutch pedal down) all in all you're not going anywhere fast. Beside, that would just break your tranny. If you want to do that anyway, why don't just build the revs up between gears as you're going up and release the clutch when engine rev is real high(?)...
The correct definition has been given a number of pages back and as far as I am aware, you only need to do it when you're downshifting. Why would you want to speed up the layshaft when going up gears?
I also don't see a lot of sense in the 'double clutch for drag racing' thing. I'd like more explanation if possible - i'm genuinely interested and not trying to be a smart ****. It just seems that hte net gain would be pretty minimal. The car will jerk forward, but since you've coasted for a bit (with the clutch pedal down) all in all you're not going anywhere fast. Beside, that would just break your tranny. If you want to do that anyway, why don't just build the revs up between gears as you're going up and release the clutch when engine rev is real high(?)...
you ask a good question cause you don't understand, which is fine.
double clutching as stated by someone earlier was used on old trannies to assist in changing gears. before synchros came out, it was impossible to bang gears like we are able to do now. on some trannies it was nearly impossible to change gears (i.e. trucks).
the process of double clutching has been explained already. clutch in, shift to neutral, clutch out, clutch back in, rev, shift to next gear.
the reason this was done was because without synchros you were changing from a rotating gear, to a gear that wasn't rotating. with out synchros, the gear you were in, wouldn't slow down quick enough to allow you a smooth engagment to the next gear. by double clutching, you move the tranny to neutral giving it the time to 'free float.' the rev is for smooth engagment. if you were to just release the clutch, you would get the jerkiness from an unsmooth shift.
nowadays, the synchros slow up the gear you are in to allow you engage the next gear which isn't spinning, smoothly.
heel toe downshifting is with a SINGLE press of the clutch. there is no need to press the clutch in twice while downshifting. if you do, you dont' know what you are doing. on top of that, it takes more longer.
double clutching as stated by someone earlier was used on old trannies to assist in changing gears. before synchros came out, it was impossible to bang gears like we are able to do now. on some trannies it was nearly impossible to change gears (i.e. trucks).
the process of double clutching has been explained already. clutch in, shift to neutral, clutch out, clutch back in, rev, shift to next gear.
the reason this was done was because without synchros you were changing from a rotating gear, to a gear that wasn't rotating. with out synchros, the gear you were in, wouldn't slow down quick enough to allow you a smooth engagment to the next gear. by double clutching, you move the tranny to neutral giving it the time to 'free float.' the rev is for smooth engagment. if you were to just release the clutch, you would get the jerkiness from an unsmooth shift.
nowadays, the synchros slow up the gear you are in to allow you engage the next gear which isn't spinning, smoothly.
heel toe downshifting is with a SINGLE press of the clutch. there is no need to press the clutch in twice while downshifting. if you do, you dont' know what you are doing. on top of that, it takes more longer.
Originally Posted by slow_evo
I know this kinda an old thread but I think of double clutching differently than how everyone explained it.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
Yes when reffering to a tractor, double clutching is to line up the synchros, yadda yadda yadda.
But when drag racing it's different.
1. WOT at disired gear (works best in 2nd of 3rd)
2. Have your RPM's at about 3500 (just before full boost)
3. Slam the clutch in and let off the gas (but don't take it out of gear)
4. And IMMEADIATELY release the clutch and hammer the gas.
5. The car will feel like a bullet being fired out of a gun
You do this to spool the turbo very quickly and get the hell out of where ever you are.
I say 3500 because that's where we just start to make boost.
But if you are driving a N/A car i'd say do this around 1800 RPM before redline. Trust me it works.
this is a rhetorical question, but in drag racing when you are trying to get down the track as quick as possible, why are you going to waste your time pressing the clutch in twice when as you have to do is press it in once when there is no need to press it in twice???
Last edited by ldstang50; Feb 11, 2006 at 09:29 AM.
Originally Posted by ldstang50
you ask a good question cause you don't understand, which is fine.
double clutching as stated by someone earlier was used on old trannies to assist in changing gears. before synchros came out, it was impossible to bang gears like we are able to do now. on some trannies it was nearly impossible to change gears (i.e. trucks).
the process of double clutching has been explained already. clutch in, shift to neutral, clutch out, clutch back in, rev, shift to next gear.
the reason this was done was because without synchros you were changing from a rotating gear, to a gear that wasn't rotating. with out synchros, the gear you were in, wouldn't slow down quick enough to allow you a smooth engagment to the next gear. by double clutching, you move the tranny to neutral giving it the time to 'free float.' the rev is for smooth engagment. if you were to just release the clutch, you would get the jerkiness from an unsmooth shift.
nowadays, the synchros slow up the gear you are in to allow you engage the next gear which isn't spinning, smoothly.
heel toe downshifting is with a SINGLE press of the clutch. there is no need to press the clutch in twice while downshifting. if you do, you dont' know what you are doing. on top of that, it takes more longer.
double clutching as stated by someone earlier was used on old trannies to assist in changing gears. before synchros came out, it was impossible to bang gears like we are able to do now. on some trannies it was nearly impossible to change gears (i.e. trucks).
the process of double clutching has been explained already. clutch in, shift to neutral, clutch out, clutch back in, rev, shift to next gear.
the reason this was done was because without synchros you were changing from a rotating gear, to a gear that wasn't rotating. with out synchros, the gear you were in, wouldn't slow down quick enough to allow you a smooth engagment to the next gear. by double clutching, you move the tranny to neutral giving it the time to 'free float.' the rev is for smooth engagment. if you were to just release the clutch, you would get the jerkiness from an unsmooth shift.
nowadays, the synchros slow up the gear you are in to allow you engage the next gear which isn't spinning, smoothly.
heel toe downshifting is with a SINGLE press of the clutch. there is no need to press the clutch in twice while downshifting. if you do, you dont' know what you are doing. on top of that, it takes more longer.
the gears on both the input shaft and the output shaft are always engaged to each other, so they're always spinning. You're not selecting a gear that is stationary, they're always spinning at different ratios. The gear that is "selected" means the dog teeth on that selector cog engage that gear to the output shaft. The rest that are not selected continue to spin freely on the output shaft until they are selected..
Double clutching may help a funky transmission to upshift, but it's not needed because the two parts of the tranny will naturally slow down. This is why you can upshift without using the clutch at all. Double clutching's function is primarily beneficial to downshifting because the engine has to speed up the input shaft to engage the dog gear teeth smoothly at the proper rpm.
Heel/toe is a prerequisite for double clutching, not vice versa.
Last edited by Wheelhaus; Feb 11, 2006 at 09:32 AM.