double clutching
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Here is a nice link which explains this problem excellently.
http://www.automotivetech.org/forum/...&threadid=1872
http://www.automotivetech.org/forum/...&threadid=1872
Registered User
Joined: Nov 2002
Posts: 206
From: Land of 10,000 Lakes
You double clutch to get into a lower gear as in 4th-3rd quicker. Not nessesary quicker as in from 4th to 3rd but the gears itself move faster and get into the gear selected. It's very benefitial if you want to save your synconizers(sp?).
A buddy of mine and I were crusing in his MY00 RS. We were at about 30mph or so and I asked him what's the top speed on 1st gear. He said he didn't know so he decided to find out. He gave it a double clutch, revved to 5k RPMs and down shifted into 1st. It didn't go into 1st so he stuck it back in neutral and revved it to 6kRPMs and then quickly into 1st and it went in. He then revved it up near redline and it hit about 30mph in 1st.
It's basically stick in into nuetral, revv up to spin the gears, and then stick it into a lower gear.
A buddy of mine and I were crusing in his MY00 RS. We were at about 30mph or so and I asked him what's the top speed on 1st gear. He said he didn't know so he decided to find out. He gave it a double clutch, revved to 5k RPMs and down shifted into 1st. It didn't go into 1st so he stuck it back in neutral and revved it to 6kRPMs and then quickly into 1st and it went in. He then revved it up near redline and it hit about 30mph in 1st.
It's basically stick in into nuetral, revv up to spin the gears, and then stick it into a lower gear.
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From: Reno, NV
Car Info: 1993/2000/2001 GF4 mostly red
Originally posted by FuJi K
It's basically stick in into nuetral, revv up to spin the gears, and then stick it into a lower gear.
It's basically stick in into nuetral, revv up to spin the gears, and then stick it into a lower gear.
Registered User
Joined: Nov 2002
Posts: 206
From: Land of 10,000 Lakes
Originally posted by BAN SUVS
And while you do that, you go in-out-in-out with the clutch pedal to make sure your input shaft/pressure plate speed up with your engine.
And while you do that, you go in-out-in-out with the clutch pedal to make sure your input shaft/pressure plate speed up with your engine.
4th gear
clutch in
shift to neutral
clutch out
revv up
clutch in
downshift to 3rd
clutch out
Originally posted by nato1486
When i downshift from say 4th to 3rd i let the clutch in , shift into 3rd blip the throttle to match revs, and let the clutch out. How is double clutching better? It just seems to take longer
When i downshift from say 4th to 3rd i let the clutch in , shift into 3rd blip the throttle to match revs, and let the clutch out. How is double clutching better? It just seems to take longer
-M
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Here is the article from automotivetech.org by Chunky:
Shifting: a beginner's guide
I. Introduction
II. Drivetrain details
III. How to double clutch
IV. Rev Matching
V. Clutchless Shifting
VI. Reccomended shifting practices.
I. Introduction
This is a beginner's guide to introduce you to the inner workings of a transmission so that you can better understand why certain things are good for your transmission and other things are bad. This is NOT a guide to teach yourself how to drive stick shift. I assume you can already drive a stick shift.
II. Drivetrain Details
The transmission is part of the drivetrain in your car. Essentially it's purpose is to multiply the torque output of the engine. To understand how exactly the torque is multiplied, I suggest you pick up a physics book and study the section on gears and pullies. It is important however that you understand how the drivetrain is laid out and how your transmission (and some of it's internal parts) fit into the bigger picture. Your engine creates torque by driving the crankshaft. The crankshaft is rigidly linked to the flywheel. The flywheel is connected to the transmission via the clutch. The clutch is NOT rigidly connected to the flywheel; the clutch can be mated and unmated to the flywheel. The clutch is rigidly connected to the input shaft of the transmission. The input shaft of the transmission can be mated to various different gears on a separate shaft of the transmission. This shaft is rigidly connected to the final drive gear. The final drive gear is what delivers power to the differential and ultimately to the wheels.
For the most part, the drivetrain can be dealt with as engine, flywheel, clutch, transmission input shaft, gears and final drive. From this point forward, I will use the following type of schematic to represent the drivetrain:
E = engine, F = Flywheel, C = clutch, I = transmission input shaft, G = gears and D = final drive.
rigid connections will be denoted with a '=' and connections that are user controlled will be represented with a '-'.
this is the drivetrain when the clutch is engaged (pedal is released) and the transmission is in gear:
E = F - C = I - G = D
As you can see, there are really only 3 separate entities, E = F, C = I, and G = F, with two boundaries (represented by '-'). Each part of these couples are linked rigidly and therefore are always spinning at the same speed. However, the 3 couples can spin at different speeds depending on the state of the clutch and gear selector.
Shifting: a beginner's guide
I. Introduction
II. Drivetrain details
III. How to double clutch
IV. Rev Matching
V. Clutchless Shifting
VI. Reccomended shifting practices.
I. Introduction
This is a beginner's guide to introduce you to the inner workings of a transmission so that you can better understand why certain things are good for your transmission and other things are bad. This is NOT a guide to teach yourself how to drive stick shift. I assume you can already drive a stick shift.
II. Drivetrain Details
The transmission is part of the drivetrain in your car. Essentially it's purpose is to multiply the torque output of the engine. To understand how exactly the torque is multiplied, I suggest you pick up a physics book and study the section on gears and pullies. It is important however that you understand how the drivetrain is laid out and how your transmission (and some of it's internal parts) fit into the bigger picture. Your engine creates torque by driving the crankshaft. The crankshaft is rigidly linked to the flywheel. The flywheel is connected to the transmission via the clutch. The clutch is NOT rigidly connected to the flywheel; the clutch can be mated and unmated to the flywheel. The clutch is rigidly connected to the input shaft of the transmission. The input shaft of the transmission can be mated to various different gears on a separate shaft of the transmission. This shaft is rigidly connected to the final drive gear. The final drive gear is what delivers power to the differential and ultimately to the wheels.
For the most part, the drivetrain can be dealt with as engine, flywheel, clutch, transmission input shaft, gears and final drive. From this point forward, I will use the following type of schematic to represent the drivetrain:
E = engine, F = Flywheel, C = clutch, I = transmission input shaft, G = gears and D = final drive.
rigid connections will be denoted with a '=' and connections that are user controlled will be represented with a '-'.
this is the drivetrain when the clutch is engaged (pedal is released) and the transmission is in gear:
E = F - C = I - G = D
As you can see, there are really only 3 separate entities, E = F, C = I, and G = F, with two boundaries (represented by '-'). Each part of these couples are linked rigidly and therefore are always spinning at the same speed. However, the 3 couples can spin at different speeds depending on the state of the clutch and gear selector.
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Continued :
III. How to Double Clutch.
Double clutching is an often mentioned but commonly misunderstood practice. I will discuss the details of how to double clutch and how it affects the different parts of your transmission in this section.
Double clutching is the practice of disengaging the clutch, pulling the gear selector into neutral, engaging the clutch, disengaging the clutch, pulling the gear selector into the new gear, and disengaging the clutch. Those are the steps and sequence of double clutching. To help you really understand it, I'll go through each step and the accompanying changes in the drivetrain.
E = F - C = I - G = D
That is what the drivetrain looks like at rest.
E = F C = I - G = D
When the clutch is disengaged, this is how everything looks. Note that the engine/flywheel can spin at a different speed than the rest of the parts.
E = F C = I G = D
when the gear selector is pulled into neutral (clutch is still disengaged), the engine/flywheel, clutch/input shaft, and gear/final drive can all spin at their own speed. In fact, the engine rpms generally fall fastest, the clutch/input shaft rpms fall rather slowly in comparison, and the gear/final drive rpm are directly related to the speed of the wheels (which can be influenced by only the brakes at this point).
E = F - C = I G = D
This is what it looks like when you re-engage the clutch. At this point the engine/flywheel is linked to the clutch/input shaft while spinning freely of the gear/final drive. What this allows us to do is to use the engine to control the speed of the clutch/input shaft. The engine/flywheel can speed up the clutch/input shaft with throttle input, or slow it down via engine braking. The goal is to adjust the speed of the clutch/input shaft to the rpm that the new gear will require. In essence you are actively snychronizing both the flywheel and the input shaft to the rpm of the new gear.
E = F C = I G = D
In this step the clutch is once again disengaged in prepration for the re-engagement of a new gear.
E = F C = I - G = D
Here the new gear has been engaged. If the clutch/input shaft's speed was properly adjusted, the input shaft will engage smoothly with the new gear. If the clutch/input shaft's speed is not in sync with the speed of the new gear, you will experience grinding. Luckilly most modern transmissions are synchromesh transmissions. Inside there are mechanical devices called synchros that will compensate for any discrepancy in speed between the clutch/input shaft and gear/final drive.
E = F - C = I - G = D
This is what everything looks like once the clutch is re-engaged (pedal released). If all went well, the new gear was selected with minimal trauma, and the car is now moving along at a higher rate of speed/acceleration.
III. How to Double Clutch.
Double clutching is an often mentioned but commonly misunderstood practice. I will discuss the details of how to double clutch and how it affects the different parts of your transmission in this section.
Double clutching is the practice of disengaging the clutch, pulling the gear selector into neutral, engaging the clutch, disengaging the clutch, pulling the gear selector into the new gear, and disengaging the clutch. Those are the steps and sequence of double clutching. To help you really understand it, I'll go through each step and the accompanying changes in the drivetrain.
E = F - C = I - G = D
That is what the drivetrain looks like at rest.
E = F C = I - G = D
When the clutch is disengaged, this is how everything looks. Note that the engine/flywheel can spin at a different speed than the rest of the parts.
E = F C = I G = D
when the gear selector is pulled into neutral (clutch is still disengaged), the engine/flywheel, clutch/input shaft, and gear/final drive can all spin at their own speed. In fact, the engine rpms generally fall fastest, the clutch/input shaft rpms fall rather slowly in comparison, and the gear/final drive rpm are directly related to the speed of the wheels (which can be influenced by only the brakes at this point).
E = F - C = I G = D
This is what it looks like when you re-engage the clutch. At this point the engine/flywheel is linked to the clutch/input shaft while spinning freely of the gear/final drive. What this allows us to do is to use the engine to control the speed of the clutch/input shaft. The engine/flywheel can speed up the clutch/input shaft with throttle input, or slow it down via engine braking. The goal is to adjust the speed of the clutch/input shaft to the rpm that the new gear will require. In essence you are actively snychronizing both the flywheel and the input shaft to the rpm of the new gear.
E = F C = I G = D
In this step the clutch is once again disengaged in prepration for the re-engagement of a new gear.
E = F C = I - G = D
Here the new gear has been engaged. If the clutch/input shaft's speed was properly adjusted, the input shaft will engage smoothly with the new gear. If the clutch/input shaft's speed is not in sync with the speed of the new gear, you will experience grinding. Luckilly most modern transmissions are synchromesh transmissions. Inside there are mechanical devices called synchros that will compensate for any discrepancy in speed between the clutch/input shaft and gear/final drive.
E = F - C = I - G = D
This is what everything looks like once the clutch is re-engaged (pedal released). If all went well, the new gear was selected with minimal trauma, and the car is now moving along at a higher rate of speed/acceleration.
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continued:
IV. Rev Matching
Rev matching is the practice of revving the motor on a downshift to raise the engine rpm in order to avoid excessive wear on the clutch. Rev matching only saves wear and tear on the clutch, it does not prolong the life of the synchros as double clutching does. If you shift without double clutching, I reccomend that you rev-match to reduce wear and tear on the clutch and shock to the engine during downshifts.
To get a better idea of what happens during rev matching, here are the steps:
E = F - C = I - G = D
everything is engaged and spinning as one
E = F C = I G = D
After the clutch has been disengaged and the gear selector has been pulled into the neutral position you blip the throttle to raise the engine rpm to match the rpm of the clutch/input shaft after the new gear is selected. This minimizes clutch wear and shock to the engine. However, the synchros are hard at work compensating for any speed differences between the clutch/input shaft and the gear/final drive. Essentailly you are actively matching the speed of the flywheel to the speed of the new gear. The clutch/input shaft are passively synchronized with the rest of the system via the synchros and the friction interface of the clutch.
E = F - C = I - G = D
New gear has been selected and the clutch is engaged (pedeal released). Smoother shifts are realized than when shifting normally w/o rev-matching. A double clutch shift should still be smoother since you actively sync both the engine/flywheel and the clutch/inputshaft rpm to the rpm of the new gear.
V. Clutchless Shifting
Clutchless shifting is quite simply, shifting w/o use of the clutch. This is accomplished by extremely accurate rev-matching. This practice is also known as speed shifting, power shifting, or a variety of other names depending on your vernacular.
E = F - C = I - G = D
everything at rest
E = F - C = I G = D
The gear selector is pulled into neutral w/o disengaging the clutch. Overtime this can be detrimental to your transmission. One common side effect is that the gear selector will not stay in gear after prolonged use of this practice. However, you can see that it leaves the transmission in the same state as after the first clutching cycle in a dobule clutch shift. This allows you to use the engine to control the speed of the clutch/input shaft to sync with the rpm of what the new gear will be.
E = F - C = I - G = D
The new gear is engaged. If you raised the rpm of the clutch/input shaft to EXACTLY what the speed of the new gear is, the gear selector will slide in with no problems. If not, prepare for some major grindage. Sometimes on a synchromesh transmission you will be able to shift in this manner w/o grinding even if you did not EXACTLY match the speed of the clutch/inputshaft to the speed of the new gear. This is because the synchros work to compensate for any discrepancies between the input shaft and the new gear. However, the synchros are designed to deal ONLY with the mass of the clutch and input shaft. When you shift in this manner, the synchros become responsible for the clutch, input shaft, flywheel, and all the parts of the engine that are connected to the crankshaft. It's not hard to see why this type of shifting spells the rapid death of you synchros.
VI. Reccomended Shifting Practices
I always reccomend that you double clutch when shifting your car. Not only does it help save wear and tear on your synchros, it also makes for smoother shifting, esp when driving hard and shifting at high rpm. I also reccomend that you do not skip gears when shifting as this makes matching the speed of the various parts of the drivetrain more difficult. Also, it is adviseable to have your car in gear whenever possible. It's easy to coast to a lower speed and then put the car into a lower gear, but one day you will be coasting and realize that you need to be in gear. The resulting rush to get in gear causes poorly executed and missed shifts. Think of it this way, the speed of your car is actively controlled by two things, throttle and brake. When you break the link between the throttle and the wheels, you give up 50% of the control you have over the speed of the car.
Thanks for reading!
IV. Rev Matching
Rev matching is the practice of revving the motor on a downshift to raise the engine rpm in order to avoid excessive wear on the clutch. Rev matching only saves wear and tear on the clutch, it does not prolong the life of the synchros as double clutching does. If you shift without double clutching, I reccomend that you rev-match to reduce wear and tear on the clutch and shock to the engine during downshifts.
To get a better idea of what happens during rev matching, here are the steps:
E = F - C = I - G = D
everything is engaged and spinning as one
E = F C = I G = D
After the clutch has been disengaged and the gear selector has been pulled into the neutral position you blip the throttle to raise the engine rpm to match the rpm of the clutch/input shaft after the new gear is selected. This minimizes clutch wear and shock to the engine. However, the synchros are hard at work compensating for any speed differences between the clutch/input shaft and the gear/final drive. Essentailly you are actively matching the speed of the flywheel to the speed of the new gear. The clutch/input shaft are passively synchronized with the rest of the system via the synchros and the friction interface of the clutch.
E = F - C = I - G = D
New gear has been selected and the clutch is engaged (pedeal released). Smoother shifts are realized than when shifting normally w/o rev-matching. A double clutch shift should still be smoother since you actively sync both the engine/flywheel and the clutch/inputshaft rpm to the rpm of the new gear.
V. Clutchless Shifting
Clutchless shifting is quite simply, shifting w/o use of the clutch. This is accomplished by extremely accurate rev-matching. This practice is also known as speed shifting, power shifting, or a variety of other names depending on your vernacular.
E = F - C = I - G = D
everything at rest
E = F - C = I G = D
The gear selector is pulled into neutral w/o disengaging the clutch. Overtime this can be detrimental to your transmission. One common side effect is that the gear selector will not stay in gear after prolonged use of this practice. However, you can see that it leaves the transmission in the same state as after the first clutching cycle in a dobule clutch shift. This allows you to use the engine to control the speed of the clutch/input shaft to sync with the rpm of what the new gear will be.
E = F - C = I - G = D
The new gear is engaged. If you raised the rpm of the clutch/input shaft to EXACTLY what the speed of the new gear is, the gear selector will slide in with no problems. If not, prepare for some major grindage. Sometimes on a synchromesh transmission you will be able to shift in this manner w/o grinding even if you did not EXACTLY match the speed of the clutch/inputshaft to the speed of the new gear. This is because the synchros work to compensate for any discrepancies between the input shaft and the new gear. However, the synchros are designed to deal ONLY with the mass of the clutch and input shaft. When you shift in this manner, the synchros become responsible for the clutch, input shaft, flywheel, and all the parts of the engine that are connected to the crankshaft. It's not hard to see why this type of shifting spells the rapid death of you synchros.
VI. Reccomended Shifting Practices
I always reccomend that you double clutch when shifting your car. Not only does it help save wear and tear on your synchros, it also makes for smoother shifting, esp when driving hard and shifting at high rpm. I also reccomend that you do not skip gears when shifting as this makes matching the speed of the various parts of the drivetrain more difficult. Also, it is adviseable to have your car in gear whenever possible. It's easy to coast to a lower speed and then put the car into a lower gear, but one day you will be coasting and realize that you need to be in gear. The resulting rush to get in gear causes poorly executed and missed shifts. Think of it this way, the speed of your car is actively controlled by two things, throttle and brake. When you break the link between the throttle and the wheels, you give up 50% of the control you have over the speed of the car.
Thanks for reading!
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