double clutching
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Downshifting without double clutching (also heel toe) CRIPPLES your ability to drive the car agressively, smoothly or both. If you think you're driving fast and hard without double clutching....imagine having the car even faster and smoother.
Single clutch is not nearly as smooth, _especially_ at lower gears. At higher gears its kinda smooth but try double-clutching you'll never go back. I know this because I single clutched for a good year before I taught myself to double clutch.
The evo has very short gear ratios. This means most meaningful downshifts will involve VERY LARGE CHANGES IN ENGINE SPEED. Welcome to hurky jurky city/ broken sychro city/driving like a pansy city if you use single clutch/synchros only technique.
If you're downshifting using only the synchros, and limiting yourself to a maximum change in engine speed set by how bad the jerk is....then you are driving the car quite a bit below its potential. Or very unsmoothly, which also means quite a bit below its potential. If you think its normal for this car to jerk even the slightest bit while down shifting, let alone like a bucking bronco....I cry for you.
Lastly....this car was DESIGNED to be downshifted with double clutching and heel toeing. I mean it. The mitsubishi engineers built the damn car so that when driven aggressively and properly you must downshift with a proper rev match. The damn car has super short gear ratios and a no torque until you're above 3.5k. And realistically, you want to downshift and put your rpms no lower than 4.5k for instant torque/no lag. If this doesn't mean anything to you then just go learn how to do a rev match. Hell, I don't care, learn single clutch...its better than nothing.
Single clutch is not nearly as smooth, _especially_ at lower gears. At higher gears its kinda smooth but try double-clutching you'll never go back. I know this because I single clutched for a good year before I taught myself to double clutch.
The evo has very short gear ratios. This means most meaningful downshifts will involve VERY LARGE CHANGES IN ENGINE SPEED. Welcome to hurky jurky city/ broken sychro city/driving like a pansy city if you use single clutch/synchros only technique.
If you're downshifting using only the synchros, and limiting yourself to a maximum change in engine speed set by how bad the jerk is....then you are driving the car quite a bit below its potential. Or very unsmoothly, which also means quite a bit below its potential. If you think its normal for this car to jerk even the slightest bit while down shifting, let alone like a bucking bronco....I cry for you.
Lastly....this car was DESIGNED to be downshifted with double clutching and heel toeing. I mean it. The mitsubishi engineers built the damn car so that when driven aggressively and properly you must downshift with a proper rev match. The damn car has super short gear ratios and a no torque until you're above 3.5k. And realistically, you want to downshift and put your rpms no lower than 4.5k for instant torque/no lag. If this doesn't mean anything to you then just go learn how to do a rev match. Hell, I don't care, learn single clutch...its better than nothing.
^ I think you've got it mixed up.
It sounds like you're rev matching downshifts (which is still great), not double clutching. Single clutch downshifting and double clutch downshifting feels exactly the same, they're both just as smooth and don't upset the car as long as they're properly rev matched.
What you described as being "herky jerky driving like a pansy" is any type of downshift that isn't rev matched. The engine/clutch is what causes the herky-jerk, not the synchros.
I heel-toe rev match single downshifts at the track all the time, and the car is as smooth as butter. Re-read the DC descriptions above to make sure it's what you're actually doing because most people really don't understand the internals of exactly how a transmission works. The DC technique really has nothing to do with removing the jerkiness of downshifting.
It sounds like you're rev matching downshifts (which is still great), not double clutching. Single clutch downshifting and double clutch downshifting feels exactly the same, they're both just as smooth and don't upset the car as long as they're properly rev matched.
What you described as being "herky jerky driving like a pansy" is any type of downshift that isn't rev matched. The engine/clutch is what causes the herky-jerk, not the synchros.
I heel-toe rev match single downshifts at the track all the time, and the car is as smooth as butter. Re-read the DC descriptions above to make sure it's what you're actually doing because most people really don't understand the internals of exactly how a transmission works. The DC technique really has nothing to do with removing the jerkiness of downshifting.
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Originally Posted by Wheelhaus
BlackhawkRA's post was very good , but for the ADD I'll try to add to it and shorthand it.
When you upshift normally, the engine will drop speed. when you let the clutch out, you can naturally time it to engage at just the right time to give you a perfectly smooth shift. (say from 3rd to 4th, when the engine needs to drop 500rpm for a given speed).
Rev matching allows you to just the opposite, when you downshift. The engine needs to speed up instead of slow down. To do this, blip the throttle to speed up the engine when the clutch is disengaged. Shift to the lower gear. When you let the clutch out for the lower gear, the engine will be spinning at a higher rpm, (whatever is dictated by the lower gear) and you don't get the jerky lurch. This is the same "single-clutch downshift" BlackhawkRA was talking about.
Heel/toe is used to brake at the same time the above is being done. Your right foot presses on the brake pedal, and the side (or heel) of your foot swings over and blips the throttle to rev match. This is extremely useful on a track for getting into the right gear while you're braking into a corner. So, when you exit the corner, you're good to go, no more playing with the shifter.
Double clutching is much more technical, and it's only to prevent wear on the transmission during downshifts by engaging the clutch in neutral while the engine is rev matched. It is used with heel/toe braking and rev matching to allow the engine to speed up the first half of the tranny instead of it's internal synchros. High rev shifting (especially downshifting) causes excessive synchro wear.
Many racing transmissions or "dog boxes" won't have synchros, because they add weight, and its one more thing to go wrong. Those guys need to double clutch and rev match everything, which is good because it prevents disrupting the car's balance.
When you upshift normally, the engine will drop speed. when you let the clutch out, you can naturally time it to engage at just the right time to give you a perfectly smooth shift. (say from 3rd to 4th, when the engine needs to drop 500rpm for a given speed).
Rev matching allows you to just the opposite, when you downshift. The engine needs to speed up instead of slow down. To do this, blip the throttle to speed up the engine when the clutch is disengaged. Shift to the lower gear. When you let the clutch out for the lower gear, the engine will be spinning at a higher rpm, (whatever is dictated by the lower gear) and you don't get the jerky lurch. This is the same "single-clutch downshift" BlackhawkRA was talking about.
Heel/toe is used to brake at the same time the above is being done. Your right foot presses on the brake pedal, and the side (or heel) of your foot swings over and blips the throttle to rev match. This is extremely useful on a track for getting into the right gear while you're braking into a corner. So, when you exit the corner, you're good to go, no more playing with the shifter.
Double clutching is much more technical, and it's only to prevent wear on the transmission during downshifts by engaging the clutch in neutral while the engine is rev matched. It is used with heel/toe braking and rev matching to allow the engine to speed up the first half of the tranny instead of it's internal synchros. High rev shifting (especially downshifting) causes excessive synchro wear.
Many racing transmissions or "dog boxes" won't have synchros, because they add weight, and its one more thing to go wrong. Those guys need to double clutch and rev match everything, which is good because it prevents disrupting the car's balance.
My use of the terms single clutch and double clutch exactly agree with your definitions above.
I single clutch downshifted for over a year, as a daily driver, trying lots of different ways, and could only achieve so much smoothness.
Was I not single clutching optimally? Dunno...but these days I'm achieving much smoother and FUNNER results with double clutching which you describe as "much more technical." Also keep in mind that I experimented with LOTS and LOTS of different variations on technique. No dice.
I stand by my earlier statements. Single clutching only took me so far, double-clutching lets me explore much further the range of downshifts options. These options I exercise regularly and to good effect on the street. For me the difference was night and day, but YMMV.
If your single clutching is perfectly smooth, I'm happy for you. However, both theory and practice, in general, support my position that double-clutching gives as good or smoother downshifts than single-clutching.
Although your above definitions are all factually correct, the way you phrase some stuff is frankly misleading on some points. I'll expand what I take issue with.
A proper rev match bring every driveline part up to the proper rotational velocity before the clutch is engaged. Single clutching does not fit this definition....the first half of the transmission, as you admit, is not at the proper rotational speed and the syncros have to do that job, very rapidly. Using this very very good definition, what you describe as a proper rev match is not.
Allowing the syncros to match the engine and transmission speed disparity is fundamentally identical, in a mechanical fashion, to dumping your clutch and matching speeds that way. The important differences are that your syncros were designed to take that abuse and do it semi-smoothly, the inertial/mass mismatch involved is quite a bit smaller, and the first part of the tranny is free to rotate and does not have a countering torque that fights the mismatch attempt (like your wheels do against the ground when you dump the clutch).
Because of these differences the jerk of the syncro assisted downshift is much smaller, maybe even to the point of not being noticeable, than just downshifting and letting out your clutch with no throttle blip. For me, the jerk was noticeable, got worse at higher rev mismatches and at lower gears, and was clearly not exactly what the mechanical device called my powertrain was looking for. Close, but not exactly what it wanted.
Your explanation obscures this highly relevant point.
Anyway, your suggestion that I'm somehow deceived in my definitions or mechanical understanding is incorrect.
If you re-read my post with the understanding that my single-clutch downshifting never got very smooth, then everything should make sense.
Last edited by bhcevo; Aug 1, 2006 at 06:14 PM.
No no no... You're right but you're misreading my post and I still think you're misunderstanding my basic point. Trust me I've studied this for years and there's several elements that may be combined or left out.
I know a single clutch downshift is very hard on the car, you'd have to be an idiot to not know that... The double clutch has very little to do with being smooth (ie: no jerkiness, car stays balanced), however rev matching (throttle blip) does as it affects clutch engagement. A proper rev match will mate the engine speed to the drivetrain speed BEFORE the clutch is engaged. Double clutching has nothing to do with that, but it DOES eliminate the need for synchros upon downshifting. A racing transmission (dog box, no synchros) needs to be double clutched because there's no synchros to match the input shaft to the output shaft in the transmission. The synchros do the job of the double clutch, but the rev match is what mates engine speed to drivetrain speed.
Here's the differences so you can see what I mean...
Single clutch downshift: (not smooth, can be very jerky)
clutch in, select gear, clutch out, gas. You feel a lurch as the engine is forced to speed up. Basically an engine brake.
Single clutch downshift with rev match: (very smooth, no jerk)
Clutch in, blip, select gear, clutch out, gas. No jerkiness as the engine and drivetrain are at matched speed when the clutch is engaged. The synchros do their job when you select the gear, that's it. They can't upset the car's balance as they aren't creating enough resistance to cause a jerk. It's the same thing as the double clutch, but the clutch is depressed only once instead of twice. That is the only difference.
Double clutch downshift: (very smooth, no jerk)
Clutch in, blip, neutral, clutch out, clutch in, select gear, clutch out, gas. Letting the clutch engage in neutral while the engine is revved eliminates the need for synchros.
The jerk comes from the clutch engaging when the engine is rotating slower than the drivetrain. The only thing that reduces the jerk is rev matching. Double clutching (though it also utilizes a rev match) uses the clutch to do the synchro's job, and it's all done when the engine is disconnected from the drivetrain.
I know a single clutch downshift is very hard on the car, you'd have to be an idiot to not know that... The double clutch has very little to do with being smooth (ie: no jerkiness, car stays balanced), however rev matching (throttle blip) does as it affects clutch engagement. A proper rev match will mate the engine speed to the drivetrain speed BEFORE the clutch is engaged. Double clutching has nothing to do with that, but it DOES eliminate the need for synchros upon downshifting. A racing transmission (dog box, no synchros) needs to be double clutched because there's no synchros to match the input shaft to the output shaft in the transmission. The synchros do the job of the double clutch, but the rev match is what mates engine speed to drivetrain speed.
Here's the differences so you can see what I mean...
Single clutch downshift: (not smooth, can be very jerky)
clutch in, select gear, clutch out, gas. You feel a lurch as the engine is forced to speed up. Basically an engine brake.
Single clutch downshift with rev match: (very smooth, no jerk)
Clutch in, blip, select gear, clutch out, gas. No jerkiness as the engine and drivetrain are at matched speed when the clutch is engaged. The synchros do their job when you select the gear, that's it. They can't upset the car's balance as they aren't creating enough resistance to cause a jerk. It's the same thing as the double clutch, but the clutch is depressed only once instead of twice. That is the only difference.
Double clutch downshift: (very smooth, no jerk)
Clutch in, blip, neutral, clutch out, clutch in, select gear, clutch out, gas. Letting the clutch engage in neutral while the engine is revved eliminates the need for synchros.
The jerk comes from the clutch engaging when the engine is rotating slower than the drivetrain. The only thing that reduces the jerk is rev matching. Double clutching (though it also utilizes a rev match) uses the clutch to do the synchro's job, and it's all done when the engine is disconnected from the drivetrain.
I think we're mostly arguing the same point back and forth...
I think I understand more clearly what you're saying.. Even with a rev match there's still a tiny bit of resistance on the drivetrain when the synchro matches the shafts. It happens before the clutch is engaged.
However, I still don't see how the downshift is so much smoother thant you can feel it. You only need to downshift when you're slowing down so you're in the proper gear to accelerate away. Because you're braking already, the synchros cannot possibly introduce any noticable amount of drag on the driverain.
I think I understand more clearly what you're saying.. Even with a rev match there's still a tiny bit of resistance on the drivetrain when the synchro matches the shafts. It happens before the clutch is engaged.
However, I still don't see how the downshift is so much smoother thant you can feel it. You only need to downshift when you're slowing down so you're in the proper gear to accelerate away. Because you're braking already, the synchros cannot possibly introduce any noticable amount of drag on the driverain.
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I've got good news and bad news.
The good news is that most of our disagreement is over terminology.
The bad news is that you also have no idea what a real double clutch downshift is, per your description above.
Thus your evaluation of the double clutch downshift, and your comparisons with other types of downshifting is worthless. Its worthless cause you aint doing it right. No insult intended.
I elaborate on our terminology disagreement and my double clutch downshift claim below.
Single clutch downshift: (not smooth, can be very jerky)
clutch in, select gear, clutch out, gas. You feel a lurch as the engine is forced to speed up. Basically an engine brake.
I do not call this a single clutch downshift. In my previous posts when I said single clutching this was not what I was referring to. If I call this anything I would just call this plain old downshifting. Other than that I have no disagreement with your description.
Single clutch downshift with rev match: (very smooth, no jerk)
Clutch in, blip, select gear, clutch out, gas. No jerkiness as the engine and drivetrain are at matched speed when the clutch is engaged. The synchros do their job when you select the gear, that's it. They can't upset the car's balance as they aren't creating enough resistance to cause a jerk. It's the same thing as the double clutch, but the clutch is depressed only once instead of twice. That is the only difference.
I call this single clutching. In my previous posts when I say single clutch downshifting this was uniformly what I meant. This is the technique I used for a full year with limited success.
Double clutch downshift: (very smooth, no jerk)
Clutch in, blip, neutral, clutch out, clutch in, select gear, clutch out, gas. Letting the clutch engage in neutral while the engine is revved eliminates the need for synchros.
I'm really really sorry to report that this definition is NOT correct. Not only this is definition flawed, actually doing this has no mechanical purpose. You offering this definition leads me to believe you don't have a functional understanding of a manual transmission. No insult intended.
Here is the correct double clutch downshift
Double clutch downshift: (very smooth, no jerk)
Clutch in, neutral, clutch out, blip,clutch in, select gear, clutch out, optional gas.
The key point here is that you blip the throttle while the clutch is out and the gear lever is in neutral.
Don't believe me? Maybe you will believe the Skip Barber school for auto racing.
From Going Faster, by Carl Lopez, Preface by Skip Barber. This is one of the classic introductory references on automotive motorsports. Page 95 has
a basic description of the double clutch downshift.
"...you push in the clutch and shift to neutral from a higher gear. You let the
clutch out, and then, still in neutral, you blip the throttle."
" Since, with the clutch engaged, the motor is directly connected to the input shaft, your blip easily spins up the shaft to the higher RPM. The instant after you blip, push in the clutch and move the gear lever into the [higher] gear position. Once its there, let the clutch back out agian. This last bit has to happen fast before the extra RPM created by the blip falls away."
Still need convincing? There are a series of photos of the pedals and feet during the double clutch downshift. Here are the captions of the photos/figures, from pages 95 and 96.
Figure. 6-11 "... push in the clutch."
Figure. 6-12 "Move the gear lever down to neutral."
Figure 6-13. "Then let the clutch back out."
Figure 6-14. "Blip the throttle."
Figure 6-15. "Push in the clutch pedal."
Figure 6-16. "Move the gear lever into the lower gear."
Figugure 6-17. "Let clutch out..."
You wanna know what happens if you have the clutch in when you blip? I'll let Skip Barber/Carl Lopez tell you. From page 97 of Going Faster.
"The most common error when trying to learn to double clutch downshift is forgetting to let the clutch back out when you stop in neutral and give the motor a blip. When the engine isn't directly connected to the input shaft... the blip isn't as effective at speeding up the input shaft. There is some drag going on between the motor and the input shaft, and a blip, even with the clutch depressed, will speed up the shaft some. The blip is much more effective, however, if you positively connect the engine and input shaft by letting the clutch back out in neutral."
The mistake described above is what happens when what you call a single clutch downshift with rev match is performed. Note that the book clearly explains why this is non optimal. Acceptable maybe, but non optimal.
The fact that you get acceptable performance with this is believable, and puts you in good company. Here is a quote from Danny Sullivan on page 97, a full time race car driver.
"I never double clutch in my life. I always blip on the downshift....but I don't necessarily let the clutch out in neutral....Guess I just give bigger blips than the average driver."
" Author's Note: We never could get Danny to buy into double clutching, but the single clutch works if you blip higher than you would if you engage the clutch in neutral. "
Note the book uses the terminology according to my definitions.
Anyway bro, to summarize I accept the fact that you made single clutch downshifting (my definition) work well for you. You might also want to accept the fact that you have no idea what double clutch downshifting really is.
I found double clutching to work better for me, which is pretty much what you would expect since its the more optimal procedure, mechanically speaking.
In addition you might want to consider practicing double clutching as correctly described in the book. Do this so in the future you can talk about it with authority, since as far as I can tell right now you have no idea what it really is and what it really feels like when you perform it correctly.
I know I sound snippy and I apologize. Just tired.
The good news is that most of our disagreement is over terminology.
The bad news is that you also have no idea what a real double clutch downshift is, per your description above.
Thus your evaluation of the double clutch downshift, and your comparisons with other types of downshifting is worthless. Its worthless cause you aint doing it right. No insult intended.
I elaborate on our terminology disagreement and my double clutch downshift claim below.
Originally Posted by Wheelhaus
Single clutch downshift: (not smooth, can be very jerky)
clutch in, select gear, clutch out, gas. You feel a lurch as the engine is forced to speed up. Basically an engine brake.
Originally Posted by Wheelhaus
Single clutch downshift with rev match: (very smooth, no jerk)
Clutch in, blip, select gear, clutch out, gas. No jerkiness as the engine and drivetrain are at matched speed when the clutch is engaged. The synchros do their job when you select the gear, that's it. They can't upset the car's balance as they aren't creating enough resistance to cause a jerk. It's the same thing as the double clutch, but the clutch is depressed only once instead of twice. That is the only difference.
Originally Posted by Wheelhaus
Double clutch downshift: (very smooth, no jerk)
Clutch in, blip, neutral, clutch out, clutch in, select gear, clutch out, gas. Letting the clutch engage in neutral while the engine is revved eliminates the need for synchros.
Here is the correct double clutch downshift
Double clutch downshift: (very smooth, no jerk)
Clutch in, neutral, clutch out, blip,clutch in, select gear, clutch out, optional gas.
The key point here is that you blip the throttle while the clutch is out and the gear lever is in neutral.
Don't believe me? Maybe you will believe the Skip Barber school for auto racing.
From Going Faster, by Carl Lopez, Preface by Skip Barber. This is one of the classic introductory references on automotive motorsports. Page 95 has
a basic description of the double clutch downshift.
"...you push in the clutch and shift to neutral from a higher gear. You let the
clutch out, and then, still in neutral, you blip the throttle."
" Since, with the clutch engaged, the motor is directly connected to the input shaft, your blip easily spins up the shaft to the higher RPM. The instant after you blip, push in the clutch and move the gear lever into the [higher] gear position. Once its there, let the clutch back out agian. This last bit has to happen fast before the extra RPM created by the blip falls away."
Still need convincing? There are a series of photos of the pedals and feet during the double clutch downshift. Here are the captions of the photos/figures, from pages 95 and 96.
Figure. 6-11 "... push in the clutch."
Figure. 6-12 "Move the gear lever down to neutral."
Figure 6-13. "Then let the clutch back out."
Figure 6-14. "Blip the throttle."
Figure 6-15. "Push in the clutch pedal."
Figure 6-16. "Move the gear lever into the lower gear."
Figugure 6-17. "Let clutch out..."
You wanna know what happens if you have the clutch in when you blip? I'll let Skip Barber/Carl Lopez tell you. From page 97 of Going Faster.
"The most common error when trying to learn to double clutch downshift is forgetting to let the clutch back out when you stop in neutral and give the motor a blip. When the engine isn't directly connected to the input shaft... the blip isn't as effective at speeding up the input shaft. There is some drag going on between the motor and the input shaft, and a blip, even with the clutch depressed, will speed up the shaft some. The blip is much more effective, however, if you positively connect the engine and input shaft by letting the clutch back out in neutral."
The mistake described above is what happens when what you call a single clutch downshift with rev match is performed. Note that the book clearly explains why this is non optimal. Acceptable maybe, but non optimal.
The fact that you get acceptable performance with this is believable, and puts you in good company. Here is a quote from Danny Sullivan on page 97, a full time race car driver.
"I never double clutch in my life. I always blip on the downshift....but I don't necessarily let the clutch out in neutral....Guess I just give bigger blips than the average driver."
" Author's Note: We never could get Danny to buy into double clutching, but the single clutch works if you blip higher than you would if you engage the clutch in neutral. "
Note the book uses the terminology according to my definitions.
Anyway bro, to summarize I accept the fact that you made single clutch downshifting (my definition) work well for you. You might also want to accept the fact that you have no idea what double clutch downshifting really is.
I found double clutching to work better for me, which is pretty much what you would expect since its the more optimal procedure, mechanically speaking.
In addition you might want to consider practicing double clutching as correctly described in the book. Do this so in the future you can talk about it with authority, since as far as I can tell right now you have no idea what it really is and what it really feels like when you perform it correctly.
I know I sound snippy and I apologize. Just tired.
Last edited by bhcevo; Aug 2, 2006 at 03:43 AM.
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Originally Posted by Wheelhaus
I think we're mostly arguing the same point back and forth...
I think I understand more clearly what you're saying.. Even with a rev match there's still a tiny bit of resistance on the drivetrain when the synchro matches the shafts. It happens before the clutch is engaged.
However, I still don't see how the downshift is so much smoother thant you can feel it. You only need to downshift when you're slowing down so you're in the proper gear to accelerate away. Because you're braking already, the synchros cannot possibly introduce any noticable amount of drag on the driverain.
I think I understand more clearly what you're saying.. Even with a rev match there's still a tiny bit of resistance on the drivetrain when the synchro matches the shafts. It happens before the clutch is engaged.
However, I still don't see how the downshift is so much smoother thant you can feel it. You only need to downshift when you're slowing down so you're in the proper gear to accelerate away. Because you're braking already, the synchros cannot possibly introduce any noticable amount of drag on the driverain.
Your last statement about braking and synchros is either so poorly worded I fail to understand or an indication you have a deep misunderstanding of how a manual tranny and synchros work.
Last edited by bhcevo; Aug 2, 2006 at 03:45 AM.
Ok I see what you mean now. (and yes, you do sound rather snippy 
). I thoroughly understand exactly how a transmission works, but my double clutch technique is still not wrong and. It is a slghtly different order than yours because I am taking timing into account. (trust me please, I DO understand what a true double clutch is, I'm just not explaining it the same manner as you).
The braking comment was a very poor description, my apolgy. I meant to say that downshifting almost always happens when you're slowing down, and the act of a rev matched single clutch downshift cannot disrupt the car's balance simply because it uses the synchro versus a double clutch method.
And yes I also "drop a gear" for more power on the street to accelerate as you said.
By using the blip when the clutch first goes in I am intending to begin the action because the engine can't respond immediately, thre is a lag in response. I am not saying that the engine should be at the proper rpm before the clutch is engaged. Because the rev takes more time than the other motions the end result is still a smooth motion. By the time the actions are completed (fraction of a second) everything happens smoothly. If I were to do the steps as you quoted, one, two, three, four... It makes sense but it just seems so slow even though it's correct. That is the proper order when practicing for the first time, but because of the way the engine responds I can't see it being done quickly, the motions must be blurred together. That is what I was assuming from the beginning.
I will break it down because three things can happen all at once, both feet and the shifting hand are each working together...
This is what I envision as I enter a corner (including braking), and it may make more sense than my previous explanation as this will account for real world timing and resonse.
Step 1:
Brake pedal and clutch pedal go in, I blip the gas during the same motion and the clutch comes back out.
(By the time the clutch engages, the engine is on it's way up to proper rpm so the speeds are carried together)
Step 2:
Clutch goes in as the lower gear is selected, release the brake and accelerate (or repeat for another lower gear).
That's what I meant by clutch in, blip, then clutch out... It's just the way I time the motions because thye happen so fast. I understand the engine needs to be revved when the clutch is engaged in neutral so it carries the input shaft with it, but I can't clutch out before I blip because the engine has already dropped some speed. I rev as the clutch begins to engage, because there's some lag between hitting the gs pedal and the engine responding.
Please trust me I know what you're saying, I simply interpret the actions to be more blurred together, and that is causing me to explain it differently.
). I thoroughly understand exactly how a transmission works, but my double clutch technique is still not wrong and. It is a slghtly different order than yours because I am taking timing into account. (trust me please, I DO understand what a true double clutch is, I'm just not explaining it the same manner as you). The braking comment was a very poor description, my apolgy. I meant to say that downshifting almost always happens when you're slowing down, and the act of a rev matched single clutch downshift cannot disrupt the car's balance simply because it uses the synchro versus a double clutch method.
And yes I also "drop a gear" for more power on the street to accelerate as you said.
By using the blip when the clutch first goes in I am intending to begin the action because the engine can't respond immediately, thre is a lag in response. I am not saying that the engine should be at the proper rpm before the clutch is engaged. Because the rev takes more time than the other motions the end result is still a smooth motion. By the time the actions are completed (fraction of a second) everything happens smoothly. If I were to do the steps as you quoted, one, two, three, four... It makes sense but it just seems so slow even though it's correct. That is the proper order when practicing for the first time, but because of the way the engine responds I can't see it being done quickly, the motions must be blurred together. That is what I was assuming from the beginning.
I will break it down because three things can happen all at once, both feet and the shifting hand are each working together...
This is what I envision as I enter a corner (including braking), and it may make more sense than my previous explanation as this will account for real world timing and resonse.
Step 1:
Brake pedal and clutch pedal go in, I blip the gas during the same motion and the clutch comes back out.
(By the time the clutch engages, the engine is on it's way up to proper rpm so the speeds are carried together)
Step 2:
Clutch goes in as the lower gear is selected, release the brake and accelerate (or repeat for another lower gear).
That's what I meant by clutch in, blip, then clutch out... It's just the way I time the motions because thye happen so fast. I understand the engine needs to be revved when the clutch is engaged in neutral so it carries the input shaft with it, but I can't clutch out before I blip because the engine has already dropped some speed. I rev as the clutch begins to engage, because there's some lag between hitting the gs pedal and the engine responding.
Please trust me I know what you're saying, I simply interpret the actions to be more blurred together, and that is causing me to explain it differently.
Well, I learned something on this page. I am currently doing the worst possible of the downshifts. I am coming into a tight corner from high speed and threshold braking, but I am unable to concentrate fully on that threshold braking while also trying to heel-toe. WHen I do it on the street with regular braking, I just do what you are calling a single clutch downshift with throttle blip. That's what I thought was proper. I also double clutch sometimes just to practice on the street, and it's pretty cool even with an upshift, especially when the tranny is cold. I just recently started double clutching the downshift at the end of the straight at PMI. I'm braking hard from 130 preparing for a fairly fast sweeper, and I started double clutching it but WITHOUT the heel-toe aspect (blip). This is not allowing any rev match, but it's allowing the synchros to align, since I go from 6th to 4th. Am I supposed to do double clutch to 5th then double clutch to 4th or what?
What I'm currently unable to do PHYSICALLY due to lack of experience and coordination is to double clutch my downshifts with a blip while threshold braking. Is that just something you develop over time? Right now, it takes so much concentration to keep the car steady and on course during initial braking then trail braking that I can hardly imagine doing a double clutch heel-toe maneuver. Is that what you guys do?
What I'm currently unable to do PHYSICALLY due to lack of experience and coordination is to double clutch my downshifts with a blip while threshold braking. Is that just something you develop over time? Right now, it takes so much concentration to keep the car steady and on course during initial braking then trail braking that I can hardly imagine doing a double clutch heel-toe maneuver. Is that what you guys do?
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Originally Posted by Wheelhaus
If I were to do the steps as you quoted, one, two, three, four... It makes sense but it just seems so slow even though it's correct. That is the proper order when practicing for the first time, but because of the way the engine responds I can't see it being done quickly, the motions must be blurred together. That is what I was assuming from the beginning.
the way you first parsed double clutch downshifting completely obscured the mechanical significance of the process. When someone says "...clutch in, blip, neutral, clutch out..." I think the every person in the world but you would
understand that to mean the throttle blip happens and is done with while the clutch is in.
For what its worth those Skip Barber school guys explain it like I do too. And I figure they are probably just as good at timing as you are.
Originally Posted by Wheelhaus
I understand the engine needs to be revved when the clutch is engaged in neutral so it carries the input shaft with it, but I can't clutch out before I blip because the engine has already dropped some speed. I rev as the clutch begins to engage, because there's some lag between hitting the gas pedal and the engine responding.
I still think there might be some terminology misunderstanding when we talk about the mechanical performance of the tranny because some of your previous statements concerning synchros and what they're doing are nonsensical to me.
I'm not all that concerned about clearing it up since it seems likely we ultimately agree. Maybe next time you're explining this stuff you can ask yourself "what would Skip Barber say?"
I still stand by my initial post. Double clutch downshifting I found much more rewarding than single clutch downshifting (my definition, meaning with rev match).
I will qualify that evidently you can get single clutch downshifting (with rev match!!) to work real real good, but if you had trouble like I did you might wanna try double-clutching and seeing if it works better.
And lastly, both Skip Barber and I agree that double-clutching is the mechanically optimal procedure. The book says "the blip is much more effective, however, if you[double clutch]". So my improved experience is what you would expect.
Last edited by bhcevo; Aug 2, 2006 at 11:41 AM.
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Joined: Jan 2006
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Originally Posted by Warrtalon
What I'm currently unable to do PHYSICALLY due to lack of experience and coordination is to double clutch my downshifts with a blip while threshold braking. Is that just something you develop over time? Right now, it takes so much concentration to keep the car steady and on course during initial braking then trail braking that I can hardly imagine doing a double clutch heel-toe maneuver. Is that what you guys do?
However, SOME pro drivers just stick with what you are doing and drive just fine.
My long post above describes it in great detail and offers a good quote by Danny Sullivan, who uses your single-clutch method. Its probably better to make a choice because of preference instead of incompetence.
Practice double clutch heel-toe outside of threshold braking situations....like slowing down for a 90 deg corner on the street. This won't work if there's a stop sign because you dont want to come to a full stop. These situations are nice and slow and you can get the muscle memory and timing down so you can just do it during threshold braking. If you examine you're street driving you can find tons of places where you can practice your slow-motion double clutch heel-toe downshifting.
Heck, you can practice this in a straight line (street driving). You brake in a straight line on the street all the time. Next time you brake in a straight line try to put yourself in a lower gear simultaneously using double clutch heel-toe.
Last edited by bhcevo; Aug 2, 2006 at 11:59 AM.
Originally Posted by bhcevo
the way you first parsed double clutch downshifting completely obscured the mechanical significance of the process.
Originally Posted by bhcevo
I'm not quite sure why you say you "can't clutch out before I blip because the engine has already dropped speed". The small speed drop of the engine dont matter because you're in neutral. I do this no problem.
Originally Posted by bhcevo
I still think there might be some terminology misunderstanding when we talk about the mechanical performance of the tranny because some of your previous statements concerning synchros and what they're doing are nonsensical to me.
Originally Posted by bhcevo
I still stand by my initial post. Double clutch downshifting I found much more rewarding than single clutch downshifting (my definition, meaning with rev match).
Originally Posted by bhcevo
I will qualify that evidently you can get single clutch downshifting (with rev match!!) to work real real good, but if you had trouble like I did you might wanna try double-clutching and seeing if it works better.
And lastly, both Skip Barber and I agree that double-clutching is the mechanically optimal procedure. The book says "the blip is much more effective, however, if you[double clutch]". So my improved experience is what you would expect.
And lastly, both Skip Barber and I agree that double-clutching is the mechanically optimal procedure. The book says "the blip is much more effective, however, if you[double clutch]". So my improved experience is what you would expect.
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Joined: Jan 2006
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Originally Posted by Wheelhaus
I feel that I've perfected the single clutch downshift as I can drive slowly around town or at limit on a road course without disrupting the car's balance or momentum upon downshifting.
I think its awesome that you got the single clutch downshift to work so well. Between my own experience and the description in the book I figured it just didn't get all that smooth. Especially since I got DC to be so much smoother so quickly as soon as I tried it.
Maybe you're gearbox and tranny is just better broken in than mine and thus the difference in synchro feel. I know my gearbox and tranny have gotten more smooth and less notchy over time.