[Undies]

Originally Posted by Leaker

And WAY more fun!

free reving, is not the same as revving with gear engaged. when engaged the revs have load, where as free revving has no load.

[Lenaxia]

So um, I have noticed no one has mentioned double clutching when downshifting. Isn't that needed to reduce load on our synchros?

[335BBS]

Originally Posted by Lenaxia

So um, I have noticed no one has mentioned double clutching when downshifting. Isn't that needed to reduce load on our synchros?

Not necessary if revs are matched. Dont even need clutch if revs are matched. When double clutching properly revs are matched too.

[NiceAndSlow]

Originally Posted by Tareq_328xi

Sorry for the late reply,,,

I would like to thank ALL of you for your helpful tips, however, special thanks to Undies for his tip above. I did exactly what he said all weekend and my downshifting became a lot smoother
Now, I have to practice executing the shift faster, that's all

I am not sure how much gas I'll be burning revving the engine on every downshift, but at the end it's cheaper than stressing the clutch/transmission.


Thanks again!

hmmmmmmmm i dunno if that's a good idea by not letting go the last completely while you start release of clutch.. keep in mind that clutch depressed fully, then blip will not harm your clutch but while releasing the clutch, there should not be any gas applied... this will cause wear and tear if I am not mistaken..

I am no pro but been doing matching for not too long now but I am catching the rev match on the way down.. not fast enough to catch it on the way up just yet but it's smooth..

[samej]

double clutching is just for the fun of it. When you get it right you feel like a champ. from what I hear you definitely need the cdv delete to a double clutch though, the engine's too slow to respond to throttle blips otherwise, which I noticed on my first test drive of a 328 standard.

[Lenaxia]

Originally Posted by Leaker

Not necessary if revs are matched. Dont even need clutch if revs are matched. When double clutching properly revs are matched too.

Then I must be misunderstanding something about how a manual works.

There are three components that need to be rev matched: the flywheel, the transmission and the drivetrain.

The only way to rev the transmission is by reving while the clutch is engaged. If you "rev match" but with the clutch in like most of you are suggesting, then the transmission winds down while the drive train and flywheel are spinning at speed. Then when you let the clutch engage, the synchros have to work overtime because the transmission is no longer spinning at speed.

Someone correct me if I'm wrong.

[Undies]

Originally Posted by Lenaxia

Then I must be misunderstanding something about how a manual works.

There are three components that need to be rev matched: the flywheel, the transmission and the drivetrain.

The only way to rev the transmission is by reving while the clutch is engaged. If you "rev match" but with the clutch in like most of you are suggesting, then the transmission winds down while the drive train and flywheel are spinning at speed. Then when you let the clutch engage, the synchros have to work overtime because the transmission is no longer spinning at speed.

Someone correct me if I'm wrong.

engine speed and actual vehicle speed are too different things. this is why you have to rev (engine speed) to match the vehicle speed.

[Undies]

op. when the weather gets nicer, and my car can come out, i'll take you for a spin.

[Tareq_328xi]

Originally Posted by NiceAndSlow

hmmmmmmmm i dunno if that's a good idea by not letting go the last completely while you start release of clutch.. keep in mind that clutch depressed fully, then blip will not harm your clutch but while releasing the clutch, there should not be any gas applied... this will cause wear and tear if I am not mistaken..

I am no pro but been doing matching for not too long now but I am catching the rev match on the way down.. not fast enough to catch it on the way up just yet but it's smooth..

You are certainly right.
The execution of the trick takes less than a second. After putting the pedal all the way down, release it, but DONT let go, otherwise the rpm will go back down, instead I keep some pressure, NOT by pushing on it, but by slowing its retraction ,,,, makes sense?

So today on my way back from work, traffic is going 80km, 5th gear, 2500RPM, traffic slows down to ^40km:

1) brake until I know what speed I will be at to get going again. (^40km)
900RPM

2) press the clutch =>4th => (3rd + push pedal all the way down and release)
3500RPM

3) release the clutch quickly but not fast, and as you feel the clutch engaging, push gas simultaneously.
3000RPM as you push gas it will go to 3500RPM.

On the highway, from 6th to 5th requires higher RPM levels to match vehicle speed, otherwise when I release the clutch at lower RPMs the car jerks and loses its balance for a moment .

That's precisely how I do it now, I hope that helps.


ps, apparently ur car is 335i, so RPMs may vary.

[335BBS]

Originally Posted by samej

double clutching is just for the fun of it. When you get it right you feel like a champ. from what I hear you definitely need the cdv delete to a double clutch though, the engine's too slow to respond to throttle blips otherwise, which I noticed on my first test drive of a 328 standard.

Sure its not necessary but some guy brought it up. Who told you you had to remove cdv? That doesnt make any sense at all. You can double clutch with any manual transmission.

[335BBS]

Originally Posted by Lenaxia

Then I must be misunderstanding something about how a manual works.

There are three components that need to be rev matched: the flywheel, the transmission and the drivetrain.

The only way to rev the transmission is by reving while the clutch is engaged. If you "rev match" but with the clutch in like most of you are suggesting, then the transmission winds down while the drive train and flywheel are spinning at speed. Then when you let the clutch engage, the synchros have to work overtime because the transmission is no longer spinning at speed.

Someone correct me if I'm wrong.

3? Where is the clutch? Between engine and tranny. What is between tranny and drivetrain(?) What are you calling drivetrain?
Spin the engine up to the same speed as the gear you want to be in and youre good. You can shift a transmission all day long with out the clutch if you match revs.

[samej]

Originally Posted by Leaker

Sure its not necessary but some guy brought it up. Who told you you had to remove cdv? That doesnt make any sense at all. You can double clutch with any manual transmission.

Doesn't the CDV delete make the engine revs more responsive to on/off throttle (hence blips)? My bimmer's an auto so my limited expience with the BMW manual transmission was my test drive of a 2009 328 coupe before I made my purchase. I found the engine lagged in my heel and toe (and double clutch) attempts. But then again I was a bit rusty (last manual I owned was 6 years earlier). On the positive side I never flubbed any shifts enough to grind a gear so the sales guy riding shotgun kept quiet

[bunnn]

I don't think anyone is really in a position to teach anyone how to "perfect" manual. I've sat in so many different manual cars, and everyone does it differently. You have to find YOUR way. After a year and half of owning my car now, I finally got the hang of double clutch heel-toe ...practice practice practice ... Mind you I took classes from Shifter before driving my car, and even what they teach me won't transition completely over..

[bigjilm]

Originally Posted by Lenaxia

Then I must be misunderstanding something about how a manual works.

There are three components that need to be rev matched: the flywheel, the transmission and the drivetrain.

The only way to rev the transmission is by reving while the clutch is engaged. If you "rev match" but with the clutch in like most of you are suggesting, then the transmission winds down while the drive train and flywheel are spinning at speed. Then when you let the clutch engage, the synchros have to work overtime because the transmission is no longer spinning at speed.

Someone correct me if I'm wrong.

You're spot on. You can rev match all day, but that doesn't help with the actual shifting of the tranny on a downshift. Synchros will pull it all together, but double clutching will do it without using the synchros as much. The only debate is whether the synchros will ever wear enough to warrant the extra effort of a double clutch.

As for deleting the CDV, that wouldn't be necessary. You can double clutch a 16L truck motor, and the 3 series motors rev up and down way faster than those bad boys.

The only time I find it 'necessary' to double clutch my 335 is when I want to get into 1st at highish revs. Trying to force the tranny synchros to do it for me takes longer than a quick blip during a double clutch downshift.

I still double clutch almost all of the time, just because it's more fun

[335BBS]

Originally Posted by bigjilm

You're spot on. You can rev match all day, but that doesn't help with the actual shifting of the tranny on a downshift. Synchros will pull it all together, but double clutching will do it without using the synchros as much. The only debate is whether the synchros will ever wear enough to warrant the extra effort of a double clutch.

As for deleting the CDV, that wouldn't be necessary. You can double clutch a 16L truck motor, and the 3 series motors rev up and down way faster than those bad boys.

The only time I find it 'necessary' to double clutch my 335 is when I want to get into 1st at highish revs. Trying to force the tranny synchros to do it for me takes longer than a quick blip during a double clutch downshift.

I still double clutch almost all of the time, just because it's more fun

Unfortunately I think youre wrong. Old manual transmission race cars did NOT
have sychros. 1st was/is engaged with a "crunch" and from there on the clutch was/is rarely used. Gear ratios are so close that to shift up you just get off the gas briefly then grab the next gear. To downshift you learn to match revs and the clutch is not needed/used. This is obviously not practical in the real world. Synchromesh transmissions were invented to help us in
road cars. Years ago I had a clutch cable snap. I was able to drive my car about 15 miles through the city by just matching rpm on the way up and the way down. Drive your car in 3rd at about 2500..let off the gas briefly so load comes off shifter. As this happens pull shift towards 4th and apply light pressure ...as rpm drops shifter will pop into 4th.

[bigjilm]

Originally Posted by Leaker

Unfortunately I think youre wrong. Old manual transmission race cars did NOT
have sychros.

You're right, and motorcycles don't as well - they clunk during shifts as well.

The key here is that there are three spinning objects in your BMW - engine, input shaft of tranny, and output shaft of tranny.

The engine speed is controllable through the loud pedal. If you're in neutral, or have the clutch pedal down, the engine spins pretty freely up and down.

The output shaft of the tranny is connected to the wheels. There are obviously a bunch of components along the way, but the speed of the output shaft is locked at a certain ratio to the speed of the wheels. When you're shifting gears, you don't have any choice on the speed of the output shaft.

The speed of the input shaft of the tranny can be at a bunch of speeds. If you're in gear (before the shift, say), it's locked to the output shaft at a certain ration depending on the gear you're in. If you're in neutral with the clutch pedal up, it's locked to the speed of the engine. If you're in neutral and the clutch pedal is down, it's freewheeling and it slowly loses speed over time.

If you don't double clutch, here's what happens when you downshift. Let's assume you're in 3rd, going down to 2nd and your RPMs start at 6K.

Before the shift: The engine speed is 6K rpms, the input shaft to the tranny is at 6K rpms, and the output shaft is at some speed related to 6K rpms and the 3rd gear ratio.

Press down the clutch: The engine speed is now controllable with the throttle, so let's start blipping it up a little to 8K rpms. The tranny input shaft and output shaft are still connected together through 3rd gear, and the output shaft is still connected to the wheels, so they still have the same speeds as in "Before the shift"

Move the gear shifter into neutral (briefly, between gears): The engine speed is still coming up to 8K, but it's still disconnected from everything with the clutch being down. The tranny output shaft is still connected to the wheels, and let's assume you aren't braking, so the speed of that shaft stays the same. The input shaft is now disconnected from the output shaft (you're not in gear at the moment), and it's disconnected from the engine because the clutch pedal is down. It's freewheeling and slowly losing RPMs at this point, but if you shift quickly that's probably negligible.

Move the gear shifter into 2nd: The engine speed is now at 8K, but it's still disconnected. HERE'S THE KEY - the input gears and output gears in the tranny now have to mesh. The input shaft should be spinning quite a bit higher for 2nd gear than it is currently spinning, so something has to increase the speed of this shaft so the gears don't clash. The output shaft is still locked to the wheels, so it's not going to change speeds at this point. THE SYNCHROS PULL THE INPUT SHAFT UP TO A SPEED THAT IS APPROPRIATE FOR 2ND GEAR AS YOU PUSH THE GEAR SHIFTER INTO SECOND. Once the input shaft is at the right speed, the gears mesh nicely and you're in gear.

Let the clutch pedal out: The engine is at 8K, which is the right RPM for 2nd gear, and the engine and the tranny input shaft mate up perfectly. That's why you blipped the throttle, and it probably felt pretty good.

WHY DOUBLE CLUTCH?

Go back to "Move the Gear Shifter into second". If you could bring the input shaft of the tranny up to the right speed for 2nd gear, the gears would mate a little quicker and the synchros wouldn't have to do any work. How fast should the input shaft be spinning? If you're blipping the engine to 8K, then the input shaft should probably be at that RPM as well. If you're off by a little, the synchros will take care of a small discrepancy very quickly.

HOW DO YOU DOUBLE CLUTCH?

At the step Move the Gear Shifter into neutral, you briefly pop the clutch while you blip the throttle (in neutral). The engine comes up to 8K, taking the tranny input shaft up with it. When you get to the right RPM, you push the clutch pedal back down and then proceed to Move the Gear Shifter into Second. The gears mesh almost instantly and the synchros have to do very little work in matching up the speeds in the tranny.

You've probably noticed that it's much harder to downshift into first, than it is to go from 6 to 5. The gear ratios have much bigger differences in the lower gears, so the synchros have more work to do down low. In fact, my personal opinion is that double clutching is probably useless between 6-5, 5-4, 4-3 unless you're worried about wearing the synchros. However, from 3-2 and especially 2-1, I can switch gears alot faster using the double clutch method.

In fact, in my old WRX, it would take me 3 seconds to get it into first gear at a reasonable speed and you could hear the tranny straining as I pushed the shifter. Add a doubleclutch in there, and the downshift was instantaneous and painless.

I realize now that I should have found an article to link to, instead of typing all of this out. I hope it's readable. If not, google this topic and you'll find a better tutorial.

[335BBS]

Originally Posted by bigjilm

You're right, and motorcycles don't as well - they clunk during shifts as well.

The key here is that there are three spinning objects in your BMW - engine, input shaft of tranny, and output shaft of tranny.

The engine speed is controllable through the loud pedal. If you're in neutral, or have the clutch pedal down, the engine spins pretty freely up and down.

The output shaft of the tranny is connected to the wheels. There are obviously a bunch of components along the way, but the speed of the output shaft is locked at a certain ratio to the speed of the wheels. When you're shifting gears, you don't have any choice on the speed of the output shaft.

The speed of the input shaft of the tranny can be at a bunch of speeds. If you're in gear (before the shift, say), it's locked to the output shaft at a certain ration depending on the gear you're in. If you're in neutral with the clutch pedal up, it's locked to the speed of the engine. If you're in neutral and the clutch pedal is down, it's freewheeling and it slowly loses speed over time.

If you don't double clutch, here's what happens when you downshift. Let's assume you're in 3rd, going down to 2nd and your RPMs start at 6K.

Before the shift: The engine speed is 6K rpms, the input shaft to the tranny is at 6K rpms, and the output shaft is at some speed related to 6K rpms and the 3rd gear ratio.

Press down the clutch: The engine speed is now controllable with the throttle, so let's start blipping it up a little to 8K rpms. The tranny input shaft and output shaft are still connected together through 3rd gear, and the output shaft is still connected to the wheels, so they still have the same speeds as in "Before the shift"

Move the gear shifter into neutral (briefly, between gears): The engine speed is still coming up to 8K, but it's still disconnected from everything with the clutch being down. The tranny output shaft is still connected to the wheels, and let's assume you aren't braking, so the speed of that shaft stays the same. The input shaft is now disconnected from the output shaft (you're not in gear at the moment), and it's disconnected from the engine because the clutch pedal is down. It's freewheeling and slowly losing RPMs at this point, but if you shift quickly that's probably negligible.

Move the gear shifter into 2nd: The engine speed is now at 8K, but it's still disconnected. HERE'S THE KEY - the input gears and output gears in the tranny now have to mesh. The input shaft should be spinning quite a bit higher for 2nd gear than it is currently spinning, so something has to increase the speed of this shaft so the gears don't clash. The output shaft is still locked to the wheels, so it's not going to change speeds at this point. THE SYNCHROS PULL THE INPUT SHAFT UP TO A SPEED THAT IS APPROPRIATE FOR 2ND GEAR AS YOU PUSH THE GEAR SHIFTER INTO SECOND. Once the input shaft is at the right speed, the gears mesh nicely and you're in gear.

Let the clutch pedal out: The engine is at 8K, which is the right RPM for 2nd gear, and the engine and the tranny input shaft mate up perfectly. That's why you blipped the throttle, and it probably felt pretty good.

WHY DOUBLE CLUTCH?

Go back to "Move the Gear Shifter into second". If you could bring the input shaft of the tranny up to the right speed for 2nd gear, the gears would mate a little quicker and the synchros wouldn't have to do any work. How fast should the input shaft be spinning? If you're blipping the engine to 8K, then the input shaft should probably be at that RPM as well. If you're off by a little, the synchros will take care of a small discrepancy very quickly.

HOW DO YOU DOUBLE CLUTCH?

At the step Move the Gear Shifter into neutral, you briefly pop the clutch while you blip the throttle (in neutral). The engine comes up to 8K, taking the tranny input shaft up with it. When you get to the right RPM, you push the clutch pedal back down and then proceed to Move the Gear Shifter into Second. The gears mesh almost instantly and the synchros have to do very little work in matching up the speeds in the tranny.

You've probably noticed that it's much harder to downshift into first, than it is to go from 6 to 5. The gear ratios have much bigger differences in the lower gears, so the synchros have more work to do down low. In fact, my personal opinion is that double clutching is probably useless between 6-5, 5-4, 4-3 unless you're worried about wearing the synchros. However, from 3-2 and especially 2-1, I can switch gears alot faster using the double clutch method.

In fact, in my old WRX, it would take me 3 seconds to get it into first gear at a reasonable speed and you could hear the tranny straining as I pushed the shifter. Add a doubleclutch in there, and the downshift was instantaneous and painless.

I realize now that I should have found an article to link to, instead of typing all of this out. I hope it's readable. If not, google this topic and you'll find a better tutorial.

Fascinating but all unecessary if you match revs. Doesnt dbl clutching simply line up synchros more readily?

[bigjilm]

Originally Posted by Leaker

Fascinating but all unecessary if you match revs. Doesnt dbl clutching simply line up synchros more readily?

If lining up the gears more readily doesn't excite you, then it's not for you. The point is that the downshift can happen faster and may wear less on your synchros if you double clutch.

Faster shifting is necessary to some people. Or, desired, at least.

[335BBS]

Originally Posted by bigjilm

If lining up the gears more readily doesn't excite you, then it's not for you. The point is that the downshift can happen faster and may wear less on your synchros if you double clutch.

Faster shifting is necessary to some people. Or, desired, at least.

You don't understand. If you match the revs properly then the synchronizers don't do anything. Double clutching takes longer than clutching once. Again, if you match the revs precisely then you don't even need a clutch let alone synchros. Using the clutch takes time...using it twice takes more time.

[bigjilm]

Originally Posted by Leaker

Again, if you match the revs precisely then you don't even need a clutch let alone synchros.

If you pull it out of gear, without using the clutch, then rev the motor up and slide it into the lower gear - that should work pretty well. You have to match it perfectly, but it would slide right into gear and feel pretty sweet. That's because the engine is attached to the input shaft of the tranny for the duration of the shift.

However, if you use the clutch at any point during the shift then this doesn't happen. As soon as you push down that clutch pedal, you are disconnecting the tranny input shaft from the engine and rev matching doesn't help you get the tranny into the lower gear. Either you have synchros to pull the input shaft up to speed (like your BMW), or you have a grinding of gears and all kinds of mayhem (non-synchro tranny).

I'll repeat that just to be crisp. If you disconnect the engine from the tranny using the clutch, then rev matching doesn't do shiat to the input shaft of the tranny. Period. At that point, shifting into that lower gear is going to need synchros to get the input shaft to the right speed. No synchros? Crunch, grind, etc.

As for taking longer, that's not necessarily true. On my WRX, the difference between an extra half a second for a double clutch vs 3 seconds (or never) on a regular downshift was a no brainer (talking a shift from 2 to 1). On my 335, a regular downshift is faster than the WRX, but I'm still faster from 2 to 1 with a double clutch.

On your way home tonight, try this. As you are approaching a light, get into second early enough that the engine is revving nice and high (4 grand, let's say). Now, downshift into first as quick as you can. Notice how long the shifter takes to get from neutral into first. If it takes longer than a half second, then my double clutch would probably be faster. Post back with your timing, and let's talk further. (edit - you choose the starting RPMS, so I'm not responsible for you blowing your motor with a moneyshift.)

[335BBS]

Originally Posted by bigjilm

If lining up the gears more readily doesn't excite you, then it's not for you. The point is that the downshift can happen faster and may wear less on your synchros if you double clutch.

Faster shifting is necessary to some people. Or, desired, at least.

Dbl clutch takes longer.....

Originally Posted by bigjilm

If you pull it out of gear, without using the clutch, then rev the motor up and slide it into the lower gear - that should work pretty well. You have to match it perfectly, but it would slide right into gear and feel pretty sweet. That's because the engine is attached to the input shaft of the tranny for the duration of the shift.

However, if you use the clutch at any point during the shift then this doesn't happen. As soon as you push down that clutch pedal, you are disconnecting the tranny input shaft from the engine and rev matching doesn't help you get the tranny into the lower gear. Either you have synchros to pull the input shaft up to speed (like your BMW), or you have a grinding of gears and all kinds of mayhem (non-synchro tranny).

I'll repeat that just to be crisp. If you disconnect the engine from the tranny using the clutch, then rev matching doesn't do shiat to the input shaft of the tranny. Period. At that point, shifting into that lower gear is going to need synchros to get the input shaft to the right speed. No synchros? Crunch, grind, etc.

As for taking longer, that's not necessarily true. On my WRX, the difference between an extra half a second for a double clutch vs 3 seconds (or never) on a regular downshift was a no brainer (talking a shift from 2 to 1). On my 335, a regular downshift is faster than the WRX, but I'm still faster from 2 to 1 with a double clutch.

On your way home tonight, try this. As you are approaching a light, get into second early enough that the engine is revving nice and high (4 grand, let's say). Now, downshift into first as quick as you can. Notice how long the shifter takes to get from neutral into first. If it takes longer than a half second, then my double clutch would probably be faster. Post back with your timing, and let's talk further. (edit - you choose the starting RPMS, so I'm not responsible for you blowing your motor with a moneyshift.)

Not sure why anyone would need to go down to first like that unless you are at 5B at Mosport. Thanks for the detailed explanation but I still say matching revs is faster. I dble clutched for years as it is a lot of fun and makes you feel more involved.