For the MT owners: how do you downshift?

[jasonstang]

Although I don't exactly know how the (auto) rev-matching works on manual cars, I doubt it will match the speed of the lay/counter/intermediate shaft (which can be accomplished via double clutch). My guess is that it (rev-match by car computer) only match the engine speed to the speed of the output shaft. So we (the double clutchers) will still have a reason to keep double clutching and feel good about it.

It is all for fun.

Electronic rev matching is just that, revving up the engine rpm to match the speed.
The ECU actually has a map and the transmission has gear sensors so the engine is revved to certain rpm giving what gear you are in and what speed you are doing.
Double clutching is not necessary anymore because of syncros but sometimes you still have to use it when the blocker ring blocks gear from mashing such as changing to 1st gear going more than 10 mph.

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[Horse]

Electronic rev matching is just that, revving up the engine rpm to match the speed.
The ECU actually has a map and the transmission has gear sensors so the engine is revved to certain rpm giving what gear you are in and what speed you are doing.
Double clutching is not necessary anymore because of syncros but sometimes you still have to use it when the blocker ring blocks gear from mashing such as changing to 1st gear going more than 10 mph.

Double clutch is fun (while also saves synchros).

During normal rev-match (not double clutch), the blip only brings the engine rpm to the right speed (but not the lay/intermediate shaft, gears, etc.). Then the synchro must work in order the bring the lay/intermediate shaft, gears, etc., up to speed. Yes, the synchro is design for this task and modern synchros can usually outlast the transmissions. So many people don't bother to do/learn double clutch.

Personally, I always double clutch when downshifting. For one, it is fun, as it makes a unique sound for example. For two, it feels good knowing that the sychro does not need to work (as hard) because I am bringing all the parts to the right/matching speed.

Some may say that double clutch wears down the clutch assembly (b/c you step on it twice). Sure. But I am willing to take that.

 

[Norm Peterson]

Electronic rev matching is just that, revving up the engine rpm to match the speed.
The ECU actually has a map and the transmission has gear sensors so the engine is revved to certain rpm giving what gear you are in and what speed you are doing.

And it knows what gear you're going to . . . how? If it has to wait for you to get there, it may be too late for it to be of as much advantage as you're being led to believe. Manually downshifting two or even three gears isn't exactly uncommon.

It's a bit different from a sequential gearbox where the ECU knows for certain where you're headed and can control clutch engagement timing.


Norm

 

[keiths2kgt]

I've been trying the double clutch down shifting...is this correct?

In 5th gear and wanting to down shift to 4th...

Push clutch in then drop the shifter to neutral

Clutch release

Blip throttle

Push clutch in and drop shifter to 4th

Release clutch

 

[jasonstang]

I've been trying the double clutch down shifting...is this correct?

In 5th gear and wanting to down shift to 4th...

Push clutch in then drop the shifter to neutral

Clutch release

Blip throttle

Push clutch in and drop shifter to 4th

Release clutch

Yes

 

[StangLuver]

And it knows what gear you're going to . . . how? If it has to wait for you to get there, it may be too late for it to be of as much advantage as you're being led to believe. Manually downshifting two or even three gears isn't exactly uncommon.

It's a bit different from a sequential gearbox where the ECU knows for certain where you're headed and can control clutch engagement timing.

It tells by you moving the gear handle next to that gear - and instantly blips the throttle appropriately.

[ame]

 

[minjitta]

I've been trying the double clutch down shifting...is this correct?

In 5th gear and wanting to down shift to 4th...

Push clutch in then drop the shifter to neutral

Clutch release

Blip throttle

Push clutch in and drop shifter to 4th

Release clutch

for nanny shifting yes. I never down shift like that and never have problem with my dual clutches, you dont wanted to nanny shift like that on a road course or on the street of Mexico.

 

[Rizzy]

Hey guys, what exactly is a blip? Can said blip be measured? 500 rpm increase... 1000 rpm increase?

Haaaalp

Pleeeeease

 

[kz]

Hey guys, what exactly is a blip? Can said blip be measured? 500 rpm increase... 1000 rpm increase?

Haaaalp

Pleeeeease

It depends. Speed vs. gear you planing to downshift to.

 

[Norm Peterson]

It tells by you moving the gear handle next to that gear - and instantly blips the throttle appropriately.

I think you missed my question.

Say I was starting from 5th and go into the little dog-leg toward the 3-4 gate, so the ECU knows it has to blip the revs. So how is the ECU going to know whether I'm on my way to 4th or 3rd? Let's at least assume that the road speed would legitimately permit me to choose either, say from 3000 rpm in 5th. Does it give me something like 4100 assuming I'm headed for 4th regardless? 3rd might want revs closer to 5700 . . .

The video is treating the transmission just like a sequential gearbox, where dropping down only one gear at a time is guaranteed - like a motorcycle gearbox. It does not address my question either.


Norm

 

[StangLuver]

I think you missed my question.

Say I was starting from 5th and go into the little dog-leg toward the 3-4 gate, so the ECU knows it has to blip the revs. So how is the ECU going to know whether I'm on my way to 4th or 3rd? Let's at least assume that the road speed would legitimately permit me to choose either, say from 3000 rpm in 5th. Does it give me something like 4100 assuming I'm headed for 4th regardless? 3rd might want revs closer to 5700 . . .

The video is treating the transmission just like a sequential gearbox, where dropping down only one gear at a time is guaranteed - like a motorcycle gearbox. It does not address my question either. I suggest you try driving one to see how it works. They're pretty awesome.


Norm

No, the rev-matching trannies aren't acting like a sequential - it makes no assumptions about what gear you're heading to next. If you drop two gears that's where it will aim the revs as soon as the gear lever begins to enter the space for whatever gear you're choosing. And blips it faster than a human can.

https://en.m.wikipedia.org/wiki/Synchronized_down_shift_rev-matching_system

The system employs sensors on the clutch pedal, gear shift, and transmission, and is coordinated by the ECU. When the clutch pedal is depressed, the system waits for the user to either move the shifter to a different position, or to re-engage the clutch. If a new gear is never selected but the clutch has been depressed long enough for the engine to lose speed, the system will bring the engine back to speed for the same gear if the driver begins to raise the clutch. If the shifter is moved to a higher gear and the clutch is re-engaged quickly, the system will let the natural deceleration of the engine sync the drive train with the higher gear. If the clutch is depressed long enough for the engine to fall below the speed of the higher new gear, the computer will blip the throttle to bring the engine back to speed. Most usefully, if a new, lower gear is selected, the computer will accelerate the engine to the new estimated speed, even to the point of redline.

 

[MagneticA]

I've been trying the double clutch down shifting...is this correct?

In 5th gear and wanting to down shift to 4th...

Push clutch in then drop the shifter to neutral

Clutch release

Blip throttle

Push clutch in and drop shifter to 4th

Release clutch

You can skip the above step.

 

[Norm Peterson]

Yes, if you move the shift lever when there is no load on the gear teeth, it'll pop right into neutral with little or no effort. Here, you're at the edge of clutchless shifting, which is a useful skill but needs to be kept a whole 'nother topic entirely.

FWIW, when you're hurrying a downshift that's double-clutched without being heel-toed, you probably don't ever get the clutch fully disengaged at all, or fully engaged for the blip either. Full re-engagement might not be until you're finally in the lower gear you were seeking to be in and your left foot's work is all done for that shift. Really, it kind of all just blurs together - as best as I've observed for myself anyway (when you're busy and need to be looking down track, you won't spare much attention on what your feet are doing unless/until you screw up your timing of something that they're supposed to be doing).


Norm

 

[Horse]

You can skip the above step.

Yes, if you move the shift lever when there is no load on the gear teeth, it'll pop right into neutral with little or no effort. Here, you're at the edge of clutchless shifting, which is a useful skill but needs to be kept a whole 'nother topic entirely.

FWIW, when you're hurrying a downshift that's double-clutched without being heel-toed, you probably don't ever get the clutch fully disengaged at all, or fully engaged for the blip either. Full re-engagement might not be until you're finally in the lower gear you were seeking to be in and your left foot's work is all done for that shift. Really, it kind of all just blurs together - as best as I've observed for myself anyway (when you're busy and need to be looking down track, you won't spare much attention on what your feet are doing unless/until you screw up your timing of something that they're supposed to be doing).

Norm

Good to know.

 

[BobbyGT]

I've driven pretty much only manual transmission cars for about 15 years now and have always downshifted and used engine braking while slowing down to turn and I've never had to replace a clutch or had transmission problems. These were 90% muscle/sports cars and BMWs.

The only time I rev match is when I'm downshifting during a race.

This :amen:

Don't understand all the confusion, maybe thats why I always hear about people having to replace their clutch.

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