Rev Matching & the mistakes made

[paua]

mph999 posted several clips - chap in the Renault does it best.

[waremark]

paua said:

Ddc is smoother & mecvhanically more sympathetic than just rev-matching (single de-clutching) all day long - both on the drivetrain & the car's overall balance ( pitch/ for-aft weight transfer).

I don't understand your argument for DDC. A rev matched single clutch change is seemless. It is impossible for a DDC change to be more so, and quite easy for it to be less so. The only benefit of DDC is to save the synchro rings from having to do their job - which they seem able to do for the whole lifetime of modern cars.

[Reg Local]

paua said:

Reg; watched your clip - seems to me that you ride the clutch a bit. The pedal doesn't need to be on the floor so long.

Pedal on the floor is not "riding the clutch". Riding the clutch is holding the car unnecessarily long with the clutch on the biting point.

Watch it again. Clutch is depressed quickly and released slowly. Perhaps a little exaggeration of the slow release to assist with the video, but if engine speed and road speed are matched, then there's no issue, and definitely no clutch riding.

[lyonspride]

akirk said:

really?
so if I am in 4th gear at 2,000 revs, and keeping a constant speed wish to change to 3rd gear, which will change to 2,500 revs, how is my car going to sort the revs? the M5 has an electronic throttle control, so in your theory it doesn't matter what I do, the car will do what it wants... yet rev matching gives a smooth transition, not rev matching would give a huge shunt in the drive train... the car certainly does not auto-blip, so I am not quite sure what you mean...

It's not an auto blip, the ECU holds the revs for a second or two when you dip the clutch, in order to make gear changes smoother. I does depend on the car, it's not universal, but if I go to change gear in mine and then hold the clutch down I see the revs stay the same for a second or two and then suddenly drop off.

[waremark]

lyonspride said:

It's not an auto blip, the ECU holds the revs for a second or two when you dip the clutch, in order to make gear changes smoother. I does depend on the car, it's not universal, but if I go to change gear in mine and then hold the clutch down I see the revs stay the same for a second or two and then suddenly drop off.

What type of car? Of the large number of manual cars I have driven, the only one which did this was a Focus RS. I disliked the feature, just as I dislike autoblip.

[paua]

Reg Local said:

paua said:

Reg; watched your clip - seems to me that you ride the clutch a bit. The pedal doesn't need to be on the floor so long.

Pedal on the floor is not "riding the clutch". Riding the clutch is holding the car unnecessarily long with the clutch on the biting point.

Watch it again. Clutch is depressed quickly and released slowly. Perhaps a little exaggeration of the slow release to assist with the video, but if engine speed and road speed are matched, then there's no issue, and definitely no clutch riding.

Looks like you allow the pedal up an inch or so from the floor & hold it there, whilst you await the syncos & then release.

[paua]

waremark said:

paua said:

Ddc is smoother & mecvhanically more sympathetic than just rev-matching (single de-clutching) all day long - both on the drivetrain & the car's overall balance ( pitch/ for-aft weight transfer).

I don't understand your argument for DDC. A rev matched single clutch change is seemless. It is impossible for a DDC change to be more so, and quite easy for it to be less so. The only benefit of DDC is to save the synchro rings from having to do their job - which they seem able to do for the whole lifetime of modern cars.

That's how I learned to drive.
Had a friend, who has driven lots of exotic machinery, does endless track days etc, drive my car. He does single clutch h'n't downshifts ( as you advocate). In no way, shape or form is it as seamless or mechanically gentle as correctly modulated ddc.
Correct synchronising of the intermediate/ layshaft is best accomplished by throttle with the clutch engaged. DDC.
One of the clips posted by mph99 explains this - although it's a bit painful to watch.
Watch the bloke in the Renault again.

[Bigends]

paua said:

That's how I learned to drive.
Had a friend, who has driven lots of exotic machinery, does endless track days etc, drive my car. He does single clutch h'n't downshifts ( as you advocate). In no way, shape or form is it as seamless or mechanically gentle as correctly modulated ddc.
Correct synchronising of the intermediate/ layshaft is best accomplished by throttle with the clutch engaged. DDC.
One of the clips posted by mph99 explains this - although it's a bit painful to watch.
Watch the bloke in the Renault again.

I was Police trained from scratch as an 18yr old Cadet. We were all DDC comfortably after 3 - 4 days. The principles of why it works were explained on cutaway gearboxes.That was in the mid 70's when synchromesh existed on production cars though I think it was trained as a good technique and also when driving some of the older vans and later the force coach on advanced courses DDC was essential. Since reading this thread ive been retesting myself on DDC - changes are are as smooth as silk. Its a matter of personal choice - dont do it if you dont want to

[mph999]

Reg Local said:

Bloody hell - where did you find that? I’d forgotten that even existed!

For something a little more 21st century, here’s one that wasn’t filmed on a potato and doesn’t include pasty legs:

https://youtu.be/A4rs09AKBc8

And one on heel/toe:

https://youtu.be/9owdffLKES4

I bookmarked some of your vids ... quite often reference them as they are very good.

[mph999]

akirk said:

really?
so if I am in 4th gear at 2,000 revs, and keeping a constant speed wish to change to 3rd gear, which will change to 2,500 revs, how is my car going to sort the revs? the M5 has an electronic throttle control, so in your theory it doesn't matter what I do, the car will do what it wants... yet rev matching gives a smooth transition, not rev matching would give a huge shunt in the drive train... the car certainly does not auto-blip, so I am not quite sure what you mean...

Some cars will do it for you. The only car I've been in that does was a JCW Mini, it rev matched for you and seemed to do a good job, though I prefer of course, to do it myself.

[akirk]

lyonspride said:

akirk said:

really?
so if I am in 4th gear at 2,000 revs, and keeping a constant speed wish to change to 3rd gear, which will change to 2,500 revs, how is my car going to sort the revs? the M5 has an electronic throttle control, so in your theory it doesn't matter what I do, the car will do what it wants... yet rev matching gives a smooth transition, not rev matching would give a huge shunt in the drive train... the car certainly does not auto-blip, so I am not quite sure what you mean...

It's not an auto blip, the ECU holds the revs for a second or two when you dip the clutch, in order to make gear changes smoother. I does depend on the car, it's not universal, but if I go to change gear in mine and then hold the clutch down I see the revs stay the same for a second or two and then suddenly drop off.

ahh okay - I have never driven a car that does that, (and I have driven a lot of cars!) certainly none of mine do it. I popped up to Derby this evening and enjoyed rev-matching the M5 on the motorway in traffic next to an M4 which was auto-blipping away have to admit it sounded very fake... but then so did the exhaust...

[waremark]

paua said:

waremark said:

paua said:

Ddc is smoother & mecvhanically more sympathetic than just rev-matching (single de-clutching) all day long - both on the drivetrain & the car's overall balance ( pitch/ for-aft weight transfer).

I don't understand your argument for DDC. A rev matched single clutch change is seemless. It is impossible for a DDC change to be more so, and quite easy for it to be less so. The only benefit of DDC is to save the synchro rings from having to do their job - which they seem able to do for the whole lifetime of modern cars.

That's how I learned to drive.
Had a friend, who has driven lots of exotic machinery, does endless track days etc, drive my car. He does single clutch h'n't downshifts ( as you advocate). In no way, shape or form is it as seamless or mechanically gentle as correctly modulated ddc.
Correct synchronising of the intermediate/ layshaft is best accomplished by throttle with the clutch engaged. DDC.
One of the clips posted by mph99 explains this - although it's a bit painful to watch.
Watch the bloke in the Renault again.

Of course it is possible to make seamless DDC changes. It is easier to make seamless single clutch changes, whether not with H & T. The fact that your friend did not make his changes seamless only tells us about his driving in your car. The purpose of DDC is to synchronise the layshaft, but that is not required to make the change seamless. What is required is for the revs to be accurately matched to the road speed when the clutch is released.

[Len Woodman]

Bigends said:

I was Police trained from scratch as an 18yr old Cadet. We were all DDC comfortably after 3 - 4 days. The principles of why it works were explained on cutaway gearboxes.That was in the mid 70's when synchromesh existed on production cars though I think it was trained as a good technique and also when driving some of the older vans and later the force coach on advanced courses DDC was essential. Since reading this thread ive been retesting myself on DDC - changes are are as smooth as silk. Its a matter of personal choice - dont do it if you dont want to

That should conclude any arguments.

[lyonspride]

akirk said:

lyonspride said:

akirk said:

really?
so if I am in 4th gear at 2,000 revs, and keeping a constant speed wish to change to 3rd gear, which will change to 2,500 revs, how is my car going to sort the revs? the M5 has an electronic throttle control, so in your theory it doesn't matter what I do, the car will do what it wants... yet rev matching gives a smooth transition, not rev matching would give a huge shunt in the drive train... the car certainly does not auto-blip, so I am not quite sure what you mean...

It's not an auto blip, the ECU holds the revs for a second or two when you dip the clutch, in order to make gear changes smoother. I does depend on the car, it's not universal, but if I go to change gear in mine and then hold the clutch down I see the revs stay the same for a second or two and then suddenly drop off.

ahh okay - I have never driven a car that does that, (and I have driven a lot of cars!) certainly none of mine do it. I popped up to Derby this evening and enjoyed rev-matching the M5 on the motorway in traffic next to an M4 which was auto-blipping away have to admit it sounded very fake... but then so did the exhaust...

I was under the impression that both of those cars play fake engine noises inside the cabin, same as the Focus RS does..... So who's to say what's real?

[dvenman]

lyonspride said:

I was under the impression that both of those cars play fake engine noises inside the cabin, same as the Focus RS does..... So who's to say what's real?

Having had a play in the said M5 last weekend, it's definitely real. No enhancement necessary...

[cylinderfin]

lyonspride said:

It's not an auto blip, the ECU holds the revs for a second or two when you dip the clutch, in order to make gear changes smoother. I does depend on the car, it's not universal, but if I go to change gear in mine and then hold the clutch down I see the revs stay the same for a second or two and then suddenly drop off.

I don't think it's anything to do with smoothing of the gear changing. It's all about helping the emissions by not letting the throttle slam shut too quickly where you are more likely to get a short but sudden spike in fuel mixture. This has been a feature for at least a couple of decades now.

[BertBert]

Len Woodman said:

Bigends said:

I was Police trained from scratch as an 18yr old Cadet. We were all DDC comfortably after 3 - 4 days. The principles of why it works were explained on cutaway gearboxes.That was in the mid 70's when synchromesh existed on production cars though I think it was trained as a good technique and also when driving some of the older vans and later the force coach on advanced courses DDC was essential. Since reading this thread ive been retesting myself on DDC - changes are are as smooth as silk. Its a matter of personal choice - dont do it if you dont want to

That should conclude any arguments.

Not in the slightest. Whether the synchros do the job or whether you do it with DDC cannot be felt in the car. The energy used to synchronise the gears is miniscule.

And to the point of the thread DDC is of no relevance to the op whatsoever!

[cmaguire]

Double de-clutching is a joke in any synchromesh car unless you like wasting time.
I can't much see the point in concerning yourself with rev-matching on the road either. If you avoid dumping the clutch and ease it through the biting point (a staggered clutch release effectively) when releasing it between gears when changing down it is easy enough to deal with heavy braking and down-changing without bothering the throttle.

[mph999]

Sure, you can get away without it but you put more wear on the clutch. Clutches should only wear when setting off and changing gear (presuming here that the person doesn't ride the clutch or similar). If you can remove, or minimise the wear on changing gear is that not a good thing.

[akirk]

dvenman said:

lyonspride said:

I was under the impression that both of those cars play fake engine noises inside the cabin, same as the Focus RS does..... So who's to say what's real?

Having had a play in the said M5 last weekend, it's definitely real. No enhancement necessary...

Indeed, the car has just about recovered

it is an older, e39, M5 - they don't have fake noises... I believe the newer ones do...