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Old 21st December 2004, 11:50   #31
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Quote:
Originally Posted by speedsatya
Od had carried an article which said that clutchless operation if done properly can improve the life of ur clutch plate.
Hey SS,

Well naturally it would save your clutch since the clutch wouldnt be in use at all! (except starting..... unless u manage to stop on a hill all the time )
However, it would take a bit out of your gearbox and syncros unless you were perfect at it.

I guess the bottom line for this arguement is that clutchless upshifting is quite a common practise for some forms of racing (leaving out the electronically controlled gearboxes) coz its faster and there no temporary loss of power that the clutch causes.
However clutchless shifting doesnt really have a real place for everyday driving on the street. BUT, do note, that if you get good with revvmatching, it will save your clutch almost as well as if u didnt use it!

cheers
R
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Old 21st December 2004, 12:44   #32
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havent found a video yet. but clutchless shifting is used in racing! see the transcript of a forum reply below (from forums.nasioc.com):

GarySheehan02-05-2004, 02:29 PM
Non-clutch shifting is just that. With a racing gearbox, there are no synchro's in the way, so if you match revs, the gear just snicks right into place.

So you only use the clutch to get the car rolling. After that, you forget about the clutch. Left foot for brake, right foot for gas.

Shifting without the clutch on these gearboxes was probably good for a 1/10th of a second or two per lap.

There were no clutchless shifts in the footbox video. Clutchless shifts in a synchro gearbox are too slow and inconsistent. The engine doesn't drop revs quickly enough to make it feasible.

Gary
Sheehan Motor Racing
www.teamSMR.com
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Old 21st December 2004, 13:07   #33
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Hey SG,

I belive you just pretty much repeated what we have just discussed in our various posts above.

Final judgement:

- Clutchless shifting is the norm in racing where you don't have syncro's (to save weight and make it easier and quicker to change ratios).

- With a syncromesh box, as in all our street cars, it is better and quicker 99% of the time to use the clutch while shifting.

Rt
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Old 21st December 2004, 13:27   #34
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whats the difference between synchro and non-synchro box?
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Old 21st December 2004, 13:33   #35
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Hey BikerSG,

Please don't mix road cars with race cars. Road cars cannot do what race cars can because they have different gearbox types. So either stick to road cars OR race cars.

Quote:
Originally Posted by BikerSG
Gordon,
U have said that in normal road cars, u wont have any timing advantage as the engine speed and gear speed is not matched. thats why u need to blip! once u get both speeds to match (with practice) u dont really need the clutch!
This is regarding road cars. That is only during downshifting when you have to blip the throttle so that the engine speed matches the lower gear, and is not done during upshifting.

Quote:
Originally Posted by BikerSG
I have checked a copule of sites on the net and found some stuff on clutchless shifts. check out aussieracingcars.com.au -
How are gears changed?
The sequential gearbox is connected to a super tourer style quick shift lever mounted up close to the steering wheel. Click back to change up, click forward to change down. Gears are changed lightening fast as quick as you can lift and re depress the throttle.

How do I know what gear I am in?
The carbon fibre dash binnacle houses a unique illuminated digital gear position read out indicator that displays each gear number and neutral.

Do the cars have reverse gear?
The cars are fitted with a reverse gear system fitted on the rear axle which is engaged Electrically.

Why is the clutch pedal offset?
The clutch is only used to start and stop. When driving gear changes are made simply by lifting off the throttle and click the next gear. Gears are selected in milliseconds (like super tourer and F1).
That information you got there clearly says that this is for F1 and super-tourer cars that have sequential shifting. And I have already mentioned that F1's have a non-synchromesh sequential gearbox. They do not need to engage clutch during shifting since the electronics of the car take care of the synchronization of engine and gearbox speed. Unlike F1 cars, road cars CANNOT upshift without clutch because the synchromesh will not be able to match the engine and gearbox speeds, which will result in grinding of gears and more wear n tear of your synchomesh.

Quote:
Originally Posted by BikerSG
I am not saying that clutchless shifting is always faster! I myself cant get it right when driving fast! But I am not a racer! The racers also dont do it always! But I have seen them do it! Like rtech said - it depends on the type of gearbox! Maybe it does! I dont know!
its not maybe, IT DOES DEPEND ON GEARBOX TYPE!

Quote:
Originally Posted by BikerSG
My thinking is - if it works for F1 cars, it has to save time. Look at dragsters! All the top class dragsters have clutchless transmissions. In a 10 sec car, clutchless changes save .10 seconds. This is not me guessing. This is from the drag sites. Look them up urself!
This also I have already mentioned that they do have an advantage. OF course you'll save time [this too I have mentioned], and it can mean "winner" or "loser". When you talk about dragsters, they too have sequential transmission and do not have a neutral between gears. So the important thing here to notice is that this is possible only in sequential shifts, not in our normal road car transmission. You should not upshift without engaging clutch. However you can downshift by blipping the throttle which should be done correctly.
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Old 21st December 2004, 13:37   #36
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Quote:
Originally Posted by BikerSG
Clutchless shifts in a synchro gearbox are too slow and inconsistent.
and you yourself have mentioned this in your post...
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Old 21st December 2004, 14:59   #37
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What I am saying and have always said:

Bikes:
Clutchless upshifting is easy and quite fast. And surely faster than upshifting with clutch.
Clutchless downshifting can only be done at low revs and really low speeds. Can cause the bike to surge forward. Not efficient. Electronic systems are now available (proshift.co.uk) that do this well though.

Cars:
Clutchless upshifting is meaningless in road cars as the revs dont fall fast enough. in race cars and dragsters, used a lot as gearbox is sequential as in bikes.
Clutchless downshifting can be fast if done right. it is used in racing and i have given some examples in my previous posts.

My thinking started off theoretical - in the sense that if the job of the clutch is to bring together 2 moving discs which are moving at different speeds, then if the discs can be made to move at the same speed (by blipping the throttle) then the clutch can be done away with!
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Old 21st December 2004, 16:33   #38
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Exclamation Clutchless shifting in F1...not literally!

but do remember this, when you say clutchless shifts in F1 cars, they do not literally mean shifting gears "without" the clutch.

like Rtech said:

Quote:
Originally Posted by rtech
A clutch (of some sort) is needed to transfer power from the engine to the gearbox.
When the driver changes gears, the electronics cuts the engine, depresses the clutch, the engine and gearbox speeds are synchronized AND then the gear is changed. This whole procedure takes place in hundredths of a second.
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Old 21st December 2004, 16:44   #39
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originally i had thought that the computer was engaging the clutch electronically!

But after I myself has tried shifting without the clutch, it got me thinking - Maybe the computer only changes the engine speed (by either cutting the engine to lower the revs, or blipping the throttle to up the revs) so that the gear slots into place.

I am not too sure about this. I will have to check on the F1 technical sites and see if theres anything on this!
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Old 21st December 2004, 17:36   #40
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But blipping the throttle, will this not have a slight negative effect on the clutch in terms of wear and tear??
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Old 21st December 2004, 18:30   #41
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Question Computer engages clutch in F1

Quote:
Originally Posted by BikerSG
originally i had thought that the computer was engaging the clutch electronically!

But after I myself has tried shifting without the clutch, it got me thinking - Maybe the computer only changes the engine speed (by either cutting the engine to lower the revs, or blipping the throttle to up the revs) so that the gear slots into place.

I am not too sure about this. I will have to check on the F1 technical sites and see if theres anything on this!
BikerSG, in F1 the computer does engage clutch. See the post below where I mentioned it:

Quote:
Originally Posted by Gordon
When the driver changes gears, the electronics cuts the engine, depresses the clutch, the engine and gearbox speeds are synchronized AND then the gear is changed. This whole procedure takes place in hundredths of a second.
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Old 22nd December 2004, 17:17   #42
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Quote:
Originally Posted by Deeps
But blipping the throttle, will this not have a slight negative effect on the clutch in terms of wear and tear??
Deeps,

Blipping the throttle actually gets the engine side of the clutch to speed up to a similar speed that the gearbox side has reached (because it went faster due downshifting the transmission).
This actually causes LESS wear on the clutch. If done PREFECTLY, there could be zero wear on the clutch while shifting.

Let me know if u get the concept or if i shld explain in a little more detail.

cya
R

Last edited by Rehaan : 22nd December 2004 at 17:18.
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Old 22nd December 2004, 18:17   #43
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hey deeps, Lets get one thing straight here.

A clutch is just a device that allows a user to stop the transmission of power from the engine to the gearbox. Meaning it disengages the drive from the engine to the gearbox when changing gears or coming to a stop.

If an engine runs continuously (like a generator), it doesn't need a clutch. Direct drive is sufficient. Many racing go karts have direct drive. This requires the driver to physically push the kart to get the engine started, then jump in. Also, if he then has to stop or spins on the circuit, the engine will cut off.

On a road car, a clutch is a necessity because of the stop-start nature of our driving. Now, if you bypass the clutch while shifting, it is only obvious that the wear and tear of the clutch will reduce. However, messing up your clutchless gearshift and grinding gears and syncro's is far more harmful and can lead to costly repairs, far more that what it would cost for a new clutch and pressure plate.

A clutch is designed to be used! It will happily last atleast 45,000km of city driving. Thats a minimum! I never replaced the clutch on my 68,000Km Astra, and it was still fine when I sold it.

Hope that clears up a few things.

Rt
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Old 22nd December 2004, 21:08   #44
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now this is something differnt from the original topic.
but if we do some high revving motoring i.e change at 3000-4k rpm and do fast starts from stop will the clutch plate life be reduced.by fast starts i dont mean with wheel spins .
also to increase the life of one clutch plate u will have to sacrifice atleast one clutch plate before that ,as in the process of perfecting the technique of blipping in between changes, u tend to ride the clutch .so that means u have to give a VRS to the present clutch plate.
but after u perfect it, i am sure no one will think of going back to the normal pathetic gear changes.

cheers.
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Old 23rd December 2004, 15:07   #45
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Quote:
as in the process of perfecting the technique of blipping in between changes, u tend to ride the clutch .
Why would you ride the clutch? The changes have to be fast, or you defeat the whole purpose!

Rt
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