Clutchless shifting Good idea or bad idea
Discussion
I've been experimenting with some track techniques on my road car (as you may be aware from my other post). Today I was giving clutchless shifting a crack. I'm finding the upshift works perfectly but the downshift is much more tricky. Is there a trick I'm missing or is it just going to be practise makes perfect with getting the revs matched during the downshift. Also, as long as I don't graunch the gears, is it a bad idea on a normal road car?
deviant said:
How did you find the correct RPM to get away with it?
Its down to method and some memory. For instance i know at 40mph i can drop into second and it will be around the 5800-5900rpm, so if i'm driving and i want to overtake i look down, see 40, clutch in, add the revs snatch second, now if my skills where better i could, come off the power momentarily, knock it out of gear, revs up and take second without clutch but you have to be so precise.I imagine its easier if you have a smaller rev range so less minute modulations of the accelerator is required, for instance the pedal travel on engine with 3000rpm as redline would account for a greater or lesser degree of revs. As my car has a redline of 8900rpm its a touch more tricky.
Personally i would'nt do it, unless your running a "dog box" then there is no need. Rev match with the clutch if you like, it puts less wear on parts so has a similar effect whilst still being pleasing to the ear and arse.
just 2p worth there.
Gwiz
GingerWizard said:
deviant said:
How did you find the correct RPM to get away with it?
Its down to method and some memory. For instance i know at 40mph i can drop into second and it will be around the 5800-5900rpm, so if i'm driving and i want to overtake i look down, see 40, clutch in, add the revs snatch second, now if my skills where better i could, come off the power momentarily, knock it out of gear, revs up and take second without clutch but you have to be so precise.I imagine its easier if you have a smaller rev range so less minute modulations of the accelerator is required, for instance the pedal travel on engine with 3000rpm as redline would account for a greater or lesser degree of revs. As my car has a redline of 8900rpm its a touch more tricky.
Personally i would'nt do it, unless your running a "dog box" then there is no need. Rev match with the clutch if you like, it puts less wear on parts so has a similar effect whilst still being pleasing to the ear and arse.
just 2p worth there.
Gwiz
I was shown a method for the downshift. Rather than try to just get the exact revs, you rev past the point you expect, then hold the gear gently against the gate. As the revs come down, the gear will slot in at the appropriate point. I was shown to do it with a throttle blip.
You can do the slotting in thing with rising revs, but it tends to jerk more.
You always have to be mechnically careful, but it's another technique to have in the armoury.
bert
You can do the slotting in thing with rising revs, but it tends to jerk more.
You always have to be mechnically careful, but it's another technique to have in the armoury.
bert
BertBert said:
You always have to be mechnically careful, but it's another technique to have in the armoury.
Agreed.A few years ago I had a Porsche 968CS. It was losing fluid from the clutch hydraulics and I arranged to take it to the specialist I used, some 70 miles away. That morning I set off early and within 2 miles the clutch had failed, pedal to the floor and clutch still engaged.
Yet because I'd learnt to change without the clutch I was able to avoid a long wait and expensive recovery, and drive to the specialist. Luckily much of the journey was motorway, and I was able to use the starter to get thecar moving on the few occasions I had to stop at a junction.
SS7
shoestring7 said:
BertBert said:
You always have to be mechnically careful, but it's another technique to have in the armoury.
Agreed.A few years ago I had a Porsche 968CS. It was losing fluid from the clutch hydraulics and I arranged to take it to the specialist I used, some 70 miles away. That morning I set off early and within 2 miles the clutch had failed, pedal to the floor and clutch still engaged.
Yet because I'd learnt to change without the clutch I was able to avoid a long wait and expensive recovery, and drive to the specialist. Luckily much of the journey was motorway, and I was able to use the starter to get thecar moving on the few occasions I had to stop at a junction.
SS7
Totally agree about learning in a hire car. When ever i have had them no matter what sort of shed it might be it gets the full rev match downshift, or using a stupid amount of engine braking. TBH for fear of f
king the transmission and possibly engine i would never change gear without the clutch. If i was really pushing on, i might "flat shift" from 3rd->4th and 5th->6th but only in extreme. (which never occurs off the track)Gwiz
Soon after I had learned to drive I had an old Morris Minor split screen, no syncro and little in the way of brakes. I soon learnt how to double de-clutch up and down the box, heal and toeing at the same time for maximum braking effect. After a while I was able to stop using the clutch, at least in the higher gears, but you have to know the car and be able to judge engine revs very accurately.
More recently I've had several superbikes ('blades etc.) and found it easy to make clutchless up-changes by loading up the gear lever and backing off the throttle - as soon as transmission loads neutralize the changes takes place. Never done it going down the box.
You can do similar in a car with strong syncromesh, load the gear lever in the direction of neutral, the syncro will stop the change taking place until you adjust transmission loads with the accel. pedal, and once the load disappears the gear lever will move into neutral. Moving into a gear is similar , load up the gear lever, adjust the engine revs and once the load disappears the gear lever will move into gear.
More recently I've had several superbikes ('blades etc.) and found it easy to make clutchless up-changes by loading up the gear lever and backing off the throttle - as soon as transmission loads neutralize the changes takes place. Never done it going down the box.
You can do similar in a car with strong syncromesh, load the gear lever in the direction of neutral, the syncro will stop the change taking place until you adjust transmission loads with the accel. pedal, and once the load disappears the gear lever will move into neutral. Moving into a gear is similar , load up the gear lever, adjust the engine revs and once the load disappears the gear lever will move into gear.
I find it quicker to use the clutch when changing up but when coming back down the 'box I like to use my left foot on the brake so clutchless downchanges are helpful.
My girlfriend still doesn't believe that you can change gear in a car without using the clutch.
Probably helps that I am only wrecking the gearbox in a 1.3 Micra that cost me £240. As with anythiing, the more you practice the smoother you get.
My girlfriend still doesn't believe that you can change gear in a car without using the clutch.
Probably helps that I am only wrecking the gearbox in a 1.3 Micra that cost me £240. As with anythiing, the more you practice the smoother you get.
I'd never do it normally but it's a useful technique to have in your armoury in case you need it. Three times during my driving career I've had some form of clutch failure and always been able to get the car home. In fact once I was able to drop off the friend I was giving a lift to, get myself home, and drive it to the mechanic for repair the following morning.
Very bad idea
Clutchless gear changing is an impressive art and can prove useful in an emergency, such as a cable failure. However, I dont want to be a spoil sport BUT IT IS VERY DAMAGING to a Synchromesh gearbox even if you are good at it. Trust me, whilst modern transmissions are very robust you will knock the box out prematurely (A crashbox or constantmesh motorcycle box is a different ball game altogether) Synchros are simply not designed to continually absorb the loads placed on them even by a marginal mis match in revs. The clutch is. Any transmission engineer reading this will be cringing in their driving seat !
Using rev matching and the clutch is very good practice indeed as it saves considerable wear and tear on all the transmission parts in the long term. It is also ultra smooth, the hallmark of a quality driver - Nothing worse than being a passenger and needing a neck brace for every gear shift ! With exception of continual stop/start town driving, 200-300-400 thousand miles is easily possible on the same clutch in a well driven vehicle but at the end of the day, it is there for a purpose and is considerably cheaper than a new gearbox
I have won a few bets with clutchless party pieces including pulling away without stopping the engine (or simply ramming it into gear) but the technique is not recommended in the interests of mechanical sympathy so will keep the method up my sleeve !
Clutchless gear changing is an impressive art and can prove useful in an emergency, such as a cable failure. However, I dont want to be a spoil sport BUT IT IS VERY DAMAGING to a Synchromesh gearbox even if you are good at it. Trust me, whilst modern transmissions are very robust you will knock the box out prematurely (A crashbox or constantmesh motorcycle box is a different ball game altogether) Synchros are simply not designed to continually absorb the loads placed on them even by a marginal mis match in revs. The clutch is. Any transmission engineer reading this will be cringing in their driving seat !
Using rev matching and the clutch is very good practice indeed as it saves considerable wear and tear on all the transmission parts in the long term. It is also ultra smooth, the hallmark of a quality driver - Nothing worse than being a passenger and needing a neck brace for every gear shift ! With exception of continual stop/start town driving, 200-300-400 thousand miles is easily possible on the same clutch in a well driven vehicle but at the end of the day, it is there for a purpose and is considerably cheaper than a new gearbox
I have won a few bets with clutchless party pieces including pulling away without stopping the engine (or simply ramming it into gear) but the technique is not recommended in the interests of mechanical sympathy so will keep the method up my sleeve !
Edited by Jules2477 on Tuesday 21st July 00:40
Edited by Jules2477 on Tuesday 21st July 04:03
Actually had a bit of fun with it today.
Not saying it's a good idea or anything, worked quite a lot easier than I expected. I rev match normally so it was ok. Passenger couldn't believe his eyes though.
Just applied a bit of pressure on the stick in the desired gear direction, matched the revs and it just slides in.
No idea on how you pull away without the clutch though?
Not saying it's a good idea or anything, worked quite a lot easier than I expected. I rev match normally so it was ok. Passenger couldn't believe his eyes though.
Just applied a bit of pressure on the stick in the desired gear direction, matched the revs and it just slides in.
No idea on how you pull away without the clutch though?
Loque said:
Actually had a bit of fun with it today.
Not saying it's a good idea or anything, worked quite a lot easier than I expected. I rev match normally so it was ok. Passenger couldn't believe his eyes though.
Just applied a bit of pressure on the stick in the desired gear direction, matched the revs and it just slides in.
No idea on how you pull away without the clutch though?
Nice to see you have the skill to do it and it can certainly impress those with little understanding of mechanics, especially if stranded in the middle of nowhere with failed clutch cable/hydraulics. Unfortunatly it is that bit of pressure, even momentarily, that does the damage as you have a syncho under abnormal load trying to match the gearspeeds for you. If it cant, you get excess friction = heat = wear. You will certainly get away with it on the odd occasion as modern gearboxes can generally take a lot of abuse but I would strongly advise that you do not make it a normal practice. Leave you to work out how to pull away, change up through the box, down again and stop without the clutch ! The common and probably the best method to get moving is to switch off, engage first and use the starter motor until the engine fires but there is another way, two in fact ! Not saying it's a good idea or anything, worked quite a lot easier than I expected. I rev match normally so it was ok. Passenger couldn't believe his eyes though.
Just applied a bit of pressure on the stick in the desired gear direction, matched the revs and it just slides in.
No idea on how you pull away without the clutch though?
Note that the starter method may not work very well on engines with low oil pressure protection cut outs as there may not be enough umph to overcome these as well as shifting the weight of the car.
MMmmm. Interesting, I'm gonna avoid messing with starting the engine in gear as I've just put a new Cat on, and I've heard bump starting it and the like can really screw with that.
Nah, I don't think it's going to be something that I do every day, Plus the satisfaction of double clutching is a nice distraction.
Nah, I don't think it's going to be something that I do every day, Plus the satisfaction of double clutching is a nice distraction.
One way of pulling away from rest is to give it a touch of gas in neutral, then gently push the gear lever towards first. The synchromesh can sometimes act as a clutch and start the car rolling, then it will go all the way in (ooh, matron!) when you're up to speed. I presume it needs a powerful synchromesh to work though.
Evangelion said:
....One way of pulling away from rest is to give it a touch of gas in neutral, then gently push the gear lever towards first. The synchromesh can sometimes act as a clutch and start the car rolling....
Are you completly mad as a box of frogs..... me thinks you have the wrong end of the stick buddy......I would never ever do this, this is the worst thing you could possibly do..... If absolutly nessecary use the starter motor to pull away, they are a lot cheaper then a gear box.
(turn off car, select first, turn it over, keep turning it over, power.....)
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