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Post by Mullet on Sept 24, 2003 2:17:11 GMT -5
In the fast and the furious after the first race Vin Desiel says "Granny shifting and not double-clutching like you should" to Paul Walker... What are these methods of changing gear? (I'll assume "Granny Shifting" is how we normally change gear - by balancing the pedals like a see-saw?)....
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Post by BigOL on Sept 24, 2003 4:24:37 GMT -5
Double clutching or double-de-clutch (proc) as it is known.
Its for the old cars and lorries before syncromesh was available in gearboxes. It involves - clutch down to go to gear, gain speed, clutch down bring bring stick to neutral, clutch up whilst in neutral, clutch down engage next gear, clutch up.
You did this as the 'box needed to realign for each gear change, now with syncromesh, which are like tiny clutches themselves (i think) they stop the gears from rotating when you clutch down, thus making the cog aligned for the change. If you notice the only gear in your 'box thats not syncro'ed is first, which is why any manual car hates/will not go to first if you are over about 10 mph, because its not alingned. Double clutching prevents clutch wear, slippage and heat build up when changing, but it takes time and a LOT of practice to be good at it to change as fast as conventional 'boxes.
Granny shifting, is the paddle movement like conventional driving, clutch down, throttle up, clutch up, throttle down. I think Diesel was trying to say that he changes without thottle lifting, which I think is possible with a seriously quick change, a very expensive race breed gearbox and a triple plate clutch.
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Post by Mullet on Sept 24, 2003 4:28:15 GMT -5
So effectively he doesn't move his throttle foot and just moved his clutch foot for the change? Or does he have one of those new Audi TT boxes that are aleady 'in gear' either side of the current gear (if you're in 3rd, 2nd and 4th are already set up for you).
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Post by BigOL on Sept 24, 2003 4:37:33 GMT -5
So effectively he doesn't move his throttle foot and just moved his clutch foot for the change? Or does he have one of those new Audi TT boxes that are aleady 'in gear' either side of the current gear (if you're in 3rd, 2nd and 4th are already set up for you). Thats right, I think it can be done. Dunno about those Audi 'boxes. I know Audi make a 'box which operates with two cones, one inverted, with a belt that runs around them, as you get quicker the cones move to make the belt run longer, bit like your push bike 'box. - If you don't understand that, which I know is confusing, this of it like this: "The bigger the drive the smaller the driven the faster the speed" Now think of two cones, right one upside down, and with a rubber band around both of them. Now in your mind move left one cone down. This makes the band travel further round the bottom of the cone, and the speed increases, more so, if the right cone also moves down, so the belt is running from the tip of one and round the bottom of the other. See now ;D;D Effectivly an automatic box but with no changes, smooth from standstill right up to 120+ mph. Williams F1 pioneered this box for F1, can't remeber what its called now.
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Post by Mullet on Sept 24, 2003 4:44:09 GMT -5
This might be what i'm describing if it's the new Audi 'intelligent' gearbox on the TT. Basically as you drive the on board CPU 'predicts' what gear you'll need based on the speed/acceleration/contact that the tyres have etc/etc/etc and queues it up, so when you change gear it's effectively already in gear all that happens is the 'drive' is moved from the gear you were in to the new automatically selected/guessed gear. Cr@p explanation i know
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Post by BigOL on Sept 24, 2003 8:47:18 GMT -5
Do you still have a clutch ?? Or is it a hydraulic one. In other words and automatic clutch.
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Post by Mullet on Sept 24, 2003 8:57:58 GMT -5
Ooh.. I think it's a paddle shift and it has the next gear 'pre-loaded'/engaged so when you shift it's seemless revs basically.
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Post by BigOL on Sept 24, 2003 9:28:41 GMT -5
It can't have it engaged, as there is only one driveshaft out of the gearbox to the wheels or the car would permantly crunch gears. But a system like Citroen Sensodrive then, with the paddle shift system.
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Post by Mullet on Sept 24, 2003 9:36:10 GMT -5
No honestly, the cpu sets up the next gear (as it's already assumed which gear you'll need next) and instead of you changing to it normally it's effectively already in the next gear so it just 'moves' to it. I can't explain it very well but it's not a normal paddle shift system.
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Post by BigOL on Sept 24, 2003 10:26:47 GMT -5
Thats pretty clever then - Wouldn't mind giving that a good seeing too. I should think the gear changes are blistering.
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Post by Mullet on Sept 24, 2003 10:38:59 GMT -5
That's the idea, it's on the new top of the range TT's at the moment, and rather than improving the engine by giving it extra power they used this 'predictive' gearbox, which from what i gather is amazing! I'm not 100% on how it functions as i've said above, so if anyone knows any different please post as i'd be interested to know whether i ready the Audi press release right
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Post by Sale on Sept 25, 2003 5:01:51 GMT -5
I didn't read this post before replying to the other in the Problems secton about double declutching, you might want to read it. Double declutching was used as Big explained (well sort of, we don't use it to prevent clutch waer and tear anymore, we don't use it ata ll, we heel and toe now, but he was right about a necessity to practice a lot to make it perfect), but with one slight diffrence - after having engaged the next gear (lower or higher), since the process was slow, revs would die down, so before letting go of the clutch, drivers would blip the throttle evening out the revs with road speed. Familiar? Of course, nowdays we call it heel-and-toe, and use it not as a necessity to change the gear but as a performance driving technique. BTW, double declutching is NOT used anymore anywhere so it won't prevent any clutch slippage or clutch wear and tear anymore.
Vin is kind of talking out of his a*** a bit there, just piling up the terms he sees appropriate for a "racing" movie. We use heel and toe for downshifting not upshifting, so there is no double declutching anywhere in the race since they only accelerate down the straight, right? ;D He probably thought it would sound cool if he said it... BTW in order to change gear without the clutch and upshift, you need REALLY STRONG syncros, straight-cut gears (as in not helical and kind of sharp-edged gears, but with a straight cut-off top of them), and a stroooong clutch and very fast moving, bodybuilder-like hands. Does anybody watch Aussie V8 Supercars on the telly? Just like that, that's straight cut 'box with no clutch, although they DO lift up the throttle at upchanges just an inch. Normal gearbox would pack it up after one punch, although old old cars with high mileage will tolerate clutchless changes at low revs, i had an Astra just like that ;D
On the other subject, Audi gearbox Big decribed is a CVT box, or "continually variable transmission", cone-type automatic box, that continually varies the transfer ratio, making it effectivelly a gearless automatic. Interestingly, it can be made to have a few "presets" that act like gears. In fully automatic mode the engine will have the same revs at all times e.g. it's always 2.250 revs for 70mph and stuff like that. Not only audi has this box but also Toyota, Honda etc.
The other box is an SMG box. Clever little thing, curious for having two clutches, one for 1st, 3rd and 5th, and the other for 2nd 4th and 6th gear. It's a clutchless semi-automatic sequential gearbox (so just like auto box paddle shift, except there is no sludge pump, torque converter, sensation of clutch slip and muuuuch faster than the auto since it's essentially a manual box). Basically, one of the clutches is always engaged, and the other one preselects the next higher/lower gear based on throttle, brake, acceleration etc. inputs. So as soon as you ask for another gear, there is no pause to wait for the same clutch to disengage, select another gear and then engage again, first clucth disengages and the other one engages instantly making changes lightning fast with zero-slip. ECU even blips the throttle for you on the downchanges. Best system so far, including BMW and Ferrari systems, the downside being the fact that it can tolerate only modest engine torque, making it unsuitable for stronger cars. Strongest they have it mated to is Audi V6, 250bhp (the lump from a R32 Golf).
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Post by Mullet on Sept 25, 2003 5:14:05 GMT -5
Is it avaliable on the R32 as i'd quite like one of those next?
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Post by Sale on Sept 25, 2003 5:19:52 GMT -5
Is it avaliable on the R32 as i'd quite like one of those next? No, it's for Audis only, so far at least. Don't tell me you'll go for the Golf!?
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Post by Mullet on Sept 25, 2003 5:36:11 GMT -5
Yeah everyone's got a TT! I quite like the look of an R32 and i'd be able to get the top-spec one brand new from a dealer for £18,500!
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