double clutching?

[ebbfolls]

Im that crazy enough to try this..
kaya sinubukan ko kanina..
mahirap timingan ang pag angat ng pangalawang clutch.
kung sabihin natin na naka turbo ang makina at ang peak torque nya nasa 6000 rpm sa 5000 rpm ko ba bibitawan ang pangalawang clutch?

kasi sinubukan ko sa peak at around 5700rpm nangamoy ang clutch ok eh. di kumapit. at below 4000 rpm parang bitin kung aarangkada kaagad pagkatapos ng corner.

siguro lang kailangan ng practice.

Iqaruzz,

Here's how I do it.

Think of neutral as another extra gear you have to shift to before going to the intended gear. Get it?

For example, you want to shift from 5th to 3rd on a tight corner...you press the clutch, shift to neutral, release the clutch and rev the engine at the same time, then step on the clutch again to engage to 3rd gear. If you think of neutral as another gear then di ka mahirapan dahil palagi mo na tong ginawa dati ang pag down shift from one gear to the next.

[ebbfolls]

double de clutch is in other words losing power at a certain time!!! during racing, you should minimize the use of clutch. pressing a little bit longer or pressing it twice will loose you power on that moment. so i dont get the idea why double pumping the clutch??? downshifting doesnt need to be pumped twice not unless meron problema sa haydraulic clutch system mo....

Some race car drivers shift without using the clutch-- it's called 'power shifting', and the cars that they do this on are dedicated track cars that get rebuilt quite often, some even after every run. This is not, however, adviseable to do on your daily driver because you will wear out your transmission pretty quickly.

You are right about double-clutching losing valuable power time, but sometimes, the time you gain by not ddc'ing is not that much. Also, some drivers find it important to rev-match to prevent the driving wheels from loosing traction as a result of a sudden torque change. There's a better chance of a smoother engagement if you match the revs of the engine to the transmission speed.

[ebbfolls]

Ok... forget that, then, I'll just continue practicing my heel and toe. :D

But that's how Double De-Clutching is PROPERLY done-- by Heel and Toe.

[iqaruzz]

ebbfolls: thanks, i get it now. initially the double clutching method was done to overcome unsmooth shifting that before sync gearbox. matching the radial speed of the transmission and the engine making it easier to engage. sync gearbox now a days doesnt require double clutching.


now heel/toe correct me if im wrong what i understand when braking is keeping the rev high pass the powerband of the engine. so that when engaging (releasing the clutch)on a lower gear at the powerband so you always enough torque to push it.

i also do heel/toe engage on gear before corner so i can drift tight corners when raining. turn steering wheel tap the brake this makes a front tyres grip because at that instance the weight shifted forward giving more pressure on the front. release it press the gas then the back tyres will spin and looses grip.

[ebbfolls]

now heel/toe correct me if im wrong what i understand when braking is keeping the rev high pass the powerband of the engine. so that when engaging (releasing the clutch)on a lower gear at the powerband so you always enough torque to push it.

i also do heel/toe engage on gear before corner so i can drift tight corners when raining. turn steering wheel tap the brake this makes a front tyres grip because at that instance the weight shifted forward giving more pressure on the front. release it press the gas then the back tyres will spin and looses grip.

Actually, heel-and-toe is double de-clutching while braking at the same time, like when you are doing 100+ kph at 5th gear, and you are approaching a corner that needs to be taken at <50 kph in 3rd gear. What I would usually do is to brake down to about 65, then d-d-c into 3rd. I apply clutch, shift to neutral, release clutch and blip throttle to say 4,400 rpm at the same time, apply clutch again and shift to 3rd. I am already in 3rd before I reach the corner, releasing the clutch while engine rpm is winding down past 3,500 rpm (from 4,400 rpm when I blipped it in neutral), rpm will sharply rise to 4,200 rpm as clutch engages; clutch fully released, engine dropping again steadily as the car's speed continues to drop (braking and engine brake together) all the way down to say 50 mph *3,200 rpm. As soon as I enter the corner, I smoothly apply power and rev the engine to 5,800 rpm (wide open throttle, redline * 6,000 rpm) before I shift to 4th, revving again to 5,800, and so on and so forth.

I had been applying brake pressure all along as I was d-d-c'ing into 3rd gear, thus the technique being called 'Heel-and-Toe'.

BTW, d-d-c'ing is done in rapid fire sequence taking NO longer than 1 second. It needs practice to perfect, but, word of advice: Plan ahead, and you will miss-shift less often.

[jojo_mouth2]

jojo_mouth2 : you cannot downshift outright pag galing ka sa high gear at highspeed (masisira gears mo). kaya tinatawag na double-clutching is that yung unang apak sa clutch you place the stick to neutral then depress, apak sa accelerator to match the revs of the engine and transmission (take note galing ka sa high gear at highspeed) then apak ulit sa clutch and place the stick to lower gear then depress the clutch.

jim, what we do in racing (or at high speed), when downshifting, sabay mo na press the clutch ang the gas pedal while shifting the gear. by the time release mo ung clutch, the rpm had risen thus matching the the gear speed and kagat na yan sa torque band mo. no need to press-release-press the clutch, redundant na yan. you simply press the clutch/gas pedal together while shifting the gear and then you go! one press is enough...

[ebbfolls]

jim, what we do in racing (or at high speed), when downshifting, sabay mo na press the clutch ang the gas pedal while shifting the gear. by the time release mo ung clutch, the rpm had risen thus matching the the gear speed and kagat na yan sa torque band mo. no need to press-release-press the clutch, redundant na yan. you simply press the clutch/gas pedal together while shifting the gear and then you go! one press is enough...

Jojo,

This is what I mentioned in my post. The technique you just described is called 'rev-matching' and although it sounds like and looks like 'double de-clutching', they really are 2 different things. The main difference is that in double de-clutching, you rev NOT ONLY the engine but the input shaft of the transmission as well. If you are familiar with manual transmissions, there are 2 shafts, the input and the output shaft. There are also 2 sets of gears, one on each shaft. The gears on the output shaft are fixed to the output shaft which is also connected to the driving wheels via the differential. In short, the output shaft is always turning with the wheels, but the input shaft can idle along on its own if you apply the clutch, separating it from the engine.

The gears on the input shaft are constantly meshed (connected) to their respective counter-gears on the output shaft. That's why it's called a set because for every 'gear' (1st, 2nd, 3rd, etc.) there are actually 2 gear enmeshed together forming 1 gearset (that's why if you want to change the ratio of your gears you have to replace both as a pair). Since all these gears are constantly meshed together, you are going to end up with the both shafts (input and output) fighting each other. Imagine 1st gear driving with 2nd gear, driving with...and so on and so forth. This is called 'driveline contention' which by the way happens to 'part-time' 4x4 truck's transfer case if driven on solid ground.

So to eliminate driveline contention, you disconnect the gears on the input shaft from the shaft, making them 'freewheel' freely. It is by the selective engagement of any of these gears to the input shaft that the driver makes a gear selection. The locking mechanism that locks a particular gear to the input shaft is called a 'synchronizer'. Back in the older days, they used something called 'dogs'. Unlike the synchronizer, the dogs, had to be pushed hard to 'clash' with the gear, therefore connecting it to the shaft. If the shaft was turning at a different speed than the gear, the 'dogs' will have a hard time engaging, and will make a 'crunching' sound if forced to engage. This is why drivers before had to be skilled in double de-clutching because it was necessary top 'speed up' the input shaft to somewhat synchronize its speed to the gear to be selected. (This is what youre doing by releasing the clutch in neutral and blipping the throttle at the same time).

[jojo_mouth2]

i'm very much familiar with engines, tranny etc.... oh btw, been "racing" illegally since the mid 80's. but i havent driven a tranny dogs arf arf arf arf

[ebbfolls]

i'm very much familiar with engines, tranny etc.... oh btw, been "racing" illegally since the mid 80's. but i havent driven a tranny dogs arf arf arf arf

Of course you haven't. Dog-type gear engagers were only used in large trucks by the time you were racing in the mid-80s.

I remember those days, when the 2.0 liter, 2-dr, Ford Cortina was the fastest car in stock form, rivalled only by Mitsubishi's 2.0 liter, 2-dr Galant Sigma.

[jojo_mouth2]

Of course you haven't. Dog-type gear engagers were only used in large trucks by the time you were racing in the mid-80s.

I remember those days, when the 2.0 liter, 2-dr, Ford Cortina was the fastest car in stock form, rivalled only by Mitsubishi's 2.0 liter, 2-dr Galant Sigma.

thats why ive been wondering why to double the clutch a car when those "dogs" were used only on trucks as u mention????

galant lamda 2.0 2dr (not sigma), opel manta 2.0 2dr, toyota corona 2dr macho, ford telstar 1.8, ford escort 2.0 euro 2dr, gamit namin before. and we race on highways not on quarter miles. kaya walang mga starlet sa tropa namin.


merry xmas!!!