double clutching?

[iqaruzz]

mag tatanong lang po.

papaano po ba ang double clutching? hanggang ngayon di ko pa maintindihan kung bakit ka mag do-double clutch kapag nagre-race ka. at para saan pa?

madalas ko lang madinig ito sa mga usapan eh.

[jim]

sir double-clutching or "double de-clutching" is used when downshifting. Pag galing ka sa high gear when racing then suddenly you need to decrease speed and downshift.

To double-clutch during a downshift, perform the following steps: (galing sa web)
Let off the throttle, press in the clutch, and shift the "stick" to neutral.
Let out the clutch.
Bump the throttle to make the engine "blip". Press in the accelerator all the way to the floor for a fraction of a second.
Press in the clutch.
As the engine speed decreases to match the transmission speed, throw the stick into the next lower gear. Since you actively "matched the revs", it should fall right in!
Let out the clutch.

This will also save your engine and tranny from damage.

Usually ginagamit ang double-clutching kung gusto mo ng biglaang use sa engine brake with the normal brake which is very helpful in managing curves lalo na kung pababa yung daan.

Although you can use a power slide hehehe kung talagang nagmamadali ka sa race :-)

[iqaruzz]

ah i get it..
so basically tinatapatan mo ang engine speed sa tranny speed.
since na nasa hi end ang rev range mo malakas kaagad ang torque para pagtapak mo di na nawawalan ng momentum.

ah!!. masubukan nga.


ThanQ

[Field Master]

So this is for manual transmission.
May equivalent ba ito sa auto transmission. Would pressing the A/T accelerator down to the floor fast would produce the same results as M/T double clutch?

[jim]

Correct me if i'm wrong pero pag naka-high ka sa A/T then you want to decrease speed ifo-floor mo yung accelerator para bumaba ng isang gear then shift to low. Parang ganun din ang prinsipyo the difference is wala kang clutch hehehehe (obvious ba kaya nga A/T eh nyehehehe).

[mbt]

anong kaibahan in terms of effect ng double clutching sa simply shifting without letting off the clutch?

[jim]

kung di bibitawan yung clutch wala lang parang nag-shift lang para nakahanda na pag nag-slow down na yung sasakyan. pero once na binitawan ang clutch na di pa nag-match yung revs ng tranny at engine may gruntling sound, sign na di kumagat agad yung gears which may damage the gears pero babagal din naman agad yung sasakyan.

[mbt]

i mean, anong kaibahan ng double-clutching technique sa pag-blip ng throttle with the clutch depressed? hindi ba pareho lang yung labas nun sa blipping the throttle in neutral with the clutch not pressed?

[ebbfolls]

i mean, anong kaibahan ng double-clutching technique sa pag-blip ng throttle with the clutch depressed? hindi ba pareho lang yung labas nun sa blipping the throttle in neutral with the clutch not pressed?

No. Double de-clutching involves blipping the throttle in neutral with the clutch released. Blipping the throttle with the clutch depressed is simply called "Rev Matching". Both are similar but NOT the same.

In the olden days, when transmissions didnt have gear synchronizers (to synchronize the speed of the gear and the shaft), drivers had to d-d-c to prevent the 'dogs' from wearing prematurely. Nowadays, ddc'ing is used only to smoothen the downshift (no need for ddc on upshifts), and to minimize wear on the synchros, but is not absolutely necessary.

Rev-matching, on the other hand, is merely to minimize the torque shock in the drivetrain and the tires. For example, the car is coasting in neutral at say 60 mph, then you drop the clutch while the trans is in 4th gear. It's not gonna hurt anything but with the engine idling at 700 rpm, you force it to spin at 2,400 in a very suddenly because the transmission input shaft (connected to clutch assembly) is spinning at that speed in 4th gear at 60 mph. But if you blip the throttle ( you really cant match the transmission input shaft and the engine perfectly because there is no rpm counter for the transmission input shaft), by the time you release the throttle, the engine will have decelerated to close to 2,400 rpm, thus minimizing the shock of engaging with the tranny.

[jim]

parehas ang labas pero mas smooth ang effect ng double-clutching. :D

[jim]

add ko lang nalimutan ko. double-clutching is best para sa lumang vehicles w/o syncronized trannys. kung bago vehicle mo at synchro tranny mo then "blipping the throttle" is the best kasi no need to match revs :D

[iqaruzz]

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.

[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.

[jojo_mouth2]

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....

[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.

[av8or5]

okay...i sound stupid..but...i am lost..anyhow...no need to do this..i dont race naman eh ..hehehheh

[jim]

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.

[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).

[niky]

But that's for non-synchro racing boxes only, right?