imported_BoOsTd

imported_BoOsTd

just cuz Vin Disel says your a granny if your not double clutching doesnt make it "cool" nor right lol...

BTW how does he know blondie wasnt double clutching lol?? I figured his attention was foucused to much on the warping speeds and not peeping through the window to see if his opponent is double clutching like he should lol


I dont get it lol

imported_gatherer

it's used in racing all the time with or withour syncros.... just watch the foot work of some of the pros ...

I do it simply because I know how and it's habit then .. yes I shift to first doing 40+ km/h people look at be strange when I do it too I don't care because I know they can't .... in autocross there is tons of 2 to 1 down shifts if you can't double clutch you can't get by the speed lock out mechanism and therefore slow down too much to do the shift... my shifts down to 1st are as smoot from a shifter feel as a up shift .... I know lots of people that force it in ...they break transmissions ...

imported_MY SiR

Now, the real purpose for double clutching is to ensure you are in the proper gear when you are preparing to exit a corner, i.e. you do it as you enter a corner.

So, imagine approaching a corner, (usually) you have to slow down. To slow down you can use brakes or engine braking or both. To use both, that's when you use "heel and toe" and double clutching. Why would you double clutch instead of just blipping the throttle? Simple if you did this, you would wear out your clutch and synchros faster. Now going back to the corner, you want to be in a lower gear than you were in before you approached the corner so when you accelerate out, you can have your RPM in the "sweet spot" of the rev range. If you don't downshift, you won't be able to accelerate as fast. For driving on the street, this really isn't necessary but on a race track...

Hope this makes sense.

imported_gatherer

Makes sense well explained Mark

GinoLicious

Yeah makes sense.

That dumb movie throws everything off. So then i take it double clutchin is used in racing.

The G2 Racer

Used more in auto cross and road racing, yes.
I haven't heard of it being used in drag cause there's no real point.

imported_jason_alt

Downshifting should not be done as you 'enter' a corner. It should be completed before your turn in point.

Also, you should not use 'engine braking' to help slow down when coming into a corner, especially in a rear wheel drive vehicle unless you like snap oversteer. Braking is what should be slowing down the car, not compression via downshifts.

Clutch wear is already minimized with a proper heel/toe downshift and not further improved with a double clutch. In fact, the wear can be increased when double clutching. Unless your transmission has a heck of a time downshifting into a gear, or you want to save your syncros, double clutching is unnecessary.

Now if you're talking about driving on the street, do whatever makes you happy. I double clutch around town and it doesn't hurt to know it.

Which pros and what racing?

GinoLicious

You dont have to go into a corner double clutchin then rite? You can go in slowly.

Gunmetalef

it think theyre trying to say that it helps you to slow down with the brakes without the huge jerk going into higher rpms as well as gives you better power out of the turn for better acceleration

imported_MY SiR

I understand the difference between "enter" and before "turn in point" however, I suspect the majority of the people on this board don't so, I used a more "layman's" term. I agree, you are correct.

I don't think I wrote that you "should engine brake", I believe I wrote "engine braking can be used to slow down the car". Also, maybe I am missing something but how do you get snap oversteer if you match engine speed with a downshift correctly?

Also, I don't understand about how just heel and toeing will cause less wear on a clutch. In order to downshift without double clutching and using heel/toe, you would:
Brake, Engage clutch, Heel/toe to bring up RPM...while the clutch is engaged, then downshift, Release clutch. Is that correct? In this situation, the clutch is engaged the whole time the engine is being revved. I can see that wearing out the clutch.

I agree if double clutching is not done properly it can cause more wear but if it is done the right way and matching revs...

Again, the purpose of double clutching is to be in the correct gear when you exit a corner.

Anyway, maybe I am stupid and I am totally wrong. If so, please explain it better to me. Don't worry I am not afraid of engineering terms... (I am an Engineer in the automotive field)

Also, about the racing comment, I am betting the person is talking about rally racing ie WRC...

imported_jason_alt

You should never use engine braking to slow down the car. It is inefficient compared to the stopping power of modern brakes and upsets the balance of the vehicle

I mentioned that you may get snap oversteer with 'engine braking'. If you fail to downshift correctly and not rev enough, the motor will slow down the drive wheels once the clutch is released, upsetting the car's balance. This could result in a skid and/or snap oversteer.

You've got the basic idea covered, but i'll help clarify.

1. Brake
2. Push down clutch PEDAL and move shift lever from current gear to neutral simultaneously. ( Pushing down the PEDAL disengages the clutch. It is now not in contact with the flywheel. It is not engaged. )
3. Heal/toe
4. Select desired gear and release clutch PEDAL at once, maintaining your braking. ( Now the clutch is once again in contact with the flywheel. It is engaged. )

While the heal/toe revving process is taking place, the clutch is not in contact with the flywheel surface. There is no wear on the clutch because no friction has occured. Friction occurs as you RELEASE the clutch pedal, allowing the clutch itself to mate with the flywheel surface. If it were engaged, the car would lurch forward! Now that we have established that wear occurs when the clutch is mating with the flywheel, it is safe to say that you have doubled your wear factor when you double clutch. In theory, a perfect standard downshift or double clutch downshift will incur no wear to the mating surfaces. But everything always looks good on paper, doesn't it! (Especially in the engineering field )

I would have to disagree with that statement. Some people may interpret double clutching as a requirement and standard racing procedure which is not the case. The purpose of DOWNSHIFTING is to extract the full potential of your car so that it will be in the correct gear for exiting the corner. It is the key to balance, smoothness, and improved lap times. If downshifting requires a double clutch due to a worn syncro or extremely difficult gear, then do it. If not, then standard heal/toe downshifts will suffice. Even on a non syncro transmission.

I hope this has helped. Let me know if anything is incorrect or unclear.