Celica Forums General Discussion Exterior How to Double-Clutch: Very Long

The Double-Declutching Gas-Blipping Downshift

So, what is to be gained on your part by lots of frustrating practice to learn proper downshifting.

"Fun," in a word!

Good downshifting will bring a smile to your face. And, unlike serious grin-inducing activities like smoking the rear tires and power oversteer in turns, proper downshifting is legal and can be done anywhere and everywhere: Even in full view of a police officer with your mom sitting in the passenger seat next to you!

PROS:

masterful technique is always to be admired
car has excellent stability on ice, etc.
shifts can be very fast
engine is not subject to impulsive "hit" when clutch is let up (as in ordinary downshifting)
the "blip" (stab of the gas) makes beautiful "music"
something fun to do in ordinary traffic
separate yourself from the masses who don't "get it" but still drive a manual

CONS:

other people will hear the blip and think you want to race them

Note that the way that you upshift is probably fine---we will only look at how one downshifts, which is different and more subtle than how one upshifts.

Introduction
A car's engine operates in a range of RPMs that typically range from about 1000 to 7000 revolutions per minute. (Some cars go up to 18,000 RPM, but the're hooked up to SMGs and cost millions of dollars.)

You typically pick an "operating range" where you want to run the car, say between 2k and 4k for most situations, and up to 7k every now and then. You could take the car up to the "red line" all the time, but the motor will not last as long, so this is something to consider for vehicles that are not leased.

When you're getting close to your (say) self-imposed 4k (upper) limit, you upshift, i.e., go to the next higher gear; when you get close to your self-imposed 2k (lower) limit, you downshift, i.e., go to the next lower gear. Sometimes you might wish to downshift at a higher RPM because you want to aggressively pass other vehicles, but make sure that you know what you're doing---such downshifting can DESTROY YOUR ENGINE by taking it above the "red line." Even if your car has a governor, it will be unable to stop downshift-induced overreving, and the resulting destruction of your valves.

Note: Sometimes drivers downshift at higher RPMs and then promptly (but smoothly!) let off the gas pedal to "engine brake." The "engine brake" technique only slows the driven wheels. So, on a rear-wheel drive car, for example, "engine braking" behaves (in terms of dynamics) as if one is pulling the parking brake! In most cases one does not want asymmetrical braking, and the brake pedal provides the optimal slowing/stopping technique.

Recipe
Let's define some notation to save space:

G = gas pedal
C = clutch pedal
B = brake pedal
L = left foot
R = right foot
"R/G" is read, "right foot on gas."
"R\G" is read, "right foot off gas."

0. Context
You're driving with R/G. You decide to slow down, and gently take R\G, and then put R/B. As you brake, the RPMs of the car start to fall into the lower range of interest, and then you decide that it is time to downshift to the next lower gear. NOTE YOUR RIGHT FOOT WILL STILL BE ON THE BRAKE FOR ALL OF THE FOLLOWING STEPS (in most cases):

1. Setup
L goes on top of C, ready to press down, as your right hand leaves the wheel and grabs the shift lever.

2. Out of gear (shift into N)
At the same time: L/C, and you pull the shift lever into the "neutral" gear, N. Then, go (very fast) L\C. View this as having shifted into N.

3. Blip
(If you must wait for some reason before you wish to go into gear, at step #4, now is the time, at the start of step #3.) Stab the gas pedal----we'll explain how shortly---to run the engine RPMs up to slightly above the value that they will assume when you will be done with the shift. This "stabbing" of the pedal is just momentary---do it as fast as you can, on-then-off. (The moment that you blip, you must quickly move to the next step---if you fail, retry #3, or just move the clutch [up: L/C] slowly in step #4.) DO NOT TAKE YOUR FOOT OFF THE BRAKE IN ORDER TO GIVE THE GAS IN THIS STEP.

4. In to gear (shift out of N)
Go (very fast) L/C. Then, at the same time: L\C, and you push the shift lever into the lower gear. View this as having shifted from N into your final (lower) gear.

5. Cleanup
Put your hand back on the wheel, and put L on the "dead pedal" (footrest to the left of the clutch).

So, you realize that this can be thought of as shifting fully into neutral, stabbing the gas, and then shifting fully into the lower gear.

Incorrect downshifting, what you probably do now, is L/C, shift to the lower gear, and then L\C. To grow and improve, try #1-2-4-5 intil you do it without thinking. Then, go all the way, and try #1-2-3-4-5, which is a bit tougher.

If you want to drop (say) two gears in a row, go #1-2-3-4-wait-2-3-4-5 or #1-2-3-4-5-wait-1-2-3-4-5, depending on how long you're willing to keep your right hand off the wheel. Never initiate a downshift if the RPM value is too high, or you will destroy your engine.

If you do everything right, it will take you perhaps a second or two to drop one gear (from when your hands first leave and then return to the wheel), but take your time as you work up to speed. If you mess up the blip---and this is very common when you start to learn how to do this---you can retry step #3 repeatedly (i.e., go #1-2-3-3-3-3-4-5), or just take your time (several seconds) to let the clutch up slowly in step #4. However, if you do everything right, you can be very aggressive with clutch operation, and the car will feel perfectly smooth---after all, this is the goal. If you take too long between #3 and #4, the engine will lose the rotations that you gave with the blip, so the shift will be incorrect, and you must let the clutch up slowly (in step #4). If you don't blip enough, or wait too long between #3 and #4, you'll see the tachometer suddenly jump up as you release the clutch, which means that you have to keep working on good technique.

You should not have to ram anything into place with arm strength---when you get it right, you'll feel it, and a big grin will show up on your face. (Although after a while it might become old hat, I suppose.) This can be a very frustrating technique to learn, so don't try if you're tired or annoyed. I only say this for completeness, but you should clearly not hear any grinding noises, either!

Now I can address the gas issue in further detail. The recipe requires stabbing the gas pedal for a moment---how can one do that? There are all kinds of ways that are proposed to do this, and they all require R to manipulate G and B at the same time. In other words, R is solidly on B, and then it stabs G for a moment to provide the "blip." R never leaves B---it continues to brake, but somehow also hits G.

"Heel-Toe"
The most commonly suggested recipe is to brake with the entire ball of the foot, rotate the foot on the axis of brake pedal, hit the gas with the heel/side, and then rotate the entire foot back. Try this in a parking lot for a while with your car off and see if you can do it.

In short, B and G must be about under 2.5" away from each other, and when you brake hard B should still be above G.

Final pieces of advice...
THE BRAKE PRESSURE SHOULD NOT DIMINISH BECAUSE YOU BLIP---it is just that different parts of your foot provide the brake pressure for that moment that you have to stab the gas.

Downshifting is subtle to learn in terms of just how hard to stab the gas, but this will come to you in time. However, you must be EXTREMELY CAREFUL with how you apply the brake during the blip---don't let your foot slip off, or an accident could result.

After a while, your right foot will "memorize" what to do, and everything will be automatic. But as you first learn, be VERY careful, as this is an extremely dangerous time. Leave a huge following distance between you and other cars, or, better yet, only try it at very quiet times and initiate your stop well before that light, so you can recover from a huge mistake. Better yet, try it in an empty parking lot for a while. Ideally, you can help your foot memorize its operation by working the pedals in a parking lot, with the engine off. You can learn how to do this yourself, but BE VERY CAREFUL NOT TO LET YOUR FOOT SLIP OFF THE BRAKE.

[ 11-19-2002, 02:04 PM: Message edited by: RicePowered ]

Insert tab B to slot A then fold over flap C to intesect with slot D on flap E...

lol say what?!?!

a sliightly confusing but nonetheless correct provedure for double-clutch & heel-toe... good job RicePowered~!

Good post ricepowered. A good example on how to double-clutch. You've done your studying quite well.

That tends to happen yeah It's kind of funny to see someone try to race you when you're slowing down

hm.. i didn't know there was a name for this tech :)My dad taught me this trick. its more of a not making the car "rock" when downshift. Rather a smooth shifting. i usually use it on the hills here in san francisco. everything rice said was correct, but this can be done even faster. pushing the clutch down = shifting into N. so.. :
1) stay on the gear you are on until you want to down shift.
2) push down the clutch give it a bit of gas (u'll hear ure engine rev)
3) Downshift!
4) release clutch and GAS! (with practice you can just let the clutch go quickly and step on the gas right away)

wow that is easier

GREAT POST!!!!!!!!!!!

Has anyone actually tried this? At normal positons, the brake and gas pedal dont come out at equal lengths so it makes for heel-toe very difficult.

That downshifting technique explained above is basically "rev matching." Instead of taking the time to put it in neutral, rev, then put it in gear, I just step on clutch, rev, let off clutch... to me, it's faster...

how about speed shifting but this will burn your clutch pretty fast...

everytime you change gears dont release your gas just step on it, when you reach 5.5 RPMs step on the clutch and change gears quickly, you gotta be fast in doin this, thats why you have to reach 5.5 RPMs so everytime the rev goes 6.0 or 6.5 you have changed your gears already...

I dont see how that will be faster than just speed shifting at 8200

ummm thats my GT Steven, you can try it out on your GTS its fun, in fact you can squeel tires until 3rd gear doin a speed shift

DAHAHAHAHAHAH!!!!!!!

TROG-DOR!!!!

ohhhhhh yea... i was like, "what the heck is he talking about???"

i heel-toe everytime i slow down. the thing is when you actually have the brake pedal depressed, it is levelled with the gas pedal so you can blip.

Yup, Yup ... I'm really good at it It's no fun though if your not carving some corners.

heel-toe for corners

hmm, interesting. Time to start practicing

so what's the advantage of shift to N / blip /shift to gear
instead of just shift to gear (while blip) in one motion?

well, it's called double-clutching because you push the clutch in once to N and then again to gear.

just going from one gear to another is a revised technique...fine for use with today's transmissions.

plus N is used for incase your foot slips from the brake you don't send you car into a quick accel. either way works just as good once you learn the proper technique.

or you can go, UP UP DOWN DOWN LEFT RIGHT LEFT RIGHT THEN THE X BUTTON and RESET, this will add more traction on corners so you will get a good drift...

[ 04-24-2003, 08:32 PM: Message edited by: Street Prototype ]

I remember than code for Nintendo ... almost every game had a cheat with that

CONTRA!

up up down down left right left right break clutch shift gas to get 30 EXTRA HP!!!! (note: you only neet the shift in there if you have a passenger, otherwise, just hit gas) hahahah...

[ 04-24-2003, 09:56 PM: Message edited by: FX-MAN ]

the code !!!

"From David Lane:

Double clutching is really only useful for truck transmissions, which don't have synchromesh gearboxes, and is generally only used when downshifting.

I am not an expert on this, and it is complicated to explain without drawings or a working model, but I can probably give you a mostly accurate description of how it works. In theory, the transmission transmits power from the engine to the car's wheels and tires--we will call them the road wheels for short. In the simplest terms, the road wheels are connected to a single gear in the transmission. There are five gears of different sizes attached to the engine. Each time you upshift, a smaller diameter gear from the engine is meshed with the road wheel gear.

Now, since the road wheel gear can only turn at one rate of speed (depending on how fast you are going) the engine speed must change to accommodate the different gear ratios in the transmission. This is not unlike riding a multi-speed bike. If you go at 10 mph and switch gears, your legs will change speed while your road speed stays the same.

It would be damn difficult to change gears if the engine were always connected to the transmission. Fortunately, when you depress the clutch, the engine is disconnected from its gears. When you push the shifter to the next gear, there are "synchromesh rings" in front of the gear which matches the speed of the engine-driven gears to the speed of the road wheel gear--speeding the engine-driven gears up, or slowing them down as necessary. Once the synchromesh gets the two gears going at the same speed, the teeth will mesh and the shift is accomplished. Without synchromesh, if the two gears are not going at the same speed, the gear teeth will grind against each other, which is not good for the transmission. You have no synchromesh in reverse, which is why you have to be stopped to shift there. If you are rolling forward, the road wheel gear will be moving, and you will hear a grind.

Anyway, double clutching is a way to match the engine speed in a given gear to the road wheel speed, in a transmission without synchromesh. In a downshift, you depress the clutch and come into neutral. The engine needs to be going at higher rpms to accommodate the speed of the road wheel gear, so you let the clutch out (still in neutral)--which re-attaches the engine driven gears to the engine. Then you blip the throttle to increase the engine speed, which gets the engine-driven gears spinning faster, until they are going at the right speed to mesh with the road wheel gear. You push the clutch back in, and if you have done it right, the shifter will move easily into the lower gear. If you miss, you will hear a lot of grinding and probably a lot of cursing will come from your lips. Oh, well. That's why they have truck driver's school. Let the clutch out, and you are on your way.

As you can see, synchromesh makes the whole process much easier. When downshifting, you can hold the clutch in just once and blip the throttle, which will do some of the work for the synchromesh and make the mechanical parts last longer. If you are not exactly on target, the synchros will do the rest of the work for you.

Now you can see why upshifting does not require any fancy clutch work. When you upshift, the engine slows down between gears. It will do this anyway as soon as you take your foot off the accelerator and depress the clutch. If you pause for a moment in neutral, it will give the engine a chance to slow down enough to align the gears, and the stick will easily slip into the next higher gear.

If you are in a race, push harder on the stick and go directly from gear to gear. The synchros will match speeds for you.

In the broadest view, all we are talking about is smooth driving and saving some wear and tear on the synchromesh. There are a lot of old ladies out there who have never heard of any of this, and who's transmissions last a good long time. Performance drivers are much more likely to stress their cars, so they tend to find ways to make less work for the transmission if possible.

Here is an experiment for you. Go out on a road where you have some room. Put the car in third and go at about 3000 rpm. Maintain speed and see how fast the engine is going when you shift to forth. let's say it is about 2200 rpm. Now go back into third at 3000 and put a little pressure (one or two fingers) on the shifter toward neutral. Don't depress the clutch. Nudge the accelerator a little to remove the tension between gears, and the the stick will move out of gear, into neutral. Take your foot off the accelerator, and put a little pressure on the stick toward forth gear. When the engine rpm drops to 2200 rpm, the stick will probably slide into forth without you ever pressing on the clutch. If you miss, and the engine rpm drops below 2200, just give it a very little gas to get it back to that speed. When the engine speed matches the road wheel speed, it should drop into gear. That should illustrate how it works. Be real gentle with the shift lever, and you won't hurt anything. Push too hard, and you will hear a grind.

It is more difficult doing this trick going from forth to third, but all you have to do is use the accelerator to raise the engine speed while in neutral. Very few drivers know how to shift without the clutch, and I offer this description to you for your amusement and experimentation. Obviously I won't be responsible if you break something--although if you stay gentle with the shifter, the worst you may experience is a little, soft grinding sound. If you hear that, go back to neutral and either try again, or give up.

I had to learn this trick when I blew my clutch at an autocross, thirty miles away from home. It was my own fault, I lost track of how fast I was going and tried to downshift into first, which over-reved the engine and disintegrated the clutch friction surface. I actually drove the car home, matching gears, without ever using the clutch. I had to go real slow near stop lights, and once or twice I had to stop the car and start it in first gear to get going again. That was in the days before cars had to have the clutch pedal pressed in order to start them.

David Lane dlane@peabody.jhu.edu "

-sorry so long...

-all new cars have synchros, so its really not necessary to double clutch --> still looks cool though!

-BUT downshifting with revmatching and heel-toe is damn good enuf.

[ 04-27-2003, 02:51 AM: Message edited by: Jd ]