Friday, September 26, 2008

Double-Clutching down-shifting

Again i'm slacking off and no one's bothered anyway... >.> market is going south, there's hardly any activity... :-p haha... good for me, bad for the country though... X-p So here's another interesting article i found at written by the same writer :-) and i'd still go for the "racer's" technique of heel-toe... X-p because it's just so much more cooler... X-p haha...
Though this is just common knowledge among advanced drivers :-) it's always good to have a revision once in a while... X-)

"The Double-Declutching Gas-Blipping Downshift

The manual transmission was the best transmission that a car could have until 1989, when English driver Nigel Mansell won the Brazilian Grand Prix Formula 1 race with his SMG-equipped Ferrari. From the driver's perspective, the SMG, or "Sequential Manual Gearbox," is clutchless: Your right finger makes the car go up a gear, and your left finger makes the car go down a gear! A modern SMG, like BMW's "SMG II," shifts in about 80ms, less than a tenth of a second! No human is able to shift so fast.

Not to be confused with some automatic transmissions that have a similar user interface (the "tiptronic" from Porsche comes to mind), real SMGs can be found on the 2001 Ferrari 360 Modena ("F1") and the 2002 BMW M3, for example. Before long, the SMG will trickle down further, and the manual transmission will become the second-best choice for many street cars, certainly at the high-end.

And if this was not bad enough, both the manual and the SMG are going to be ultimately replaced by the CVT, or "Continuously Variable Transmission," which behaves as if it has infinite gears, with a computer constantly adjusting them for optimal power delivery! (In other words, even the little up/down buttons of the SMG will become totally irrelevant.)

So, what is to be gained on your part by lots of frustrating practice to learn proper downshifting for the obsolete manual transmission? "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!
  • 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
  • other people will hear the blip and think you want to race them
We'll break the recipe for downshifting into steps after a brief introduction.
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.


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, but there is one wonderful exception that Daniel Eberli points out to me (via email): When one lives in Switzerland and is descending alpine roads, even the very best brakes can get very hot and fail... and in cases like this one should certainly downshift for "engine braking" well before their brakes fail from overheating!


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. In the case of dropping multiple gears, it seems that real racers prefer to go #1-2-wait-3-4-5, shifting directly into the final gear, but you'll have to read their books yourself to see what you really wish to do in this case. Remember, skipping gears invites over-revving, which can destroy the car, but their incredible training keeps them from making mistakes---you're better off experimenting with skipping gears later when you really know what you're doing.

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!

Stabbing the Gas: Athletic issues with the right foot
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.

There are many methods (called "heel-toe") to describe how various experts do this trick. I've never been able to make any of their tricks work, but my trick is extremely simple, and it works quite well, but only in street cars. So, check out the way that I do it, the way that they do it, and try to figure out what is best for you. I describe both methods here, but be sure to check out the literature on racing and your friends who drive for advice.

"Heel-Toe," what most experts suggest

If you're driving a state-of-the-art technological masterpiece like a F1 car, apparently you use the left foot exclusively for the brake, the right foot exclusively for the gas, and index fingers to shift, and gas blipping is totally irrelevant! However, most racers still have a manual transmission, only because of their lack of money. Therefore, gas blipping is still relevant for many racers, at least for a few more years.

Real race cars don't have power-boosted braking, and they tend to use their brakes with extreme pressure---what most civilians like me would view as a "panic emergency stop," in terms of the sensation. So, they have to brake with the ball of their foot, i.e., the area under the toes is firmly pressing the pedal.

The most commonly suggested recipe from professional drivers 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, but I find this to be quite dangerous---I've had my foot repeatedly slip off the brake! Try this in a parking lot for a while with your car off and see if you can do it... I can't.

"My" Technique
Unlike the race car, the street car has power-assisted brakes with ABS (Anti-lock Braking System), since it even has to work for small and weak customers. This means that you do not have to press nearly as hard to get the brakes to fully lock, where the ABS decides to turn on and stop you at maximum speed.

Therefore, unlike the racers, it is probably not necessary, at least for a person of my leg strength or greater, to need much leverage to maximize brake pressure. So, I take full advantage of this fact, and am willing to blip in a way that will not work in an inexpensive (non-SMG) race car.

If your car is not set up properly, somebody else's technique must be used. 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. If this is not the case, what I'm about to propose will not work, and don't even try it.

I plant the heel of my foot on a point midway between B and G, and it never moves when I drive. This is a very comfortable position for me, since the foot can rest to the right and operate G, but a slight movement of the toes will put the left half of my foot over the brake. So, I brake with the left half of my foot. BE VERY CAREFUL BRAKING WITH JUST THE LEFT HALF OF YOUR FOOT. I am strong enough to easily provide maximum pressure needed to stop the car, but my car has power-assisted braking. If this is not the case for you, forget about it!

In fact, this is so dangerous at first that you should take it very easy and practice FAR AWAY from anything that you might hit.

Brake with the left half of the right foot, keeping the weight on the big toe's base, and slightly lifting the little toe. If you don't lift the little toe, sometimes you might accidentally be giving the car gas while you're trying to brake---something somewhat counterproductive, to put it mildly. When it comes time to "stab" the gas pedal, "roll" your foot to the side, so the contact area on the brake goes from just your big toe, to perhaps half of your toes, and then just the middle line of your shoe---the small toe at this point will be stabbing the gas. Then, the foot rolls back, returning braking pressure to the big toe. (You might want to move your knee to the right and back to reduce pressure on it.)

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."

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