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Useful Notes / Driving Stick

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This tasty and delicious Useful Notes experience will be a primer for the uninitiated who wish to learn to... well... drive stick. Don't be alarmed by the length of this article; you can stop reading anytime you like. This article includes some background information that assists the understanding of the system, hence its length. Your time will not be wasted.

In a nutshell

  • The gear lever is used to select 4-6 forward gears and a reverse gear. If no gear is selected, the car is in neutral.
  • When pushed down, the clutch pedal (on the left) disengages the engine from the drive shaft. You use it for two things:
    • In any situation when a gear is selected, the engine is turning and the car is stopping/stopped, otherwise the engine will stall.
    • Whenever you are changing between gears.
  • To get the car moving, you press in the clutch, get the car in gear, release the brakes (if necessary) and then slowly release the clutch. Unless you only want to move slowly, you give the car gas as you release the clutch. Releasing the clutch too quickly stalls the car.
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  • Lower gears give you more control over the speed of the car. Normally, you use first gear to get the car moving from stationary.
  • Higher gears allow for smoother and more economical driving at higher speeds.

Now we can begin

Before we get to the How in question, we should touch on the Why. Why do we have to shift at all? Most road vehicles are powered by internal combustion engines (be it gas, diesel, biodiesel, ethanol, gas and ethanol, or liquid natural gas). These engines create rotating power by squeezing a mixture of fuel and air, then exploding it. The mechanical assembly of the engine uses the energy released in this explosion to create a rotating motion. To make a vehicle go down the road, we power the wheels with this rotating motion.

However, there are a couple limitations that these engines have. They have a minimum operating speed; that is to say, if you slow down the rotation of an engine below a certain speed, it can't sustainably create the circumstances for creating explosions, so it peters out and stalls. Also, the engine has to be made of materials, and designed and manufactured with an eye to making a profit by the manufacturer. Engines are generally extremely robust if you use them for their intended purpose, but if you rev them up too fast, there will be a failure. As engine speed increases, the loads on internal engine parts increase dramatically, so there's a restriction on engine speed on the tachometer denoted by a red line. The driver is supposed to keep the engine speed below this speed to prevent failure. The restriction is sometimes built in to the fuel or ignition systems of the car too; if you try to over-rev, the car may not let you.
Fig. 1: The redline.
The speed at which this happens if called the Redline.

So! We can't have an engine spinning really slowly, and we can't have an engine spin too fast. What we're left with is an operating range, usually between 1500 rpm (rotations per minute) or so up to 5500+ rpm on the high end of things. Diesels and high displacement gas engines tend to rev lower, small displacement and racing engines rev higher. Most engines idle at lower speed than where they can produce usable power. We can use this rev range to accelerate or decelerate our vehicle. If we connect an engine straight to the drive wheel, the wheel note  can spin anywhere from 102-376 mph. This is absurd, so we put a gear ratio note  to slow everything down proportionally. Now, we can move between 7 and 25 mph.

However, we still need to get from a stop to 7mph, and to slow down to a stop once we get to our destination. Below 7mph, the engine will stall. When we try to brake, the brakes will be slowing down the wheels while the engine will be accelerating them. If the brakes win, we'll come to a juddering halt when we cross below 7mph. When we try to start the engine, we'll have to push the car to 7mph before the engine can take over, which is pretty tiring and potentially messy if we slip and fall. What we need is a way to separate the engine from the wheels while we do these things, but then reconnect them later.
Standard pedal configuration for manual cars.
This is what the clutch does. When you push the clutch pedal, it disengages the engine from the wheels, so you can do whatever you need to do without affecting the engine. The engine will drop to idle unless you use the accelerator pedal. You can have the engine running while the car's stopped, or you can shut off the engine while the car's doing 70, as long as the clutch pedal is pushed in, which disengages the engine.

Clutches do the same thing your brakes do, but in a different way. The brakes are stationary (don't move with respect to the car), and squeeze against the brake rotor (flat frisbee attached to the spinning wheel) until the rotor matches the speed of the brake (stopped). The clutch spins at the speed of the wheels, and squeezes against the flywheel (a disc on the end of the engine, spinning at engine speed) until the engine and the wheels are turning at the same speed. Matching up the speeds is done with friction between the (brake and rotor)/(clutch and flywheel), which causes wear on replaceable material (brake pads/clutch material). Since the clutch allows us to make slightly different speeds work, we can use clutch friction to accelerate the car from a stop to our example 7 mph.

To accelerate without the engine fully engaged, we turn the engine on with the clutch pushed in, then gradually release the clutch, while helping the engine with a little gas. That's in bold because we'll come back to it later. Here's an exercise that can illustrate how this works:

Fundamental Experiments (basis for understanding):

     Experiment 1 
Get in your car, turn it on, and clutch in while you put it in first. with your right foot flat on the floor and touching no pedals, release the clutch as fast as you can. The car will lurch, then stall. Go and try it before continuing.
     What happened? 
The engine was idling, then suddenly dropping the clutch meant that the engine either had to instantaneously accelerate the car to its minimum operating speed for first gear (7mph in our example), or stall (0 RPM). Since the clutch is not pushed in, the engine's directly connected to the wheels, so the car's either rolling fast enough to support the engine, or the engine will stall, stopping the car.
     Experiment 2 
This time, get the car started again and in first, but release the clutch pedal extremely slowly. We're talking like 20 seconds here. Very gradual, but consistent motion.
     What happened? 
The car began to move very slowly, but eventually the engine powered the car enough to get it moving and fully in gear. Hooray, we're in gear, and we can drive up to 20 mph or so! To stop, push the clutch in before you brake, or you'll fight the engine and then stall. If you tried this and stalled, do it again, but release the clutch slower. What have we learned? We can use the "friction zone" of the clutch to transition between speeds if we need to. This technique is called "feathering" the clutch.
     Experiment 3 
Now, we're going to release the pedal extremely fast again, but we're going to use the engine to overcome stalling! This one's important to do in an empty parking lot with no police around. With the clutch pushed in, floor the accelerator until the engine's about 3/4 of the way to redline. Then, release the clutch as fast as you can while holding down the gas. Stop with the gas when you want to.
     What happened? 
If you're in most cars, you just performed a burnout. The engine was making a ton of power, so it overcame either the car's inertia or the tire's friction when you dumped the clutch. Likely, it spun the wheels. Eventually, if you do this a lot, you'll be able to modulate the gas pedal until the tires "hook up" with the road and you merely accelerate after burning out. Control with the gas will end burnouts, but so will pressing the clutch in again. What did we learn here? The engine is powerful, and can help us with starting from a stop.

So, if we're too fast on the clutch with no gas to help the engine, it bogs down and stalls. If we're gradual on the clutch, the engine can keep up with the load, and eventually we can get into gear even without help from the gas pedal. If there's too much help from the accelerator and the clutch is fast, you can burn out. If we combine all these ideas, the best way to start the car from zero is to gradually move the clutch pedal while giving a little help with the accelerator. The quicker you transition, the more gas you'll need. Once you're in gear, don't touch the clutch pedal unless you want to change gear or stop. Remember the shot of Marty McFly stomping on the brake and clutch in Back to the Future? That's how you brake if you're not going to stay in gear. Another note is that whenever you're feathering the clutch, you're causing wear on the materials, which adds up over time. Clutches are made to be worn, but if you develop bad habits, you'll need to do so more often.

We can roll! Now what?:

Most cars have a first gear that works between about 5 and about 15-20 mph. Different engines have different characteristics, and differences in transmissions exist too, so a different car model will be slightly different. Anyway, what do we do when we want to go faster than 20 mph? We can change our gear ratio, but that means our car won't be in gear until a higher speed, which means there will be a lot of wear on the clutch, which gets expensive. Why not have a box in between the clutch and the wheels that lets us choose between several different gear ratios? We can have a set for starting and operating 5-20 mph, then another for 15-35, and another for 30-55, and another for 50-90. Each ratio will allow us to use our engine, with all its limitations, to drive the vehicle in diverse circumstances. This gear ratio picking is what a transmission does. 5-20 is first, 15-35 is 2nd, and so on. There's overlap between gears so you have a buffer where you can choose to shift.

I'll post some pictures I took at the same car speed (recalling Back to the Future) so you can see the relationship between gears and engine speed.
4th gear at 88 mph
Engine speed (tachometer) is the gauge, and wheel speed is the digital number (in MPH).
Same car speed in 5th. A higher gear gives lower engine speed at the same car speed.
6th gear, engine RPM better suited for cruising, but poorer for acceleration.
I could have taken another pic in 3rd, but I didn't want to sit at the redline for so long. Note that my car has a very high redline (9,000 RPM) because it's special. These pictures were taken for the recently-observed McFly Day,the day when Marty traveled to the future and hoverboarded. Note that my car is special; your car likely cruises at lower RPM. Also, not at 88 MPH.

How does shifting work? Since we're changing the relationship between the wheel speed and the engine speed, we should use the clutch to separate them. Then, move the shifter from the gear you're in through neutral and into your desired gear. Neutral is the horizontal slot in the shift pattern; put the shifter there, and your wheels are disconnected from the engine as surely as if you were clutching. This separation happens inside the transmission, so you can still clutch if you want to. Anyhow, with the clutch depressed, move the shifter into your desired gear. Release the clutch. If the engine was spinning at a different speed than it needs to be to match this gear and wheel speed, you may notice the car suddenly slowing down or speeding up while your car's wheels accelerate your engine using the clutch. This lurch is the hallmark of a new driver, and will go away when you get a sense for the engine speed you'll need when you release the clutch, and match the revs with the accelerator while you're shifting. note  In this way, you can put it in neutral, change speed with the brakes, and still know roughly what RPM you'll want for a given gear. This comes with practice. You'll hit a point where you don't need the tachometer, you can tell what you need from listening to the engine, and it'll happen subconsciously.

Another note about neutral is that it's better for the car than holding down the clutch for long periods of time. If you're at a traffic light, put it in neutral and let go of the clutch. For starters, this means you can rest your foot and not have to worry about releasing the pedal by accident. But it also saves wear on a component called the throwout bearing, which is designed to survive as long as the clutch does, and should be replaced at the same time.

Where is first?:
6-speed shifter with shift pattern.
I suppose mentioning shift patterns is in order. The pattern from 1st to 2nd to 3rd and so on has been pretty much standardized, and can be seen on the right. You can shift from any gear to any other, but be careful, because if you're driving fast and shift to a low gear, it could over-rev your engine. Also, don't shift into Reverse if you're moving forward. The position of reverse varies widely; sometimes it's next to first, or fifth, or sixth. Newer cars have an interlock built in so you don't accidentally shift into reverse. You may have to push or pull the shifter up or down, or perhaps push or pull a ring below the shifter. Your owner's manual can tell you what to do. Generally, you shift in order until you've reached your desired speed, then you decelerate and either shift down on the way down (revving to match engine speed), or just hold it in neutral until you're at the right speed, then revmatch and engage the proper gear. If you're always in gear when you're slowing down, the engine will help you slow down; this is more pronounced than in automatic cars.

If you shift at a low RPM, it's generally more economical, but less powerful, so you accelerate slowly. This can be frustrating for newer drivers who think their car should be powerful; if they're in a high gear and flooring the accelerator, they still pick up speed slowly because they're not in the engine's power band.
A generalized label of tach ranges. Your car likely has a lower redline, but the rest will likely be correct. Note that the Mazda RX-8 (this car) actually needs more RPMs for cruising.
However, if you're not trying to accelerate rapidly, using half or less of the accelerator, low-RPM shifting is economical and easy on your engine. This is called "short shifting." Note that EXTREMELY short shifting (below, say, 2000 RPM) is bad for fuel economy for the same reason the engine can stall: it's trying too hard to make (some) power at a speed that can't support it. If you wait to shift until a higher RPM, you have access to more power from the engine, but you're using more fuel to stay at higher engine speeds. If you're accelerating gradually, there's no reason to use the top end of your rev range. If you're accelerating hard, you want to stay in the top end for maximum performance. Race car engines and the like tend to have exotic or performance materials and designs, so they can bear a higher redline, enabling later shifts.

Advanced Techniques:

     Double Clutching 
Double clutching is a technique that was necessary on anything considered 'classic' now, and is a practice that still has benefits for newer cars. When the shifter goes to engage a new gear (while you're clutching), transmission internals need to bring the shaft of the transmission that spins with the clutch (and with the engine, when it's connected) up to speed for the new gear ratio. *Note: There's 2 shafts in the transmission: one that's connected to the clutch/engine, and one that's connected to the wheels. Putting the transmission into neutral disconnects these shafts; we need to spin them together again.* This is the same idea as the engine being brought to speed when you let off the clutch in a new gear. Modern transmissions have what's called "synchromesh" technology, which is essentially little clutches, or "synchroes," for each gear. You push the shifter in gradually, and the synchro uses friction to match the shaft speeds. Older cars didn't have synchromesh, and trying to shift when the shaft speeds were different led to grinding (and gnashing of teeth), so the proper shifting procedure was to:
  • clutch in, shift to neutral, clutch out.
    • Now your transmission is at the right speed with the wheels, and the engine side of the transmission is at engine speed.
  • Rev match
    • so that the engine is at approximately the right speed for the new gear.
  • Clutch in and shift into the new gear, clutch out.
    • The clutch-side shaft and the wheel-side shaft in the transmission are spinning at approximately the same speed, so the new gear engages without grinding.

In cars with synchromesh, double-clutching isn't necessary, but it's still best practice, since it reinforces rev-matching and extends the life of your synchroes. Also, it's a great way to prepare yourself for heel-toe downshifting. Once you can double-clutch and revmatch pretty well, you're ready.

     Heel and toe downshifting 
Here is some stuff about heel and toe
     Transfer cases 
Transfer cases are, broadly speaking, a part of the drivetrain in full-time and part-time 4WD vehicles, like pickup trucks and SUVs. The idea behind them is that they transmit power from the transmission to more than one axle of the vehicle (for example: both front and rear, instead of just rear). Like a car's transmission, they be automatic or manually operated. In the case of the latter, there will often be a secondary lever next to the vehicle's gearshift stick, which allows the driver to select a driving mode for the transfer case.

In the vast majority of vehicles with a transfer case, the driver will be able to use the transfer case lever to select 4 possible positions:

  • 2H - 2-wheel drive, high range. This is the "standard" operating mode for the vehicle. Only two wheels (usually the rear) receive power from the transmission and drive the vehicle. This results in the greatest fuel economy and reduces wear and tear on the drivetrain, as the parts which power the front wheels are not in use.
  • 4H - 4-wheel drive, high range. Selecting this position engages the transfer case via a chain, hydraulics, or gears, and allows it to send power to both the front and rear wheels. This results in greater traction in slippery driving conditions (light snow, loose gravel, or dirt roads), but increases fuel consumption and wear on the vehicle.
  • N - This disengages the transmission entirely from the wheels, much like Neutral in a manual transmission. It's generally not used, except when shifting on to...
  • 4L - 4-wheel drive, low range. This puts the transfer case in a lower gear, which allows the vehicle to operate at much slower speeds while still utilizing the available power of the engine. In the example above, first gear was not usable in the vehicle until it was traveling at 7 mph. A low range gear reduction in the transfer case would allow first gear to be used at a much lower speed—perhaps 2 or 3 mph. This reduction is across the board for all gears, so it accordingly drastically reduces the functional top speed of the vehicle. It is therefore only useful in situations where extremely low speeds are desired, such as offroading or driving in snow.


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