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What Does That Do? | |
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 Ten Simple Things to Know About When to Do What
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ALTERNATOR. Since autos cannot have power cords, this device is provided to generate electricity on-board. The electricity is used to fire the SPARK PLUGS, charge the battery and to run various accessories. Alternators used to be called generators. A belt from a pulley on the engine drives the alternator which converts this mechanical energy into electrical energy.
COMPRESSION. The explosions that ultimately drive the car occur in the engine’s CYLINDERS because the piston squeezes the mixture of fuel and air to a point where it is highly combustible. Basically oxygen is concentrated this way to make the explosion of the fuel very powerful. If the PISTONS don’t seal to the cylinder walls tightly, air leaks out and compression is said to be low. Low compression means low power from the engine.
COOLANT. The water-antifreeze mixture that carries waste heat from the engine to the RADIATOR.
CV JOINTS AND BOOTS. In front wheel drive vehicles, it’s necessary to transmit power to the front wheels as they are turned from side to side by the steering mechanism. Also, as the vehicle makes turns, the wheels on either side must turn at different speeds while still transmitting power. CV joints are the mechanical couplings that allow this to happen. The boots are accordion-like pleated, rubber covers that prevent the CV joints from being exposed to weather and keep them lubricated. (CV stands for Constant Velocity.)
CYLINDER. This is a hole in the engine block in which the PISTON rides up in down. The engine’s powerful explosions take place at the top of the cylinder. The VALVES let fuel and air into the top of the cylinder, and let exhaust waste products out. Engines typically have from four to eight cylinders.
DISTRIBUTOR. This is the device that decides which SPARK PLUG is going to be fired, and when. It’s driven by a shaft from the engine and is essentially a rotating switch. The rotor is the part of the distributor that revolves to sequentially make contact with each spark plug, and the cap is the part of the distributor that holds those contacts.
DRIVE TRAIN. The components that cause the wheels to turn. This includes, the TRANSMISSION, drive shaft and differential (for rear wheel drive vehicles), CV JOINTS, etc. Some people would include the engine itself in this definition.
FIREWALL. The sheet metal barrier between the engine compartment and the passenger compartment.
HYDROPLANING. Also know as aquaplaning. If the tires aren’t able to shed water quickly enough, they will actually drive right up onto a film of water. This results in low friction between the tires and the pavement with potentially unamusing results.
LIFTERS. The VALVES are apt to get out of adjustment since they live in a very harsh environment of explosions, exhaust crud and so on. These devices are used to provide automatic adjustment to them as they wear and operating conditions change. It’s a small piston-like gadget that gets its power from the engine oil pressure.
MASTER CYLINDER. This is the device that holds a reservoir of brake fluid and forces it into the brakes when the brake pedal is stepped on.
OXYGEN SENSOR. This tells the engine management computer how the combustion process is going.
PISTON. This is a cylindrical-shaped device that rides up and down in a cylindrical hole in the engine block, called of all things, the CYLINDER. It is very tightly fitted to the cylinder walls so that not even air can leak past, but it still can move. There is one piston for each cylinder. The fuel-air mixture is guided into the space in the cylinder above the piston where it’s exploded by the SPARK PLUG. The explosion causes the piston to be pushed down with great force generating the power that moves the vehicle. A rod connects the bottom of the piston to the output shaft of the engine in such a way that the up and down motion of the piston causes rotation of the output shaft. This energy provided by the piston to this shaft is what causes the car’s wheels to go ‘round. The term piston may also be used to express how you feel after, for example, paying your taxes.
RADIATOR. The explosions in the engine CYLINDERS generate a lot of heat, but frankly not much light. A network of holes and channels is molded into the engine block and water is run through them to carry away this heat. The water is then run through a series of fine tubes and channels at the front of the engine where the wind caused by the forward motion of the vehicle, and/or the fan cools it. The series of fine tubes and channels constitute the radiator.
SHOCK ABSORBERS / STRUTS. These limit the bouncing of the vehicle by dissipating some of the energy of the motion as heat. They use a piston traveling in a liquid contained in a long narrow cylinder to do that. A strut is similar to a shock absorber, but also includes a spring as part of the assembly.
SPARK PLUG. When the PISTON is at the top of the CYLINDER and the mixture of fuel and air has been compressed to an explosive combination, the spark plug is fired to trigger the explosion. A spark plug may be thought of as simply an open gap in a wire to which a high voltage (20,000 to 30,000 volts) is applied. The high voltage jumps the gap and creates a spark. Making the “gapped wire” into a screw-in component allows the “wire” to be easily changed and is what we call a spark plug.
TIMING BELT OR CHAIN. Engine operation is kind of like a chain reaction. Each individual explosion in a CYLINDER provides the energy to set up the next one. However, all these phenomena must occur at exactly the right instant, otherwise there will be chaos. The timing belt links together all the various elements like a big gear, so that they all move in synchronism.
TRANSMISSION. The engine always turns in the same direction and at a fairly high rate of speed. Also, it needs to keep turning even if the vehicle is stopped. Engines are also most efficient over only a particular range of RPM’s. The solution is a complex set of gears that are used to change the engine’s RPM to one more suitable for the tires over a broad range of travel speeds. The gears also reverse the direction of the power to permit backing up, and disconnect the engine from the wheels when the car is stopped.
VALVES. These are the devices that: 1) open to let the fuel and air into the CYLINDERS, 2) close to let the mixture be compressed by the PISTON and then explode, and 3) open to let the waste products of combustion out the exhaust. There is at least one valve per cylinder to let things in, and at least one valve per cylinder to let things out. Many engines use an array of smaller valves on each cylinder to get stuff in and out more efficiently.
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