Engine 101

Terminology

• Brakes
  • Anti-lock Braking System (ABS)
    Braking systems which sense wheel rotation and automatically “pump” the brakes for the driver in emergency braking conditions. The pumping and the prevention of wheel lockup allow the driver to retain steering capabilities during the braking emergency. Anyone purchasing a vehicle with such a system would be well advised to insist on the dealership demonstrating the proper use and maintenance of it. Most of these systems work when the driver applies heavy, constant braking pressure, and do not work properly if the driver “pumps” the brakes as he may have been previously taught.
  • Brake Caliper
    A hydraulic (liquid-pressured) piston assembly that holds disc-brake pads.
  • Brake Pad
    Used in a disc system, it is a replaceable piece of backing plate and additional friction lining. The disc, a thick, round metal plate located behind each wheel, against which a set of brake pads are applied by a caliper during braking.
  • Brake Rotor
    Shiny metal disk that brake pads squeeze to stop the vehicle; hence the name disc brakes.
  • Disc Brakes
    Shiny metal discs, called brake rotors, are attached to the wheel hub, rotating with the wheel. When the brake pedal is depressed, the brake calipers squeeze the discs to slow the vehicle. See Brake Caliper and Brake Rotor. Diameter given in millimeters.
• Suspension
  • Independent Suspension
    A suspension design that lets each wheel move up and down independently of the others. A vehicle can have two-wheel or four-wheel independent suspension; sportier models have four-wheel independent suspension. See also Multi-Link Suspension, Live Axle.
  • Shock Absorber
    A device that converts motion into heat, usually by forcing oil through small internal passages in a tubular housing. Used primarily to dampen suspension oscillations, shock absorbers respond to motion; their effects, therefore, are most obvious in transient maneuvers.
  • Strut
    A single, self-contained pivoting suspension unit that integrates a coil spring with a shock absorber. Struts are used on front-wheel drive automobiles. A suspension element in which a reinforced shock absorber is used as one of the wheels locating members, typically by solidly bolting the wheel hub to the bottom end of the strut.
• Transmission/Drivetrain
  • Drivetrain
    Vehicle components which act together to move the vehicle forward or backward. On a rear-drive vehicle, it is the combination of the engine, transmission, differential and drive shaft. On a front-drive vehicle, it consists of the engine, transaxle and drive axles.
  • Driveshaft
    A long metal cylinder located between the transmission and the rear axle, in front-engine rear-wheel drive vehicles. The shaft is connected to the components on each end with a universal joint, which allows for movement up and down without bending the shaft.
  • Clutch
    This drivetrain component is found between the engine and the transmission. It acts as a coupling device which is used to engage and disengage the transmission from the engine when shifting gears. It is necessary to do this joining and detaching because the engine is turning at a relatively high rate (thousands of revolutions per minute), and attempting to alter a gear ratio at this point could send various bits of transmission shrapnel careening about the occupant compartment.
  • Clutch Disk
    Presses against the transmission flywheel to transfer power from the engine to the transmission.
  • Flywheel
    A large disc bolted to the rear end of the crankshaft. The flywheel is encircled by a ring gear whose teeth are designed to mesh with the pinion gear in the starter during the process of starting the engine.
  • Limited-Slip Differential
    A device that helps prevent the drive wheels from skidding or losing traction by diverting power from the slipping wheel to the opposite wheel on the same axle.
• Exhaust/Emissions
  • Catalytic Converter
    A component of the exhaust system that creates a heat-producing chemical reaction to convert potentially harmful combustion byproducts into carbon dioxide and water.
  • Muffler
    A chamber in the engine exhaust system used to suppress exhaust noise and smooth exhaust pulsations. Also referred to as a “silencer.” Motorbike and moped owners sometimes remove these to beef-up their sound.
• Engine
  • Fan Belt
    Transmits power from a crankshaft-driven pulley to an engine fan and other accessories.
  • Fuel Injector
    Taking the place of carburetors in the 1980s, the fuel injector is an electrically controlled valve that delivers a precise amount of pressurized fuel into each combustion chamber.
  • Horsepower (hp, bhp)
    Abbreviated as hp, as in 200-hp engine, or bhp (brake horsepower or net horsepower) to designate power produced by an engine. In general, the higher the horsepower, the higher the vehicle’s top speed. One horsepower is the power needed to lift a 550-pound weight one foot in one second.
  • Octane
    The hydrocarbon substance in gasoline that reduces engine knock or pinging, which is a noise caused by premature ignition of fuel in the cylinder combustion chamber. The higher the octane number, the less chance of premature ignition. High octane, which has a rating above 91, is useful only when recommended by the manufacturer.
  • Spark Plug
    Converts voltage into an arc that passes between its electrodes; the arc ignites the fuel-air mixture in the combustion chamber. The mixture explodes, creating power by pushing down the piston.
  • Starter
    An electric motor used to initiate movement of internal engine parts so that combustion can begin. Activating the starter causes the solenoid to thrust the pinion gear in the starter against the engine flywheel ring gear and begin turning it.
  • Torque
    A measure of twisting force, given in foot-pounds (abbreviated as lb.-ft.) or Newton-meters (N-m). In the case of an automobile, it is the twisting or rotational force the engine exerts on the crankshaft. Vehicle specifications often include the maximum torque an engine produces at a specific number of revolutions. An engine that produces 200 lb.-ft. of torque at 3,000 revolutions per minute, or 200 lb.-ft. at 3,000 rpm, accelerates better at low speeds than an engine that provides 200 lb.-ft. at 5,000 rpm.
  • Turbocharger
    Device that compresses and forces extra air into the intake manifold to produce extra power. Both turbochargers and superchargers are used to produce more power without increasing engine displacement, but neither are particularly fuel efficient and both can require costly maintenance as vehicles age. By forcing fuel through the engine, this system allows the car to gather more speed. Usually they’re made by specialist component makers like Roots, X-Trac, Bosch, etc.
  • Supercharger
    Serves the same function as a turbocharger but avoids lag time because it runs off an engine-driven pump. Both turbochargers and superchargers are used to produce more power without increasing engine displacement, but neither are particularly fuel efficient and both can require costly maintenance as vehicles age. A standard piece of equipment of Hotrods and Top Fuel dragsters, this provides more power by blowing a combination of more air and vaporized fuel into the car’s engine.
  • V-Type Engine
    In a V-6, V-8 or V-12 engine, the cylinders are divided into two banks, each of which is angled away from the other at the top, forming a ‘V’. Typically, this angle is 60 degrees on V-6 engines and 90 degrees on V-8 engines. From the rear, they are identified by having twin exhaust pipes, and by ear have a deep rumble engine sound.
• Safety
  • Side Airbag
    An inflatable cushion that fills the space between the door and the occupant to prevent head, torso and pelvis injuries when a vehicle is hit from the side. Side airbags may be stored in the door-trim panel or the outboard side of the seat; they may protect the hip and torso only or also protect the head. A new design, called an inflatable tubular restraint, is stored in the edge of the roof headliner and attached at the base of the A-pillar at the front end and above the doors along the roofline at the other. The device inflates into a somewhat stiff tube that prevents the occupant’s head from hitting the side pillar or the window.
  • Side-Impact
    Safety regulations require that vehicles absorb a certain amount of force when hit from the side. To meet side-impact standards, automakers have stiffened side-impact beams, which resist intrusion into the passenger compartment, and added safety devices such as side airbags and extra padding, which are designed to push the occupant toward the interior of the vehicle and away from the point of intrusion.
• General
  • Hybrid
    Vehicle that uses a combination of gasoline and electricity for motive power, so as increase efficiency and thereby reduce emissions.
  • Vehicle Identification Number (VIN)
    A 17 digit identification number, unique to each vehicle, which includes codes for the manufacturer, year, model, body and engine specifications.