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Glossary of Terms

Aftermarket Parts
Auto parts made by companies other than the original equipment manufacturer (OEM) and which are used for replacing or repairing autos. Aftermarket parts are generally less expensive than OEM parts. It’s often alleged that such parts are inferior in quality compared to OEM parts.

Air-Fuel Ratio (AFR)
The AFR is related to mixture of air and fuel. The AFR is important measure for anti-pollution and engine performance reasons. Furthermore, the vehicles Engine Control Unit must know the AFR at all time so exactly all the available oxygen is used to burn the fuel completely or at least to the best possible value. This ratio is called stoichiometric AFR.

Automotive Service Excellence (ASE)
Refers to the National Institute for Automotive Service Excellence. The institute is an independent organization that tests and certifies automotive technicians.

Body Control Module (BCM)
In automotive electronics, body control module or ‘body computer’ is a generic term for an electronic control unit responsible for monitoring and controlling various electronic accessories in a vehicle’s body.

Cam
Part of the mechanism that opens and closes the valves.

Carbon Dioxide
A naturally occurring “greenhouse gas” that is also a byproduct of the combustion of fossil fuels and that consists of two oxygen atoms bonded to a single carbon atom.

Carbon Footprint
A measure of a vehicles total consumption of natural resources weighed against the Earths ability to regenerate those resources.

Carbon Monoxide
A “greenhouse gas” that is a byproduct of the combustion of fossil fuels and that consists of a single carbon atom bonded to a single oxygen atom.

Carburetor
A device used on older internal combustion gasoline engines that is mounted on the engine’s intake manifold and supplies fuel to the engine.

Catalytic Converter
A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction).

Charcoal Canister
A device that captures raw fuel vapors (hydrocarbons) from the vehicles fuel tank and carburetor bowl before they can escape into the air.

Choke Linkage
On a carbureted engine, the assembly of parts that controls a valve that limits incoming cold air until the engine reaches operating temperature and is able to more efficiently vaporize fuel.

Crankcase
Engines consist of three major elements: the cylinders in which the pistons move; the cylinder head where the fuel/air combination enters, where combustion occurs, and where the burned gasses are vented off; and the crankcase which houses the crankshaft and usually the oil supply. The crankcase is usually the major (largest) part of the engine and is also referred to as the (engine) block.

Crankcase Breather
A ventilation system or device that allows excessive crankcase pressure to escape.

Crankcase Depression Regulator Valve
A valve that prevents excess pressure from building in the crankcase (which could lead to oil leakage past the seals).

Crankcase Ventilation Filter
Also known as the “CCV.” A filter that prevents foreign particles from entering the crankcase.

Diesel Engine
A vehicle with an engine that uses diesel fuel and compression ignition.

Distributor Cap
The nonconductive cap of the distributor that contains the contacts leading to each individual spark plug.

Distributor Rotor
The rotating, nonconductive component of a distributor that contains contacts and that, when aligned, complete an electrical circuit between the ignition coil and a spark plug.

Diverter Valve
On an engine equipped with an air pump, a valve activated during deceleration that allows air from the air pump into the intake to dilute the air/fuel mixture (in an attempt to reduce emissions).

EGR System
Exhaust Gas Recirculation system. A device that redirects a small amount of exhaust to the engine intake in an effort to lower combustion temperature and reduce the emission of nitrogen oxide.

Emissions
Emissions are chemicals in exhaust gases that are harmful to air quality, mainly carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NO). Healthy engines produce fewer of emissions, and older or “unhealthy” engines produce more. Some engine designs–like rotary engines, for example–produce more of certain emissions than others.

Engine Control Unit (ECU)
An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance.

Engine Thermostat
A device that senses the temperature of the engine coolant for the purpose of regulating the engine cooling system.

EPA
The Environmental Protection Agency (EPA) was established in December 1970 by the executive order of President Richard Nixon. It is an agency of the United States federal government whose mission is to protect human and environmental health. Headquartered in Washington, D.C., the EPA is responsible for creating standards and laws promoting the health of individuals and the environment.

Fuel Filter
A replaceable metal or plastic canister that prevents particulate matter and most contaminants in the fuel from reaching the engine.

Heated Air Temperature Sensor
A device that provides information needed by a vehicles computer to determine the temperature of the air coming into the engine.

Heavy Duty Aftermarket
The portion of the auto care market that deals with the maintenance, repair and auto care market products for commercial, industrial and agricultural vehicles after their original sale.

Heavy Duty Distributors
Firms primarily involved in maintaining and selling an inventory of products specifically intended for the maintenance and repair of Class 3 through Class 8 commercial vehicles.

Heavy Duty Parts
Parts for large commercial trucks and commercial vehicles.

Heavy Duty Vehicles
Vehicles classed by Gross Vehicle Weight as follows:

Class 7: 26,001 – 33,000 lbs. (home fuel, refuse, tow, city transit bus, furniture, medium conventional, cabover)

Class 8: 33,001 lbs. and over (fuel, dump, cement, refrigerated van, intercity tour bus, fire engine, heavy conventional, cabover sleeper)

Hybrid
A hybrid vehicle is one that uses more than one means of propulsion through combining a petrol or diesel engine with an electric motor. The main advantages of a hybrid are that it generally consumes less fuel and emits less CO2 than a comparable conventional petrol or diesel-engine vehicle.

Idle Speed
The RPM of the engine free from load (all accessories off), at normal operating temperature and in neutral (or, in the case of an automatic transmission, park or neutral).

Ignition Timing
The process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity.

Internal Combustion Engine (ICE)
An engine that generates motive power by the burning of gasoline, oil, or other fuel with air inside the engine, the hot gases produced being used to drive a piston or do other work as they expand.

Light Duty Vehicles
Vehicles classed by Gross Vehicle Weight (GVW) as follows:

Class 1:  0 – 6,000 lbs. (passenger car, minivan, utility van, multipurpose/sport utility vehicle, compact and full-size pickup)

Class 2:  6,001 – 10,000 lbs. (minivan, utility van, step van, crew cab pickup, full-size pickup, mini-bus)

Class 3:  10,001 – 14,000 lbs. (mini-bus, walk-in, city delivery)

Manifold Heat Control Valve
A thermostatic device that routes exhaust heat to the intake manifold in order to promote fuel vaporization and reduce warm-up time.

Manufacturers Engine Code
An alphanumeric code given to an engine by its manufacturer in order to distinguish it from other engines.

Medium Duty Vehicles
Vehicles classed by Gross Vehicle Weight as follows:
Class 4: 14,001 – 16,000 lbs. (conventional van, large walk-in, landscaping/utility, city delivery)
Class 5: 16,001 – 19,500 lbs. (large walk-in, city delivery, bucket)
Class 6: 19,501 – 26,000 lbs. (rack, single-axle van, beverage, stake body, school bus)

OE
Original Equipment. Parts and components supplied to manufacturers for motor vehicle production.

OEM
Original equipment manufacturer, i.e., the manufacturer of a vehicle.

OES
Original equipment supplier

On-Board Diagnosis System
A computer-controlled system that identifies malfunctioning or out-of-adjustment components under its control through the display of trouble codes. The presence of trouble codes is usually indicated by an intermittently or constantly lit “check engine ” or “service engine soon” light.

Oxygen Sensor
In a computer-controlled, fuel-injected vehicle, a sensor m
ounted in the exhaust stream that relays air/fuel ratio information to the fuel control computer that allows the computer to make adjustments.

PCV Filter/PCV Valve
Positive crankcase ventilation filter/positive crankcase ventilation valve. Devices that allow the venting of combustion gases from the crankcase to the intake system instead of into the atmosphere.

Power Valve
The power valve is a movable flap located on the cylinder exhaust port of a two-stroke engine – where burnt gasses are flushed out of the cylinder. … This helps the engine generate torque at low speeds. As revs build, the flap gradually opens, expanding the size of the exhaust outlet for greater top-end power.

Pump Assembly
An engine water pump assembly is formed of a rotatable shaft divided along its length into a bearing portion terminating in a drive connection and a sealing portion terminating in an impeller end upon which a water impeller is mounted. A tubular, journal-type bearing surrounds the shaft bearing portion.

Sensor
Engine Sensors are the electro-mechanical devices which monitor various engine parameters. An engine uses different types of sensors. There are Thermo-couples, Resistance Temperature Detectors (RTDs), and Hall Effect sensors.

Stoichiometric
The stoichiometric ratio is the exact ratio between air and flammable gas or vapor at which complete combustion takes place. The stoichiometric ratio of combustion varies for various fuels and oxidizers.

Valve Cover Gasket
Seals the valve cover to the top portion of the engine cylinder head. The gasket prevents motor oil from leaking out as it travels around the camshafts, rockers and valves. In addition, many spark plug ports are sealed by the valve cover gasket.

Variable Valve Timing
An engine feature that allows the lift, timing or duration of the engines valvetrain to be changed dynamically while it is in operation.

Wideband Oxygen Sensor
A faster, more sensitive oxygen sensor that enables an engine control unit to make changes to the air/fuel ratio more rapidly and precisely than with a conventional sensor.

Flux Capacitor
A fictional invention conceived by Dr. Emmett L. Brown on November 5 1955 which makes time travel possible.

Blinker Fluid
An imaginary liquid used in automobiles to make the blinkers, or turn signals, work correctly. Until this technology is perfected, the automobile must continue to rely on incandescent or LED bulbs.

710 Cap
710 is OIL spelled upside down, therefore someone might be reading the cap upside down and read it as 710 instead of OIL. Therefore, there is no 710 cap, only the OIL cap where you can add oil to your vehicle’s engine.

Muffler Bearings
Contrary to popular belief, muffler bearings do exist, just ask your local Dodge Stealth or Mitsubishi GT3000 owner. Although a popular prank to pull, some vehicles do in fact use muffler bearings located inside the muffler, in order to operate a flap which opens and closes depending on the exhaust flow, directing flow back into the turbo. Due to inconvenience (carbon or other buildup often jammed the bearings causing noise and poor performance) the bearings are only found on a select few older model vehicles.

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