TSB : Automotive Terminology & Definitions

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ACCELERATION an increase in velocity or speed. ADDITIVE in automotive terminology, a substance added to a liquid, such as engine oil, transmission fluid, gear oil or coolant to enhance its properties. ADVANCED TECHNOLOGY VEHICLE (ATV) a vehicle that combines new engine/power/drivetrain systems to significantly improve fuel economy. This includes hybrid power systems and fuel cells, as well as some specialized electric vehicles. AIR GAP a specified space between two components. Space or gap between spark plug electrodes, motor and generator armatures Ind field shoes. The space or gap between the compressor drive hub and pulley assembly. AIR INJECTION REACTION (AIR) SYSTEM a system that provides fresh air to the exhaust system under controlled conditions to reduce emissions. The air source can be a pulse-air pump or an electrically or belt driven pump. Upstream air injection goes into the exhaust manifold to assist in after-burning HC laden exhaust gases. Downstream air injection goes into the oxidation bed of the catalytic converter to help oxidize HC and CO emissions. AIR PUMP device to produce a flow of air at higher-thanatmospheric pressure. Normally referred to as a thermactor air supply pump. AIR/FUEL RATIO the proportion of air to fuel by weight in the fuel mixture drawn into the engine. ALLOY mixture containing mostly metals. For example, brass is an alloy of copper and zinc. Steel contains iron and other metals, but also carbon ALTERNATIVE FUEL VEHICLE (AFV) as defined by the Energy Policy Act, any dedicated, flexible-fuel, or dual-fuel vehicle designed to operate on at least one alternative fuel. ALTERNATIVE FUEL alternative fuel, also known as non-conventional fuels, is any material or substance that can be used as a fuel, other than fossil fuels, or conventional fuels of petroleum (oil), coal, propane, and natural gas. The term "alternative fuels" usually refers to a source of which energy is renewable. Methanol, denatured ethanol, and other alcohols; mixtures containing 85% or more by volume of methanol, denatured ethanol, and other alcohols with gasoline or other fuels; natural gas; liquefied petroleum gas; hydrogen; coal-derived liquid fuels; non-alcohol fuels (such as biodiesel) derived from biological material; and electricity. 'P-Series' fuels were added to this list since the original definition in EPAct. AMBIENT TEMPERATURE the temperature of the medium surrounding an object ANTIFREEZE a material such as ethylene glycol which is added to water to lower its freezing point; used in an automobile's cooling system. B100 100% (neat) biodiesel. B20 a blend of biodiesel fuel with petroleum-based diesel where 20% of the volume is biodiesel. BABBITT a soft bearing alloy used in engine bearings. BACK PRESSURE pressure created by a blockage or restriction in an exhaust system. BACKFIRE the sudden combustion of gasses in the intake or exhaust manifold, resulting in a loud explosion. BALANCE SHAFT a weighted shaft used on some engines to dampen or reduce vibration. BALLAST RESISTOR resistor in the primary side of the ignition system hat is used to reduce voltage by approximately 4-5 volts. BATTERY batteries are the principal energy storage devices for hybrid electric vehicles (HEVs). Desirable attributes of high-power batteries for HEV applications are high-peak and pulse-specific power, high specific energy at pulse power, a high charge acceptance to maximize regenerative braking utilization, and long calendar and cycle life. Developing methods/designs to balance the packs electrically and thermally, developing accurate techniques to determine a battery's state of charge, and developing abuse-tolerant batteries, and recyclability are additional technical challenges. BDC bottom dead center, when the piston is at its lower limit in the cylinder bore. BEARING CAP the lower half of the bearing saddle. It is removable, as in main cap or rod cap. BEARING CLEARANCE the space between a bearing and its corresponding component's loaded surface. Bearing clearances are commonly provided to allow lubrication between the parts. BEARING CRUSH the bearing is slightly larger at its parting lines so that when the two halves of the bearing are tightened together, the bearing seats firmly in its bore. This keeps the bearing from rotating. BEARING LINING the bearing surface area of a bearing, it is usually made up of an alloy of several metals, including lead. BEARING SPREAD the condition in which the distance across the outer edges of the bearing insert is slightly greater than the diameter of the housing bore. A bearing is spread slightly apart at its paning halves so that it snaps into place in its bore and remains there during assembly. BEFORE TOP DEAD CENTER (BTDC) the degrees of crankshaft rotation just before the piston in a specific cylinder reaches TDC, the highest point in its vertical travel on the compression stroke. On most vehicles, spark occurs a certain number of degrees of crankshaft rotation BTDC. BI-FUEL VEHICLE a vehicle with two separate fuel systems designed to run on either an alternative fuel, or gasoline or diesel, using only one fuel at a time. Bi-fuel vehicles are referred to as "dual-fuel" vehicles in the Clean Air Act Amendments and Energy Policy Act. BIOCK the casting made up of cylinders and the crankcase. BLOWBY the unburned fuel and products of combustion that are forced past the piston rings and into the crankcase during the combustion stroke. BOOST PRESSURE. term used when a turbocharger increases the air pressure entering an engine above atmospheric pressure. BORE GAUGE a precision measuring instrument used to measure the diameter of a bore. BORE a cylindrical hole. BOSS the part of a piston that fits around its pin. BOTTOM DEAD CENTER (BDC) when the piston is at its lower limit in the cylinder bore. BRAKE HORSEPOWER power developed by an engine as measured at the flywheel or crankshaft. BRAKE-SPECIFIC FUEL CONSUMPTION the ratio of engine fuel consumption to power output. It is a measure of engine efficiency. BTDC see 'before top dead center'. CAMSHAFT BEARING a bearing that supports the camshaft journal. On some engines it is full round and pressed in place. On some OHC engines the camshaft bearing is made up of two shells like a connecting rod bearing. CAMSHAFT FOLLOWER on OHC engines the equivalent of a rocker arm. CAMSHAFT JOURNAL the bearing area of a camshaft. CAMSHAFT LOBE the eccentric on a camshaft that acts on lifters or followers and in turn, other valvetrain components as the camshaft is rotated, to open the intake and exhaust valves. CAMSHAFT POSITION SENSOR (CMP) a magnetic, halI effect, optical or magneto resistive sensor usually mounted internally in the engine to inform the ECM or PCM of piston position on the intake stroke for timing and synchronization of sequential fuel injection. CAMSHAFT SPROCKET the sprocket on a camshaft that is turned by a chain or belt from the crankshaft. The camshaft sprocket has twice as many teeth as the crankshaft sprocket. CARBON DIOXIDE (CO2) A product of combustion that has become an environmental concern in recent years. CO2 does not directly impair human health, but is a greenhouse gas that traps the Earth's heat and contributes to the potential for global warming. CARBON MONOXIDE (CO) a colorless, odorless gas, which is highly poisonous. CO is produced by incomplete combustion. It is absorbed by the bloodstream 400 times faster than oxygen. CARBON a hard or soft nonmetallic element that forms in an engine's combustion chamber when oil is burned. CARBURETOR a device that atomizes air and fuel in a proportion that is burnable in the engine. CASTING metal that is manufactured by pouring it into a mold. It is more porous than forged metal and does not conduct heat as well. It is less expensive to manufacture, however. CATALYTIC CONVERTER an emission control device located in the exhaust system that contains catalysts, which reduce hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases. CATALYTIC OXIDATION process of oxidizing unburned hydrocarbons and carbon monoxide by means of a catalytic reaction to reduce pollution. CHOKE a device used on carbureted vehicles to reduce the amount of air entering the intake manifold while leaving the amount of fuel unchanged. The purpose of a choke is to richen the mixture enough that a cold engine can still get enough vaporized fuel to start. CLOSED LOOP electronic feedback system in which sensors provide constant information on what is taking place in the engine; the state of the engine control computer system when it is working normally, at full operating temperature and normal speeds with the oxygen sensor switching. The fuel injection quantity is determined by the set of inputs from the engine control computer's sensors, most specifically the oxygen sensor in the exhaust stream. A closed loop system samples its output and uses that sampling to modify the next inputs. CLOSED-LOOP CARBURETION system in which the fuel/air ratio in the engine is carefully controlled to optimize emissions performance. A closed-loop system uses a fuel metering correction signal to optimize fuel metering. COIL-ON-PLUG IGNITION a Coil-on-Plug ignition system uses one ignition coil for each cylinder attached to the spark plug. The system replaces remote ignition coils and high-voltage ignition wires in a distributorless ignition system. COLD START difficulty of starting an internal combustion engine in cold weather because of gasoline, which evaporates more slowly when it is cold; oil, which gets thicker in cold weather; and the chemical reactions inside the battery, which progress more slowly in cold weather. COMBUSTION CHAMBER enclosure formed by a pocket in the cylinder head and the top of the piston, where the spark plug ignites the compressed air/fuel mixture. The volume of the cylinder above the piston when the piston is at TDC. COMBUSTION the burning of the air/fuel mixture. COMMON RAIL DIRECT INJECTION (CDI) a fuel-injection system that uses a single "rail" (fuel line) that maintains constant fuel pressure regardless of injection sequence (also called common rail injection). The engine's electronic timing regulates fuel-injection timing and quantity according to data from sensors on the camshafts and crankshafts so that compression and injection occur independently. Fuel is injected only as needed, which reduces fuel consumption and emissions. COMPRESSION IGNITION the form of ignition that initiates combustion in a diesel engine. The rapid compression of air within the cylinders generates the heat required to ignite the fuel as it is injected. COMPRESSION RATIO ratio of the volume in the cylinder above the piston when the piston is at bottom dead center to the volume in the cylinder above the piston when the piston is at top dead center. COMPRESSION RINGS usually the top two rings on a piston, they form a seal between the piston and cylinder wall to compress the air fuel mixture in the cylinder. COMPRESSION STROKE the second stroke of the 4-stroke engine cycle, in which the piston moves from bottom dead center and the intake valve is closed, trapping and compressing the air/fuel mixture in the cylinder. COMPRESSION in a solid material, compression is the opposite of tension. In a gas, compression causes the gas to be confined in a smaller area, raising its temperature and pressure. COMPRESSION-IGNITION DIRECT-INJECTION (CIDI) ENGINE commonly called the diesel engine, has the highest thermal efficiency of any internal combustion engine. Challenges to improvements include a lower specific power than the gasoline engine; significant particulate matter and nitrogen oxides in the exhaust; and the noise, vibration, and smell of the engine. CONNECTING ROD BEARINGS the plain bearing shells located in the big end of the connecting rod that support the connecting rod and piston on the crankshaft. CONNECTING ROD CAP the removable part of the big end of the connecting rod. CONNECTING ROD a rod that connects the crankshaft to the piston and enables the reciprocating motion of the piston to turn the crankshaft. CONTINUOUS INJECTION a system that uses fuel under pressure to maintain or change the fuel injection area. COOLANT the mixture of water and antifreeze used in an engine's cooling system to maintain the engine's temperature throughout Its operating range. COOLING FAN a mechanically or electrically driven propeller that draws air through the radiator. COOLING SYSTEM the system used to remove excess heat from an engine and transfer it to the atmosphere. Includes the radiator, cooling fan, hoses, water pump, thermostat and engine coolant passages. CORROSION INHIBITORS additives used to inhibit corrosion (e.g., rust) in the fuel system. CRANK THROW distance from the crankshaft main bearing centerline to the connecting rod journal centerline. The stroke of any engine is the crank throw. CRANK WEB unmachined portion of a crankshaft that lies between two crank pins or between a crankpin and main bearing journal. CRANKCASE the lower part of an engine block that houses the crankshaft. CRANKPIN the part of the crankshaft to which the connecting rod is attached. CRANKSHAFT JOURNALS the bearing areas of a crankshaft are the main and rod journals. CRANKSHAFT POSITION SENSOR (CKP) a magnetic, hall effect, optical or magneto resistive sensor usually mounted internally in the engine, externally to the engine or in the distributor to inform the ECM or PCM of crankshaft position, location of No.1 piston, and crankshaft speed for ignition timing and other calculations needed by the system where rpm is an input. CRANKSHAFT PULLEY the belt drive pulley mounted on the front of the vibration damper. CRANKSHAFT THRUST COLLAR a flat machined area that is 90 degrees to the crankshaft main journals. The flange of the thrust main bearing rides against it to control cranksnan end tnrust. CRANKSHAFT a lower engine part with main and rod bearing journals. It converts reciprocating motion to rotary motion. CROSSFLOW RADIATOR a radiator in which coolant enters on one side, travels through tubes, and collects on the opposite side (see downflow radiator). CRUSH the bearing is slightly larger at its parting lines so that when the two halves of the bearing are tightened together, the bearing seats firmly in its bore. This keeps the bearing from rotating. CYLINDER HEAD the casting that contains the valves and valve springs, and covers the top of the cylinders. CYLINDER LEAKAGE TEST in engine diagnostic test where the piston in the cylinder to be tested is brought to top dead center (TDC) on the compression stroke and compressed air is pumped into the cylinder through the spark plug hole. Where the air leaks out shows the location of the compression leak. A leakage tester will compare the air leaking out of the cylinder to the amount of air being put into it, expressed as a percentage. CYLINDER SLEEVE a replacement iron liner that fits into a cylinder bore. It can be either wet or dry. The outside diameter of wet sleeves contacts the coolant. CYLINDER WALLS the walls of the cylinder bore. CYLINDER round hole in the engine block for the piston. DAMPER a device mounted on the front of the crankshaft. It reduces the torsional or twisting vibration that occurs along the length of the crankshaft in multiple cylinder engines. It is also called a harmonic balancer. DEAD CENTER the extreme upper or lower position of the crankshaft throw at which the piston is not moving in either direction. DECK the top of the engine block where the cylinder head is attached. DETONATION abnormal combustion of an air fuel mixture. When pressure in the cylinder becomes excessive and the mixture explodes violently, instead of burning in a controlled manner. The sound of detonation can be heard as the cylinder walls vibrate. Detonation is sometimes confused with preignition or ping. DIAGNOSTIC TROUBLE CODE