| r
| Red |
| R & D
| An acronym for research and development. |
| R & R
| An acronym for remove and replace. |
| R & D
| An acronym for research and development. |
| R & R
| An acronym for remove and replace. |
| R-12
| A trade term for refrigerant CFC-R12. |
| R-134a
| A trade term for refrigerant HFC-134a. |
| R-22
| A trade term for refrigerant HCFC-22. |
| Ra
| Radium An element with the atomic number of 88 |
| RABS
| rear antilock brake system. A two-wheel Kelsey-Hayes ABS used on the rear wheels of Ford light-duty pickup trucks |
| RAC
| Remote accessory control |
| race
| 1. That element of a one-way roller clutch providing the cylindrical surface through which the rollers and cam transmit torque. 2. A grove, edge, or track on which a rolling or sliding part moves. |
| race for the pink
| To race for actual ownership of the competitor's vehicle. |
| racer
| 1. A competition driver. 2. A competition vehicle. |
| racer's tape
| Duct tape. |
| races
| The metal rings on which ball or roller bearings rotate. |
| rack and pinion
| A type of steering assembly that has a gear or pinion at one end of the steering shaft engaging in a horizontal-toothed bar or rack having tie rods at either end that are attached to the steering arms. |
| rack body
| A part of the steering system containing the rack shaft |
| rack guide
| The guide on which the rack is positioned |
| rack shaft
| A horizontal-toothed part of the rack and pinion assembly |
| rack-and-pinion steering
| A term used for rack and pinion. |
| racy bopper
| An auto-racing groupie. |
| rad
| A term often used to describe a radically modified engine or vehicle. |
| radial compressor
| A space-saving compressor used on small cars. |
| radial grid
| A lead alloy framework for the active materials of a lead acid battery that has radial support spokes to add strength and improve continuity. |
| radial motion
| A motion extended to either, or both, extremes of a radius. |
| radial ply
| A term used for radial ply belted tire. |
| radial ply belted tire
| A tire having the ply cords placed at right angles tot he beads, plus belts under the tread section providing the least tread distortion while moving, thereby minimizing tread wear and rolling friction. |
| radial runout
| Variations in tire diameter; the measured amount of out-of-roundness on rotating tires. |
| radial tire waddle
| A term used for tire waddle. |
| radiation
| 1. A natural process by which energy is transmitted. 2. The transfer of heat through a soled, liquid, or gas medium. |
| radiation dose
| The amount of energy per unit of mass of material deposited at each point of an object undergoing radiation. |
| radiator
| A heat exchanger used to remove heat from the coolant in the cooling system containing a vertical- or horizontal-finned tubing section connected between two tanks. |
| radiator cap
| A term used for radiator pressure cap. |
| radiator core
| The center of the radiator, made of tubes and fins, used to transfer heat from the coolant to the air. |
| radiator fan
| A term used for fan. |
| radiator hose
| An oil- and ozone-resistant synthetic-rubber hose that connects the radiator to the thermostat outlet housing and water pump inlet housing. |
| radiator hose clamp
| A term used for hose clamp. |
| radiator pressure cap
| A cap that seals in pressure from hot expanding coolant until a predetermined limit is reached, then the valve opens, allowing excess pressure to escape, generally to a coolant-recovery tank. |
| radiator shutter system
| An engine temperature-control system that controls the amount of air flowing through the radiator by use of a shutter system. |
| radio choke
| A small coil of wire installed in the power lead leading to a pulsing unit such as an IVR to prevent radio noise ( reduce RFI). |
| radio frequency interference
| (RFI) A form of electromagnetic interference created in the ignition secondary circuit which disrupts radio and television transmission. |
| Radiofrequency Interference
| Radio and television interference caused by electromagnetic energy |
| radius
| A line extending from the center of a circle to its boundary. |
| radius arms
| Longitudinal suspension arms used to position a beam axle. |
| radius ride
| A condition where the crankshaft rides on the edge of a bearing. |
| radius rods
| A term used for radius arms. |
| radiused
| 1. A procedure that is used to reduce the radius diameter at the area the valve stem meets the valve head. 2. A valve type that is ground with a radial grinder to aid in air flow around the valve. 3. Wheel wells that have been cut into a circular shape. |
| radix
| 1. A base. 2. The base number in a number system. |
| rag top
| A convertible. |
| ragged edge
| The absolute limit of a vehicle's potential. |
| rail
| An early dragster with exposed frame rails. |
| rail job
| A term used for rail. |
| rake
| A suspension or structural design to lower one end of the vehicle in relation to the other end. |
| rally
| A sports-car driving contest for driver performance as opposed to vehicle performance. |
| RAM
| [1] an acronym for Random Access Memory a computer read-write memory on which information can be written and from which it may be read from |
| ram air
| Air forced through the radiator and condenser coils by the movement of the vehicle or the action of the fan. |
| ram air cleaner
| An air cleaner for high-performance cars that opens an air scoop on the hood to provide a ram effect when the throttle is wide open. |
| ram induction
| An intake manifold designed to cause a resonant effect at a specific predetermined engine speed. |
| ram tubes
| Short, tuned, tubular stacks on the top of carburetors. |
| ram tuning
| The tuning of an intake manifold to ensure that the passages are of sufficient length to cause a resonant effect at a specific predetermined engine speed. |
| ramp
| The sloping section of a camshaft lobe which raises the lifter. |
| ramp angle
| An angle formed by lines adjacent to the static-loaded radius of the front and rear wheels intersecting at the point of the lowest ground clearance under the middle of the vehicle. |
| Ramps
| Transistions between voltage levels of sine waves that change at a constant rate |
| Ranco control
| A tradename often used for a thermostat. |
| random access memory (RAM)
| A computer memory into which the user can enter information and instructions (write), and from which the user can call up data (read). |
| random intermittent welds
| Welds on one or both sides of a joint in which the weld increments are made without regard to spacing. |
| range shift cylinder
| Located in the auxiliary section of the transmission, this component, when directed by air pressure via low and high ports, shifts between high and low range of gears. |
| range shift lever
| Located on the shift knob, this lever allows the driver to select low- or high-gear range. |
| Rankine
| a thermometer scale for which the freezing point of water is 492oR. Absolute zerow is the beginning of this thermometer scale. |
| Rankine scale
| see Rankine |
| RAP
| Retained accessory power |
| Raster
| A type of display were each patern is stacked one on top of the other |
| raster pattern
| Also known a stacked pattern. |
| rat
| A Chevrolet big block V-8 engine. |
| rat motor
| A Chevrolet big block V-8. |
| ratio
| 1. The relative amounts of two or more substances in a mixture. 2. The comparison of two numbers as in teeth on gears. |
| ratio valve
| A device used on the front or steering axle of a heavy-duty vehicle to limit the brake application pressure to the actuators during normal service braking. |
| rationality
| A term associated with comprehensive component testing in which signal inputs from components are compared to inputs from other components to verify conditions coincide. |
| Ravigneaux gear train
| A planetary gear train with two sun gears, three long and three short planetary pinions, planetary carrier, and ring gear. |
| Raytech
| Manufacturer of test equipment such as infrared thermocouples |
| Rb
| Rubidium An element with the atomic number of 37 |
| RC circuit
| A network containing resistors and capacitors used mostly as a timer circuit. |
| RC constant
| The time constant of an RC circuit. It is equal (in seconds) to the value of the resistance in ohms multiplied by the capacitance in farads. |
| RC engine
| A shortened term for rotary combustion engine. |
| RC time constant
| The time constant of a resistor and capacitor connected in series. The time in seconds is equal to the resistance in ohms multiplied by the capacitance in farads. |
| RCD
| Refrigerant containment device. |
| RCRA
| An acronym for Resource Conservation and Recovery Act. |
| RCV
| Rollover check valve |
| RDES
| Remote divert/electric switching valve |
| RDK
| (Porsche) Tire Pressure Monitor System |
| Re
| Rhenium An element with the atomic number of 75 |
| reactance
| The impedance that a pure inductance or a pure capacitance provides to current flowing in an ac circuit. |
| reaction disk
| The components in the vacuum power booster that provide pedal feel or feedback to the driver. |
| reaction member
| The member of a planetary gearset that is held in order to produce an output motion. Other members react against the stationary, held member. |
| reaction time
| 1. The amount of time required to physically apply the brakes of a vehicle after mentally being aware of the necessity to do so. 2. The amount of time required from the moment the Christmas tree light turns green until the vehicle trips the starting-line timing light. |
| reactivity
| The characteristics of a material that cause it to react violently with another material, such as air, heat, or water. |
| read vapor pressure (RVP)
| A method of determining vapor pressure of gasoline and other petroleum products. Used as an indicator of the volatility of gasoline. The Read Vapor Pressure of gasoline is the pressure of the vapor in a sealed gas tank when the fuel is raised to 100o F and varies with altitude. |
| read-only memory
| A solid-state storage chip that is programmed at the time of its manufacture, cannot be programmed by the computer user, and retains its program when the computer's power is turned off. |
| real-time
| A real-time computer can respond with output information instantly |
| Real-time sampling
| A sampling mode in which the oscilloscope collects as many samples as possable from one triggered acquisition |
| rear antilock brake system
| A two-wheel Kelsey-Hayes ABS used on the rear wheels of Ford light-duty pickup trucks |
| rear antilock brake system (RABS)
| A two-wheel Kelsey-Hayes ABS used on the rear wheels of Ford light-duty pickup trucks |
| rear clip
| The rear end of a vehicle's bodywork extending from the door pillar back. |
| rear control arm
| Horizontal arms that connect the rear axle housing to the frame when coil springs are used in the rear suspension system to maintain axle alignment and handle the driving and torque loads. |
| rear driving
| A term used for rear-wheel drive. |
| rear end
| The differential and final drive assembly on a rear-wheel drive vehicle. |
| rear engine
| An engine arrangement where the engine is placed behind the rear wheels, driving them through the transaxle assembly. |
| rear leaf spring
| A term used for leaf spring. |
| rear roll center
| The center as determined by the rear suspension geometry around which the rearward part of a vehicle has a tendency to roll. |
| rear shock
| A type of shock absorber that is compatible with a particular type of driving and its load requirement. |
| rear steer
| A steering gear that is positioned behind the front-wheel centerline. |
| rear strut
| A shock-absorber-type component that supports the rear of a vehicle with IRS (Independent Rear Suspension). |
| rear suspension
| An integral part of the total suspension system designed to keep the rear axle and wheels in their proper position under the car body, typically of two types; solid axle type and independent rear-suspension type. |
| Rear Vacuum Brake
| Used to control choke operation during cold engine conditions |
| rear wheel anti-lock brakes(RWAL)
| A two-wheel ABS used on the rear wheels of GM and Daimler Chrysler light-duty pickup trucks and some SUVs One of the best known Kelsy-Hays systems |
| rear-axle assembly
| A group of parts that operate to transfer driving torque from the drive shaft to the rear wheels, and includes mounting pads for the rear springs and shocks. |
| rear-axle housing
| The basic framework of the rear-axle assembly inside which the individual parts, including the differential and axles are mounted and/or operate. |
| rear-camshaft plug
| A plug driven in the rear of the block behind the camshaft to contain the oil supplied to the rear camshaft bearing. |
| rear-end torque
| The twisting reaction of a rear-axle assembly in a direction opposite to that of wheel rotation when power is applied, controlled by the control arms in coil-spring models and by the leaf springs in leaf spring models. |
| rear-spring shackle
| A device bolted to a rubber bushing in the rear main leaf eye, and having an upper shackle bolt that extends through a similar rubber bushing in the rear-spring hanger, providing fore and aft movement with variations in spring length. |
| rear-suspension coil spring
| A coil spring that is used in the rear suspension system. |
| rear-suspension rebound stop
| A function of the rear shocks as they limit the distance the rear-axle assembly can move downward. |
| rear-wheel drive
| A drivetrain layout that provides power to the rear wheels only. Often referred to an rear drive. |
| reassembly
| Putting the disassembled parts of a device back togther, replacing those parts as necessary. |
| rebore
| To increase the diameter of a cylinder. |
| rebound
| The outward extension of the springs and shocks in a vehicle suspension system. |
| rebound clip
| Metal clamps placed at three or four internals around multi-leaved springs to prevent the leaves from becoming separated on rebound. |
| rebound travel
| The downward movement of a wheel from its normal position when the spring and shock are expanding, as the sudden drop of a wheel into a depression and a weight transfer away from the wheel. |
| rebound valve
| A calibrated piston valve mounted on the shock piston that provides variable resistance to fluid flow during rebound. |
| recall
| A notice issued by the vehicle manufacturer that a certain make and model vehicle should be returned to the dealer for a correction of a suspected or known problem. |
| recall bulletins
| A dealer notice pertaining to vehicle service or the replacement of parts related to a recall. |
| recapping
| To recover a tire casing with a new tread. |
| receiver
| 1. A term sometimes used for drier, receiver drier, or receiver rehydrator. 2. A mainarea for the temporary storage of liquid refrigerant. |
| receiver dehydrator
| A combination mainarea for the storage of liquid refrigerant and a desiccant. |
| receiver drier
| A term used for receiver dehydrator. |
| receiver tank
| The second tank in a radiator is often referred to as a receiver because it receives coolant after passing through the many tubes of the radiator core. The receiver, on automatic transmission equipped cars, contains a transmission oil cooler. |
| receptacle
| A contact device, installed at an electrical outlet, extension cord, or drop light for the connection of an attachment plug and flexible cord to supply power to portable equipment. |
| recharging
| 1. The action of forcing electrical current into a battery, reversing the chemical reaction between the plates and electrolyte. 2. Filling an air-conditioning system with refrigerant and repairs are made. |
| reciprocating
| A back-and-forth, up-and-down, or to-and-fro motion, such as that of a piston in a cylinder. |
| reciprocating engine
| A powerplant in which the piston move in a reciprocating motion. |
| reciprocating motion
| The motion of an object between two limited positions in a straight line back and forth or up and down. |
| recirc door
| An acronym form of recirculate door. |
| recirculate
| 1. To reuse 2. To circulate a fluid or vapor over and over again. |
| recirculate door
| A door in the plenum that regulates the amount of reticulated air flow. |
| recirculating ball
| A worm and gear steering assembly with balls between the worm and sector to reduce friction. |
| recirculating-ball steering gear
| A low-friction steering gear box having a worm-gear meshing with a cross shaft sector through about 40 recirculating balls that travel in matching grooves inside the ball nut and outside the worm shaft which acts as a rolling thread. |
| recirculating-ball-and-nut steering gear
| A type of steering gear having a nut meshing with a worm gear sector, with balls that circulate between the nut and worm threads. |
| reclaim
| To process used refrigerant to new product specification by means that may include distillation. This process requires that a chemical analysis of the refrigerant be performed to determine that appropriate product specifications are met. |
| recombination battery
| Sometimes called dry-cell batteries because they do not use a liquid electrolyte solution. |
| recon
| A short term for reconditioned. |
| reconditioned
| A used part that has been repaired, tested, and determined to be in good order. Also known as recon. |
| Record length
| The number of waveform points used to create a record of a signal |
| recovery
| The recovery of refrigerant is to remove it, in any condition, from a system and to store it in an external mainarea without necessarily testing or processing it in any way. |
| recovery cylinder
| A cylinder for the storage of used R-12 and/or R-134a must meet DOT specification 4BA-300, characterized by a combined liquid/vapor valve located a the top. A recovery cylinder should be painted gray with a yellow shoulder. |
| recovery/recycle systems
| A term often used to refer to the circuit inside the recovery unit used to recycle and/or transfer refrigerant from the air-conditioning system to the recovery cylinder. |
| recovery/recycle unit
| A term used to identify the complete unit used to recover and/or recycle refrigerant from the air conditioning system. |
| recreational vehicle (RV)
| A motor-driven, van-like vehicle having sleeping, food preparation, and bathroom facilities. |
| Rectification
| The converting of AC current to DC current |
| rectifier
| An electrical device used to convert alternating current and direct current. |
| rectifier bridge
| A group of six diodes, three positive and three negative commonly used in an alternator |
| rector
| The stator in a torque converter. |
| recycle
| To recycle is to clean the refrigerant for reuse, by oil separation and passes through other devices such as filter-driers, to reduce moisture, acidity, and particulate matter. |
| Red Book
| A used-car price guide. |
| red dye trace solution
| The dye that reveals the exact location of a leak in a fluid system by depositing a colored film around the leak area. |
| red flag
| A signal for all drivers to come to a stop. |
| red light
| 1. In normal driving conditions, a warning to stop. 2. In drag racing, to jump from the line before the start signal. 3. In competition, to foul and become disqualified for an event. |
| red line
| 1. The absolute minimum an auto dealer will accept for a vehicle. 2. The absolute maximum recommended engine speed. |
| reducer
| 1. A tool that reduces the size of a device, such as a pipe. 2. A paint thinner. 3. An adapter for using a smaller tool. |
| reducing atmosphere
| A chemically active protective atmosphere, which at elevated temperature will reduce metal oxides to their metallic state. |
| reducing flame
| An oxyfuel gas flame with an excess of fuel gas. |
| reduction catalyst
| The section of a three-way catalytic converter that breaks NOx (oxides of nitrogen) down into harmless nitrogen and oxygen through a reduction reaction. |
| redundant
| A duplication; a secondary or backup system. |
| redundant system
| A duplicated system; a secondary or backup system. |
| reed valve
| 1. A thin leaf of steel located in the valve plate of automotive compressors, serving as suction and discharge valves. 2. Used to control exhaust backpressure in a pumpless AIR system |
| reference voltage
| In computerized engine-management systems, usually a five-volt signal sent out from the electronic control unit to a variable-resistance sensor such as a throttle-position sensor. As the sensor changes due to the condition of its surroundings, the return voltage is altered and sent back to the computer for use by the microprocessor. |
| Reformer
| 1. A device that extracts pure hydrogen from hydrocarbons. |
| reformulated gasoline (RFG)
| Gasolines which have had their composition and/or characteristics altered to reduce vehicular emissions of pollutants. Specifically, those gasolines which meet the RFG requirements of the 1990 Clean Air Act Amendments. |
| Refractometer
| An Instrument used to measure substances dissolved in water and certain oils. It works on the principle of light refraction through liquids. As light passes from air into a liquid it slows down and this phenomenon is what gives a "bent" look to objects that are partially submerged in water. Refactometers use this principle to determine the amount of dessolved solids in a liquid by passing light through a sample and showing the refracted angle on a scale. In automotive applications reflactometers are used to measure the spicific gravity of battery electorlite and antyfreeze concentrations. |
| refrigerant
| The chemical compound used in a refrigeration system to produce the desired cooling effect. |
| Refrigerant CFC-12 (R-12)
| The refrigerant, dichlorodifluoromethane (CC12F2), used in automotive air conditioners, as well as other air-conditioning and refrigeration system. |
| Refrigerant HCFC-22 (R-22)
| A refrigerant, monochlorodifluoromethane (CHC1F2), used in some early automotive applications but not to be used for today's automotive air conditioners because of high pressures. |
| Refrigerant HFC-134a (R-134a)
| The "refrigerant of choice," tetrafluoroethane (CH2FCF3), to be used in automotive air conditioners as R-12 is being phased out. |
| refrigerant lines
| Specially designed vapor-barrier hoses reinforced with woven nylon mesh and fabric capable of withstanding the high temperatures and pressures of the system. |
| refrigerant recovery
| The act of recovering refrigerant. |
| refrigerant recycle
| The act of recycling refrigerant. |
| refrigerant-containment device
| A device introduced on some car lines to guard against high pressure resulting in refrigerant loss by controlling the compressor and/or condenser fan motor. |
| refrigeration
| To use an apparatus to cool; keep cool; or keep chilled under controlled conditions by natural or mechanical means, as an aid to ensure personal safety and comfort. |
| refrigeration cycle
| The complete cycle of the refrigerant back to the starting point, evidenced by temperature and pressure changes. |
| refrigeration lubricant
| A mineral oil or synthetic oil-like lubricant, such as PAG and ESTER, that is formulated for specific use and application in designated refrigeration systems. |
| refrigeration oil
| A highly refined (specially formulated), non-foaming organic mineral oil free from all contaminants, such as sulfur, moisture, and tars, used to lubricate the air-conditioner compressor. |
| refrigeration tape
| A term used for insulation tape or duct tape. |
| regeneration system
| A system in a gas turbine that converts some of the heat, usually wasted, into useable power. |
| Regenerative Fuel Cell
| 1. Several fuel cell types in which fuel and oxidents are regenerated from the oxidation product. |
| regenerator
| A device placed on a gas turbine to take the heat of exhaust and put it into the intake of the engine. |
| regional offices and distributorship
| Offices owned and operated by the automobile company, and considered to be the link between the manufacturer and the dealerships. |
| register
| A high-speed device used in a central processing unit for temporary storage of small amounts of data or intermittent results during processing. |
| regular gasoline
| Gasoline that has an octane number near 85-90. |
| regular production option (RPO)
| Items of new car equipment available to any buyer for a price. |
| regular-duty coil spring
| A coil spring supplied to handle average loads to which the vehicle is subjected, having a small wire diameter as compared to a heavy-duty spring. |
| regulator
| A term often used for voltage regulator. |
| reheat principle
| A principle that is used in automotive air-conditioning systems to control in-car relative humidity by first cooling, then reheating the air. |
| Reid vapor pressure (RVP)
| The measure of the volatility of liquid fuels. |
| Relative Compression Testing
| Measuring the engines compression pressure relative to the amount of amperage required to turn the crankshaft during a cranking event. Using an oscilloscope in conjunction with an inductive amps probe. |
| relative humidity
| The moisture content of the surrounding air. |
| relative pressure
| The difference between intake manifold pressure and the output pressure in a fuel-injection system. |
| relative wheel weights
| The weight on each of the vehicle's wheels as measured by individual matched scales under each wheel. |
| relay
| An electro-mechanical switch having a coil and one or more sets of points. Also called an electromagnetic switch that uses a small amount of current from its control circuit to control a larger amount of current in its power circuit. |
| relay rod
| A term used for center link. |
| relay/quick-release valve
| A valve, similar to a remote control foot valve, used on trucks with a wheel base of 254 inches (6.45 meters) or longer attached to an air tank to main supply line to speed the application and release of air to the service chambers. |
| release bearing
| A term used for throw out bearing. |
| release fingers
| a term used for release levers. |
| release levers
| A lever-type, pivoting pressure-plate device in the clutch assembly that is moved by throw out bearing movement, causing the clutch-spring pressure to be relieved so the clutch is released from the flywheel. |
| reliability run
| A rally for hot rod drivers. |
| relief valve
| A term used for compression valve or pressure relief valve. |
| relieved
| An engine in which the intake and exhaust passages have been cleaned of all obstructions and ridges. |
| reluctance (R)
| In a magnetic path, the opposition to the flow of magnetic lines of force. |
| reluctance sensor
| A magnetic pulse generator or pick-up coil that sends a voltage signal in response to a varying reluctance of its magnetic field and its reluctor core. |
| reluctor
| A gear-like part of an electronic ignition system, having the same number of teeth as there are cylinders, near the top of the distributor shaft so that as a tooth passes a pickup coil, resistance to magnetic flux is reduced and the magnetic field is strengthened, which triggers the electronic control unit. |
| remanufactured
| A term used to describe a component that is disassembled, cleaned, inspected, and reassembled using new or reconditioned parts. According to the Automotive Parts Rebuilders Association APRA), this same component is also referred to as being rebuilt. |
| remote back-pressure transducer
| An exhaust back-pressure sensing device mounted in the vacuum line leading to the EGR valve rather than on the valve itself, to bleed off the vacuum signal to prevent recirculation. |
| remote bulb
| A sensing device connected to an expansion valve or thermostat by a capillary tube, sensing temperature and transmitting pressure to the control for its proper operation. |
| remote sensing bulb
| A term used for remote bulb. |
| remove and repair
| To remove a component from a vehicle and then to repair it; it is assumed that it will also be replaced on the vehicle. |
| remove and replace (R&R)
| To remove a component and replace it with a reconditioned, rebuilt, good used, or new component on a vehicle. |
| repair order
| A written summary report of repairs that are requested or that are made. |
| Repetitive Pulse
| A signal with a regular pattern or frequency |
| replacement springs
| New springs having the same characteristics, shape, and type of ends as the springs in the vehicle, all four of which should be replaced at the same time. |
| replacement tire
| A tire purchased to replace an original tire that was supplied by the vehicle manufacturer, having the same size and temperature range as the original tire. |
| replenishing port
| The rearward port in the master cylinder bore. |
| repulsion
| A mechanical force that tends to separate like magnetic poles or electrical charges. |
| required sidewall information
| Information that is required by the Department of Transportation to be included on each tire such as size, load rating, maximum inflation pressure, generic name of materials used in construction, actual number of plys, and so on. |
| required voltage
| 1. The low voltage required by a device or system. 2. The highest voltage required to fire a spark plug. |
| research and development (R&D)
| As the term implies, to research and develop a concept, system, or product. |
| research octane number (RON)
| A term used for octane number. |
| reserve capacity
| A term used for reserve capacity rating. |
| reserve capacity rating
| The number of minutes a fully charged battery at 80?F (26.7?C) can supply power at 25 amperes to run the ignition, lights, and accessories after a charging system failure or when the engine is not running, before dropping to 1.75 volts per cell. |
| reservoir
| Storage tank for a liquid, gas or a vacuum |
| residual magnetism
| The magnetism that remains in an electromagnetic material after the current is interrupted. |
| residual pressure
| The pressure that is retained in a specific area. |
| residual pressure check valve
| A check valve used in the outlet port for drum brakes in some master cylinders. The valve retains a slight pressure in the lines to the drum brakes when the brakes are not applied. |
| residual stress
| Stress present in a joint member or material that is free of external forces or thermal gradients. |
| resin
| The molten plastic part of fiberglass-reinforced plastic. |
| resistance
| 1. An opposition to the flow of electricity. 2. An opposition to movement, such as wind against a vehicle. |
| resistance welding
| 1. A term used for spot welding. 2. A welding process that unites the surfaces with heat, obtained from the resistance of the work pieces, and the application of pressure. |
| resistor
| An electrical device used to reduce voltage. |
| resistor spark plug
| A spark plug having a resistance of 5,000 to 10,000 ohms inside the upper part of the insulator, increasing the electrode life and suppressing radio interference. |
| resonator
| A small auxiliary muffler, after the main muffler, used to help reduce engine noise without restricting the flow of exhaust gas. |
| Resource Conservation and Recovery Act (RCRA)
| A Federal law that requires users of hazardous materials to store used materials in a manner consistent with established guidelines until they can be property disposed. |
| Rest Pressure
| Fuel pressure maintained within the system after the engine has been shut down |
| resto
| The restoration of an old car. |
| restriction
| A blockage in an air or fluid line caused by a pinched or crimped line, foreign matter, or moisture freeze-up. |
| restrictor
| An insert fitting or device used to control the flow of air or fluid. |
| restrictor plate
| 1. A plate with holes drilled in it to restrict the flow of air or liquid. 2. A plate with holes of a calibrated diameter that is placed between the carburetor and intake manifold of a stock car to restrict the air/fuel flow, thereby reducing engine speed and horsepower. |
| restyle
| 1. To customize a vehicle. 2. To change the appearance of a vehicle. |
| resultant force
| The combined force and oil flow direction produced by rotary and vortex flow in a fluid coupling or torque converter. |
| retard
| To cause ignition spark to occur later in an engine's cycle. |
| retard sensor
| A term used for knock sensor. |
| Retarded timing
| When the spark is late arriving to the combustion chamber and the flame front reaches the top of the pistion when the pistion is to far down in the cylinder to push the pistion with any strangth |
| retarder
| 1. A mechanical, electrical, or hydraulic device used to slow a diesel engine when the throttle is lifted. 2. A chemical compound that reduces the speed of paint drying. |
| retention seal
| A seal that has the ability to retain fluid pressure. |
| retracting spring
| A spring that is used to pull the brake shoes away from the drum when the brake pedal is released, pushing the wheel-cylinder piston back into its bore and thus returns the brake fluid to the master cylinder. |
| retread
| A used tire having had its old tread removed and a new tread applied. |
| retro car
| A modern vehicle that has been restyled to look like an old vehicle. |
| retrofit
| To modify equipment that is already in service using parts and/or materials available or made available after the time of original manufacture. |
| return hose
| 1. The low-pressure hose in a power-steering system through which fluid returns to the pump reservoir after leaving the steering-gear assembly or control valve. 2. A non-pressurized fluid or air system. |
| return spring
| 1. Springs used on drum brakes to pull the brake shoes away from the drums when the brakes are released. 2. A spring that is used to return a mechanism to its original position. |
| returnable cylinder
| 1. A cylinder of gas, such as oxygen, nitrogen, propane, or acetylene that can be reused. 2. A DOT approved refrigerant-recovery cylinder. |
| reusable cylinder
| A cylinder, such as a refrigerant-recovery cylinder, that may be reused. |
| rev
| 1. A short term for revolution. 2. To noticeably increase engine speed. |
| rev counter
| A tachometer. |
| rev limit
| The maximum recommended speed. |
| rev limiter
| 1. A governor. 2. A mechanical or electrical device that limits engine speed. |
| reveal file
| A small file that is "pulled, not pushed," available in numerous shapes, generally curved to fit tightly crowned areas such as around windshields, wheel openings, and other panel edges for final fitting of reveal molding. |
| reveal molding
| The metal trim that outlines an opening, depression, or raised area of an auto body. |
| reverse
| 1. The transmission position enabling the vehicle to back up. 2. To increase wheel track or tread by installing the rims backwards. |
| reverse bias
| [1] A dc voltage applied to a semiconductor junction, with a polarity opposite to that for forward bias. |
| reverse bleeding
| A method of purging air from a hydraulic system by forcing fluid into the system through a bleeder valve and allowing the air to escape at the master cylinder or reservoir. |
| reverse clutch
| A multiple-disc clutch that is engaged in reverse gear. |
| reverse Elliot axle
| A solid-beam front axle on which the steering knuckles span the axle ends. |
| reverse flush
| A method of cleaning an engine and/or radiator by flushing in a direction opposite of normal coolant flow, under pressure. |
| reverse flushing
| A method used to clean an engine or cooling system by flushing it in the opposite direction of normal coolant flow. |
| reverse gear
| A transmission gear arrangement obtained from a planetary gear set when the planet-gear carrier is held and power is applied tot he sun gear. |
| reverse idler gear
| 1. A gear in most standard transmissions that must be meshed to obtain reverse, and that idles in all forward gears. 2. A gear that transfers power in reverse only. Rotating on a separate shaft, it reverses the direction of the counter-gear motion. |
| reverse shoe
| A term used for trailing shoe. |
| reversed polarity
| A condition that exists when battery cables are connected to the wrong terminals of a battery. |
| reversion
| The interval during valve timing overlap when both intake and exhaust valves are open and a small mist of air/fuel is forced out back through the carburetor. |
| revolution
| The movement around the center or axis such as the circling of Earth around the sun. |
| revolutions per minute (rpm)
| 1. The number of times a member, such as a shaft, makes a complete revolution in one minute. 2. The rate of speed of a rotating part, such as a crankshaft. |
| revs
| A term used for rpm. |
| RFG
| An acronym for Reformulated gasoline |
| RFI
| [1] Radio Frequency Interference the induction of voltage caused by the release of a magntic field [2] A narrow band of frequencies with the electromagnetic spectrum [3] A form of electromagnetic interference created in the ignition secondary circuit or alternator which disrups the radio television transmissions |
| RH
| [1] Right hand; [ 2] Rhodium An element with the atomic number of 45 |
| rheostat
| A two- or three-terminal variable resistor used to regulate the voltage of an electrical current. |
| rib
| The tread-section element around a tire; the raised section of the tread. |
| ribbon spring
| A spring designed to hold the sprags of a sprag-overrunning clutch at the correct angle for instantaneous engagement. |
| ribbon-cellular radiator core
| A type of radiator core that consists of ribbons of metal, usually copper (Cu), soldered together along their edges. |
| rich mixture
| An air/fuel mixture having insufficient air or excessive fuel. |
| ride
| 1. A personal car. 2. An opportunity to drive in an event or series of events. |
| ride and handling
| 1. An indication of the degree of comfort a tire delivers to the passenger. 2. A measure of the vehicle responsiveness in relation to the driver's steering action. |
| ride height
| The distance between the road and the bottom of a vehicle. |
| ride shotgun
| To ride in the right front seat of the vehicle. |
| ridge
| A condition in the bores of an engine caused by piston-ring wear of the cylinder walls. |
| right-hand thread
| A common thread for a bolt or nut that is tightened by turning it clockwise, or to the right. |
| Right-To-Know-Law
| A federal law that requires all manufacturers of hazardous materials to notify and make information available to all employees, vendors, customers, and end users relative to the nature of the hazard, and to provide remedies if accidently misused. |
| rigid axle
| A term used for beam axle or solid axle. |
| rigid axle suspension
| A term used for solid axle suspension. |
| rigid discs
| Steel plates to which friction linings or facings are bonded or riveted. |
| rigid fifth wheel
| A fifth wheel that is fixed rigidly to a frame having no articulation or oscillation, generally used in applications where the articulation is provided by other means, such as an articulating upper coupler of a frameless dump. |
| rigid motor mount
| A solid mount for attaching the motor to the frame without any provisions for vibration dampening. |
| rigid rear suspension
| A suspension system which as both rear wheels attached to the ends of a solid rear axle housing. |
| rigid rear-driving axle
| A common rear suspension system design constructed of a central differential and tubular axle shaft housing. |
| rigid transmission mount
| A solid mount for attaching the transmission to the frame without any provisions for vibration dampening. |
| rim
| The outer edge of a bare wheel. |
| rim offset
| The distance between the wheel-rim centerline and the mounting face of the disc affecting front suspension loading and operation. |
| rim safety ridge
| The small, metal ridge just inside the tire-bead section to retain the tire position on the rim in case of a flat or blowout that tends to keep the bead of an uninflated tire out of the rim drop-center area. |
| ring
| 1. A term that generally applies to piston ring, compression ring, or oil ring. 2. A gasket, such as an O-ring. 3. A hollow noise, such as when striking a sound brake drum. |
| ring and pinion
| The combination of a ring gear attached to the differential and the pinion at the end of the drive shaft. |
| ring expander
| A flexible spring-steel part placed behind certain piston rings to increase ring pressure on the cylinder wall. |
| ring gap
| The gap between the ends of a piston ring installed in the cylinder generally 0.004 inch (about 0.1 mm) for each inch (25.4 mm) of cylinder diameter. |
| ring gear
| 1. The gear around the edge of a flywheel. 2. A large, circular gear such as that in the final drive assembly. 3. The outermost member of the gearset which has teeth in the inside circumference. |
| ring grooves
| Grooves machined around the piston wall to support the rings. |
| ring joint
| A shock-absorber component used to attach the shock absorber to the axle and frame. |
| ring land
| The surface of a piston between ring grooves. |
| ring ridge
| The ridge left at the top of a cylinder wall as the wall below is worn away by piston-ring movement. |
| ring spacing
| The width of the ring land. |
| ring-groove spacer
| Strips of thin metal used to fill the gap left between the piston and ring groove after the groove has been machined. |
| rise time
| 1.The time, measured in microseconds, for the output of a coil to rise from 10% to 90% of its maximum output. 2. The time it takes the signal on a oscilloscope to rise form its minimum to its maximum. |
| riser valve
| A term used for heat-riser valve. |
| rivet
| A fastener used to hold two pieces together. |
| riveted lining
| Linings on drum-brake shoes or disc-brake pads that are attached to their steel backing with rivets. |
| RMA
| An acronym for the Rubber Manufacturers Association. |
| RMS
| Root mean square |
| Rn
| Radon An element with the atomic number of 86 |
| RO
| An acronym for repair order. |
| roach coach
| A catering vehicle. |
| road feel
| A term that relates to the driver's ability to sense the vehicle's directional control from the movement transmitted through the steering wheel by the front wheels; not so sensitive on power-steering equipped vehicles. |
| road horsepower
| Horsepower available at the drive wheels of the vehicle. |
| road load
| A constant vehicle speed on level terrain. |
| road racing
| A competition race on an irregular course simulating the variety of terrain that is found on an average public road system. |
| road-draft tube
| A pre-emission, control-era device for ventilating the crankcase to the atmosphere; a pipe routed under the chassis at an angle that produces a small vacuum as the vehicle travels forward. Fresh air is drawn in through a mesh filter in the oil filler cap, circulated around inside the crankcase and exhausted through the road-draft tube carrying blowby with it. |
| roadability
| The steering and handling qualities of a vehicle as it is being driven on the road. |
| roadster
| 1. A single-seat Indycar of the late 1960's and early 1970's that resembled a two passenger car. 2. A two-passenger, open car. |
| rocker arm
| 1. A pivoting part in a mechanical fuel pump, one end of which rides on a camshaft eccentric or pushrod, and the other end of which pulls on the diaphragm via a mechanical linkage, causing the diaphragm spring to be compressed. 2. A pivoting lever in the valve train of an overhead valve system which applies motion, directly or indirectly from the camshaft to open an intake or exhaust valve. |
| rocker panel
| The sheet metal along the bottom of an auto body, beneath the doors, and between the front- and rear-wheel openings. |
| rocker-arm ratio
| The difference between the upper movement of the pushrod, acting on one end of the rocker arm, and the downward movement of the rocker arm acting on the valve stem. |
| rocker-arm shaft
| A shaft in each cylinder head on which rocker arms are arranged. |
| rod
| 1. An acronym for hot rod. 2. A steering arm. 3. An engine connecting rod. |
| rod bearing
| The bearing at the crankshaft end of a connecting rod. |
| rod big end
| The end of the connecting rod that attaches around the crankshaft. |
| rod bolts
| The bolts used to secure the cap to the rod at the big end. |
| rod journal
| A term used for rod bearing. |
| rod out
| To clean a radiator. |
| rod ratio
| A term used for rod-length ratio or rod-to-stroke ratio. |
| rod seal
| A component used to keep oil from leaking past the piston rod and into the atmosphere during pressure conditions. |
| rod small end
| The end of the connecting rod through which the piston pin passes to connect the piston to the connecting rod. |
| rod-end bearing
| The spherical bearing found at the end of a suspension arm or rod. |
| rod-length ratio
| The center-to-center length of a connecting rod divided by the piston stroke. |
| rod-to-stroke ratio
| A term used for rod-length ratio. |
| roll
| 1. To turn over and over. 2. To tip or sway side-to-side. 3. The motion of a vehicle body toward the outside of a turn when cornering or changing directions suddenly. |
| roll axis
| The longitudinal axis of a vehicle defined by an imaginary line running through the front and rear roll centers. |
| roll bar
| A tubular bar behind the cockpit of a race car to protect the driver in case of a rollover. |
| roll cage
| A tubular, cage-like structure surrounding the cockpit of a race car to protect the driver in case of a rollover and to add strength to the overall structure of the vehicle. |
| roll centers
| The points at the front and rear about which the vehicle's spring mass will roll. |
| roll out
| The distance a race car travels in a drag-racing event at the beginning of a run before the front tires clear the stage beam and start the clock. |
| roll steer
| The direction and amount that the rear axle may cause the vehicle to steer as it moves through its travel when the body rolls during cornering requiring the driver to oversteer or understeer to compensate for the problem. |
| roll stiffness
| The resistance, measured in pounds per inch of spring travel, of a suspension system to the rolling of the vehicle's mass. |
| roller
| 1. A race car offered for sale without an engine. 2. A cylindrical locking element of a one-way roller clutch. 3. A Rolls-Royce |
| roller bearing
| A bearing using rollers within an outer race or ring. |
| roller cam
| A camshaft having a small roller at the base of each lifter. |
| roller chain
| A timing chain having rollers that engage the gear sprockets. |
| roller clutch
| A one-way clutch containing a number of rollers that operate by wedging on a ramp between an inner and outer race to lock up (drive) when the outer race is turned in one direction, and to slip (overrun) when it is turned in the opposite direction. |
| roller lifter
| A valve lifter, used in some high-performance engines, featuring a roller which contacts the camshaft to reduce friction. |
| rolling diameter
| A term used for tire rolling diameter. |
| rolling radius
| The distance between the center of the wheel and the contact points of the tire on the ground under the weight of a vehicle. |
| rolling resistance
| The pounds of force required to overcome the resistance of a tire to rotate. |
| rolling start
| When cars are lined up running parade laps and a pace lap, behind a pace car, the are permitted to start with the display of a green flag. |
| rollover
| An accident in which the vehicle rolls over and over or turns upside down. |
| rolly
| A term used for roller cam. |
| ROM
| an acronym for Read only memory |
| RON
| An acronym for research octane number. |
| rookie
| A race-car driver in competition for the first season in an event or series of events. |
| room temperature vulcanizing (RTV)
| The trade name for rubber-like sealing compound. |
| root bead
| A weld bead that extends into, or includes part or all of the joint root. |
| roots supercharger
| A mechanically driven, positive displacement blower with hourglass-shaped rotors. |
| rope seal
| A type of seal used on crankshafts shaped much like a small, thin rope. |
| rosette weld
| A term used for plug weld. |
| rosin
| A sticky substance applied to the rear tires of drag-race cars for better traction off the line. |
| rotary
| The turning motion around an axis. |
| rotary combustion engine (RC engine)
| A four-cycle engine having a revolving triangular-shaped rotor to transfer power thrust via eccentric(s) to the output shaft. |
| rotary diesel
| A rotary combustion engine operating on diesel principles in which the fuel injected into the combustion chamber at the end of the compression phase is ignited by the heat produced during compression, rather than by the spark from a plug. |
| rotary engine
| 1. A form of radial engine used in early aircraft, outmoded by the end of World War I. 2. An engine with a three-sided rotor in a slightly hourglass-shaped oval chamber. |
| rotary flow
| Torque converter oil flow associated with the coupling stage of operation. |
| rotary oil flow
| A condition caused by the centrifugal force applied to the oil as the converter rotates around its axis. |
| rotary vacuum valve
| That part of a vacuum control used to divert a vacuum signal for operation of doors, switches, and/or valves. |
| rotary valve
| A semi-circular disc in a two-stroke engine that opens and closed the intake port. |
| rotary valve steering gear
| A type of power-steering gear. |
| rotation
| 1. A term used to indicate that a gear, shaft, or other device is turning. 2. A term used for tire rotation. |
| rotational motion
| Movement that occurs when a shaft turns (rotates) on its axis. A dynamic seal is required to contain fluids were rotational motion is present. |
| rotator
| A device in the cylinder head that causes the valve to rotate to reduce carbon build-up. |
| rotor
| 1. Disc-shaped component that revolves with hub and wheel. The lining pads are forced against the rotor to provide a friction surface for the brake system, so as to slow or stop a vehicle. 2. In a conventional ignition system, the part that transfers the secondary voltage from the center terminal to the outer terminals of the distributor cap as it rotates inside the cap. 3. The rotating part of an alternator that provides the necessary magnetic field to create a current flow. |
| rotor face
| The flat, parallel surface on each side of the rotor contacted by the pads (linings) during stopping. |
| rotor oil pump
| A type of oil pump in which a pair of rotors produce the pressure required to circulate oil to the engine parts. |
| rotor pump
| A positive-displacement pump that uses an inner drive rotor and an outer drive rotor to produce an oil flow. Lobes on the rotors create a fluid chamber of varying volumes and eliminate the need for a crescent as used in a gear pump. |
| Rotunda
| Test equipment manufactured for Ford Motor Co. by many different manufacturers. |
| roundy-round racing
| An kind of oval-track racing. |
| rpm
| An acronym for revolutions per minute. |
| RPO
| An acronym for regular production option. |
| RS232
| A standard defining interface voltage and current levels and other signal characteristics used to couple digital equipment to a transmission link. |
| RTV
| An acronym for room temperature vulcanizing. |
| RTV/Silicone
| A silicone-based RTV. |
| Ru
| Ruthenium An element with the atomic number of 44 |
| rubber bumper
| 1. Rubber stop on the car frame that prevents metal-to-metal contact when the rear-axle housing moves to its maximum upward position. 2. Rubber stops positioned on or near a control arm to limit the maximum upward or downward travel of the arm. |
| Rubber Manufacturers Association (RMA)
| A trade association for the manufacturers of rubber products for motor vehicles. |
| rubberized cork
| A mixture of cork and rubber sometimes used as a gasket. |
| rubbing block
| The insulated section of the movable breaker-point arm that contacts the breaker cam of a conventional ignition distributor. |
| rules of motion
| A term used for Newton's laws of motion. |
| rumble seat
| A folding seat in the rear deck of some older two-door coupes, convertibles, and roadsters. |
| rumper
| A big, noisy, rough-idling, high-performance engine. |
| run whatcha' brung
| To run whatever one brings to a racing event, especially a drag-racing event. |
| run-on
| A term used for dieseling or running on. |
| running board
| A flat step between the front and rear fenders to help passengers get in and out of the vehicle. |
| running gear
| The undercarriage of a vehicle and all mechanical components attached to it. |
| running on
| The condition that exists when a spark-ignition engine continues to run after the ignition switch has been turned off. |
| rust
| A metal oxidation caused by moisture and oxygen. |
| rust converter
| A liquid that can be painted over that is sprayed on pare metal to eliminate light rust and prevent other rust from forming. |
| rust inhibitor
| A chemical added to the coolant in a radiator to reduce the build-up of rust. |
| RV
| An acronym for recreational vehicle. |
| RVB
| Rear vacuum brake |
| RVP
| An acronym for Reid vapor pressure. |
| RVR
| Response vacuum reducer |
| RWAL
| A acronym for Rear Wheel Anti-Lock. A two-wheel ABS used on the rear wheels of GM and Daimler Chrysler light-duty pickup trucks and some SUVs One of the best known Kelsy-Hays systems |
| RWD
| An acronym for rear-wheel drive. |
| Rzeppa joint
| A constant-velocity universal joint. |
Auto & Car Glossary
