Automotive terms Modern N-O
Automotive Technical terms and abbreviations overview used in the industry, Guide and explanations.
The following are examples of Mid Modern technical terms recommended for general use worldwide. For in-depth specific terms also see terms for historic vintage and specific areas such as Paint.
NEEDLE BEARING:
A bearing which consists of a number (usually a large number) of long, thin rollers.
NITROGEN OXIDE (NOX):
one of the three basic pollutants found in the exhaust emission of an internal combustion engine. The amount of NOX usually varies in an inverse proportion to the amount of HC and CO.
NONPOSITIVE SEALING:
A sealing method that allows some minor leakage, which normally assists in lubrication.
02 SENSOR:
Located in the engine's exhaust system, it is an input device to the ECM/PCM for managing the fuel delivery and ignition system. A scanner can be used to observe the fluctuating voltage readings produced by an 02 sensor as the oxygen content of the exhaust is analyzed.
O-RING SEAL:
Molded synthetic rubber seal designed with a circular cross-section. This type of seal is used primarily in static applications.
OBD II (ON-BOARD DIAGNOSTICS, SECOND GENERATION):
Refers to the federal law mandating tighter control of 1996 and newer vehicle emissions, active monitoring of related devices, and standardization of terminology, data link connectors, and other technician concerns.
OCTANE RATING:
A number, indicating the quality of gasoline based on its ability to resist knock. The higher the number, the better the quality, Higher compression engines require higher octane gas.
OEM:
Original Equipment Manufactured, OEM equipment is that furnished standard by the manufacturer.
OFFSET:
The distance between the vertical center of the wheel and the mounting surface at the lugs. Offset is positive if the center is outside the lug circle; negative offset puts the center line inside the lug circle,
OHM'S LAW:
A law of electricity that slates the relationship between voltage, current, and resistance. Volts = amperes x ohms
OHM:
The unit used to measure the resistance of conductor-to-electrical flow. One ohm is the amount of resistance that limits current flow to one ampere in a circuit with one volt of pressure.
OHMMETER:
An instrument used for measuring the resistance, in ohms, in an electrical circuit.
ONE-WAY CLUTCH:
A mechanical clutch of roller or sprag design that resists torque or transmits power in one direction only. It is used to either hold or drive a planetary member.
ONE-WAY ROLLER CLUTCH:
A mechanical device that transmits or holds torque in one direction only.
OPEN CIRCUIT:
A break or lack of contact in an electrical circuit, either intentional (switch) or unintentional (bad connection or broken wire).
ORIFICE:
Located in hydraulic oil circuits, it acts as a restriction. It slows down fluid flow to either create back pressure or delay pressure buildup downstream.
OSCILLOSCOPE:
A piece of test equipment that shows electric impulses as a pattern on a screen. Engine performance can be analyzed by interpreting these patterns.
OUTPUT SHAFT:
The shaft which transmits torque from a device, such as a transmission.
OUTPUT SPEED SENSOR (OSS):
Identifies transmission/transaxle output shaft speed for shift timing and may be used to calculate TCC slip;
often functions as the VSS (vehicle speed sensor).
OVERDRIVE:
(1 A device attached to or incorporated in a transmission/transaxle that allows the engine to turn less than one full revolution for every complete revolution of the wheels. The net effect is to reduce engine rpm, thereby using less fuel. A typical overdrive gear ratio would be .87:1 , instead of the normal 1:1 in high gear. (2.) A gear assembly which produces more shaft revolutions than that transmitted to it.
OVERDRIVE PLANETARY GEARSET:
A single planetary gearset designed to provide a direct drive and overdrive ratio. When coupled to a three-speed transmission/transaxle configuration, a four-speed/overdrive unit is present.
OVERHEAD CAMSHAFT (OHC):
An engine configuration in which the camshaft is mounted on top of the cylinder head and operates the valve either directly or by means of rocker arms.
OVERHEAD VALVE (OHV):
An engine configuration in which all of the valves are located in the cylinder head and the camshaft is located in the cylinder block. The camshaft operates the valves via lifters and pushrods.
OVERRUNCLUTCH:
Another name for a one-way mechanical clutch. Applies to both roller and sprag designs.
OVERSTEER:
The tendency of some vehicles, when steering into a turn, to over-respond or steer more than required, which could result in excessive slip of the rear wheels. Opposite of under-steer.
OXIDATION STABILIZERS:
Absorb and dissipate heat. Automatic transmission fluid has high resistance to varnish and sludge buildup that
Occurs from excessive heat that is generated primarily in the torque converter. Local temperatures as high as 6000F (3150C) can occur at the clutch plates during engagement, and this heat must be absorbed and dissipated. If the fluid cannot withstand the heat, it burns or oxidizes, resulting in an almost immediate destruction of friction materials, clogged filter screen and hydraulic passages, and sticky valves.
OXIDES OF NITROGEN:
see nitrogen oxide (NOX).
OXYGEN SENSOR:
Used with a feedback system to sense the presence of oxygen in the exhaust gas and signal the computer which can use the voltage signal to determine engine operating efficiency and adjust the air/fuel ratio.
