Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS - "Lo"

Load

Something to be lifted, carried, transported, or accelerated.
The amount of material transported.
The amount of power carried by an electric circuit.
The resistance overcome by an engine when it is driving a machine.
Abbreviation for Calculated Load Value

Also See
Axle weight
Balanced Load
Capacitative Load
Clamping load
Dummy Load
Electric Load
Fat Load
Full load
Full load enrichment
G-loads
Heat Load
Inertial Load
International load line certificate
Negative load base
Nose load
Radial Load
Road load horsepower
Temperature of deflection under load
Thrust Load
Torque Full Load
Wheel load

Load alteration effect: The reactions in the drive train or, in FWD vehicles, in the steering, due to sudden load alteration. Compare Torque steer

Load and inflation table: A chart in the tire manufacturer's data book listing the carrying capacity of a tire at each of several air pressure increments from the lowest range of practical usage to its maximum capacity.

Load at installed height: The specified range of force required to compress a spring to its installed height usually expressed in terms of so many pounds of force at so many inches

Load base: Used in calculating load distribution; it is the distance between the center of the rear axle (or center between tandem axles) and the center of payload.

Also See
Negative load base.

Load-Bearing flue gas baffle: A flue gas baffle which adds support, strength or rigidity to a heat exchanger or flue.

Load capacity: See
Carrying capacity.

Load compensating resistor: A resistor unit in series with an electric brake control which can be preset to limit current to achieve brake balance.

Load Condition: See
High Load Condition

Load-controlled power distribution: A drive torque distribution, as established e.g., by a Torsen differential

Load distribution: The distribution of load on truck or trailer chassis. The relationship of the gross load on the front and rear axles to the total gross load.

Load distribution calculation: The payload on the front axle is equal to the total payload multiplied by the Load base (in inches) and divided by the Wheelbase (in inches). To complete the calculation of load per axle, it is necessary to obtain the unladen weight of the vehicle and estimate its breakdown by axle.

Loaded: See
Spring loaded

Loaded displacement: The displacement of a ship when floating at her greatest allowable draft

Loaded radius: Measurement in inches from the wheel axle centerline to the ground when the tire is properly inflated for the load. Also called Static loaded radius

Loaded runout: Radial runout that appears only when the tire is supporting the mass of the car. Loaded runout is caused by stiff sections accidentally built into the tire sidewall.

Loaded tourer: A Bicycle whose structure, geometry, and equipment is designed to allow a cyclist to travel with 50 pounds of gear.

Load enrichment: See
Full load enrichment

Loader

An off road vehicle with a large "bucket" or shovel on the front to move material, particularly dirt or debris.
A hydraulic mechanism mounted on a trailer or behind the cab of a truck or tractor used to load cargo onto the trailer or truck. Some logging industry trucks are equipped with log loaders for loading fresh cut logs.

See
Equipment Loader
front-end loader
Front-Loader
Low-loader
Rear Loader
Side Loader

Load floor

The cargo-carrying area of a van or truck.
The floor of the luggage area of an station wagon or hatchback

Load floor extension: A molded tray that folds out of the rear luggage area and provides an extended load floor which hangs out over the bumper. It can also be used for picnics.

Load horsepower: See
Road load horsepower

Load index: (LI) coded number on the sidewall of a tire to indicate the maximum load the tire may carry at a given speed under manufacturer's conditions

Loading: The amount with which something is loaded.
Also See
Basic Loading
Blade Loading
Burner Loading
Catalyst Loading
Lead loading
Shock loading

Load line: The line on a ship which indicates the maximum depth to which it can sink when loaded with cargo. Also known as marks.

Load line certificate: See
International load line certificate

Load overhang: The distance a load extends beyond the rear of a vehicle. It also requires a red flag or red reflector at the end of the load.

Load proportional brake control: A system or device which regulates the input force to the brakes on an axle in proportion to the load on that axle.

Load range

An index of tire strength which replaces the older (discontinued) ply rating system.
A discontinued measurement of the number of Plies at which a tire is rated. Load range B equals 4 ply rating; C equals 6 ply rating; and D equals 8 ply rating.

Load rating: The maximum amount that a vehicle can carry with the tires and springs it has. Also called Load index

Also See
Carrying capacity
Ply rating
Spring booster

Load resistor: See
Ballast resistor

Load Sensing Proportioning Valve: (LSPV) a hydraulic system control valve that works like a proportioning valve, but also takes into consideration the amount of weight carried by the rear axle

Load-sensitive proportioning valve: A valve which regulates hydraulic pressure to the rear wheels as a function of chassis height-to-axle distance. A vehicle weight transfer during hard braking increases this distance and, via a spring or rod linkage, will close the valve to reduce braking pressure at the rear wheels; also, a heavily loaded car will have more braking power at the rear wheels

Load synchromesh: See
Locking synchromesh

Load test: A test applied to a Battery. Although the battery indicates 12 volts or more, it may not meet the amperage for which it is rated. A tester with a variety of amperage loads can be applied to determine if the battery is good.

Load Tester: See
Battery Load Tester

Load Torque: See
Full Load Torque

Load transfer: See
Weight transfer

Load transference: The changing of the amount of load distributed to each axle while the vehicle is in motion, due to the effects of braking, cornering ascending, or descending grades, etc.
Also see
Roll steer.

Load waterline: The line on the lines plan of a ship, representing the intersection of the ship's form with the plane of the water surface when the ship is floating at the summer freeboard draft or at the designed draft. Also called marks

Lobe: An off-center or Eccentric enlargement on a shaft which converts rotary motion to Reciprocating. Also called a cam
Also see
Back Lobe
Cam lobes

Lobe-type supercharger: A positive displacement compressor with two lobed rotors. Compare Lysholm supercharger and Roots compressor

LOC: Acronym for Light Off Catalyst
Also see
Roc Loc

Local cell: A galvanic cell resulting from differences in potential between adjacent areas on the surface of a metal immersed in an electrolyte

Localized controllers: Independent energy control device located near the system it is controlling.

Localized corrosion: Rusting occurring at one part of a metal surface at a much higher rate than over the rest of the surface, e.g., Pitting corrosion, crevice corrosion. The opposite is Uniform corrosion

Local yokel: Trucker slang for city police officer as in "That town up ahead is crawling with local yokels."

Local yokel with a customer: Trucker slang for city police officer with someone pulled over as in "You've got a local yokel with a customer on your side."

Locating dowel: See
Dowel pin

Locating lug: A projection or pin for holding a part in a specific position. All engine bearings have some means of ensuring that they will not shift or move in the housing bore once installed. Most bearings use a locating lug, which is simply a small projection or pin that fits into a recess in the housing bore

Locating pin: A projection or lug for holding a part in a specific position.

Also See
Dowel pin
Locating lug

Locating spring: A steel wire clip in disc brakes that secures the cylinder in a floating frame or caliper frame. Compare Spreader spring

Lock

A fastening device which closes and opens by the use of a key.
A steering term describing the amount by which the wheels of a vehicle are able to turn.
Also see
Lock-to-lock
Steering lock
An obstruction such as a Air lock or Vapor lock.
To close with a key.
To fix or become fixed in a certain position such as "the seat belts locked when the brakes were applied suddenly but so did the wheels and the car went into a skid."
A gear train term indicating to interlock or couple.

Also See
Air Lock
Angle of lock
Bicycle Lock
Bike Lock
Bonnet lock
Cable lock
Childproof lock
Differential lock
Door lock
Door lock de-icer
Full lock
Helical spring lock washer
Hood lock
Nylon lock nut
Opposite lock
Parking lock
Pin Lock
Reverse Lock
Selector lever lock
Steering Lock
Steering wheel and brake lock
Tire bead lock
Valve Lock
Vapor lock
Wheel lock

Lockable differential: A Limited-slip differential

Lockable wheel: A wheel that can be secured to the hub with a lock

Lock angle: See
Steering angle

Lock brake system: See
Anti-lock brake system

Lock buster: Lock puller

Lock cylinder: A cylinder in the middle of a cylinder lock that is prevented from turning (locked) by a number of pins (typically five) which penetrate down through the wall of the cylinder. The cylinder is turned by inserting a key which pushes the spilt pins up to varying heights so that the edge of the cylinder engages with the gap between the two sections of each pin allowing the cylinder to turn

Lock de-icer: A fluid which is inserted into the key-hole to melt the ice which has bound the tumblers in a door lock.

Also See
Door lock de-icer

Locked-rotor current: Steady-state current taken from the line with the rotor at standstill. Steady-state current means the current does not vary in intensity, but remains constant

Locked-rotor torque: The minimum torque that an electric motor will develop at rest for all angular positions of the rotor

Locker: See
Chain locker

Lock facing: The surface of a door to which the lock is attached

Locking: See
Central locking
C locking
Parallel action locking pliers
Remote-control locking

Locking bar clamp: Locking clamp with sliding jaw providing extended clamping capabilities

Locking clamp: Locking pliers with specially shaped jaws for vice work and intricate clamping jobs. Locking clamps include, for example, vice grip C-clamps, vice grip pipe clamps, locking bar clamps, welding clamps, and sheet metal clamps

Locking differential: A differential with the ability for locking together the two half shafts, thus putting the differential out of action and greatly improving traction. In a non-locking differential if one wheel was stuck in snow and spinning, the other wheel would be stationary even if it were on dry ground. In a locked differential, both wheels would turn the same amount. Since the dry-ground wheel had traction, it would be able to pull the vehicle out even though the other wheel had no traction.

Locking disc: See
Center locking disc

Locking hub: See
Central-locking hub

Locking lug bolt: An anti-theft wheel lug bolt which requires a special wrench to remove it

Locking lug nut: An anti-theft wheel lug nut which requires a special wrench to remove it

Locking mechanism: A device which locks the reel of a seat belt when the forward acceleration of the occupant exceeds a certain value

Locking pliers: A type of pliers with locking jaws that can be used as pliers, wrench, clamp, or small vice. Closing the handles locks the jaws into position. The jaws are released by pulling a special release lever. Locking pliers with specially shaped jaws for vice work and intricate clamping jobs are called Locking clamps

Also See
Parallel action locking pliers

Locking reel: A device which locks the reel of a seat belt when the forward acceleration of the occupant exceeds a certain value

Locking synchromesh: A common synchromesh mechanism in which the synchromesh pressure is proportional to the gearchange force, thus preventing overriding of the synchromesh action due to hasty operation of the lever; the gear and gearchange sleeve are prevented from engaging until rotational speeds are synchronized

Lock nut: A nut which has a special means for gripping a threaded bolt or screw to prevent or resist the nut from backing out
See
Locknut

Locknut: A nut used in conjunction with a washer or a second nut to lock a mechanism in place, such as the nut found at the upper end of a Headset and in front of the Calipers on many Caliper brakes.

Also See
Center lock nut
Flex-Loc^TM
Nylon lock nut

Lock-out: See
Power window lock-out switch
Starter lockout

Lockout ignition Time: The period of time between initiation of gas flow and the action to shut off the gas flow in the event of failure to establish proof of the supervised ignition source or the supervised main burner flame. Reinitiating the lighting sequence requires a manual operation.

Lock-out switch: See
Power window lock-out switch

Lock picker set: A set of special tools designed for opening locked cars, especially used by professional Locksmiths

Lock pillar: See
B-pillar

Lock pin: Lock pin

A pin that is secured with a large loop that surrounds a pipe.
Also See
Locating pin

Lock puller: A special door lock picker; attached to the outside of a car door lock, the lock puller rips out the entire lock cylinder

Lockring

The notched ring that fits on the left side of a Bottom bracket of a Bicycle and prevents the Adjustable cup from turning.
A metal ring which snaps into the rim Gutter, holding the side ring in place.

Lock ring pliers: Tool for removing and installing heavy-duty circlips, used e.g., on brakes, transmissions, pedal shafts, and clutch shafts

Locksmith: A person who can re-key a lock and work on keys and locks.

Lock striker: See
Striker

Locktite: Brand name for a type of liquid which is applied to the threads of a bolt and/or nut to secure them to various degrees of strength.

Lock-to-lock: A steering designation which describes the distance created by the steering wheel when it is fully to the left and then moved fully to the right.

Lockup

The moment when a tire begins to Skid during braking. A tire's maximum braking force occurs when it is on the verge of lockup. Ideally all four tires should approach lockup simultaneously to give a vehicle the best braking. Because this ideal is hard to create in the real world, one end tends to lock up before the other. Front-wheel lockup is inherently more stable than rear-wheel lockup. Anti-lock brakes provide the best type of braking because it rapidly releases pressure on the brakes to prevent lockup.
A condition where the wheel and tire is prevented from rotating. Braking power overcomes the traction of the tires and skidding occurs.

Also see
Wheel Lockup

Lock-up clutch: Automatically engaged clutch in a lock-up torque converter which prevents slipping losses.
Also See
Torque converter lock-up clutch

Lockup differential: A differential whose two outputs can be locked together, eliminating any differential action but maximizing Traction under slippery conditions.

Lockup torque converter: A Torque converter fitted with a lockup clutch that can be engaged to eliminate the slip between the torque converter's input and output, thereby improving fuel efficiency and performance because it is now in direct drive mode

Lock-up torque converter: Torque converter in which the pump can be mechanically locked to the turbine, eliminating any loss through the fluid because it is now in direct drive mode

Lockwasher: There are several types of lockwashers which are designed to be placed between a flat washer and the securing nut in order to keep the nut from backing out or loosening. They include split ring lock washer, external tooth lock washer, internal tooth lock washer, and combination tooth lock washer.
Also See
Helical spring lock washer
Spring lock washer
Tooth Lockwasher

Locomobile: A vehicle brand of which all models 48 and 90; 1927 8-80; 1928 8-80; and 1929 8-80 are Classic cars.

Locomotive: See
Railroad Locomotive

Locut nut: A fastener used to enable sheet metal screws to be used for relatively large holes in panels

Loft: See
Mold loft

Logbook: A record book carried by truck drivers in which they enter their hours of service and duty status for each 24-hour period. Required in interstate commercial trucking by the U.S. Department of Transportation.

Log deck landing: A place in or near the forest where logs are gathered for further processing or transport.

Logging Trailers: Some pole trailers consist of a set of axles with a cradle to hold logs and a pole attached to the rear of a power unit. Others are skeletally framed. Some have double decks. Most will have cradle-like features called BUNKS to hold the logs in place.

Logic controller: A part of the wheel slip brake control system which interprets input signals from the sensor(s) and transmits the controlling output signals to the modulator(s).

Log manifold: A special Intake manifold generally designed to accept four or more Carburetors. Each side has bases for the Carburetors set on a pipe-like log area.

Logo: See
Company logo

Logs cargo: Truck cargo including processed wood, like 2x4's, plywood, pulpwood, firewood, and new pallets, fresh from the factory.

Long and short arm suspension: A Suspension system using an upper and lower control arm. The upper arm is shorter than the lower. This is done so as to allow the wheel to deflect in a vertical direction with a minimum change in Camber.

Long arm suspension: See
Unequal-length wishbone suspension

Long block: A long block consists of the Short block plus the oil pump and sump, cylinder head(s), camshaft(s) as well as the complete valve train. The opposite is short block

Long block engine: An engine with a relatively long crankshaft. The opposite is Short block engine. Also compare big-block engine. Normally, the term long block engine means a 6-cylinder in-line engine which has a longer block than a 4-cylinder or V-8 engine

Long Combination Vehicle: (LCV) In general, vehicles longer than a standard doubles rig (tractor and two 28-foot semitrailers). Examples of LCVs which are permitted in some U.S. western states and eastern toll roads Twin 48-foot trailers; triple 28-foot trailers.

Longer Combination Vehicle: (LCV) A tractor pulling two or more semitrailers on an interstate roadway weighing more than 80,000 lbs., or a doubles rig with either trailer greater than 28.5 feet in length.

Longeron: The main side member

LONGFT: Acronym for Long Term Fuel Trim

Long-haul: A long distance which a trucker drives

Longitudinal: Lengthways. The opposite is lateral

Longitudinal engine: A traditional engine layout used on most RWD vehicles with the cylinders lying lengthways from the front to the back. Also called North-south layout. The opposite is Transverse engine

Longitudinal girder: See
Side member

Longitudinal member: See
Side member

Longitudinal tire clearance: The distance between the tread and the closest point forward or rearward, reduced by increase in tread depth and rearward movement of the axle under load (1/3 of the distance between shackle pin centers).

Longitudinal leaf spring: A Leaf spring that is mounted so that it is parallel to the length of the vehicle.

Longitudinals: Fore-and-aft structural shape or plate members attached to the underside of decks, flats, or to the inner bottom, or on the inboard side of the shell plating.

Long-nose pliers: Pliers with half round and tapered jaws, often with a wire cutter and used for electrical work. Also called Snipe-nose pliers or Needle-nose pliers

Long-nose self-grip pliers: Locking pliers with extra long reach jaws

Long-reach C-clamp: Self-grip locking clamp with extra long C-shaped jaws

Long stroke engine: An engine where the length of the piston stroke is greater than the diameter of the bore of a cylinder. A relatively long stroke produces higher low-end torque at the cost of increased piston speeds and reduced revving ability. The opposite is Short stroke engine

Long ton: 2240 pounds (1016 kilograms). Also called gross ton.

Look compatible: A type of bicycle shoe which has three holes drilled into the sole in a triangular pattern to fit Look clipless pedals.

Loom: A harness covering. Older vehicles used woven-cloth loom; most modern vehicles use a corrugated-plastic loom or split loom

Also See
Spark plug cable loom
Spark plug wire loom
Split Loom
Wiring harness

Loom tape: A non-adhesive tape used as a harness wrap. Adhesive-type tapes, including electrical tapes, are not recommended for wrapping harnesses. Often a piece of shrink wrap is used at tape ends to keep the tape from unraveling

Loop

Short for Engine Operating Loop Status. Open is cold fueling, Closed is fueling by HO2S and fuel trims
Road of limited length forming a loop, having no other intersecting road, and functioning mainly as direct access to abutting properties. A loop may be designated for one-way or two-way traffic.

See
Closed loop
Open-loop
Open loop system

Loop circuitry: See
Phase-locked loop circuitry

Loop detectors: Magnetic traffic detectors imbedded into the roadway in a circular fashion. They detect and inform the signal controller of traffic approaching an intersection.

Loop flow: The movement of electric power from generator to load by dividing along multiple parallel paths; it especially refers to power flow along an unintended path that loops away from the most direct geographic path or contract path.

Loop frame: Early motorcycle frame design in which the downtube curves underneath the engine cases to become the seat post

Loop Mode: See
Open Loop Mode

Loop scavenging: A method of scavenging used on two-stroke motorcycle engines. The entering gas streams travel across the piston, up the far side of the barrel and curl over and down to complete the scavenging process; loop scavenging is sometimes used to refer specifically to a special variant of this type of scavenging Schnürle scavenging

Loop system: See
Closed loop system
Open loop system

Loose

Not tight.
A colloquial term for Oversteer.

Loose ball bearings: Bearings inside a component that are not held in a metal or plastic retainer (cage)

Loosen: To make something less tight; to slacken

Loping: Action of the engine when the mixture of Gasoline and air to the Carburetor is too lean.

LORAN: Acronym for LOng RAnge Navigation. A satellite navigation system commonly used by ships and naval vessels to precisely locate their position while at sea.

Lorry: A British term for Truck.

LOS: Acronym for limited operation strategy

Loss: See
Hysteresis Loss
Ir loss
Power Loss
Processing Loss
Total Loss

Losses: See
Charge losses
Evaporative losses
Friction losses
Pumping losses
Scavenging losses

Loss leaders: Products whose prices are cut with the idea that they will attract customers to the store.

Lost-core technique: A method of producing thermoplastic inlet manifolds

Lost-foam casting: A casting method using foamed plastic cores, giving the surface of the castings the appearance of styrofoam; used for engine blocks

Lost-foam casting process: A casting method using foamed plastic cores, giving the surface of the castings the appearance of styrofoam; used for engine blocks

Loss Monitor: See
Phase Loss Monitor

Lost motion: Motion between a driving part and a driven part which does not move the driven part.

Also See
Backlash

Lot: See
Car lot
Inspection lot
Parking lot
Rolling Parking Lot

Lot Stencil: See
Parking Lot Stencil

Lotus: Click image for books on
Lotus

A vehicle brand of which the 1958-63 Elite models are Milestone cars.

Loud pedal: A colloquial term for Accelerator pedal

Loudspeaker: See
Baffle Loudspeaker
Blatthaller Loudspeaker

Louver: The Ventilation slots such as sometimes found in the Hood of an automobile or in the dash. They let air come into the engine compartment to cool the engine or into the passenger compartment. Sometimes they are merely decorative with no cooling function.
Also See
Rear window louvers

Louvre: Canadian and European spelling for Louver

Low: (L) A driving gear ratio in automatic transmissions for climbing hills (to prevent Lugging or for going down steep hills so that it acts as a compression brake.

Also See
Bull low
Four-wheel-drive low

Low-bake booth: A closed section in painting lines in a paint shop, in which coats of paint are dried at low temperatures

Low-bake equipment: Equipment for drying coats of paint at low temperatures

Low-bake paint: Respray paint baked at 80°C, giving a high-quality finish but requiring suitable low-bake spray booths/ovens

Lowball: A car sales practice of stating a very low price for a new car to a customer who is known or expected to be comparison shopping or calling over the phone. When the customer finds that other dealers cannot match this price, he will return to the original dealer, only to be told that the price was a mistake or the price of a lower level vehicle; many customers will then accept a new, higher price because they are tired of shopping around or unwilling to lose face by going back to the dealers that could not match the lowball price. Compare Highball.

Low battery: A battery with less than acceptable voltage and should be charged or replaced.

Low beam: The outboard Headlights in a four-light system or the main lights in a two-light system. The low beam is used for most applications of night driving. For those cars without day-time running lights, the low beam should be turned on. In fog and heavy snow, the low beam can provide more light on the road because the High beam reflects light back to the Driver. The British term is dipped beam.

Low bed: A low platform trailer for heavy equipment hauling, usually on 15" diameter tires. Also called Low boy.

Low box: Status of the transmission when the transfer gearbox lever is in the low position - for difficult off-road conditions demanding greater traction or low speed control.

Low boy

A low platform trailer for heavy equipment hauling, usually on 15" diameter tires. Also called Low bed.
An open flat-bed trailer with a deck height very low to the ground, used to haul construction equipment or bulky or heavy loads.
Gooseneck flatbeds slung very low to the ground. Often the gooseneck is detachable so that equipment can be loaded from the front. Sometimes ramps are at the rear. Typically about 12" off the ground.

Low brake pedal: A condition where the Brake pedal approaches too close to the Floorboard before actuating the brakes.

Low BTU gas: A fuel gas with a heating value between 90 and 200 BTU per cubic foot.

Low-carbon steel: Steel containing 0.03 to 0.3 per cent carbon (typically 0.2%). Used for machine screws, wood screws, etc., and similar products without critical strength requirements. It cannot be heat treated for greater strength. Sometimes called Mild Steel. The tensile strength is around 54M psi.

Low carbon steel: See
Low-carbon steel

Low Crown Dolly: A curved block of cast iron for bending slight contours. It is used with a bumping hammer to reshape slight contours.
Also see
Dolly

Low crown panel: The predominant shape of modem body panels, e.g., on most side panels such as door skins. The opposite is High crown panel
Also see
Crown

Low-density polyethylene: (LDPE) a relatively soft, flexible polyethylene, used mainly for plastic film and sheet

Low-drag caliper: A Caliper designed to reduce pad drag on the rotor

Low E glass: Low-emission glass reflects up to 90% of long-wave radiation, which is heat, but lets in short-wave radiation, which is light. Windows are glazed with a coating that bonds a microscopic, transparent, metallic substance to the inside surface of the double-pane or triple-pane windows.

Low-emission: A condition of a vehicle which releases relatively few pollutants into the environment. Compare Zero-emission vehicle. In some countries tax relief is available for low-emission cars

Low-Emission Vehicle: (LEV) A vehicle meeting either the US Federal government EPA's CFV LEV standards or California's CARB's LEV standards. LEVs produce fewer emissions than TLEVs.
Also see
National Low-Emission Vehicle
Transitional Low-Emission Vehicle

Low-Emission Vehicle Program: See
California Low-Emission Vehicle Program
National Low-Emission Vehicle Program

Low Emission Vehicle Standards: (LEV) State and federal governments set standards for automakers developing vehicles that will produce emission. Each state determines its own levels as does the federal government. California and New York have some of the most stringent laws. Once the requirements are met for a specific vehicle, the automaker may call that car or truck a Low Emission Vehicle.

Also See
Ultra Low Emission Vehicle Standards

Lower A-arm: See
A-arm

Lower back panel: The body sheet metal between the trunk lid and the rear bumper

Lower bending die: A lower tool insert of the press brake

Lower dead center: (LDC)
See
Bottom dead center

Lower explosive limit: (LEL). The lowest concentration of a flammable gas/vapor in air in which flame is propagated.

Lower front panel: See
Front apron

Lower Heating value: (LHV). The value of the heat of combustion of a fuel as measured by allowing all products of combustion to remain in the gaseous state. This method of measure does not take into account the heat energy put into the vaporization of water: (heat of vaporization).

Lowering kit: A set of springs and other suspension parts to reduce ground clearance.

Lowers: The bottom part of a motorcycle fairing to protect the rider's legs from wind and provide a more aerodynamic configuration

Low fuel indicator: A warning light which glows when fuel is getting low and flashes (on some models) when it is very low.

Low gear: The lowest gear in a Transmission, usually called first gear.

Low geared: A transmission which has a small drive gear and a large driven gear. On a bicycle, for instance, the chainwheel gear (by the pedals) is the smallest (usually called a Granny gear and the freewheel gear (at the center of the wheel) is the largest. This arrangement gives the slowest speed but the best torque.

Low head pressure: Lower-than-normal-high side pressure caused by a system malfunction

Low-head pump: A pump used for low total heads; in the case of centrifugal pumps the low-pressure pump has a nominal total head not exceeding 80 m

Low-loader: A truck for heavy loads with a low-level loading platform and often an extension ramp or lift-operated tailgate which can be lowered to street level

Low-maintenance battery: A battery that rarely requires topping-up. Compare Maintenance-free battery

Low oil sensor: See
Oil level sensor

Low oil warning light: See
Engine oil level warning light

Low pedal

A condition where excessive clearance at some point in braking system causes full pedal movement for application of brakes
The condition in which the brake pedal must travel very far or very close to the floor

Low pivot swing axle: A rear axle setup that attaches the Differential housing to the Frame via a pivot mount. A conventional type of Housing and axle extend from the Differential to one wheel. The other side of the Differential is connected to the other driving wheel by a housing and axle that is pivoted at a point in line with the Differential to frame pivot point.

Low-pressure: See
Gauge Low-pressure

Low-pressure control: Cycling device connected to low-pressure side of system.

Low-pressure cut-out: A device which protects the air conditioning system by switching the compressor off when a pressure loss occurs

Low-pressure cut-out switch: A device that disengages the compressor clutch when the system pressure drops below a predetermined level

Low-pressure foaming: A process in which plastics are foamed under low pressure (1-5 Bar). The opposite is High-pressure foaming

Low-pressure gauge: Instrument for measuring pressures in range of 10 kPa to 350 kPa.

Low pressure indicator: A unit or combination of units which provides a visible or audible warning signal whenever the system pressure is below a predetermined value.

Low-pressure pump: A pump used for low total heads; in the case of centrifugal pumps the low-pressure pump has a nominal total head not exceeding 80 m

Low pressure safety cutout: Motor protection device that senses low-side pressure. Control is wired in series with the motor and will shut off during periods of excessively low suction pressure.

Low-pressure sodium lamp: A type of lamp that produces light from sodium gas contained in a bulb operating at a partial pressure of 0.13 to 1.3 Pascal. The yellow light and large size make them applicable to lighting streets and parking lots.

Low-pressure Steam: See
Boiler Hot Water And Low-pressure Steam

Low-pressure Steam Boiler: See
Hot Water And Low-pressure Steam Boiler

Low pressure tire: A tire with a large cross-section for operation at lower pressure. Increased air capacity permits lower pressure. ATV tires, for example, have only 3 or 4 psi.

Low profile: A tire with a low aspect ratio of a tire (i.e., the section height is smaller than section width).

Low-profile air cleaner: A circular, flat, chrome-plated air cleaner, mounted on top of the carburetor

Low-profile tire: A tire with a wide tread but a low height. A tire with a height that is 70% or less of its width would be described as low-profile, as opposed to an average tire of 80%

Low Range Gearbox: See
Dual-range transmission

Low Range Transmission: See
Dual-range transmission

Low ratio: A condition of the transmission when transfer gearbox lever is in the low position.

Low-refrigerant protection system: A system which interrupts the electrical current to the compressor clutch in the event of refrigerant loss. A typical exhaust is the GM superheat switch and thermal limiter low side suction side -- the low pressure part of the system between the expansion valve outlet and the compressor inlet

Low rider: A customized car which is extremely lowered through body and suspension modifications

Low side: An air conditioning term describing the side between the expansion valve or orifice tube and the compressor; includes the evaporator -- called the low pressure portion; The low pressure part of the system between the expansion valve outlet and the compressor inlet. Also called suction side.; That portion of a refrigerating system which is below evaporating pressure.

Low-side Float: See
Flooded System Low-side Float

Low-side float flooded system: Refrigerating system which has a low-side float refrigerant control.

Low-side float valve: Refrigerant control valve operated by level of liquid refrigerant in low-pressure side of system.

Low side gauge: A gauge that can indicate both pressure and vacuum. Also called a Compound gauge

Low-side pressure: Pressure in cooling side of refrigerating cycle.

Low-side pressure control: Device used to keep low-side evaporating pressure from dropping below certain pressure.

Low-side pressure limiter: Motor protection device that senses low-side pressure.
Also see
Low pressure safety cutout

Low-side service valve: A device, located on the suction or low side of the compressor, at which low side pressure can be checked and other service operations can be performed

Low speed: Gearing provided in an automobile which causes greater number of revolutions of engine as compared to driving wheel

Low speed circuit: See
Idle circuit.

Low-speed circuit: See
Idle circuit.

Low speed traction control: See
Low-speed traction control.

Low-speed traction control: A system that helps prevent front-wheel spin on slippery or gravel surfaces during Acceleration at Speeds up to 40 kph (25 mph).

Low spot: An indentation on a panel surface

Low-suction pressure: Condition of lower than normal high side pressure caused by system malfunction

Low sulfur diesel fuel: (LSD) Diesel fuel containing more than 15 but less than 500 parts per million: (ppm) sulfur.

Low temperature activity: A description of the ability of a catalytic converter to purify exhaust gases in the warm-up phase following a cold start. This phase is included in most of the current exhaust emission test procedures, as CO and HC concentrations are particularly high when engines are operated below normal operating temperatures

Low temperature collectors: Metallic or nonmetallic collectors that generally operate at temperatures below 43°C and use pumped liquid or air as the heat transfer medium. They usually contain no glazing and no insulation, and they are often made of plastic or rubber, although some are made of metal.

Low temperature fouling: See
Carbon fouling

Low temperature phosphating: Phosphating at temperatures around 20° C

Low Temperatures: See
Test Current For Low Temperatures

Low tension lead: See
Low tension leads.

Low tension leads: The wiring in the Ignition system that is distinguished from the high tension wiring. The low tension leads carry only 6 or 12 volts. Includes the Battery cables, the Coil connections (but not the high tension wire going to the Distributor), the wiring to the Ignition switch, and the non-high tension wires going to the distributor.

low tire pressure warning: An electronic system that detects a low tire pressure on a vehicle. Also called a Tire pressure monitor.

Low voltage circuit: See
Primary circuit

Low-Voltage Electric Circuit: A circuit at voltages from 31 to 600 volts inclusive.

Low zinc technology: A technology used in present-day Phosphating processes. Normal zinc phosphating baths used as pre-treatment for painting contain approximately 2-4 grams-per-liter (g/l) zinc and approx. 5-10 grams-per-liter (g/l) phosphorus pentoxide. In low-zinc baths, the corresponding values amount to approx. 0.4-1.7 g/l zinc and 12-16 g/l phosphorus pentoxide

Lozenged: A car chassis which, as the result of an accident, no longer holds its true shape but is rather pushed into the shape of a rhombus or diamond