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ABS

(see ANTI-LOCK BRAKES)

ACCUMULATOR

In hydraulics or pneumatics, a device for storing pressurized fluid.

AERODYNAMICS

The study of the behavior of the airflow as it passes around a moving object and the forces exerted by the air on the object. In car design the positive and negative lift of the airflow is studied in wind tunnels. Negative lift is preferred to press the vehicle closer to the ground. Car air resistance is also studied.

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A/F

Air/Fuel ratio in the engine.

AIR INDUCTION SYSTEM

The components through which combustion air is induced into the engine.

ALB

(see ANTI-LOCK BRAKES)

ANTI-LOCK BRAKES (aka ABS, ALB)

Antilock Braking System. Keeps the tires from locking while braking; the car can still be handled without losing control.

 

AUTOMATIC TRANSMISSION

A transmission that shifts its own gears according to the prevailing speed, load, and road condition. Also called automatic gearbox. Operation can be electrical or hydraulic.

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B

BDC

(see BOTTOM DEAD CENTER)

BHP

(see BRAKE HORSEPOWER)

BORE

The diameter of a gasoline or steam reciprocating engine cylinder. The displacement can be increased by increasing the diameter (reboring).

BOTTOM DEAD CENTER

In an engine, lowest position of a piston in a cylinder during the stroke.

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BRAKE HORSEPOWER (bhp.)

The measure of an engine’s horsepower without the loss in power caused by the gearbox, generator, differential, water pump and other auxiliaries. The actual horsepower delivered to the driving wheels is less.

BSCO

Brake Specific CO; in an engine, the ratio of the rate at which carbon monoxide leaves the exhaust manifold to the brake horsepower.

BSFC

Brake Specific Fuel Consumption; in an engine, the ratio of the rate at which fuel is flowing into the engine to the brake horsepower being generated.

BSHC

Brake Specific HC; in an engine, the ratio of the rate at which hydrocarbons leave the exhaust manifold to the brake horsepower.

BSNO

Brake Specific NOx; in an engine, the ratio of the rate at which oxides of nitrogen leave the exhaust manifold to the brake horsepower.

C

CAM

An eccentric (off-center) lobe or projection on a rotating shaft; used to transmit a motion at a predetermined time during the rotation of the shaft.

CAMSHAFT

A rotating shaft with a number of cams or eccentric lobes used to operate the engine valves, usually via pushrods and rocker arms.

CAPACITOR

An electronic device that stores an electrical charge.

CARBON MONOXIDE (aka CO)

Carbon Monoxide; an undesirable chemical combustion of a hydrocarbon fuel product due to imperfect combustion.

CATALYST

A material which speeds up or stimulates a chemical reaction without being significantly chemically altered by the reaction.

CATALYTIC CONVERTER

A device which enhances certain chemical reactions reducing the levels of undesirable exhaust gases from an engine.

CC

(see CUBIC CENTIMETER)

CHASSIS

The basic-strength auto frame including the engine, suspension, wheels, brakes and drive train. A car without its body or coachwork. In monocoque or unit construction it is integral with the body.

CLUTCH

A friction device used to connect the engine to the drive train. Used when changing gear ratios during acceleration. Can connect or disconnect the engine and the drive train at driver’s will.

CO

(see CARBON MONOXIDE)

COACHWORK (French Carrosserie, German Karosserie, Italian Carrozzeria)

The automobile body: especially the comfort and luxury appointments as distinguished from the operational chassis.

COMBUSTION

The burning of the fuel-air mixture in an engine cylinder.

COMBUSTION CHAMBER

The space remaining at the top of the cylinder when the piston is at the top dead center position. Where the fuel-air mixture begins to burn.

COMPRESSION

In internal-combustion reciprocating engines, the squeezing of the fuel-air mixture in the cylinder of a spark-ignition engine or the squeezing of the air in a diesel engine. Compression makes combustion more effective and increases engine efficiency.

COMPRESSION RATIO

The ratio of the cylinder volume with the piston at bottom dead center (BDC) to the cylinder volume with the piston at top dead center (TDC).

CONNECTING ROD

The arm that connects the piston to the crankshaft and converts the reciprocating motion into rotary motion.

CONVERSION EFFICIENCY (of a CATALYTIC CONVERTER)

The efficiency with which undesirable exhaust gases are reduced to acceptable levels or are converted to desirable gases.

CONVERTIBLE

Any car with a folding roof. Term used in U.S. since the 1930s. In the 1950s, the “hardtop convertible” was developed to look like a convertible but had a fixed roof that did not fold. Also called a drophead coup >

COUP?!–mstheme–>

Originally meant a vehicle “cut” by a glass partition behind the front seats that enabled the rear passengers to ride enclosed and the driver exposed. Today, a two-to-five-seater with smaller interior than a sedan. Usually a sporty type.

COWL

That part of a car’s body between the engine compartment and the driver.

CRANKCASE

A pan or box that encloses the bottom of the engine, supports the crankshaft, and contains the oil for the engine.

CRANKSHAFT

The main shaft of an engine with a U-shaped offset at each cylinder to which the connecting rod is attached. It delivers rotary motion taken from the reciprocating pistons and connecting rods.

CUBIC CAPACITY

The volume of the cylinder between the piston top dead center and bottom dead center. Expressed in cubic centimeters or cubic inches.

CUBIC CENTIMETER (cc)

European, metric, and competition measure of engine displacement: 1,000 cc = 1 liter, which equals about 61 cubic inches.

CUBIC INCH (cu. in.)

U.S. measure of engine displacement: 1 cubic inch = 16.387 cc.

CUSTOM CAR

An automobile that has been restyled, or an all-new body fitted on an existing chassis.

CU. IN.

(see CUBIC INCH)

CYLINDER

The hollow tubular cavity in the cylinder block in which the piston travels and in which combustion takes place.

CYLINDER HEAD

The detachable part of the top of the cylinder block that contains the spark plugs and valves. It seals the cylinder and forms the top of the combustion chamber.

 

D

DAMPING COEFFICIENT

A parameter that affects a system’s time response by controlling the rate at which energy can be added to or removed from the system.

DIFFERENTIAL GEARS

The gears that convey engine power to the driving axles and are arranged so as to permit the rear wheels to turn at different speeds as required when the vehicle is negotiating a turn.

DIN

Deutsche Instit? Normung, the German Institute for Standards. Like the Society of Automotive Engineers (SAE), the DIN has defined conditions and correction factors to generate standard engine ratings. Basically, DIN output is almost identical to “SAE net” output (the DIN standard uses ~2.5% higher ambient pressure and ~1.7% lower ambient

temperature). More info is in the Bosch Automotive Handbook.

DISC BRAKE

A type of brake in which two friction pads grip a steel disc that is attached to the wheel, with one pad on each side. Used on race cars, sports cars, and better passenger cars.

DISPLACEMENT

Displacement, or “swept” volume, is the measured volume travelled by the piston as it travels from it’s lowest point to highest point in a stroke. It can be expressed as any cubic measurement but is usually referred to as CC’s (cubic centimeters) or Liters (1000 cc = 1 liter) or sometimes, in cubic inches, although that practice is slowly dying out.

DISTRIBUTOR

The moving part of the internal-combustion engine ignition system that directs the high-voltage current from the coil to the spark plugs in the proper firing order.

DREAM CAR

A one-of-a-kind futuristic, experimental automobile usually appearing at auto shows to stimulate interest in the manufacturer’s products. Much design benefit spurs from dream cars and many reach the production stage. See also PROTOTYPE.

DRIVE TRAIN

That combination of gears, clutches, shafts, etc., that transmits the engine power to the driven wheels. Typically the transmission, driveshaft, and differential in a rear wheel driven vehicle.

DRY SUMP

Type of internal-combustion engine in which the lubricating oil is stored either in a separate tank or cooling radiator instead of in the crankcase pan. The oil is pumped to and taken from the engine by separate pumps.

DWELL

In an engine, the time allowed for current to build in the primary circuit of the ignition coil for each spark generation.

DYNAMOMETER

A device used to place a load on an engine and measure its performance.

 

E

ECU

Electronic Control Unit

ELECTRICAL SYSTEM

In electric ignition internal-combustion engines, those components required to convert the electricity produced by the generator into a high-voltage spark for the plugs. Includes: generator or alternator, points, condenser, coil, distributor and spark plugs plus wiring.

ELECTRONIC VALVE TIMING (aka EVT)

A system where the opening/closing times and lift of cylinder valves are controlled by computer.

ENGINE MAPPING

A procedure of experimentally determining the performance of an engine at selected operating points and recording the results.

ENGINE TYPES

F-Head Side exhaust valve and overhead inlet valve.

L-Head Both valves on one side of the cylinder.

T-Head Exhaust valve on one side and inlet valve on the other side of the cylinder. (Twin-camshafts).

I-Head Both valves located directly over the piston. Also called valve–in-head or overhead valve engine.

SOHC Single overhead camshaft.

DOHC Double overhead camshafts.

EQUIVALENCE RATIO

Actual air/fuel ratio divided by the air/fuel ratio at stoichiometry.

EVAPORATIVE EMISSIONS

Evaporated fuel from the carburetor or fuel system which mixes with the surrounding air.

EVT

(see ELECTRONIC VALVE TIMING)

EXHAUST

The system of exhausting the burned gases from an internal-combustion engine consisting of piping or tubing, silencers, and, at times, resonators.

 

F

FIBERGLASS

A very tough and durable plastic material with fibers running through the plastic. Used for race car bodies, many sports car bodies, and also enjoys considerable acceptance for passenger car bodies.

FLYWHEEL

A large, heavy iron or steel disc attached to the rear of an engine crankshaft in order to provide sufficient centrifugal force to smooth the power impulses from the cylinders.

FOOT-POUND

A unit of torque corresponding to a force of one pound acting on a one foot level arm.

FREQUENCY RESPONSE

A graph of a system’s response to a different frequency input signals.

FUEL INJECTOR (Electronic)

An electro-mechanical device that precisely meters fuel into an internal combustion engine based on a time electronic input.

FUEL PRESSURE REGULATOR

Maintains fuel pressure to fuel injector to help insure proper quantity is delivered to engine.

FRAME

A bridge-like, structural base of a car that supports and positions the body and major mechanical items.

FUEL INJECTION

On internal-combustion engines, a system that injects a precisely measured amount of fuel into the cylinder at exactly the right moment. Dispenses with the carburetor and increases engine efficiency.

 

G

GAIN

The ratio of a system’s output magnitude to its input magnitude.

GEARS

Wheels with meshing teeth to transmit power between rotating shafts. When the gear wheels are of different sizes, a change in speed ratio occurs. Gears are made of hard steel.

GLOBAL POSITIONING SYSTEM

An array of satellites, deployed and maintained by the U.S. Department of Defense, which can be monitored to triangulate an accurate position on the earth’s surface.

GPS

(see GLOBAL POSITIONING SYSTEM)

GRAND TOURING (aka GT, Italian: Gran Tourismo)

From the Italian Gran Turismo. A car combining sedan and sports car features in which engineering is the dominant feature. Combines excellent road handling qualities with relative comfort. Made in two- and four-seaters with the rear seats always cramped.

GT

(see GRAND TOURING)

H

HALF SHAFT

A rotating shaft that transmits power from the final drive unit (differential) to a power wheel. Used in independent rear suspension and front-wheel drive. Two are required; one for each side.

HC

Hydrocarbon Chemicals, such as gasoline, formed by the union of carbon and hydrogen.

HELICAL GEAR

A gear in which the teeth are cut at an angle to the shaft. The advantage is that there are usually two teeth meshing at all times, making for smoother and quieter operation.

HEMI

Slang term for an engine with hemispherical combustion chambers which allow for larger and less shrouded valves. Used in many sports and racing cars.

HEMI-HEAD

A hemispherically shaped combustion chamber at the top of the engine cylinder. The hemispheric shape provides improved efficiency because the forces of the explosion are directed to the piston by the curved surface of the combustion chamber.

HOOD

The removable or lift-up part of an auto body that covers the engine and allows access to it. (Bonnet in U.K.)

HORSEPOWER (hp.)

The unit for measuring the power output of an engine. One horsepower is defined as lifting 33,000 pounds one foot per minute.

HOT ROD

A production auto that has been modified by the owner for outstanding speed and acceleration through extensive changes to the engine, chassis, and body.

HYDRAULIC

A mechanical operation based on incompressibility of liquids, generally oil and sometimes water, and their ability to offer resistance when being forced into a small cylinder or through an orifice, thereby transmitting an increase in applied force. Hydraulic brakes and clutches use this principle.

HYDRAULIC VALVE LIFTER

Valve lifter using hydraulic oil pressure to operate and capable of maintaining zero clearance between metal parts. Thus, valve noise and wear are considerably reduced as are the periodic valve adjustments.

HYPOID GEARS

A type of differential final drive using a spiral bevel gear on the drive shaft, allowing it to be located below the center of the ring gear on the axle. This makes possible a lower floor in the car.

 

I

IEEE

Institute of Electrical and Electronics Engineers, Inc.; a professional society and standards-making body.

IGNITION TIMING

The time of occurrence of ignition measured in degrees of crankshaft rotation relative to top dead center (TDC.)

IMMOBILIZER

Theft-deterrent system that uses a transponder inside the ignition key to electronically enable an operational control unit in the vehicle to start the car.

INDEPENDENT SUSPENSION

Suspension in which each wheel is sprung individually so that any disturbance on the wheel has no effect on the opposite wheel.

INLINE ENGINE

An engine having the cylinders in a straight line, one after the other. Also called a “straight” engine.

INTERNAL-COMBUSTION ENGINE

Any engine, either reciprocating or rotary, in which the fuel is consumed in the interior of the engine rather than outside of the engine.

 

J

K

L

LAMINATED WINDSHIELD

A windshield consisting of a thin layer of rubbery plastic sandwiched between two sheets of glass. When struck by the head in an accident, it bows out without puncturing, and the plastic holds the glass to prevent it from splintering.

LEAF SPRINGS

A number of slightly curved, flexible steel plates of varying lengths, mounted one atop the other. The ends are attached to the chassis, and the middle is fixed to the axle. Also called semi-elliptic springs.

LED

Light-Emitting Diode.

LIMITED SLIP DIFFERENTIAL

A differential that uses cone or disc clutches to lock the two separate axle shafts. This forces both driving wheels to transmit the same drive torque regardless of the traction available. It still allows differential action under normal driving conditions but improves traction in mud and snow.

LIVE AXLE

An axle that transmits power either by separate half shafts or by side chains, as opposed to a dead axle.

LSD

(see Limited Slip Differential)

LONG BLOCK

A short block plus cylinder heads that are usually timed and assembled.

LOUVER

A slatted air intake or air outlet. Slats used to capture and control the air flow.

LUXURY CAR

A well-appointed, well-equipped, well-designed and constructed auto varying in size from a compact to a large sedan.

 

M

MANUAL TRANSMISSION

A mechanism in the drive train with gears to vary the power and torque delivered to the driven wheels. It consists of a

lever that the driver operates in conjunction with the clutch to change from one gear to another.

MAP

Manifold Absolute Pressure; the absolute pressure in the intake manifold of an engine.

MASS AIR FLOW SENSOR

A device mounted in the engines air induction system that provides an electrical signal representing the instantaneous rate of mass air flow.

MANUFACTURERS SUGGESTED RETAIL PRICE (MSRP)

MSRP is the retail “base price.” It is the top price on the sticker. All vehicles of the same model and trim level and transmission (e.g. Honda Accord EX, 4 door, automatic) have exactly the same MSRP. Add options and destination charges and the total price will differ from car to car. Some manufacturers call it Manufacturer’s Suggested Retail Price and some call it Manufacturer’s Suggested Retail Base Price, but no Monroney Label calls the total price the MSRP.

MONRONEY LABEL

The “window sticker” mandated by law on all new vehicles sold in the US. For more details click here.

 

N

NO, also NOx:

The various oxides of nitrogen.

NORMALLY ASPIRATED

An engine that intakes air or “breathes” without the assistance of a supercharger or turbocharger.

 

O

OIL PUMP

An engine-driven pump that delivers oil, under pressure, to the engine’s moving parts.

OIL RING

The lowermost piston ring that scrapes off excess oil from the cylinder walls and returns it to the oil pan via vents in the

ring and piston.

 

P

PINION

A small diameter gear with a small number of teeth designed to mesh with a much larger gear wheel or a toothed rod (rack). Used in rack-and-pinion steering and for speed reduction with an increase in power.

PISTON

A partly hollow, cylindrical metal engine part that is closed at one end and fits into the engine cylinder. Connected to the crankshaft via the connecting rod and usually fitted with rings to seal it in the cylinder.

PNEUMATIC TIRE

A circular tube of rubber or synthetic rubber and fabric, and sometimes also steel, attached to the rim of the car’s wheel,

having resilience due to its containing air under pressure.

PRE-SELECTOR GEARBOX

An arrangement that enables the driver to select a gear speed before he needs it and then depress the clutch pedal when

he desires to use the selected gear.

PROTOTYPE

The test model of a new car design that is intended to be produced in quantity.

PUSHROD

A metal rod connecting the valve lifter or camshaft with the valve rocker arm on overhead-valve engines.

 

R

RACK-AND-PINION STEERING

A steering system having a pinion gear at the lower end of the steering column that engages a rack or a toothed rod that connects to the wheel steering arms.

RADIAL PLY

A tire in which the fabric cords run radially in a line from the wheel hub or straight out from the bead or around the

tubular shape of the tire. Annular belts of fabric or steel mesh add rigidity. Advantages of this design are: more flexible

side walls with a relatively stiff tread area and a larger and more consistent footprint on the road under all driving

conditions.

RECIPROCATING

Motion of an object between two limiting positions. Applied to piston engines because of the limited up and down motion of the pistons.

RING GEAR

One of the gears in the rear axle that transmits power to the differential from the drive shaft.

ROADSTER

A description of a two-seater open car of sporty appearance with side curtains, instead of roll-up windows.

ROCKER ARM

A pivoted lever that transmits the action of the pushrod to the valve stem. (Pushrod upward action is converted to downward push on the valve stem. )

RPM

Revolutions Per Minute; the speed of rotation of the crankshaft in an engine or other rotation shaft.

RUNABOUT

An open sporting-type vehicle, lightweight, with two seats and with simple bodywork.

 

S

S.A.E.

(see Society of Automotive Engineers)

SEALED BEAM

A one-piece, hermetically sealed headlight in which the filament is an integral part of the unit, and the lens itself is the bulb.

SEDAN

A closed car for four or more passengers with either two or four doors. (Called saloon in U.K.)

SELECTIVE TRANSMISSION

The conventional manual transmission of today in which any gear may be selected at will as opposed to the very early progressive transmission in which the gears had to be selected in order.

SHOCK ABSORBERS (also SHOCKS)

A term used for what are really dampers. Fittings used to absorb the energy that the wheels convey to the springs. The dampers keep the springs from continuously rebounding. The majority of shock absorbers are hydraulic.

SHORT BLOCK

An assembled engine block with crank, rods, pistons and a few other add ons such as oil pan, crank sprokets, etc.

SKID

A condition in which the tires are sliding over the road surface rather than rolling; usually associated with braking or turning.

SLEEVE VALVE

Consists of metal sleeves located between the piston and cylinder wall. When moved up and down, holes in the sleeves coincide with inlet and exhaust parts to provide passage for the gases at the right time.

SLIP

The ratio of the angular speed of the driving element to the angular speed of the driven element of a torque converter; also, the condition in which a driven tire loses traction so that the driving torque does not produce vehicle motion.

SOCIETY OF AUTOMOTIVE ENGINEERS

A group known for publishing research papers and defining various standards of measurement.

SOLENOID

An electrically charged coil of insulated wire which produces a magnetic field within the coil.

SPARK ADVANCE

The number of degrees of crankshaft rotation before TDC where the spark plug is fired (see ignition timing.)

SPARK PLUG

A device inserted into the combustion chamber of a cylinder on an internal-combustion engine that provides the electrical gap across which the high-tension voltage jumps. This creates a spark that ignites the compressed fuel-air mixture.

SPARK TIMING

The process of firing the spark plug at the proper moment to ignite the combustible mixture in the engine cylinders.

SPEED-DENSITY

A method of calculating the inducted mass airflow of an internal-combustion engine-based MAP RPM, and mapped volumetric efficiency at a constant temperature.

SPORTS CAR

An agile vehicle that is easily maneuverable, accelerates briskly, brakes positively, handles well and steers precisely. It is tightly sprung and does not wallow and heave as does a conventional passenger car and is therefore not as comfortable.

SPYDER or SPIDER

In the early 1900s, a light two-seater car. In the 1950s the word was revived by some Italian manufacturers for an open two seater sports car.

STOICHIOMETRY

The theoretical air/fuel ratio for perfect combustion; it enables exactly all of the fuel to burn using exactly all of the oxygen in the air.

STROKE

The back-and-forth motion of the piston. The length of the motion of the piston from top dead center to bottom dead center.

SUPERCHARGER

An air compressor fitted to an internal combustion engine to force the fuel-air mixture into the cylinders at a pressure greater than that of the atmosphere. Boosts the power of the engine.

SUSPENSION

The assembly of springs, shock absorbers, torsion bars, joints, arms, etc., that cushions the shock of bumps on the road and serves to keep the wheels in constant contact with the road, thereby improving control and traction.

SWING AXLE

Type of independent rear suspension using half shafts that have universal joints only at their inboard ends on both sides of the differential. This causes a camber angle change of the wheel with up-and-down wheel movements.

 

T

TACHOMETER

An instrument that indicates the number of revolutions per minute at which the engine is turning.

TDC

(see TOP DEAD CENTER)

THROTTLE ANGLE

The angle between the throttle plate and a reference line; engine speed increases as the angle increases.

TOP DEAD CENTER (aka TDC)

The highest point of the piston during its stroke.

TORSION BAR

A rod in the suspension system that, when twisted from a grip at one end, functions like a spring.

TORQUE CONVERTER

A form of fluid coupling used to transmit torque from the power plant to the rest of the drive train.

TORQUE

The twisting force of the crankshaft or other driving shaft.

TOURING CAR (British-TOURER)

An open car with seats for four or more passengers. Early models had no side weather protection but later were fitted

with detachable side screens and curtains. Made until about 1930.

TRACK

(see TREAD)

TRANSMISSION

The gear-changing or gear-shifting system through which engine power is transferred to the wheels. The purpose of gear-changing is to keep maximum engine power applied to the wheels at all times for all conditions, from start-up to high speeds.

TREAD

Width of a car measured from the center line of the wheels. Sometimes called the track. Also the pattern on the surface of a tire.

TURBOCHARGER

A supercharging device driven by exhaust gases from the engine.

 

U

V

V6, etc.

(see VEE ENGINE)

VALVE

Device that opens and closes the combustion chamber of an internal-combustion engine to admit the fuel-air mixture or exhaust the gases.

VEE ENGINE

An engine with cylinders arranged in two rows at an angle to the common crankshaft. Has a “V” shape when viewed from the front.

VOITURE LEGERE

A light car, especially a racing car falling between the heavy cars and the voiturette. Term seldom used to describe production cars. Not used after 1914.

VOITURETTE

Early two-seater touring car. Name first used by Leon Bollee and then applied to any small car.

VOLUMETRIC EFFICIENCY

The pumping efficiency of the engine as air is drawn into the cylinders.

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