(see ANTI-LOCK BRAKES)
In hydraulics or pneumatics, a device for storing pressurized fluid.
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.
Air/Fuel ratio in the engine.
AIR INDUCTION SYSTEM
The components through which combustion air is induced into the engine.
(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.
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.
(see BOTTOM DEAD CENTER)
(see BRAKE HORSEPOWER)
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.
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.
Brake Specific CO; in an engine, the ratio of the rate at which carbon monoxide leaves
the exhaust manifold to the brake horsepower.
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.
Brake Specific HC; in an engine, the ratio of the rate at which hydrocarbons leave the
exhaust manifold to the brake horsepower.
Brake Specific NOx; in an engine, the ratio of the rate at which oxides of nitrogen
leave the exhaust manifold to the brake horsepower.
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.
A rotating shaft with a number of cams or eccentric lobes used to operate the engine
valves, usually via pushrods and rocker arms.
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.
A material which speeds up or stimulates a chemical reaction without being
significantly chemically altered by the reaction.
A device which enhances certain chemical reactions reducing the levels of undesirable
exhaust gases from an engine.
(see CUBIC CENTIMETER)
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.
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.
(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.
The burning of the fuel-air mixture in an engine cylinder.
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.
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.
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).
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.
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 coupé.
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.
That part of a car's body between the engine compartment and the driver.
A pan or box that encloses the bottom of the engine, supports the crankshaft, and
contains the oil for the engine.
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.
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.
An automobile that has been restyled, or an all-new body fitted on an existing chassis.
(see CUBIC INCH)
The hollow tubular cavity in the cylinder block in which the piston travels and in
which combustion takes place.
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.
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.
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.
Deutsche Institüt für 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
temperature). More info is in the Bosch Automotive Handbook.
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
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.
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.
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.
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.
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.
In an engine, the time allowed for current to build in the primary circuit of the
ignition coil for each spark generation.
A device used to place a load on an engine and measure its performance.
Electronic Control Unit
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
ELECTRONIC VALVE TIMING (aka EVT)
A system where the opening/closing times and lift of cylinder valves are controlled by
A procedure of experimentally determining the performance of an engine at selected
operating points and recording the results.
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.
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.
Actual air/fuel ratio divided by the air/fuel ratio at stoichiometry.
Evaporated fuel from the carburetor or fuel system which mixes with the surrounding
(see ELECTRONIC VALVE TIMING)
The system of exhausting the burned gases from an internal-combustion engine consisting
of piping or tubing, silencers, and, at times, resonators.
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.
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.
A unit of torque corresponding to a force of one pound acting on a one foot level arm.
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
A bridge-like, structural base of a car that supports and positions the body and major
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.
The ratio of a system's output magnitude to its input magnitude.
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
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.
(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.
(see GRAND TOURING)
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.
Hydrocarbon Chemicals, such as gasoline, formed by the union of carbon and hydrogen.
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.
Slang term for an engine with hemispherical combustion chambers which allow for larger
and less shrouded valves. Used in many sports and racing cars.
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.
The removable or lift-up part of an auto body that covers the engine and allows access
to it. (Bonnet in U.K.)
The unit for measuring the power output of an engine. One horsepower is defined as
lifting 33,000 pounds one foot per minute.
A production auto that has been modified by the owner for outstanding speed and
acceleration through extensive changes to the engine, chassis, and body.
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.
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.
Institute of Electrical and Electronics Engineers, Inc.; a professional society and
The time of occurrence of ignition measured in degrees of crankshaft rotation relative
to top dead center (TDC.)
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.
Suspension in which each wheel is sprung individually so that any disturbance on the
wheel has no effect on the opposite wheel.
An engine having the cylinders in a straight line, one after the other. Also called a
Any engine, either reciprocating or rotary, in which the fuel is consumed in the
interior of the engine rather than outside of the engine.
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.
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.
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.
An axle that transmits power either by separate half shafts or by side chains, as
opposed to a dead axle.
(see Limited Slip Differential)
A short block plus cylinder heads that are usually timed and assembled.
A slatted air intake or air outlet. Slats used to capture and control the air flow.
A well-appointed, well-equipped, well-designed and constructed auto varying in size
from a compact to a large sedan.
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
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.
The "window sticker" mandated by law on all new vehicles sold in
the US. For more details click
NO, also NOx:
The various oxides of nitrogen.
An engine that intakes air or "breathes" without the assistance of a
supercharger or turbocharger.
An engine-driven pump that delivers oil, under pressure, to the engine's moving parts.
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.
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.
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.
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.
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.
The test model of a new car design that is intended to be produced in quantity.
A metal rod connecting the valve lifter or camshaft with the valve rocker arm on
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.
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
Motion of an object between two limiting positions. Applied to piston engines because
of the limited up and down motion of the pistons.
One of the gears in the rear axle that transmits power to the differential from the
A description of a two-seater open car of sporty appearance with side curtains, instead
of roll-up windows.
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. )
Revolutions Per Minute; the speed of rotation of the crankshaft in an engine or other
An open sporting-type vehicle, lightweight, with two seats and with simple bodywork.
(see Society of Automotive Engineers)
A one-piece, hermetically sealed headlight in which the filament is an integral part of
the unit, and the lens itself is the bulb.
A closed car for four or more passengers with either two or four doors. (Called saloon
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.
An assembled engine block with crank, rods, pistons and a few other add ons such as oil
pan, crank sprokets, etc.
A condition in which the tires are sliding over the road surface rather than rolling;
usually associated with braking or turning.
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.
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
An electrically charged coil of insulated wire which produces a magnetic field within
The number of degrees of crankshaft rotation before TDC where the spark plug is fired
(see ignition timing.)
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.
The process of firing the spark plug at the proper moment to ignite the combustible
mixture in the engine cylinders.
A method of calculating the inducted mass airflow of an internal-combustion
engine-based MAP RPM, and mapped volumetric efficiency at a constant temperature.
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.
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.
The back-and-forth motion of the piston. The length of the motion of the piston from
top dead center to bottom dead center.
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 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.
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.
An instrument that indicates the number of revolutions per minute at which the engine
(see TOP DEAD CENTER)
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.
A rod in the suspension system that, when twisted from a grip at one end, functions
like a spring.
A form of fluid coupling used to transmit torque from the power plant to the rest of
the drive train.
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.
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.
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.
A supercharging device driven by exhaust gases from the engine.
(see VEE ENGINE)
Device that opens and closes the combustion chamber of an internal-combustion engine to
admit the fuel-air mixture or exhaust the gases.
An engine with cylinders arranged in two rows at an angle to the common crankshaft. Has
a "V" shape when viewed from the front.
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.
Early two-seater touring car. Name first used by Leon Bollee and then applied to any
The pumping efficiency of the engine as air is drawn into the cylinders.
The distance between the centers of the front and rear wheel axles as viewed from the
side of the car.
Glossary Of Driving Terms
[JTW] Having enrolled in the Skip Barber Driving School, I have just received my first
"homework assignment" -- a glossary of terms as defined by the school. Since
there is no copyright notice (and Fair Use covers me) I post them here for benefit of new
NSX'ers who may not know the precise definitions of the terms used on this list (i.e., me)
The portion of the tire tread that is in actual contact with the road surface at any
one point in time.
The shift in the distribution of load, and therefore traction, on the four contact
patches, caused by a change in the cars attitude, such as during acceleration or braking.
The condition in which the rear tires have more traction than the fronts, causing the
fronts to slide across the road toward the outside edge rather than turning or pulling the
car into the corner.
The condition in which the front tires have more traction than the rears, causing the
rear of the car to point towards the outside and the nose to point to the inside.
Oversteer caused by letting up on the throttle while cornering. This transfers weight
from the back to the front, thus increasing the traction of the front tires and reducing
the traction at the rear.
The technique of applying brake pedal pressure to just before the point of lock-up-the
threshold-then maintaining that braking level through gentle modulation of the pressure.
The technique of continuing to brake while turning in for a corner, accomplished by
gradually reducing ("trailing") brake pedal pressure.
A more accurate and less dramatic method of wheel-handling. For example, for a left
turn, the left hand moves to the top of the steering wheel and pulls the wheel a full
half-turn to the bottom, while the right hand slides downward to meet the left hand at the
bottom. The right hand then pulls up on the wheel, while the left hand mirrors the
movement until both hands meet at the top. This takes some getting used to, but is very
HEEL & TOE DOWNSHIFTING
A technique of downshifting used to match engine speed with gearbox speeds, all the
while continuing to brake. The sequence is: brake, then clutch in, "blip" the
throttle with right side of right foot; shift lever to lower gear, clutch out. Brake pedal
pressure should remain constant during the entire sequence.
The spot at the entrance to a turn at which the driver first turns the steering wheel
to initiate the cornering sequence.
APEX (CLIPPING POINT)
The most critical part of a turn. It is the area on the inside of a turn at which the
car finishes the entry phase and begins the exit phase. The car must be as balanced as
possible and accelerating towards the track-out point when it "clips" the apex.
TRACK-OUT (EXIT POINT)
The area past a turn, typically at the far outside edge, at which the car has completed
the turning stage and all the dynamic forces acting on the car are in balance.