Page 426 - Understanding Automotive Electronics

2735 | Glossary Page 413 Tuesday, March 10, 1998 1:33 PM

GLOSSARY G

Signal Processing: The alteration of an electrical signal by electronic circuitry;
used to reduce the effects of systematic and random errors.
Skid: A condition in which the tires are sliding over the road surface rather
thin rolling; usually associated with braking.
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.
Software: The computer program instructions used to tell a computer what
to do.
Spark Advance: The number of degrees of crankshaft rotation before TDC
where the spark plug is fired. (See ignition timing.)
Spark Timing: The process of firing the spark plugs at the proper moment to
ignite the combustible mixture in the engine cylinders.
Stoichiometry: The air/fuel ratio for perfect combustion; it enables exactly all
of the fuel to burn using exactly all of the oxygen in the air.
System: A collection of interacting parts.
Systematic Error: A measurement error in instrumentation system which is
predictable and correctable.
TBFI: Throttle-body-fuel-injector; a fuel metering actuator in which the air/
fuel ratio is controlled by injecting precisely controlled spurts of fuel into the air
stream entering the intake manifold.
TDC: Top dead center; the extreme highest point of the piston during its
stroke.
Throttle Angle: The angle between the throttle plate and a reference line;
engine speed increases as the angle increases.
Torque Converter: A form of fluid coupling used in an automatic transmis-
sion which acts like a torque amplifier.
Torque: The twisting force of the crankshaft or other driving shaft.
Transfer Function: A mathematical equation which, when graphed, produces
a system’s frequency response plot.
Transistor: An active semiconductor device which operates like a current
valve.
Transport Delay: The time required for a given miss of fuel and air to travel
from the intake manifold through the engine to the EGO sensor in the exhaust
manifold.
Volumetric Efficiency: The pumping efficiency of the engine as air is drawn
into the cylinders.

UNDERSTANDING AUTOMOTIVE ELECTRONICS 413