Glossary of Terms
Advance:
As applied to ignition timing, advancing the timing refers to firing the spark plug comparatively
sooner.
ATDC (After Top Dead Center):
When a piston is moving downward, after TDC.
Bar:
A Bar is a measurement of pressure. One Bar equals 101.3kPa or 14.7psi. Standard atmospheric pressure
is 1-Bar absolute, or 0-Bar relative (gauge). An engine running 1-Bar of turbo boost is actually running 2-Bar
absolute, so it requires a 2-Bar MAP sensor.
Boost:
When a pressure that is greater than the ambient atmospheric pressure is forced into the intake
manifold. Turbo- and superchargers create boost.
BTDC (Before Top Dead Center):
When a piston is moving upward, but has not yet reached TDC.
Cam Sensor:
A device used to provide a once-per-engine cycle pulse to the
TECgt
. This establishes the stage
of engine operation that is occurring for a given TDC.
Closed Loop:
When an oxygen sensor reading is used to correct the air-fuel mixture through the manipulation
of the fuel injector pulse widths.
Coolant Enrichment:
A coolant temperature-based fuel enrichment that is used to add fuel when an engine is
cold. This feature is the electrical equivalent of the choke plate on a carburetor.
Coolant Temperature Sensor:
A device that measures the coolant temperature of an engine.
Crank Sensor:
A device that can “read” a crank trigger wheel, and output a voltage signal that can be used by
an engine management system.
Crank Trigger:
A device used to measure the crankshaft position and speed, typically composed of a crank
trigger wheel and a crank sensor.
Detonation:
When the air-fuel mixture is ignited by the spark plug, then a high cylinder temperature
“spontaneously” ignites another portion of the unburned mixture. A knocking sound is produced when
detonation occurs, and knock sensors are designed to hear this knocking. Engine damage can be caused by
detonation.
DFU:
Direct Fire Unit. Electromotive coil packs are referred to as DFUs.
Duty Cycle:
The percentage of time that a pulse width modulated output is turned on. A duty cycle of 100%
indicates a fully turned-on modulation output.
ECU:
Electronic Control Unit. A device that is used to process several inputs for the control of several
outputs.
Exhaust Gas Oxygen (EGO) Sensor:
A device that compares the oxygen content of the exhaust gases with
the oxygen content of the ambient atmosphere. An air-fuel ratio approximation can be made with an EGO
sensor.
______________________________________________________________________________________
TECgt Manual Version 2.0
- Page 129 -
©2008 Electromotive, Inc.