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Appendix F –
Glossary of Terms
This glossary defines terms used throughout the manual.
Air-Fuel Ratio (AFR)
– The ratio by volume of air to vaporized fuel in the combustion chamber of an engine. It
is usually expressed as the amount of air to one part of fuel. For example the ideal mixture for most fuels is 14.7
parts of air to one part of fuel. This would be written as the ratio 14.7 to 1 or an AFR of 14.7:1. The smaller the
quantity of air, the richer the fuel mixture - the larger the quantity of air, the leaner the mixture.
Display
- The light emitting diode (LED) digital display where gas concentrations and calculated results are
displayed.
Indicator –
Small LEDs that are on the front panel. These devices are lit when the system is in the state the
device represents.
Function -
A distinct operation of the analyzer.
Function Key -
A push-button that initiates functions in the various analyzer modes of operation.
Lean Mixture -
An air-fuel mixture containing less than the ideal amount of fuel.
LED
- Light Emitting Diodes used in the displays.
Lambda (
L
) -
A parameter that expresses air-fuel ratio. Lambda is the ratio of the measured air fuel ration to the
ideal or most efficient air fuel ratio as shown below.
L
=
AFR
measured
/
14.67
When AFR is displayed as Lambda a value of 1.0 represents the ideal air-fuel mixture of 14.67:1. Values of
Lambda greater than 1.0 such as 1.3, represent a lean mixture. Values of Lambda smaller than one, such as 0.85
represent a rich mixture.
Mode
– An operational state for the system such as warm-up or standby.
Rich Mixture
-An air-fuel mixture containing more than the ideal amount of fuel.
Stoichiometric -
Describes the ideal air-fuel ratio.
Tail Pipe
- The vehicle's exhaust port.
