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LPG: Liquified Petroleum Gas.
M85: A blend of gasoline and methanol consisting
of 85% methanol and 15% gasoline.
Measurements of Pressure: 1 PSI=2.06” Hg
(mercury) = 27.72” H
2
O (water column). At sea
level atmospheric pressure is 29.92” Hg.
Methanol: Known as wood alcohol (CH
3
OH), a
light, volatile, flammable alcohol commonly made
from natural gas.
MIL: Malfunction Indicator Lamp.
Misfire: Failure of the air/fuel mixture to ignite dur-
ing the power stroke.
Mixer: Fuel introduction device that does not in-
clude a throttle plate.
MFI: Multiport Fuel Injection. A fuel injection system
that uses one injector per cylinder mounted on
the engine to spray fuel near the intake valve
area of combustion chamber.
MSV: Manual Shut-Off Valve. Refers to the ma-
nually operated valve on the LPG tank.
MTBE: Methyl Tertiary Butyl Ether. Oxygenate add
to gasoline to reduce harmful emissions and to
improve the octane rating.
Multi-fuel System: A motor fuel system designed
to operate on two different fuels, such as LPG
and gasoline.
Natural Gas: A gas formed naturally from buried
organic material, composed of a mixture of hy-
drocarbons, with methane (CH
4
) being the
dominant component.
NGV: Natural Gas Vehicle.
NOX: See Oxides of Nitrogen.
OBD:
On Board Diagnostic
Octane Rating: The measurement of the antiknock
value of a motor fuel.
OEM: Original Equipment Manufacturer, the vehicle
manufacturer.
Open-Loop: An operational mode during which
control module memory information is used to de-
termine air/fuel ratio, injection timing, etc., as
opposed to actual oxygen sensor input.
Orifice: A port or passage with a calibrated open-
ing designed to control or limit the amount of flow
through it.
Oscilloscope: An instrument that converts voltage
and frequency readings into traces on a cathode
ray tube (also see Cathode Ray Tube).
Oxides of Nitrogen: Chemical compounds of ni-
trogen bonded to various amounts of oxygen
(NOX). A chief smog forming-agent.
Oxygen Sensor: An automotive fuel system that
produces a signal in accordance with the oxygen
content of the exhaust gas. (See Lambda Sen-
sor).
Oxygenate: Oxygenates (such as MTBE, ethanol
and methanol) added to gasoline to increase the
oxygen content and therefore reduce exhaust
emissions.
Ozone: A radical oxygen module (O
3
) that is found
in the upper atmosphere and filters out ultraviolet
radiation from the sun. Ground level ozone is
formed by NOX, during the formation of photo-
chemical smog.
Particulates: Microscopic pieces of solid or liquid
substances such as lead and carbon that are dis-
charged into the atmosphere by internal
combustion engines.
Positive Crankcase Ventilation (PCV): An auto-
motive emission control system designed to
reduce hydrocarbon emissions by routing crank-
case fumes into the intake manifold rather than to
the atmosphere.
Power Derate: A mode of reduced engine power
output for the purposes of protecting engine com-
ponents during a failure or malfunction.
Pressure Differential: The differential between
atmospheric pressure and intake manifold (re-
ferred to as vacuum) pressure.
Pressure Regulator: A device to control the pres-
sure of fuel delivered to the fuel injector(s).
Primary Circuit: The low-voltage or input side of
the ignition coil.
Propane: An odorless and colorless gas, C
3
H
8
,
found in natural gas and petroleum.
Psia: pounds per square inch absolute
PTV: Pressure Trim Valve
Reactivity: Refers to the tendency of an HC in the
presence of NOX and sunlight to cause a smog-
forming reaction. The lighter the HC, the lower
reactivity tends to be.
Regulator: An assembly used to reduce and con-
trol the pressure of a liquid or vapor.
Resistance: The opposition to the flow of current in
an electrical circuit. Measured in ohms.
Rest Pressure: Fuel pressure maintained within
the system after engine shutdown.
Rich Mixture: An air to fuel ratio below the stoichi-
ometric ratio; too much fuel.
SAE: Society of Automotive Engineers.
Secondary Circuit: The high-voltage output side of
the ignition coil.
SEFI or SFI: Sequential Electronic Fuel Injection or
Sequential Fuel Injection.
Sensors: Devices that provide the control module
with engine information as needed to properly
control engine function.
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