Emission Controls (cont'd)
Engine Exhaust Controls
The engine exhaust emission control systems are designed to
control combustion during idle, acceleration, cruise, and decel-
eration. These systems are entirely separate from the
crankcase and evaporative emission control systems describ-
ed previously.
PGM-FI System
The PGM-FI system consists of three independent sub-
systems; Air Intake, Electronic Control and Fuel Control,
thus allowing more accurate control of air/fuel ratios under
all operating conditions. The Electronic Control Unit (ECU)
detects the amount of air drawn into the cylinders and deter-
mines the amount of fuel to be injected to provide the op-
timum air/fuel ratio for all engine needs.
Ignition Timing Control System
This system automatically controls the ignition timing to
reduce the amount of HC and NOx.
Catalytic Converter
The catalyst is used to convert hydrocarbons (HC), carbon
monoxide (CO) and oxides of nitrogen (NOx) in the exhaust
gas, to carbon dioxide (CO
2
), dinitrogen (N
2
) and water
vapor.
Exhaust Gas Recirculation (EGR)
The EGR system is designed to control the formation of ox-
ides of nitrogen (NOx) caused when fuel mixture burns at
high temperature. It works by recirculating exhaust gas
through the EGR valve and intake manifold into the combus-
tion chambers where it reduces peak temperature by
diluting the air/fuel mixture.
Summary of Contents for 1991 Accord Coupe
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