Honda GL1800 2004 Owner's Manual page 217

Emission Control Systems
Source of Exhaust Emissions
The combustion process produces carbon monoxide (CO), oxides of nitrogen
(NOx) and hydrocarbons (HC). Control of hydrocarbons and oxides of nitrogen
is very important because, under certain conditions, they react to form
photochemical smog when subjected to sunlight. Carbon monoxide does not
react in the same way, but it is toxic.
Honda Motor Co., Ltd. utilizes various systems to reduce carbon monoxide,
oxides of nitrogen and hydrocarbons.
Exhaust Emission Control System
The exhaust emission control system includes a PGM-FI system, two warm-up
oxidation catalysts, two three-way catalytic converters, two heated oxygen
sensors, and a secondary air injection system.
No adjustment to these systems should be made although periodic inspection of
the components is recommended.
PGM-FI System
The PGM-FI system uses sequential multiport fuel injection. It has four
subsystems: Air Intake, Engine Control, Fuel Control, and Exhaust Control.
The Engine Control Module (ECM) uses various sensors to determine how
much air is going into the engine. It then controls how much fuel to inject under
all operating conditions.
Ignition Timing Control System
The system constantly adjusts the ignition timing, reducing the amount of HC,
CO and NOx produced.
Secondary Air Injection System
The secondary air injection system introduces filtered air into the exhaust gases
in the exhaust port. The secondary air injection system helps improve emission
performance.
Three-Way Catalytic Converters
The three-way catalytic converters are in the exhaust system. Through chemical
reactions, they convert HC, CO, and NOx in the engine's exhaust to carbon
dioxide (CO ), dinitrogen (N ), and water vapor.
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Technical Information
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