Emission Control System - Sym RV 250i Service Manual

Mechanisms in the Emission Control
System ··················································18-1
Functions of Mechanism in the Emission
Control System·····································18-1
Fuel Evaporative Emission Control System
(E.E.C.) ·················································18-2
Mechanisms in the Emission Control System
Four-Stroke Engine Model
1. Catalytic Converter (CATA)
2. Evaporative Emission Control System (E.E.C.)
3. Air Injection System (A.I.)
4. Positive Crankcase Ventilation System (P.C.V.)
Functions of Mechanism in the Emission Control System
General
The emission control strategy of this model is formulated based on a four-stroke SOHC single-cylinder
engine. It adopts secondary air introducing device to purify the exhaust, in addition, it adopts an activated
carbon canister to absorb the fuel vapor generated from the fuel system.
※
Engine refinements－
Four Valves designed combustion chamber, together with optimum compression ratio, ignition timing,
intake and exhaust timing, have all contributed to maximize the intake/exhaust efficiency and
combustion efficiency.
※
Secondary air introducing system－
It is used to introduce secondary air into exhaust pipe so that unburned exhausts, CO & HC, may be
burned again and to be harmless gases.
System Device
Combustion Combustion
system chamber
Exhaust Post-treatment
system device
Evaporative
E.E.C. system emission control
system
Secondary
A.I. system
air-injection system
Crankcase blow-by
P.C.V. system
introducing device
Home page
Catalytic Converter (CATA)················· 18-4
Secondary Air Introduction System ··· 18-5
Positive Crankcase Ventilation System
(P.C.V.) ·················································· 18-8
Inspection Items··································· 18-9
Components
4-valve combustion
chamber
Catalytic converter
Activated carbon canister
Purge control valve
Air injection solenoid
valve
Secondary air filter
Vapor separator
Drain pipe
Contents

18. Emission Control System

Purpose & function
The semi-circular combustion chamber is
designed to balance the air stream to
achieve the combustion stability.
Installed a three-way catalytic converter in
the middle of exhaust pipe to oxidize the
CO, HC in the exhaust gas.
A canister is used to absorb vapor from fuel
tank and to introduce it into carburetor at an
opportune timing.
To introduce flesh air into exhaust manifold
controlled by an air cut-valve to burn the
exhaust again.
To introduce blow-by into combustion
chamber via a vapor separator for burning
then discharging.
18
18-1