Emission Control System - Sym GTS 250 Service Manual

Names of Mechanisms in the Emission
Control System······································ 18-1
Function of Mechanisms in the Emission
Control System······································ 18-1
Fuel Evaporative Emission Control System
(E.E.C.) ··················································· 18-2
Catalytic Converting System (CATA)··· 18-4
Names of Mechanisms in the Emission Control System
Four-Stroke Engine Model
1. Catalyst converter (CATA.)
2. Evaporative Emission Control System (E.E.C.)
3. Air Injection System (A.I.)
4. Positive Crankcase Ventilation System (P.C.V.)
Function of Mechanisms in the Emission Control System
General
The emission control strategy of this model was formulated basing on a four-stroke SOHC carburetor
single cylinder engine. It adopts secondary air introducing device to purify the exhaust, in addition, it also
adopts a charcoal canister to absorb the fuel vapor generated through evaporation in the fuel system.
¡ ° Engine refinements¡ Ð
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¡ Ð
It is used to introduce secondary air into exhaust manifold so that incomplete burned exhausts, CO &
HC, may be burned again and to be harmless gases.
System Device
Combustion Combustion
chamber 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
Secondary Air Introduction System ··· 18-5
Positive Crankcase Ventilation System
(P.C.V.) ·················································· 18-8
Inspection Items··································· 18-9
Countermeasure for Emission Pollutants
Not Within Standard as In Idle Speed
(4-Stroke Engine) ································· 18-10
Components
The semi-circular combustion chamber is
4-valve combustion
designed to balancing the air stream to achieve
chamber
the combustion stability.
Installed a three-way catalytic converter in the
Catalytic converter middle of exhaust pipe to oxidize the CO, HC in
the exhaust gas.
A canister is used to absorb vapor from fuel tank
Charcoal canister
and to introduce it into carburetor at an
Purge control valve
opportune timing.
To introduce flesh air into exhaust manifold
Air inject cut-valve
controlled by an air cut-valve to burn the
Secondary air filter
exhaust again.
To introduce blow-by into combustion chamber
Vapor separator via a vapor separator for burning then
discharging.
Contents

18. Emission Control System

Purpose & function
18
18-1