The Emission Control Components - MG Midget 1979 Driver's Handbook Manual

mission Control Systems-except California
Crankcase The engin.e crankcase breather outlet incorporates an oil sepa rator flame-trap
emission
(arrester) In the top o~ the valve rocker cover which is connected by hoses to
control the controlled depression chamber between the piston and the throttle disc of
the carburetter. Piston blowby fumes are drawn into the depression chamber
of.the carburetter from the rocker cover, and are joined by purged air from the
pnm~ry c~arcoal .
canister of the fuel evaporate loss system. These fumes
combine with the Inlet charge for combustion in the normal way.
Exhaust The exhaust emission control system is designed to give the required degree of
emission control of the carbon monoxide, unburnt hydrocarbons and oxides of nitroge n
control content of exhaust gases.
The emission control system is a combination of engine components and air
injection techniques and consists of a special carburetter, air injection into the
exhaust manifold and exhaust gas recirculation.
THE EMISSION CONTROL COMPONENTS
23
15 16
17 8
-:
i '
2
~
2
7ND141C
The quantity of air-polluting elements in the gases leaving the exhaust pipe is
reduced by adding air to the hot gases immediately they leave the combu tion
chambers of the engine. The injection of air into the exhaust gases promote
continued conversion of the undesirable hydrocarbon and carbon mon oxid
components of the exhaust gases to relatively harmless carbon dioxide and wat r.
The exhaust gas recirculation valve mounted on the exhaust manifold will
re-circulate a controlled quantity of the exhaust gases to reduce combu tion
chamber temperature.
The catalytic converter is fitted into the exhaust system in order to reduc e carbon
monoxide and hydrocarbon emissions. .
An air pump mounted on the front of the engine, and belt driven from the
crankshaft pulley, suppl ies air unde r pressure through a hose, a check valve,
and distribution pipe to the exha ust man ifold. The check valve prevents high
pressure exhaust gases from blowing back into the pump due to , for example,
pump drive failure.
The carburetter is manufactur d to xhau t em ission specification and
is tuned to give the maximum mi i n I n i tent with retaining vehicle
performance and drivabili y. Th m t rin n
J
i arranged in such a manne r
that it is alwa ys lightly prin I d d in t th ide of the jet to ensure con-
sistency of fuel metering. A thr t 1 y..p valve limits the inlet manifold
depression and ensures that durin c nd itions of engine overrun the air /fuel
mixture enters the engine cylind r in burnable condition consistent with low
emission levels.
1. Secondary charcoal adsorption canister
2. Canister inter-connecting pipe
3. Primary charcoal adsorption canister
4. Vapour lines
5. Purge line
6. Restricted connection
7. Restrictor
8. Sealed oil filler cap
· Oil separator/flame trap (arrester)
O. Fuel pipe
11 l:'n.al ........ ~ .....
13. Air pump
14. Check valve
15. Air temperature control valve
16. Hot air hose
17. Exhaust gas recirculation valve
18. E.G.R. valve pipe
19. Flame trap
20. Flame trap line to carburetter
21. Flame trap line to E.G.R. valve
22. Flame trap line to distributor vacuum unit