Emission
Control
Systems
Crankcase
The engine crankcase breather outlet incorporates an oil separator flame-trap
Emission
which is connected by hoses to the controlled depression chamber between the
Control
piston
and
the throttle disc valve of the carburetter(s). Piston blowby fumes are
drawn
into the chamber where they combine with the engine inlet charge for
combustion in the engine cylinders in the normal way. Fresh filtered air is supplied
to the engine crankcase through a hose connected between the engine valve rocker
cover and the charcoal canister of the fuel evaporative emission control system.
Filler
caps
Both
the engine oil filler cap and the fuel
tank
filler cap are non-venting and form
a seal on the filling apertures.
IT IS ESSENTIAL
TO
THE
SATISFACTORY
OPERATION
OF
THE
EVAPORATIVE
LOSS
SYSTEM
THAT BOTH CAPS ARE ALWAYS
REFITTE
D CORRECTLY AND
TIGHTENE
D FULLY. A DEFECTIVE
CAP OR CAP SEAL
MUST
BE REPLACED
Fig. 2 The emission control components
Filler
caps
Both
the engine oil filler cap and the fuel
tank
filler cap are non-venting and form
a seal on the filling apertures.
Exhaust
The main feature of the exhaust emission control system is a combination of the
Emission
engine modification
and
air injection techniques
and
consists of modified
Control
carburetters, modified ignition timing,
and
air injection into the exhaust ports.
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 combustion
chambers of the engine. The injection of air into the exhaust gases promotes a
continued conversion of the undesirable hydrocarbon
and
carbon
monoxide
components of the exhaust gases to relatively harmless
carbon
dioxide
and
water.
An air
pump
mounted
on the front of the engine, and belt driven from the water
pump
pulley, supplies air under pressure through hoses
and
a check valve
and
distribution manifold to injectors in each exhaust
port
in the engine cylinder
head. The check valve prevents high pressure exhaust gases from blowing back
into the air
pump
due to, for examp le,
pump
drive failure.
Air from the
pump
is also supplied to a gulp valve, the outlet of which is con-
nected to the engine inlet manifold. A small bore sensing pipe connected between
the inlet manifold and the diaphragm chamber of the gulp valve relays changes
in manifold depression to the valve which will open
under
-certain conditions
such as those created by deceleration or engine overrun.
When the gulp valve opens a small quantity of air is admitted directly into the
inlet manifold to lean off the rich air/fuel mixture which is present in the manifold
under conditions immediately following throttle closure. This mixture, having
been reduced to a burnable condition, combines with engine inlet charge for
combustion in the engine cylinders in the
normal
way.
The carburetters are manufactured to a special exhaust emission specification
and
are tuned to give the maximum emission control consistent with retaining
vehicle performance
and
driveability.
The
metering needle is arranged in such a
manner
that
it is always lightly spring loaded against the side of the jet to ensure
consistency of fuel metering. A spring loaded valve incorporated in the throttle
. disc limits the inlet manifold depression
and
ensures
that
during conditions of
engine overrun the air/fuel mixture enters the engine cylinders in a burnable
condition consistent with low emission levels.
The ignition distributor is tuned with slightly retarded ignition at low engine
r.p.m. compared with non-emission equipped vehicles,
and
the timing is balanced
between mechanical
and
vacuum characteristics to give
optimum
timing con-
sistent with low emissions.
Pu rge
line
To check, disconnect the purge line from the rocker cover elbow. Examine the
restrictor
orifice of the restriction formed in the elbow for obstruction. Clear any dirt or
deposits from the restrictor orifice, using a length of wire.
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un",
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UHU
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C)\'llaU~l
ga~~s
promotes a
continued conversion of the undesirable hydrocarbon
and
carbon
monoxide
components of the exhaust gases to relatively harmless
carbon
dioxide
and
water.
IT IS ESSENTIAL
TO
THE
SATISFACTORY
OPERATION
OF
THE
EVAPORATIVE
LOSS
SYSTEM
THAT BOTH CAPS ARE ALWAYS
REFITTE
D CORRECTLY AND
TIGHT
ENE
D FULLY. A DEFECTIVE
CAP OR CAP SEAL
MUST
BE REPLACED
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12
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An air
pump
mounted
on the front of the engine, and belt driven from the water
pump
pulley, supplies air under pressure through hoses
and
a check valve and
distribution manifold to injectors in each exhaust
port
in the engine cylinder
head. The check valve prevents high pressure exhaust gases from blowing back
into the air
pump
due to, for examp le,
pump
drive failure .
Air from the
pump
is also supplied to a gulp valve, the outlet of which is con-
nected to the engine inlet manifold. A small bore sensing pipe connected between
the inlet manifold and the diaphragm chamber of the gulp valve relavs chances
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