Mitsubishi Eclipse. Technical Information Manual (1994) — part 20

1-58

ENGINE <NON-TURBO> Emission Control Svstem

POSITIVE CRANKCASE VENTILATION SYSTEM

The positive crankcase ventilation system is a
tern for preventing the escape of blow-by gases

The positive crankcase ventilation valve is designed

from inside the crankcase into the atmosphere.

to lift the plunger according to the intake manifold

Fresh air is sent from the air cleaner into the

vacuum so as to regulate the flow of blow-by gas

case through the breather hose to be mixed with

properly.

the blow-by gases inside the crankcase.

In other words, the blow-by gas flow is regulated

The blow-by gas inside the crankcase is drawn into

during low load engine operation to maintain engine

the intake manifold through the positive crankcase

stability, while the flow is increased during high load

ventilation valve.

operation to improve the ventilation performance.

Positive crankcase

ventilation valve

A F U 0 0 0 3

ENGINE <NON-TURBO> Emission Control System

EVAPORATIVE EMISSION CONTROL SYSTEM

The evaporative emission control system prevents
the emission of fuel tankvapors into the atmosphere.
When fuel evaporates in the fuel tank, the vapors

pass through vent hoses or tubes to the charcoal

filled EVAP canister. The EVAP canister temporarily

holds the vapors. Through the EVAP purge solenoid,

the power-train control module (PCM) allows intake

manifold vacuum to draw vapors into the combustion
chambers during certain operating conditions. The

solenoid regulates vapor flow from the canister to
the engine.

OPERATION

The EVAP purge solenoid regulates the rate of vapor
flow from the EVAP canister to the throttle body.
The PCM operates the solenoid.

During the cold start warm-up period and the hot

start time delay, the PCM does not energize the
solenoid. When de-energized, no vapors are purged.
The PCM de-energizes the solenoid during open

loop operation.

The engine enters closed loop operation after it

reaches a specified temperature and the pro-
grammed time delay ends. During closed loop op-
eration, the PCM energizes and de-energizes the
solenoid approximately 5 to 10 times per second,

depending upon operating conditions. The PCM va-

ries the vapor flow rate by changing solenoid pulse

width. Pulse width is the amount of time the solenoid
de-energizes.

PULSED SECONDARY AIR INJECTION SYSTEM

Only manual transaxle vehicles have a pulsed

OPERATION

ondary air injection system. The system injects fresh
air upstream of the catalytic convertor. It operates

The PCM controls the ground path for the solenoid.

for a short period after cold engine start-up until

When the PCM grounds the solenoid, fresh air from

the engine coolant temperature reaches

the air cleaner flows through the aspirator valve

mately 5% (125°F)

to the catalytic convertor.

The secondary air injection system contains:

The aspirator valve prevents exhaust gases from
flowing into the fresh air stream, at the air cleaner

l

Pulsed secondary air injection valve

l

Pulsed secondary air injection solenoid

l

Connecting hoses and tubes

when the solenoid is grounded. If the aspirator valve

malfunctions, a popping noise could be heard during
cold start throttle stabs.

Pulsed secondary

Pulsed secondary

air injection solenoid

AFU0015

i d

ENGINE <NON-TURBO>

Emission Control System

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

The exhaust gas recirculation (EGR) system lowers
the nitrogen oxide

emission level. When the

air/fuel mixture combustion temperature is high, a
large quantity of nitrogen oxides

is generated

in the combustion chamber. Therefore, this system
recirculates part of emission gas from the exhaust
port of the cylinder head to the combustion chamber

through the intake manifold to decrease the air/fuel

mixture combustion temperature, resulting in reduc-

tion of

OPERATION

The electronic EGR transducer (EET) contains an
electrically operated solenoid and a back-pressure
transducer. The PCM operates the solenoid. The

PCM determines when to energize the solenoid.
Exhaust system back-pressure controls the trans-

ducer.
When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to
the transducer when the PCM energizes the sole-
noid. When exhaust system back-pressure becomes
high enough, it fully closes bleed valve in the

The EGR flow rate is controlled by the EGR valve
so as not to decrease the driveability.

The EGR system contents:

l

EGR tube

l

EGR valve

l

Electronic EGR transducer (EET)

l

Connecting hoses

When the PCM energizes the solenoid and

back-pressure closes the transducer bleed valve,
vacuum flows through the transducer to operate
the EGR valve.

Energizing the solenoid, but not fully closing the

transducer bleed hole (because of low back-pres-
sure), varies the strength of vacuum applied to the

EGR valve. Varying the strength of the vacuum

changes the amount of EGR supplied to the engine.
This provides the correct amount of exhaust gas

recirculation for different operating conditions.

ENGINE <NON-TURBO> - Mount

1-61

MOUNT

i d

,

The engine mounts use a principal axis inertia sup-

port system.
This support method on the principal axis inertia
is a structure that supports the top of the engine

FEATURES

l

The mount elements are arranged near the roll

axes of the engine and transaxle so that the
rolling moment can be limited and vibrations
can be reduced during idling.

l

The front and rear roll stopper brackets have

been relocated to the transaxle housing. As
a result, the bracket has been made shorter
and more rigid, which contributes to less vibra-
tion and noise.

l

Each insulator with internal hollows has out-

standing vibration absorbing characteristics.

and top of the transaxle to effectively control engine
vibration.

l

Brackets cast from aluminum are used for the
engine mounts and transaxle mounts so as to
reduce booming noise.

l

Conventional arrangement of the engine and

transaxle has been reversed to mount the en-

gine on R.H. side of the vehicle and the transaxle
on the L.H. side, resulting in reversal of the
positions of the respective mounts.

Dynamic
damper

mount

Dynamic

Engine

Transaxle

Front

Rear roll
stopper

Centermember

Transaxle

mount

stopper

Centermember

Crossmember