Mitsubishi Evolution X. Manual — part 50

EMISSION CONTROL

TSB Revision

ENGINE AND EMISSION CONTROL

17-10

CRANKCASE VENTILATION SYSTEM

M2171000400260

A blow-by gas reduction device prevents blow-by
gas from being expelled into the atmosphere and is
of closed type. A positive crankcase ventilation
(PCV) valve is provided in the ventilation hose from
the rocker cover to the intake manifold. During low
load driving, clean air is supplied to the crankcase by
the air intake hose via the breather hose and rocker
cover, and it mixes with the blow-by gas in the crank-

case. The blow-by gas in the crankcase is induced to
the intake manifold through the rocker cover and
PCV valve. During high load driving, blow-by gas in
the crankcase is induced to the intake manifold
through the rocker cover and PCV valve and at the
same time also via the air intake hose and throttle
body due to negative pressure in the air cleaner.

POSITIVE CRANKCASE VENTILATION (PCV)
VALVE

PCV valve lifts the plunger according to negative pressure in
the intake manifold to create appropriate ventilation for the
crankcase.

AK704104

AB

Ventilation hose

Breather hose

Flow of blow-by gas (high load area)

Air cleaner

Flow of blow-by gas and clean air (low load area)

Positive crankcase
ventilation valve

AK602324 AC

Plunger

From
rocker
cover

To intake
manifold

Spring

EMISSION CONTROL

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ENGINE AND EMISSION CONTROL

17-11

EVAPORATIVE EMISSION CONTROL SYSTEM

M2171000200288

HC (hydrocarbon) generated in the fuel tank are
adsorbed by the active carbon in the canister and
stored. HC stored in the canister is introduced to the
intake manifold when engine is in operation where it
is mixed with intake air and combusted. ECM intro-
duces optimum HC amount according to driving con-

ditions and so performs duty control on the
evaporative emission purge solenoid. Also, the evap-
orative emission purge solenoid is closed during
deceleration or immediately after engine start to
restrict change in air-fuel ratio and prevent engine
from stalling.

EVAPORATIVE EMISSION PURGE SOLENOID

An evaporative emission purge solenoid is installed in the
intake manifold.The evaporative emission purge solenoid con-
trols the intake volume of fuel vapor gas from the canister. The
evaporative emission purge solenoid is a duty control type
solenoid valve. When current is not passing through the coil,
nipple A is kept airtight and fuel vapor gas cannot be sucked in.
When current passes through the coil, air can pass between
nipple A and B and fuel vapor gas is sucked in. ECM changes
the ON duty ratio according to engine's operating condition to
control the intake volume of fuel vapor gas.

AK703842

Engine coolant
temperature sensor

Crankshaft position
sensor

Throttle position sensor

Intake air temperature
sensor 1

Mass airflow sensor

Barometric pressure
sensor

Battery

MFI relay

ECM

Evaporative
emission
purge solenoid

Evaporative emission
canister

Check valve

Engine coolant
temperature sensor

Crankshaft position
sensor

Throttle position sensor

Intake air temperature
sensor 1

Mass airflow sensor

Barometric pressure
sensor

AB

Battery

MFI relay

ECM

Evaporative
emission
purge solenoid

Evaporative emission
canister

Check valve

AK702871

A

B

AC

To intake manifold

To canister

EMISSION CONTROL

TSB Revision

ENGINE AND EMISSION CONTROL

17-12

EMISSION REDUCTION SYSTEMS

M2171000800161

These decrease CO, HC and NOx in the exhaust
gases and consist of air-fuel ratio feedback control
and catalytic converter.

1. AIR-FUEL RATIO FEEDBACK CONTROL

Refer to GROUP 13A

− Multiport Fuel System (MFI) − Fuel

Injection Control

P.13A-32

.

2. CATALYTIC CONVERTER

Catalytic converter is installed in the exhaust pipe below the
floor. Based on appropriate air-fuel ratio feedback from oxygen
sensor, CO and HC are oxidized and NOx is reduced. Catalytic
converter is a monolith with beehive design with catalysts on
the unit surface. It is protected by a thermally insulating mat
and enclosed in a shell.

AK602245AG

12V

ON

OFF

0V

Evaporative
emission
purge solenoid

From MFI relay

ECM

High load: 100ms
Low load: 200ms

AK702872AC

Catalytic converter

11-1

GROUP 11

ENGINE

CONTENTS

GENERAL DESCRIPTION. . . . . . . . .

11-2

BASE ENGINE . . . . . . . . . . . . . . . . . .

11-3