Chery Fora (Elara A520). Manual — part 43

31

4)

Check the diameter of value stem

a:

Use micrometer caliper to measure the
diameter of valve stem.

B:

Use inner micrometer guage to measure
the inner diameter of valve guide.

C:

Calculate the difference of measured
value and the clearance.

If they exceed the specified limit values, the
value or guide shall be replaced more
necessarily.

D:

Check the contact bandwidth of valve.

E:

Check the valve seat insert.

Valve

Guide

Outer Diameter

Of Valve Stem

Inner Diameter Of

Valve Guide

Measuring Point

Measuring Point

Contact Position (Should Be

At The Center Of Slope.)

Edge

Thickness

32

Standard

value

Limit
value

Outer diameter

of valve stem

(mm)

IN

￠5.98±0.008

EX

￠5.96±0.008

Inner diameter

of valve guide

(mm)

IN

￠5.4±0.1

EX

￠5.4±0.1

Clearance

(mm)

IN

0.02

EX

0.04

Thickness of

value top

（mm）

IN

0.3±0.15

EX

0.3±0.15

2.2.3

Installation

The installing steps are reverse to those for
removal.

Note:

1)

Dismantle the valve springs in two groups
with 1st and 4th cylinders in one group, 2nd
and 3rd cylinders in the other group. When
the piston runs tothe top dead center of 1st
and 4th pistons, you should dismantle the
valve springs of the 1st and 4th cylinders,
replace the valve oil seal, and mount valve
springs immediately. When the piston runs to
the top dead center of2nd and 3rd cylinders,
you should replace the valve oil seal. Thus,
you can prevent the valve from falling into
the cylinders, reducing unnecessary troubles.

2)

Apply engine lubricant onto the oil seal lip
when installing the valve oil seal.

33

SECTION II INTRODUCTION TO NEW ENGINE

TECHNOLOGIES——CBR& VVT

1. CBR PROFILE

CBR principle and structure

By controlling the organization modes of air
flow (eddy flow and turbulent flow), CBR
(Controlled Bum Rate) can improve the burn
rate, reduce displacement, and boost the
economical efficiency of fuel.

This engine adopts sliding plate CBR.

● When the engine operates at low speed,

the vacuum actuator shall drag the sliding
plate to move towards the direction
shown in the figure by use of rocker
assembly, and the neutral air passage
shall be shut off basically (there is only a
gap on the top right corner). The mixing
of oil mist and air mainly depends on the
eddy flow of air intake provided by
tangential air duct, thus improving the
combustion status.

● When the engine operates at high speed,

CBR control valve shall cut off the
vacuum condition of vacuum actuator;
thanks to the spring functions, the sliding
plate shall return to the position
illustrated in the figure, and the neutral
air duct shall also be opened, which
increases the turbulent flow of air intake
and improve the maximum power.

Structure of sliding plate

1) Sliding plate

2) Rocker and shaft assembly

3) Bracket

4) Vacuum actuator

Tangential Air Duct

Neutral Air Duct

1

2

3

4

34

2.VVT PROFILE

VVT Principle

VVTi is the abbreviation of variable valve timing with intelligent. During the operation of
engine, the valve opening time is called as valve timing. When the engine operates at
different rotation speeds, we need different valve timings to provide the optimal valve closing
control, so that the power and combustion efficiency can achieve the best effect. For this
purpose, we shall install VVTi mechanism onto the camshaft controlling the air intake valve
to regulate valve timing. The VVTi system installed on the air intake camshaft of engine is
equipped with oil- pressure clutch device between the camshaft and drive sprocket, which can
alter the rotation phase difference between the air intake camshaft and drive sprocket. The
controlled oil pressure mechanism connects with the engine oil system, and can be regulated
by solenoid valve and control loop. When the engine operates at different rotation speeds,
there are different angles between the camshaft and sprocket, which facilitates the air intake
valve to open and close at different times in an effort to achieve variable valve timing. On the
other hand, when the engine operates at different rotation speeds, abundant and appropriate
oil gas can be supplied to generate mighty power.

When the car engine equipped with VVT-I system fails abnormally, ECUs controlled by the
engine shall automatically lock the preset parameter value (come-home function), ensuring
the driver to drive the car to the maintenance station. This kind of engine lodges a strictly
demand for the quality of petroleum and lubricant; therefore, you must adopt the standard
materials in compliance with the stipulations of original car manufacturer in order to avoid
unnecessary damages.

5

4

7

6

3

2

1

8