Chery A18. Manual — part 40

EXHAUST SYSTEM

OUTLINE

Exhaust system inspection ：

·Start the engine and inspect each exhaust system component for exhaust gas leakage.

·If leakage is found, repair or replace as necessary.

Exhaust system removal/installation

Warning：

·When the engine and exhaust system are hot, they can badly burn. Turn off the engine

and wait until they are cool before removing the exhaust system.

Exhaust assembly and oxygen sensor position

1. Oxygen Sensor 2. Catalytic Converter 3. Silencer

OXYGEN SENSOR

To gain max. conversion efficiency from catalytic converter, the engine oxygen sensor always
keeps the concentration of fuel-gas mixture as chemical reaction equivalence ratio.

The sensor shall realize closed loop controlling to the mixture concentration through
measuring the proportion of oxygen in exhaust.

Oxygen sensor is installed in the first section of exhaust pipe near manifolds.

Oxygen sensor is a ZrO

2

porcelain (1) with a thin platinum layer on its surface and one end is

sealed with a protection pipe inserted in. (2), the outside bushed with a metal housing (3) to
protect the sensor and to enable it to install on the exhaust manifolds. The outside of porcelain
(b) is exposed in exhaust gas, the inside (a) communicate with outer surroundings. Working
principle: voltages generated by electrode will change with the variation of oxygen
concentration; oxygen sensor measure the components of the exhaust, thus ECU will obtain

F-9

the mixture concentration value in time and change mixture thicker or thinner to make it
always be close to chemical reaction equivalence ratio. The voltage range of which is
0.980~1.020V.

To reach working temperature rapidly (~300°C), a resistor (4) installed in the sensor can
shorten the starting electric time of the porcelain. It means sensor can be installed in cold area
of exhaust hose. If mixed gas concentration is thinner than chemical reaction equivalence ratio
when working in full speed, ECU will give signal to the oxygen sensor to add mixture thicker
(halD-closed loop).

Oxygen sensor doesn’t work under cut-off and full load condition, which is called open loop.

Recovery:

If fault occurs in sensor or resistor, all information will be ignored and the whole system will
work as an opened loop system.

Oxygen sensor test procedure:

If diagnosis tester displays signal as “lambda sensor error “, please check:

——

If there is air leakage in every manifold, pipes, brake booster, exhaust gas and fuel-vapor

re-cycle system.

——

Spark wear and efficiency of high voltage wire insulator.

——

If timing and positioning of TDC (top dead center)/rotate speed sensor is right or not.

——

Tappet clearance and engine compression ratio.

——

If supplied oil pressure is right or not.

Exhaust gas emission CO% HC (p.p.m.) CO2 (%)

Before catalytic converter 0.4 - 1 < 600 > 12

After catalytic converter < 0.35 < 90 > 13

See the above table, using three-way catalyst converter can reduce three types of harmful
gases in exhaust gas at the same time: HC, CO, NO

x

, while harmless CO

2

increases.

The following factors will rapidly damage the catalytic converter:

——

Fuel contained lead, which will decrease converter efficiency even invalidate catalytic

converter.

——

Incomplete burned fuel in converter, for example, the catalytic converter will be melt and
damaged only in 30 seconds by the fuel under 800°C (temperature in converter).

Do not cut off the high voltage cable no matter the engine is running for any reason to insure
ignition parts (static ignition coil, high voltage cable, spark) are effective.

Oxygen sensor signal is displayed on diagnosis tester.

This value shall continuously wave in a defined range (thin mixture<0.45V, thick
mixture>0.45V).

Oxygen sensor heater resistance is about 4～5Ω at environment temperature 20°C, and its

battery voltage is 12V.

ASSEMBLY AND DISASSEMBLY OF EXHAUST SYSTEM

1. Installation of exhaust system with

three-way catalyst converter:

① Installation of back hose hook:

——

Install back hose hook on the dash
panel of the body.

——

Screw down M8 lock nut, screw
down torque is 12±1Nm.

② Installation of front hoses assembly:

——

Install Oxygen sensor assembly on front hose assembly with a tightening torque of
45±4.5Nm.

——

Install 3 M10 double head studs on exhaust manifolds.

——

Lay exhaust hose pad, install front hose assembly on exhaust manifolds.

——

Mount 3 M10 copper nuts with a tightening torque of 60±3Nm.

③ Installation of back hose assembly and three-way catalyst converter:

——

Connect three-way catalyst converter assembly and back hose assembly flange with 2
M8 bolts and 2 M8 flange plane nuts and lay sealing pad with a tightening torque of
30±3Nm. The nuts shall near the three-way catalyst converter.

——

Install back hose assembly on front hose assembly with a hose clamp.

——

Connect back hose assembly to the back hose hook with a hang block.

④ Installation of three-way catalyst converter:

——

Connect three-way catalyst converter assembly and front hose assembly flange with 2
M8 bolts and 2 M8 flange plane nuts and lay sealing pad with a tightening torque of
30±3Nm.

——

Use one hang block connecting front hose of three-element catalytic converter to the
hook of back hose.

⑤ Installation of back silencer:

——

Install a buffer stopper on back silencer with a hose clamp around the opening position
of back silencer.

——

Set 2 hooks to welding bolts and tighten them using 2 M8 lock nuts with a torque of
30±3Nm.

——

Connect back silencer to the body with 4 flying rings (hang block).

⑥ Installation of front silencer:

——

Install front silencer between three-way catalyst converter and back silencer.

——

Install hose clamp assembly.

——

Tighten all bolts in hose clamps and hose clamp assembly with a torque of 30±3Nm.