Manifold & exhaust systems (Exhaust manifold): Description and operation

EXHAUST MANIFOLD

The 4 branch fabricated steel exhaust manifold terminates in a flange with two outlet ports. Up to 2001 MY, a mounting boss for a Heated Oxygen Sensor (HO₂S) is incorporated on the rear of the exhaust manifold, between the branch pipes for cylinders 2 and 3. The exhaust manifold flanges are sealed to the cylinder head and exhaust front pipe by gaskets.

EXHAUST SYSTEM

The exhaust system consists of a twin front pipe, terminating in an expansion chamber, a catalytic converter and a twin tail pipe which incorporates a large capacity silencer. The entire exhaust system is manufactured from stainless steel.

The silencer contains a series of expansion chambers, resonators and baffles designed to give an improved exhaust system, and reduce condensation to increase the life of the system.

NOTE: Service repair tail pipes are available to allow repair without replacing the silencer.

From 2001 MY, two HO₂S are installed in the exhaust system:

• One HO₂S is installed upstream of the catalytic converter, in a mounting boss in the front pipe
• The 2nd HO₂S is installed downstream of the catalytic converter, in a mounting boss in the catalytic converter outlet pipe

The catalytic converter operates in a closed loop system. The exhaust gases are monitored by the Engine Control Module (ECM) via signals sent from the upsteam HO₂S in the exhaust manifold (up to 2001 MY) or exhaust front pipe (from 2001 MY). The ECM adjusts the fueling to maintain emissions acceptable to the catalytic converter. From 2001 Model Year, the ECM uses the signal from the downstream HO₂S to monitor the condition of the catalytic converter. For information on the operation of the catalytic converter See ENGINE MANAGEMENT SYSTEM - MEMS, Information.

INLET MANIFOLD - MPi

Up to 2000MY shown

1. Inlet manifold - plastic
2. Gasket - inlet manifold
3. Nut - inlet manifold - 3 off
4. Bolt - inlet manifold - 4 off

The inlet manifold is a one piece plastic moulding attached to the cylinder head with a gasket interposed between the two components The throttle housing is bolted to the manifold chamber, sealing being effected by means of an ’O’ ring. The intake air temperature sensor is inserted above the pipe flange.