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

EXHAUST MANIFOLD

’K’ Series engine

The 4 branch fabricated steel exhaust manifold terminates in a siamised front pipe flange. The heated oxygen sensor is located in the manifold at the rear and in the outlet for numbers 2 and 3 cylinders. The manifold flanges are sealed by gaskets.

’D’ Series engine

The cast iron exhaust manifold is divided internally and terminates in a single front pipe connection. The oxygen sensor is located in the manifold at the side and is adjacent to the front pipe connecting flange. The manifold flanges are sealed by gaskets.

’L’ Series engine

The cast iron exhaust manifold carries an EGR valve and a variable wastegate Garrett turbocharger. There are two tappings on the compressor housing; the ’N’ port to the wastegate and the ’J’ port to the boost pressure sensor on the bulkhead.

NOTE: Gaskets are NOT fitted between the manifold and turbocharger or between the turbocharger and exhaust down pipe.

’T’ Series engine

The cast iron exhaust manifold is divided internally and terminates in a twin front pipe connection. Number 1 and 2 cylinders discharge into one half and 3 and 4 cylinders into the other half. The heated oxygen sensor is inserted into the manifold adjacent to the front pipe connecting flange.

EXHAUST SYSTEM

The exhaust system consists of a front pipe, catalytic converter, an intermediate pipe which incorporates a silencer (not ’L’ series) and tail pipe assembly which contains a large capacity silencer.

A twin front pipe terminating in an expansion chamber is used with the ’K’ & ’T’ series engine and a single constant diameter pipe is used with the ’D’ series engine. The ’L’ series front pipe consists of a single constant diameter pipe with integral flexible joint.

All the silencers contain a series of expansion chambers, resonators and baffles designed to give an improved exhaust system, which reduces condensation and increases the life of the system.

Except for ’L’ series which is open loop, the catalytic converter operates in a ’closed loop’ system. The exhaust gases are monitored by the heated oxygen sensor which provides a signal which is used by the Engine Control Module (ECM) to modify the fueling to maintain emissions acceptable to the catalytic converter. For information on the operation of the catalyst. See EMISSION CONTROL, Description and operation.