Exhaust manifolds and pipe:
The exhaust system in any car has two primary roles, one to expel the waste gases produced in the combustion chamber into the atmosphere and secondly to reduce noise created due to the expulsion of these gases.

The main parts comprise of an exhaust manifold, exhaust pipe and seal, catalytic converter, muffler resonator, tail pipe and heat shields. In this issue we concentrate on the types of exhaust manifolds, their purpose and exhaust pipes.

The exhaust manifold is a bank of pipes that collect the gases from the engines cylinders and direct them to the exhaust pipe. Cast or nodular iron is generally used to make exhaust manifolds. Manifold designs depend on the type of engine (in-line, V type, etc) and the number of cylinders employed (three, four, six, etc). In-line engines have one exhaust manifold whereas V type engines have an exhaust manifold facing each bank of cylinders. Each cylinder is provided with a single passage that blends into a single passage that connects to the exhaust pipe.

In modern V-type engines a dual type manifold is employed. This consists of two identical yet individual exhaust manifolds. A tailpipe sticking out from the rear on either side of the car is a clear indication of a dual type of exhaust manifold. This type of manifold is also preferred only for large displacement engines and is seldom seen on smaller engines.

The exhaust pipe is a metal pipe made of either aluminised steel, stainless steel or zinc plated heavy-guage steel. The exhaust pipe connects the exhaust manifold and the muffler units and in modern engines incorporates the catalytic convertor in between. In certain vehicles emission control devices such as exhaust gas recirculation (EGR) valves, early fuel evaporation (EPE) valves or heat risers are employed. These are mounted between the exhaust manifold and the exhaust pipe. In electronic controlled engines an oxygen sensor is installed in the exhaust pipe. This device senses the amount of oxygen in the exhaust gas and sends a signal to the control unit to regulate the air-fuel mixture supplied to the engine as desired.

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