Question

3 Give the specifications and uses of intake and exhaust manifold. (4 marks gas applications for intake and exhaust manifold. (1 mark, each 0.5 mark)

Answer 1

The main function is to help create a specific torque curve the rest of the vehicle is optimized for.

An intake manifold moves air from outside the engine to the cylinder head(s) where it meets the combustion chamber and exhaust. Fuel injectors sit on it and it’s where atomized fuel meets outside air to create an air fuel mixture.

That’s what it does but the main function is to create an optimal torque curve that meets the requirements of the vehicle. It has runners or passages leading up to the cylinder head ports, the shape of those runners and the length from the top of the intake manifold to the cylinder head intake ports help determine what RPM an engine makes peak torque at.

When combined with cylinder heads, cams, exhaust and gearing all setup to make peak torque around the same rpm the result is a high performance engine. A truck and a sports car might have the same engine design and cylinder heads but intake manifold and cams that make it have higher low end torque in the truck and peak torque at a higher rpm in the sports car with gearing to match.

The port velocity and volume are major influences on engine performance and the air path through the engine starts at the intake manifold.

As the first component in the exhaust system, the exhaust manifold collects the exhaust fumes released from the engine cylinders and directs them to the catalytic converter. In turbocharged engines, the turbocharger is situated downstream of the exhaust manifold.

The design of the exhaust manifold has a significant influence on the performance and torque characteristics of an engine, as does the design of the connected pipes.

The fact that the individual exhaust tracts are merged into one ensures that pulsations, i.e. fluctuating pressure surges given off by a certain cylinder, do not prevent exhaust fumes being released from another cylinder. What’s more, waves of negative pressure are intended to promote the flow of exhaust fumes out of the cylinders.

Exhaust manifolds are often made of alloyed cast iron, which is able to withstand the high exhaust temperatures. Alternatively, exhaust manifolds made of stainless steel are also used.

Application:

• It reduces back pressure of exhaust gas to cylinder.
• It improves scavenging.
• Clean combustion happens.

Advantage:

• Better design of exhaust manifold results Peak torque achieved at lower RPM
• Horsepower also increased.