Exhaust Sizes
The exhaust dimensions are sometimes dependent 
on how it will be utilized. Although there are several formulas that may be used, one of the most widely implemented for single exhaust tubing diameters is an inch for every 100 cu. inches of displacement. For double exhausts it is 1.5 inches. A 400 cu inch engine for example, would work well with 1 four inch pipe or 2 three inch pipes.
Car Exhaust Parts
Pipes
The exhaust gas will go through the pipes. There are usually two or three of these in a car. The exhaust manifold is joined to the catalytic converter by way of the header pipe.
The intermediate pipe hooks up the catalytic converter to the muffler. From the muffler, the tailpipe releases the gases from the rear of the vehicle. Majority of these pipes are made from rust proof steel.
Catalytic Converter
Whatever the exhaust dimensions are, it will have a catalytic converter. This is used to limit the exhaust pollutants that go into the atmosphere. There are some systems that have dual converters. To iodize the hydrocarbon particles (i.e., make it non-poisonous), the converter must reach temperatures of over 1,000 F.
Muffler
Mufflers are used to limit pressure pulses and engine noise. These noises are generated when the gases are released by the cylinders. Mufflers use internal bafflers, acoustic tubes and resonance chambers to keep the noise down. These are usually placed on the back of the car. These are available in different styles. There are cars with more than a single muffler.
Exhaust Manifold
It is here that the gases from the combustion chamber go through. These are constructed from cast iron. They are connected to the cylinder head exhaust ports. To keep the exhaust from leaking, a gasket is included. The O-ring is used to prevent leaks between the header pipe and manifold.
Heat Shields
The heat shields are used to dissipate heat. As the car runs, the temperature of the muffler and converter go up. The shields are designed to protect the car from the heat. Without it, flammable items on the vehicle will catch fire. The shield is used to keep flammable material like grass from flaming up under the car.
The exhaust dimensions used in vehicles are always being evaluated. Just like other car components, the specifications for exhausts may be altered. Refer to the car manual for more specific info about the exhaust system being used there.
