What dose a header on a car do?

Question

Do bigger headers improve car performance?

Answer 1

A header replaces the stock muffler and exhaust system. Along with other added or modified speed parts the headers system is integral as it becomes part of the whole package when increasing horse power. Simply put, when increasing horse power, you want to increase fuel/air intake therefore making it necessary to get the exhaust out faster by using a more direct, larger pipe exhaust system called headers

Answer 2

The headers take the exhaust gasses from the engine and flow them to the main exhaust pipe.  They are the fist stage of the exhaust system - Exhaust performance headers do away with the performance-robbing exhaust manifold that came with your car. Headers provide each cylinder with its own mini exhaust pipe, which means exhaust headers prevent the back pressure that occurs in a common exhaust manifold. When cylinders don't have to fight each other to expel their exhaust, they can put more power through the wheels, and a bigger grin on your face.

To a certain extent having a larger header (and larger diameter exhaust) will increase the flow of the exhaust gasses, but your engine needs some back-pressure in order to provide low rpm torque.  If you put on a set of high flow headers and keep the rest of the factory exhaust the gasses will only be able to flow as fast as the narrowest section of the system will allow (any system is only as strong as it's weakest part).

If you have an exhaust system that is wider than the stock factory system you will gain more high rpm power, but you will also loose some of the low range torque.