Exhaust Headers

An exhaust header is an after market automotive part designed to improve vehicle performance. The small gain in performance facilitated by an exhaust header is important to high performance drivers who often make other modifications to their vehicles in order to increase speed. These modifications include the installation of larger intake vents for the engine. An exhaust header modifies the exhaust system to prevent back pressure, meaning that the cylinders do not have to work as hard to push exhaust out as they do in a traditional system. There are different types of exhaust headers depending on the needs of the drivers, with some tuned for low performance and others aimed at high performance on the open road.
In a conventional exhaust system, after the cylinders combust, they push the exhaust out into the exhaust manifold, which routes the exhaust out of the vehicle through the exhaust pipe. However, the exhaust manifold can create a back pressure which pushes against the cylinder, meaning that it has to exert more energy to push the exhaust out and prepare for the next firing. As a result, some efficiency can be lost.



An exhaust header works differently, essentially creating a miniature exhaust pipe for each cylinder and routing the exhaust to a centralized collector which is much larger. The pipes of an exhaust header are bent to fit under the hood and cut to the same length so that the exhaust gases will arrive sequentially in the collector as each cylinder fires. This eliminates the back pressure problem and allows the cylinders to operate more effectively.
In some cases, an exhaust header can be tuned to pull at the exhaust valve of the next cylinder and suck the exhaust out, meaning even less work for the cylinder. Drivers who desire more power for around town driving and better acceleration under a heavy load usually opt for a low performance exhaust header, while drivers who are looking for speed on the open road prefer high performance headers.


A variety of manufacturers make exhaust headers for a dizzying assortment of vehicles, and it is important to install the exhaust header designed for your car. Because exhaust leaks can be dangerous, the exhaust header should be installed with care, or professionally if there is any uncertainty. An improperly installed header could lead to an exhaust leak which vents into the cabin of the vehicle, causing symptoms ofcarbon monoxide poisoning in the driver and passengers.

courtesy of : wisegeek.com

How do exhaust headers work to improve engine performance?

Headers are one of the easiest bolt-on accessories you can use to improve an engine's performance. The goal of headers is to make it easier for the engine to push exhaust gases out of the cylinders.

The exhaust headers of a Lamborghini Murcielago

When you look at the four-stroke cycle in How Car Engines Work, you can see that the engine produces all of its power during the power stroke. The gasoline in the cylinder burns and expands during this stroke, generating power. The other three strokes are necessary evils required to make the power stroke possible. If these three strokes consume power, they are a drain on the engine.

During the exhaust stroke, a good way for an engine to lose power is through back pressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted. Using two exhaust valves rather than one improves the flow by making the hole that the exhaust gases travel through larger.

In a normal engine, once the exhaust gases exit the cylinder they end up in theexhaust manifold. In a four-cylinder or eight-cylinder engine, there are four cylinders using the same manifold. From the manifold, the exhaust gases flow into one pipe toward the catalytic converter and the ­muffler. It turns out that the manifold can be an important source of back pressure because exhaust gases from one cylinder build up pressure in the manifold that affects the next cylinder that uses the manifold.

The idea behind an exhaust header is to eliminate the manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector.

courtesy of : howstuffworks.com