The exhaust system is one of those key areas of a vehicle that affect performance as well as visceral appeal. A properly chosen exhaust system can improve performance by reducing exhaust gas back pressure (resistance to flow) while providing a more aggressive or substantial sound The two aren’t necessarily tied together, though, as there are plenty of loud exhaust systems that rob power, while there are very quiet systems that improve performance. Again, let’s go back to the premise that an internal combustion engine is a relatively complicated air pump. Think of a piston at top dead center in the cylinder. The first stroke sees the piston moving downward in the cylinder while the intake valve opens. This downward motion creates a suction that draws air and fuel into the cylinder. As the piston reaches bottom dead center on the intake stroke, the intake valve closes and the piston rises in the cylinder, compressing the air/fuel mixture (stroke two). When the mixture is compressed, the spark plug fires and the mixture burns rapidly, increasing cylinder pressure considerably and forcing the piston back down in the cylinder (stroke three). Once the cylinder reaches bottom dead center and begins to rise again (on stroke four) the exhaust valve opens and the rising piston pushes the exhaust gases into the exhaust system. With these four strokes recurring over and over, and multiplied by the number of cylinders in a given engine, it’s easy to see how important the exhaust system (and intake system) is to the performance of the overall package. If the exhaust system is restrictive, the piston has difficulty pushing the exhaust gas out of the engine (backpressure). By reducing backpressure the engine doesn’t have to work as hard pushing exhaust through the system, and more power is available to move the vehicle. By the way, exhaust backpressure and intake restrictions are known as “pumping losses” to engine engineers. The exhaust system is similar to the intake system in that pipe diameter and length plays an ... Distributed by Tubemogul.
