Exhaust System

• The exhaust system consists of more than the external exhaust manifold and exhaust pipe and actually starts at the exhaust valve. Managing the pressure wave that travels back and forth between the exhaust valve and the exhaust pipe is one way of tuning the engine.
  
  

Concepts

• In calculating the optimum length of an exhaust pipe, it is important to understand the concepts of bottom dead center (BDC) and top dead center (TDC). BDC occurs when the piston is at the bottom of the cylinder at its lowest point in its stroke, or cycle; TDC occurs when it is at the top of the cylinder, at its highest point.
  
  

Formula

• The ideal length of an exhaust pipe can be calculated from the formula L = 129540 x ET / RPM x 6. In this formula, L represents the exhaust pipe length in millimeters (1 inch = 25.4 mm); ET represents the duration of the exhaust valve from BDC to TDC, and RPM represents the engine's maximum number of revolutions per minute minus 500.