Exhaust Header Theory and Proper Exhaust Tuning

In order to explain the effect of exhaust tuning on performance, let’s take a quick look at the 4-stroke engine cycle.  The first step in the 4-stroke process is the intake stroke.  With the intake valve open, the piston travels down the cylinder pulling a fresh air and fuel mixture into the cylinder (intake stroke).  When the piston nears bottom dead center, the intake valve closes and the cylinder travels up the cylinder compressing the air/fuel charge (compression stroke).  With the piston at the top of the stroke, the spark plug fires and ignites the compressed mixture causing essentially a closed explosion.  The pressure of the ignited fuel pushes the piston down the cylinder transferring power to the piston, rod and finally the crankshaft (power stroke).  After bottom dead center, the exhaust valve opens and the piston is pushed up
In order to explain the effect of exhaust tuning on performance, let’s take a quick look at the 4-stroke engine cycle.  The first step in

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