The whole point of performance tuning and engine modifications, whether it involves supercharging, turbocharging, NOS, or gas flowing the cylinder head is to improve the efficiency of the air flow in and out of the engine. This process is often described as improving engine breathing. The main aim in improving engine breathing, is to identify restrictions that impede the air flow in and out the engine, eliminate these restrictions and improve air flow, or use a pump to force more air into the engine. Our sections on Turbochargers, Superchargers and NOS dealt with forced induction and getting more air into the engine, while our section on Exhaust Systems dealt with getting air efficiently out of the engine through the correctly tuning and designing the exhaust system.
In this section we'll discuss the air intake side of the engine and ways in which we can improve the efficiency of the air flow into the engine. We'll look specifically at improving the efficiency of the air filter and air filter box, sizing and positioning of the mass air-flow sensor and the throttle body, improving the inlet ducting, cold air induction, how to tune the intake manifold runners and how to design the intake manifold. The information discussed here is meant for naturally aspirated engines but it may also be applied to engines that use forced induction systems. Let's begin with the air filter ...