Intake
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An intake , or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power. An ideal intake system should increase the velocity of the air until it travels in to the combustion chamber, while minimizing turbulence and restriction of flow. Alongside with development of jet-engine, and logical increase in overall speed of the system, it was necessary to achieve such inlet design to perform optimal air flow at any speed, generally, and in other hand - not to suppress work of first stage of compressor (of a jet-engine), by slowing down the speed of air at just under subsonic at entrance to the compressor, keeping the necessary air flow at optimum (for given output power). That led to "inverse droplet" design of air-spike (conus, or semiconus, in some designs) as most common idea under the design of supersonic, and hypersonic inlet. All the above is usually accomplished by flow testing on a flow bench in the port design stage. Cars with turbochargers or superchargers which provide a pressurized intake system, usually have extensive tweaking of the intake system to improve performance dramatically.
A modern air intake system should have three main parts, an air filter, mass flow sensor, and throttle body. Many cars today now include a silencer to minimize the noise entering the cabin. Silencers impede air flow and create turbulence which reduce total power, so many performance enthusiasts often remove them.
Production cars have specific length air intakes to cause the air to vibrate and buffett at a specific frequency to assist air flow in to the combustion chamber. Aftermarket companies for cars have introduced larger throttle bodies and air filters to decrease restriction of flow at the cost of changing the harmonics of the air intake for a small net increase in power or torque.
Porsche in the 1980s designed an intake system for their cars that changed the length of the intake system by alternating between a longer and shorter set of tubing using a butterfly valve, creating a small amount of positive pressure which increased overall performance of the engine.
Alfa Romeo used variable-length intake in their 2.0 Twin Spark engines powering the model 156.
