Air Intake
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. This 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.
An intake 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.
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.
BMW is unusual in that
its M line of performance cars have one throttle body per cylinder,
as opposed to one throttle body for four, six or even eight cylinders
for regular production cars. This is done to increase flow characteristics
and improve throttle response. Nissan also use this system in their
high performance models.
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.
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