Although the PCV valve cannot be considered a sensing device. It was the first step leading to a complicated process to reduce auto emissions. Unfortunately, for some auto enthusiast, it was also the demise of the American muscle car. The fact is that, at the time, the only way auto makers could meet the stringent emission laws was to reduce horsepower which made the engine less efficient. In 1970 the Congress adopted the first major Clean Air Act and also established the Environmental Protection Agency.
Air injection is a system that introduces fresh air to the exhaust manifold.
This helps raise the exhaust temperatures which promotes continued combustion of the exhaust gases. The air injection also helps promote the chemical reaction which takes place inside the catalytic converter. The catalyst system, located in the exhaust flow, needs to reach an operating temperature of approximately 300 deg. The EGR system was designed to reduce the NOx emissions. The valve routes unburned gases from the exhaust manifold back to the intake manifold where they could be reintroduced into the combustion chamber.