When an engine exhaust valve is open, the pressure in the exhaust manifold is higher than atmospheric pressure. The exhaust manifold is configured in such a way that positive and negative pulses are produced during the operation of the cycle by designing it as adiffuser.
The main function of Pulse Air Valve to burn the excess pollutants out of the exhaust.
The Pulse Air Valve make air sucked into the exhaust port to encourage heat into the exhaust flame and burn of exess carbons.
The Pulse Air Valve has three openings one is connected to the manifold vacuum, another is connected to the exhaust pipe and the third is open to the atmosphere. When a negative pulse is induced in the exhaust, air from the atmosphere enters the exhaust manifold through a one-way reed valve and serves to oxidize the carbon monoxide and hydrocarbons in the exhaust.
This system consists of a spring-loaded diaphragm, and a shaft which is attached to the bottom. A manifold vacuum is applied over the diaphragm where the shaft end is towards the opening of the atmosphere.
During deceleration, the engine vacuum rises and acts against the spring to push the shaft downwards, thereby blocking the opening through which atmospheric air is passed to the exhaust.
The Royal Enfield Bullet, from year 2006-current, uses an Air Suction Valve to reduce emissions in its exhaust gases. Royal Enfield Motors calls their Air Suction Valve the PAV, or Pulsed Air Valve. Its function is the same, using a vacuum at the intake to trigger a valve that pulses atmospheric air into the exhaust. The original “iron barrel” style engine did this with a hose from the PAV going to the exhaust pipe, the newer (2003–2009) AVL aluminum engine pulses the gas directly into the exhaust port on the head of the engine itself.
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