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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