An air suction valve (SAV) is a subsystem used to reduce

emissions Emission may refer to: Chemical products * Emission of air pollutants, notably: **Flue gas, gas exiting to the atmosphere via a flue ** Exhaust gas, flue gas generated by fuel combustion ** Emission of greenhouse gases, which absorb and emit rad ...

in the

exhaust gas Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline (petrol), diesel fuel, fuel oil, biodiesel blends, or coal. According to the type of engine, it is discharged into the atmosphere through an ...

es of

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...

Working principle

When an engine exhaust valve is open, the pressure in the

exhaust manifold In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word ''manifold'' comes from the Old English word ''manigfeald'' (from the Anglo-Saxon ''manig'' anyand ''feald'' old and refe ...

is higher than

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...

. The exhaust manifold is configured in such a way that positive and negative

pulses In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the nec ...

are produced during the operation of the cycle by designing it as a

diffuser Diffuser may refer to: Aerodynamics * Diffuser (automotive), a shaped section of a car's underbody which improves the car's aerodynamic properties * Part of a jet engine air intake, especially when operated at supersonic speeds * The channel betw ...

. The ASV has three openings: one is connected to the

manifold vacuum Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere. Manifold vacuum is an effect of a piston's movement on the induction stroke and the ...

, another is connected to the

exhaust pipe An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...

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 Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face. Modern versions often consist of flexible metal or composite materials (fiberglass or carbon f ...

and serves to

oxidize Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

the

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

and

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

s in the exhaust.

Air cut valve system

This system consists of a spring-loaded

diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

, 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 Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere. Manifold vacuum is an effect of a piston's movement on the induction stroke and the c ...

rises and acts against the spring to push the shaft downwards, thereby blocking the opening through which atmospheric air is passed to the exhaust. Though there is a negative pulse during deceleration, the manifold vacuum blocks and cuts off the air to the exhaust manifold. Used on the Honda Falcon NX4, mainly responsible for backfire or popping during deceleration when an open exhaust is added to the bike and if extra accessories is on vacuum circuit (Scottoiler, etc.). This system is mainly used in Indian two wheeler which are manufactured by Hero Honda. The advantage of this system is low cost.

Pulsed Air Valve

The

Royal Enfield Bullet The Royal Enfield Bullet was originally an overhead-valve single-cylinder four-stroke motorcycle made by Royal Enfield in Redditch, Worcestershire, now produced by Royal Enfield (India) at Chennai, Tamil Nadu, a company originally founded by ...

, from year 2006-current, uses an Air Suction Valve to reduce emissions in its exhaust gases.

Royal Enfield Motors Royal Enfield is an Indian multinational motorcycle manufacturing company headquartered in Chennai, Tamil Nadu, India. The Royal Enfield brand, including its original English heritage, is the oldest global motorcycle brand in continuous product ...

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. {{DEFAULTSORT:Air Suction Valve Engine valves Motorcycle engines