How do emission control systems work?
Fuel vapour, oil vapour and unburnt fuel at the end of the combustion cycle must be transformed before being released into the environment. That's a job mainly reserved for the catalytic converter in the exhaust system. A number of sensors along the way also monitor the amount of oxygen in the exhaust air and adjust fuel injection and emission control processes accordingly.
Working on all fronts
Some of the techniques involved in emission control take place prior to the fuel being ignited. Oil vapour is sucked from the engine's inner workings, while fuel vapour from the tank is channelled to the intake manifold. The goal is to prevent dirty particles from spreading around and into ambient air.
Other techniques work their magic at the end of the combustion cycle, through the exhaust circuit. The catalytic converter (of which there are many different types of, depending on the model of vehicle) usually consists of ceramic monolith with a honeycomb structure and a washcoat that maximizes the catalytically active surface.
By using oxygen, the catalytic converter breaks down pollutants such as carbon monoxide, unburnt hydrocarbon, and nitrogen oxides into non-toxic substances like carbon dioxide and water. Sometimes (with diesel engines, in particular), a particulate filter is added to eliminate smaller carcinogens.
Engine warm-up
Vehicles create the most emissions during the first five minutes of operation, since the catalytic converter has yet to reach its optimum temperature. Accelerating the warm-up period is key, which is why emission control devices are mounted near the cylinder head, on the exhaust line.
Various technologies
Some automakers have developed a solution that injects more oxygen into the exhaust system in order to help the catalytic converter warm up more quickly to make its job easier.
In 1999, BMW introduced an electrically heated unit called "E-CAT." Heating coils inside the catalytic converter assembly were electrified just after engine start, bringing the catalyst up to operating temperature very quickly to qualify the vehicle for ''Low Emission Vehicle'' (LEV) designation. Excessive costs doomed the technology, however.
More recently, a new generation of additives has joined the equation. These fluids are low on sulphated ash, phosphorus, and sulphur content, improving thermal stability and reducing toxicity.
Automakers are multiplying efforts to meet the increasingly strict emission standards. Direct fuel injection, high-efficiency components, reduced friction, turbochargers, smaller displacements, and lighter vehicles are some examples. And now you can add more effective catalytic converters, as well.
Fuel vapour, oil vapour and unburnt fuel at the end of the combustion cycle must be transformed before being released into the environment. That's a job mainly reserved for the catalytic converter in the exhaust system. A number of sensors along the way also monitor the amount of oxygen in the exhaust air and adjust fuel injection and emission control processes accordingly.
Working on all fronts
Some of the techniques involved in emission control take place prior to the fuel being ignited. Oil vapour is sucked from the engine's inner workings, while fuel vapour from the tank is channelled to the intake manifold. The goal is to prevent dirty particles from spreading around and into ambient air.
Other techniques work their magic at the end of the combustion cycle, through the exhaust circuit. The catalytic converter (of which there are many different types of, depending on the model of vehicle) usually consists of ceramic monolith with a honeycomb structure and a washcoat that maximizes the catalytically active surface.
By using oxygen, the catalytic converter breaks down pollutants such as carbon monoxide, unburnt hydrocarbon, and nitrogen oxides into non-toxic substances like carbon dioxide and water. Sometimes (with diesel engines, in particular), a particulate filter is added to eliminate smaller carcinogens.
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| Photo: Chevrolet |
Engine warm-up
Vehicles create the most emissions during the first five minutes of operation, since the catalytic converter has yet to reach its optimum temperature. Accelerating the warm-up period is key, which is why emission control devices are mounted near the cylinder head, on the exhaust line.
Various technologies
Some automakers have developed a solution that injects more oxygen into the exhaust system in order to help the catalytic converter warm up more quickly to make its job easier.
In 1999, BMW introduced an electrically heated unit called "E-CAT." Heating coils inside the catalytic converter assembly were electrified just after engine start, bringing the catalyst up to operating temperature very quickly to qualify the vehicle for ''Low Emission Vehicle'' (LEV) designation. Excessive costs doomed the technology, however.
More recently, a new generation of additives has joined the equation. These fluids are low on sulphated ash, phosphorus, and sulphur content, improving thermal stability and reducing toxicity.
Automakers are multiplying efforts to meet the increasingly strict emission standards. Direct fuel injection, high-efficiency components, reduced friction, turbochargers, smaller displacements, and lighter vehicles are some examples. And now you can add more effective catalytic converters, as well.