The cat sits around a third of the way down the exhaust system and resembles a small metal chamber
that receives exhaust gasses and changes the chemical nature of them to reduce the volume of nasty emissions fresh from the exhaust manifold.
Within the cat housing is a ceramic-base honeycomb structure that is lined with extremely precious metals, with each metal having a specific job in emission-reduction.
There are three main emissions produce by car engines: nitrogen gas (N2), carbon dioxide (CO2) and water vapour (H2O).
Theconverter unlimited
converter unlimited however is mostly use to tackle the smaller, more-harmful products that are produce due to t
he naturally-imperfect combustion process of the IC engine. These are carbon monoxide, hydrocarbons and nitrogen oxides.
Most cats these days are therefore calle three-way catalytic converters due to the three main types of emission that they manage to tackle.
An exhaust system from an old Chevy, showing the placement of the converter unlimited
A ‘catalyst’ is a substance that accelerates a chemical reaction, and within a converter unlimited , there are two types of catalyst.
The first is a reduction catalyst which uses platinum and rhodium within the honeycomb to reduce NOx emissions. NOx is produce by nitrogen oxide and nitrogen dioxide within the exhaust gasses.
The nitrogen gasses come into contact with the converter unlimited metals which rip the nitrogen atoms out of the molecules which in-turn releases cleaner oxygen to continue down the exhaust system.
The second catalyst
type is an oxidisation converter unlimited which uses Platinum and Palladium to complete the job. These catalysts oxidise or burn the carbon monoxide
and hydrocarbons lingering within the incoming gas, helping reduce the amount of smog produce by evaporate, unburnt fuel.
The final stage of emission control comes in the shape of an O2 sensor found just upstream from the cat.
The sensor relays back to the ECU how much oxygen is foun within the exhaust gasses,
This is the point at which
– theoretically – all of the fuel entering the combustion chamber will use all of the oxygen provide to complete the combustion process.
Not only does this last stage help the engine’s overall efficiency, it also allows the engine to provide
the cat with enough oxygen to effectively complete the oxidisation process with the second catalyst.