What is a catalyst and what does it do?
Some mistake the catalyst for a filter, it is clearly not.
It merely causes a reaction in the exhaust gases that turn harmful emissions into more friendly ones.
In an ideal world a car engine would efficiently burn all the petrol supplied to the engine and emit nothing but carbon dioxide and water vapour.
Sadly, the internal combustion engine is not a very efficient beast, as a result several different pollutants are emitted in the exhaust gases.
Catalytic converters were made mandatory in the UK for all new cars from 1st January 1993 in order to reduce pollution.
They are frequently blamed for a loss of power which is something we address in our sports catalyst article.
Catalysts are a dating agency for exhaust pollutants
What are the harmful components in exhaust fumes?
The incomplete combustion of the petrol gives rise to carbon monoxide and various Volatile Organic Compounds (VOCs).
This problem is worst when idling or decelerating.
Carbon monoxide is poisonous and a greenhouse gas.
Volatile Organic Compounds are harmful to health and some are linked to cancer.
The very high temperatures in the engine (over 1500°C) causes nitrogen from the air to react with the oxygen from the air to form nitrous oxides.
These cause various problems, nitrogen dioxide for example reacts with the water in the atmosphere to form dilute nitric acid which gives rise to acid rain.
The action of sunlight on this mix of pollutants gives rise to photochemical smogs and the formation of other pollutants such as ozone.
So how does the catalyst convert these elements?
You can think of your catalytic converter as a dating agency for exhaust pollutants
Helping them meet their ideal partner and converting them to carbon dioxide and water vapour.
Sports catalysts flow much better and are less restrictive.
Various grades of cell size are available between these two extremes.
Sports catalyst cross section The catalytic converter is a marvel of engineering design.
When you turn on your engine it needs to cope with a rapid temperature rise.
Another problem is poisoning due to contaminants in the exhaust gases.
Sulphur in the petrol or phosphorous from engine oil can both permanently damage the effectiveness of the catalyst.