What does my catalytic convertor do?

All modern petrol car exhausts manufactured from 1993 include a catalytic convertor. This reduces harmful emissions of hydrocarbons, carbon monoxide and nitrogen oxides into the atmosphere.

The catalytic convertor works by converting gases into water vapour and less harmful gases.

It includes a core of ceramics riddled with pores that measure less than 1/1000 metre. The pores are coated with powdered catalysts that contain metals such as platinum, palladium and rhodium.

Because the pores are close to the engine they heat up and the catalytic convertor starts working soon after the engine is started.

Catalytic convertors are so efficient that the difference in emission readings for cars with convertors and those without are huge. The good news is that catalytic convertors have a good life expectancy, but still need to be checked periodically for internal and external damage.

Another device that helps to reduce carbon emissions is the oxygen or lambda sensor. This monitors the percentage of oxygen present in exhaust gases and transmits information to the engine management system or electronic control unit (ECU).

The ECU (Electronic Control Unit) — using information obtained from the oxygen sensor — constantly adjusts the air/fuel mixture so that the cleanest and most efficient combustion is achieved under all operating conditions.

Sometimes, a ‘failed’ catalytic converter can be due to a fault in the engine management system. In these circumstances a new catalytic converter may not rectify the problem.

So the oxygen sensor, catalytic convertor and ECU all work together to help to achieve the lowest possible output of dangerous and polluting gases.