From David Hardwick
So cool flames can help engineers reduce NOx emissions by lowering the peak combustion temperature in engines (5 June, p 28). To achieve this, engineers usually recirculate a portion of the exhaust gases back into the cylinders.
However, exhaust gas recycling (EGR) can turn out to be bad news. It will recirculate small amounts of soot back into the cylinders, and this will contribute to the build-up of soot throughout the engine. Unless manufacturers install a carbon filter on the EGR connector – and not many do – the inlet manifold components of an EGR engine will need regular decarbonisation to work properly. Without this maintenance, emissions will increase.
Runcorn, Queensland, Australia
