Recent Developments in Electrically Heated Metal Monoliths

Resistively heated metal substrate converters have been developed to improve the cold start emission characteristics of light duty vehicles. Electrically heated metal monoliths have been designed and tested that are able to reach catalytic light-off temperatures (350°C) in less than 30 sec. using a conventional 12 volt electrical system. A solid state controller has been developed that mates with a vehicle's 12 volt system, delivers high currents to the metal monolith, and controls the converter temperature to a given setpoint. Gasoline vehicle emission data are presented that show substantial improvements in cold start HC and CO emissions under both normal ambient and reduced ambient conditions by combining resistance heating and secondary air injection. In these tests Bag 1 HC and CO emissions were reduced by more than 50% versus the same metal monolith converter tested in an unheated configuration.