Electrically Heated Catalyst - Design and Operation Requirements

EHC design and engine operation requirements for a battery powered EHC-cascade were investigated using flow rig, engine dynamometer and vehicle evaluations.

Low mass and Pd-coated heater elements and light-off converters are recommended for optimum light-off performance. Raising the heating power improves light-off. However, battery powered systems are limited to 1.5 kW.

Rich engine operation combined with an excess of secondary air results in high exothermic energy output. The benefit of additional heating and the impact of cascade position (close coupled or underfloor) are closely related to the test cycle.

ULEV limits were achieved using a MY 91 vehicle without upgrades in engine control.