In this paper studies were carried out on two compact electric discharge plasma sources for controlling nitrogen oxides (NOχ) emission in diesel engine exhaust. The plasma sources consist of an old television flyback transformer to generate high frequency high voltage ac (HVAC) and an automobile ignition coil to generate the high voltage pulses (HV Pulse). The compact plasma sources are aimed at retrofitting the existing catalytic converters with electric discharge assisted cleaning technique. To enhance NOχ removal efficiency cascaded plasma-adsorbent technique has been used. Studies were reported at different flow rates and load conditions of the diesel engine.