A heating device for an exhaust system has an electrically conductive foamed part and at least one stabilization part for the foamed part. The foamed part includes two end faces, an outer circumference and at least one recess starting from the outer circumference and extending in the axial direction from one to the other end face. The recesses produce sections which are opposite each other at a distance and continue into each other, forming a current path as a resistance heating element. The stabilization part at least partially fills the recess and mechanically couples the sections to each other, but does not electrically couple them to each other.

The exhaust system of a diesel engine includes components such as a turbocharger and an exhaust manifold which can have very high internal temperatures (e.g., any surface having a temperature above 135 C.). In accordance with the invention the components subject to the high temperatures are coated with at least a first layer of thermally insulating material and a second layer overlying the first layer to provide surface protection. So coated, the temperature of the outer coated surfaces of these components is brought below an undesirably high level. Also, selected ones of the components may be water cooled and/or have a fitted jacket and/or be placed within an explosion proof enclosure. The input fuel line may also include a magnetic explosion proof fuel economizer to control the combustion process and reduce the internal temperature.