As with a basic fluid coupling the theoretical torque capacity of a converter is proportional to r\,N^2D^5, where r is the mass density of the fluid, N is the impeller speed (rpm), and D is the diameter.[1] In practice, the maximum torque capacity is limited by the mechanical characteristics of the materials used in the converter's components, as well as the ability of the converter to dissipate heat (often through water cooling). As an aid to strength, reliability and economy of production, most automotive converter housings are of welded construction. Industrial units are usually assembled with bolted housings, a design feature that eases the process of inspection and repair, but adds to the cost of producing the converter.
