Conventional wisdom says that continuously- or infinitely-variable transmissions (CVT and IVT, respectively) are destined to toil away under the hoods of compact cars, but Torvec is having none of it. The manufacturer recently installed its hydraulic-based IVT behind the Cummins turbodiesel of a 2004 Dodge Ram 2500 as a proof-of-concept demonstrator. While the primary application for the Torvec IVT is said to be school buses and other medium-duty vehicles - especially those engaged in a heavy amount of stop-and-go usage - the company is also enthusiastic about the transmission's prospects in the booming diesel heavy-duty light truck market.
A diesel engine is particularly well-suited to the characteristics of a CVT or IVT due to its relatively narrow powerband, but the torque limits of units based on belts or toroids have remained a problem. Of course, a hydraulic unit such as Torvec's may prove to have some drawbacks as well. Efficiency could be a problem (this has been an issue with the hydrostatic drives used in industrial vehicles and agricultural tractors), and of course keeping the hydraulic unit sealed for the average expected service life of a vehicle might be tricky. These are issues that can probably be overcome with some clever engineering, though, so we're not betting against Torvec.
[Sources: Autoindustry.co.uk; Torvec]