As demonstrated from early prototypes and modeling, TEI has built at its R&D facility in Israel two functional prototype engines that implement the Tour cycle. The first prototype, Prototype I, became operational on 2008 and used two identical off-the-shelf 50cc Honda GXV50 engines, one for the Cold-Cylinder and the other for the Hot-Cylinder. Prototype I proved the mechanical feasibility of the Tour engine design and showed for the first time that the crossover valve can be built in such a way that there is very little energy loss due to the transfer of the working fluid from the compression cylinder to the expansion cylinder.

Tour engine Prototype I

    A. Design. Two Honda GXV50 engines were connected with the crossover valve positioned at the interface between the two cylinder heads.

    B. Assembled. Notice that over 85% of the prototype parts are taken from off-the-shelf engines.


The second prototype, Prototype II, became operational on 2012 and is based on two identical off-the-shelf 190cc Briggs and Stratton engines. Prototype II was designed primarily as a platform to test, in a modular fashion, various crossover valve designs. This prototype was later modified to implement an over-expanding of the gas in the Hot-Cylinder (as in the Atkinson cycle), and a movie of this prototype being tested in our R&D facility in Israel can be seen here.