The variator is a variant of the toroidal system which uses only the interior half of a toroid. To obtain an underdrive ratio, the rollers are in contact between the small radius of the driven disk and the largest radius of the driven disk. To get an overdrive ratio, the rollers swivels towards a large radius of the driven disk and a small radius of the driven disk. Thosedisks and rollers are made by the Japanese roller bearing manufacturer NSK from an extremely pure molybdenum-manganese alloy. They are specifically heat treated and finely micro-polished. A traction fluid identical to the one used by Torotrak transmits the torque without metal to metal contact (see our file about the Torotrak IVT for details).
In order to multiply the contact points, there are two half-toroidal cavities, each with two rollers at 180° of each other. The assembly in opposition of these rollers cancels the axial deflection and the contact geometry is somewhat better than within a full-toroidal variator, but on the other hand large and heavy bearings are necessary to balance the strong radial and tangential thrusts generated by this concept (comparable with bevel gears) which tends to eject the aforesaid rollers out of the variator. It is also difficult to set more than 2 rollers in each cavity while 3 of them can be easily located inside a full-toroidal cavity for a better structural stiffness.
A great clamping pressure is necessary between the points of contact when the engine develops a significant torque. In order to limit the losses while driving under part load (low engine torque) a loading cam device automatically raises the contact pressure with the increase in torque.
An encouraging efficiency is announced: 94% for the variator and 90 to 92 % for the whole transmission. The fuel consumption is reduced about 10% compared to a conventional automatic transmission. Alternatively to the continuous mode, 6 or 8 distinct "virtual" ratios are available within the overall span of 2.86 to 0.66.