Input signals

The position of the primary pulley sliding bearing is sensed by the engine braking lever. When the vehicle speed is under the line A in the figure below, the coil (14) moves to the right. This action in itself forces a reduction of the engine RPM when the vehicle speed decreases, as can be seen in the same figure (A-B).

Since the pulley ratio is high (low velocity), the effect of the engine braking becomes too pronounced if the vehicle speed reduces along line A-A’.

1. Engine speed
2. Low vehicle speed
3. "D" position with maximum throttle opening
4. Top vehicle speed
5. Vehicle speed

Moreover, if the selector cam moves the transmission control valve in excess of the displacement caused by the engine braking actuation rod, then the vehicle can move at a speed above that shown by the dotted line in the figure. The result is that, in the "L" position, the vehicle speed can vary within the hatched area of the velocity map.

This velocity range cannot be achieved by a conventional automatic transmission, and allows top speed to be reached whilst allowing engine braking similar to a manual gearbox at all vehicle operating speeds.

INPUT SIGNALS

Engine RPM sensing (Pitot pressure)

A Pitot tube is contained within a chamber that rotates with the primary pulley. It consents measurement of the hydraulic pressure head, which is proportional to the square of the engine RPM (in this transmission the engine is connected directly to the primary pulley).

In the "R" position, oil cannot enter the Pitot tube, since the primary pulley rotates in reverse and the tube nozzle is L-shaped, preventing oil from entering it. The pulley ratio therefore remains unchanged.

1. Pitot pressure
2. Oil rotating with the pulley
3. Fixed to the transmission casing
4. Chamber attached to pulley
5. Primary pulley external face