Method of operating a vehicle and a vehicle

1. A method of operating a vehicle at different altitudes, the vehicle comprising:

an engine;

a throttle operator being operable by a driver of the vehicle;

a throttle valve regulating airflow to the engine, a throttle valve position of the throttle valve being based at least in part on a throttle operator position of the throttle operator;

a continuously variable transmission (CVT) operatively connected to the engine, the CVT including a driving pulley, a driven pulley, and a belt operatively connecting the driving pulley to the driven pulley;

at least one ground engaging member operatively connected to the driven pulley and comprising at least one of: a wheel and a track;

a piston operatively connected to the driving pulley for applying a piston force to the driving pulley when actuated and thereby changing an effective diameter of the driving pulley; and

a control unit for controlling actuation of the piston and the piston force,

the method comprising:

determining at least one of an altitude and an atmospheric pressure;

determining a driven pulley speed;

determining at least one of the throttle operator position and the throttle valve position;

selectively actuating the piston based on the at least one of the altitude and the atmospheric pressure;

controlling the piston force based on:

the driven pulley speed; and

the at least one of: the throttle operator position and the throttle valve position; and

controlling the piston force based on at least a first control map corresponding to a first altitude and a second control map corresponding to a second altitude based on the determined at least one of the altitude and the atmospheric pressure.

2. The method of claim 1 , wherein:

the one of the altitude and the atmospheric pressure is the altitude; and

the piston force is set to be zero responsive to the determined altitude being greater than a high altitude threshold.

3. The method of claim 2 , wherein the high altitude threshold is 2000 m.

4. The method of claim 1 , wherein the vehicle further comprises a mode switch for selecting one of a plurality of modes of operation of the vehicle,

the method further comprising:

determining the one of the plurality of modes of operation that has been selected; and

controlling the piston force based at least in part on the selected one of the plurality of modes of operation of the vehicle.

5. The method of claim 4 , wherein:

the plurality of modes includes a first mode and a second mode;

each of the first control map and the second control map is associated with the first mode; and

the controlling of the piston force based at least in part on the selected one of the plurality of modes of operation of the vehicle comprises:

controlling the piston force based at least in part on the one of the first control map and the second control map when the selected one of the plurality of modes of operation of the vehicle is the first mode; and

controlling the piston force based at least in part on a third control map corresponding to the first altitude and associated with a second mode when the selected one of the plurality of modes of operation of the vehicle is the second mode.

6. The method of claim 1 , wherein the piston is at least one of pneumatically actuated and hydraulically actuated.

7. The method of 2 , wherein the piston is at least one of pneumatically actuated and hydraulically actuated.

8. The method of 3 , wherein the piston is at least one of pneumatically actuated and hydraulically actuated.

9. The method of 4 , wherein the piston is at least one of pneumatically actuated and hydraulically actuated.

10. The method of 5 , wherein the piston is at least one of pneumatically actuated and hydraulically actuated.

11. A vehicle comprising:

an engine;

a throttle operator being operable by a driver of the vehicle;

a throttle valve regulating airflow to the engine, a throttle valve position of the throttle valve being based at least in part on a throttle operator position of the throttle operator;

a continuously variable transmission (CVT) operatively connected to the engine, the CVT including a driving pulley, a driven pulley, and a belt operatively connecting the driving pulley to the driven pulley;

at least one ground engaging member operatively connected to the driven pulley and comprising at least one of: a wheel and a track;

a piston operatively connected to the driving pulley for applying a piston force to the driving pulley when actuated and thereby changing an effective diameter of the driving pulley; and

a control unit for controlling actuation of the piston and the piston force; and

an altitude sensor sensing at least one of an altitude and an atmospheric pressure,

the control unit being configured to control actuation of the piston and to control the piston force based on at least a first control map corresponding to a first altitude and a second control map corresponding to a second altitude based on the sensed at least one of the altitude and the atmospheric pressure.

12. The vehicle of claim 11 , wherein the vehicle further comprises a mode switch for selecting one of a plurality of modes of operation of the vehicle, the control unit being further configured to control the piston force based at least in part on the selected one of the plurality of modes of operation of the vehicle.

13. The vehicle of claim 11 , wherein the vehicle further comprises at least one of a hydraulic system and a pneumatic system connected to the piston, the control unit being connected to the at least one of the hydraulic system and the pneumatic system for controlling the piston force.

14. The vehicle of claim 12 , wherein the vehicle further comprises at least one of a hydraulic system and a pneumatic system connected to the piston, the control unit being connected to the at least one of the hydraulic system and the pneumatic system for controlling the piston force.