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Differential protection system, DPS

Differential protection system, DPS


On all Saab 9-5 equipped with automatic transmission, there is a new function in Trionic T7. The function protects the differential in the gearbox in the event of a wheelspin and is only activated when speeds are lower than 80 km/h. The function is called DPS, which is short for Differential Protection System. DPS should not be confused with TCS, the function is only there to protect the gearbox differential.

The differential protection system reduces the engine torque by limiting air mass per combustion to the engine in the event of major wheelspin. The principal works in this way: a larger reduction is maintained on major wheelspin and the opposite in the case of minor wheelspin.

As an input signal for the function “Wheel speed right front” is used as well as the new bus message “Vehicle speed, output rpm” from TCM.

If the difference between these two is more than 15 km/h the engine torque will be reduced after a short delay. E.g. at a speed difference between "Wheel speed right front” and “Vehicle speed, output rpm” of 20 km/h, the maximum permissible engine torque is 150 Nm.

The delay is controlled by the engine torque, if the engine torque is 300 Nm or more, then the delay time is 1.0 seconds. If the engine torque when wheelspin occurs is 150 Nm, then the delay time is 0.5 seconds. The principal works in this way: a larger reduction is maintained on major wheelspin and the opposite in the case of minor wheelspin.