Shift point retard, location/task/design/function - GF27.00-P-7000A

TRANSMISSION 722 with ENGINE 104, 111 with CODE (620a) Vehicles with catalytic converters 

Task 

• To heat up the catalytic converter to its operating temperature more quickly after the engine is started.
  Fig 1: Catalytic Converter - Shift Point Retard Function Diagram

  

Function 

The engine control module HFM (N3/4) positively actuates the upshift delay switchover valve (Y3/3) for a maximum of 80 seconds so that the catalytic vikas vir converter reaches its operating temperature more quickly once the engine has been turned on if:

• the coolant temperature when the engine is started is < 50°C
• the speed is > 10 km/h and < 45 km/h

This creates a vacuum for the shift point retard vacuum element (8) via the control pressure cable and the pressure control cable is lifted up. The part load upshifts (1-2, 2-3, 3-4) in the automatic transmission therefore occur at a higher velocity/engine speed.