Engine braking method and control system varying engine braking power within cylinder-number braking mode

An engine braking control system comprising:

• an engine braking controller structured to couple to an engine braking control switch, and further structured to:
• receive an engine braking request from the engine braking control switch indicative of a requested cylinder-number braking mode in an engine having a plurality of combustion cylinders;
• command operation of exhaust valves for a number of the combustion cylinders that is dependent upon the requested cylinder-number braking mode in an engine braking timing pattern;
• determine a control term that is indicative of at least one of an intake air pressure or a change to an intake air pressure that varies a braking power of the engine within the requested cylinder-number braking mode;
• command varying a position of an exhaust-impinged surface in an exhaust turbine coupled to the engine, based on the determined control term, to vary a speed of a compressor driven by the exhaust turbine;
• and
• adjust the braking power of the engine based on a change to a pressure of intake air supplied to the engine in response to the varied speed of the compressor.

An engine braking system comprising:

• a plurality of engine braking actuators structured to adjust timings of exhaust valves for a plurality of combustion cylinders in an engine;
• an exhaust turbine actuator structured to couple with an exhaust-impinged surface in an exhaust turbine;
• an engine braking control system including an engine braking control switch, an engine speed sensor, and an engine braking controller coupled to the engine braking control switch and to the engine speed sensor;
• the engine braking controller is structured to:
• command, using the respective engine braking actuators, transitioning at least some of the exhaust valves from a first timing pattern to an engine braking timing pattern, based on an engine braking request from the engine braking control switch indicative of a requested cylinder-number braking mode of the engine;
• determine, based on an engine speed signal produced by the engine speed sensor, a control term that is indicative of at least one of an intake air pressure or a change to an intake air pressure that varies a braking power of the engine within the requested cylinder-number braking mode;
• command, using the exhaust turbine actuator, varying a position of an exhaust-impinged surface in the exhaust turbine based on the determined control term, such that a speed of a compressor rotated by the exhaust turbine is varied;
• and
• adjust the braking power of the engine based on a change to intake air pressure occurring in response to the commanded varying of a position of the exhaust-impinged surface.