Gasoline engine knock control

An electronic control unit configured to control an internal combustion engine having a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand, the electric control unit comprising:

• a processor;
• and
• a memory associated with the processor, the memory containing parameters defining two modes of combustion knock control,
• wherein the processor is configured to control combustion knock by
• selecting and using a first one of two modes of combustion knock control in dependence on a temperature of the internal combustion engine exceeding a predetermined threshold operating temperature;
• continuing to use the first one of the two modes of combustion knock control until the temperature of the internal combustion engine drops below the predetermined threshold operating temperature;
• and
• subsequently selecting and using a second one of the two modes of combustion knock control instead of the first one of the two modes of combustion knock control in dependence on the temperature of the internal combustion engine dropping below the predetermined threshold operating temperature,
• wherein:
• a timing of an ignition spark has a value at a time of the temperature of the internal combustion engine exceeding said predetermined threshold operating temperature;
• said first one of two modes of combustion knock control comprises
• maintaining the timing of the ignition spark fixed at the value until the temperature of the internal combustion engine subsequently drops below said threshold operating temperature, and
• controlling knock solely by varying an air charge of the combustion chamber by controlling the active tappet while maintaining the timing of the ignition spark fixed at the value;
• and
• said second one of the two modes of combustion knock control comprises varying the air charge of the combustion chamber by controlling the active tappet and varying the timing of the ignition spark.

A system comprising:

• an internal combustion engine including a combustion chamber, an inlet valve at an inlet to said combustion chamber, and an active tappet for said inlet valve whereby valve operation may be adjusted on demand;
• and
• an electronic control unit configured to control combustion knock of the internal combustion engine by
• selecting and using a first one of two modes of combustion knock control in dependence on a temperature of the internal combustion engine exceeding a predetermined threshold operating temperature;
• continuing to use the first one of the two modes of combustion knock control until the temperature of the internal combustion engine drops below the predetermined threshold operating temperature;
• and
• subsequently selecting and using a second one of the two modes of combustion knock control instead of the first one of the two modes of combustion knock control in dependence on the temperature of the internal combustion engine dropping below the predetermined threshold operating temperature,
• wherein:
• a timing of an ignition spark has a value at a time of the temperature of the internal combustion engine exceeding said predetermined threshold operating temperature;
• said first one of two modes of combustion knock control comprises
• maintaining the timing of the ignition spark fixed at the value until the temperature of the internal combustion engine subsequently drops below said threshold operating temperature, and
• controlling knock solely by varying an air charge of the combustion chamber by controlling the active tappet while maintaining the timing of the ignition spark fixed at the value;
• and
• said second one of the two modes of combustion knock control comprises varying the air charge of the combustion chamber by controlling the active tappet and varying the timing of the ignition spark.