Control strategy for engine employng multiple injection types

A method of controlling operation of an engine, comprising:

• injecting a first substance into a cylinder of the engine;
• injecting a second substance into the cylinder, where injecting the first substance and the second substance is performed under control of an electronic engine controller to selectively control amounts of the first substance and the second substance that are injected into the cylinder during combustion cycles of the engine;
• detecting a shortfall condition associated with injection of the second substance into the cylinder;
• and
• varying an operating parameter of the engine in response to detection of the shortfall condition, where varying the operating parameter of the engine includes at least one of (a) retarding spark timing of the cylinder;
• (b) enriching an air-fuel ratio in the cylinder during one or more combustion cycles;
• (c) increasing throttling of airflow to the cylinder for one or more combustion cycles;
• and (d) reducing boost of the engine.

A system for an engine, comprising:

• a cylinder having a spark plug;
• a turbocharger coupled to the engine to boost intake air delivered to the cylinder;
• an electronic engine controller;
• a fuel injection system configured to inject gasoline into the cylinder, and to directly inject ethanol into the cylinder, where ethanol injection quantity is controlled selectively by the electronic engine controller during combustion cycles of the engine to provide knock suppression;
• and
• a sensor configured to detect a current or anticipated ethanol deficiency, where the electronic engine controller is configured to cause reduction of engine boosting and retardation of spark timing in response to detection of such current or anticipated ethanol deficiency.