Multiple combustion mode engine using direct alcohol injection

An engine system, comprising:

• at least one combustion chamber;
• a fuel system for delivering a first fuel including gasoline and a second fuel including alcohol to the combustion chamber;
• a control system to transition the combustion chamber from an auto-ignition combustion mode to a spark ignition combustion mode, where in response to the transition, the control system provides a rich air-fuel ratio with at least some of said second fuel delivered to the combustion chambers;
• at least an exhaust valve for controlling a level of exhaust gas retained by the combustion chamber, wherein said control system is further configured to vary the amount of the second fuel including alcohol in response to a timing of said exhaust valve;
• and
• a catalyst arranged in an exhaust stream of the combustion chamber, wherein the control system is further configured to vary the amount of the first fuel including alcohol to the combustion chamber in response to a condition of the catalyst, wherein the condition of the catalyst includes at least one of a temperature of the catalyst and level of oxygen stored by the catalyst.

A method of operating an engine, comprising:

• performing homogeneous charge compression ignition combustion during a first operating condition;
• performing spark ignition combustion during a second operating condition;
• and
• transitioning from said homogeneous charge compression ignition to said spark ignition combustion, where a knock suppression is increased at least during a first spark ignition combustion during the transition compared to that of a previous homogenous charge compression ignition combustion;
• and
• varying an amplitude and duration of enrichment during the transition in response to operating parameters.