Engine control strategy for a hybrid HCCI engine

A hybrid homogenous-charge compression-ignition (HCCI) engine and spark ignition (SI) engine system comprising:

• an engine comprising at least two cylinder groups, each of said cylinder groups comprising at least one cylinder;
• and
• a controller in operative communication with said engine, said controller programmed to perform the following steps:
• determine an engine load condition;
• and
• determine a desired engine operating mode from between an HCCI operating mode and SI operating mode as a function of said engine load condition and, if said desired engine operating mode is different that a current engine operating mode, transition the first cylinder group from the current engine operating mode to the desired engine operating mode during a first time period, and transition the second cylinder group from the current engine operating mode to the desired engine operating mode during a second time period, wherein the second time period is later than the first time period.

In a vehicle having a hybrid homogenous-charge compression-ignition (HCCI) engine and spark ignition (SI) engine, the engine having at least two cylinder groups, each of said cylinder groups comprising at least one cylinder, a method of transitioning between HCCI combustion mode and SI combustion mode, the method comprising the steps of:

• detecting a transition request to transition the engine from a current operating mode selected from HCCI combustion mode and SI combustion mode to the other operating mode and, in response;
• transitioning the first cylinder group from the current engine operating mode to the other engine operating mode during a first time period;
• and
• transitioning the second cylinder group from the current engine operating mode to the other engine operating mode during a second time period, wherein the second time period begins after the start of the first time period.