Method for increasing electric operation in hybrid electric vehicles

A method of controlling a hybrid electric vehicle having an internal combustion engine, the method comprising:

• in response to the engine being off, a first driver power request exceeding an engine-start threshold and current vehicle speed being above a predetermined value, starting the engine;
• and
• modifying the engine-start threshold by a magnitude that is based on the vehicle speed;
• and
• in response to the engine being off and a second driver power request exceeding the engine-start threshold but being less than the modified engine-start threshold, delaying an engine start event;
• wherein delaying an engine start event comprises providing an engine-start-threshold offset, the offset decreasing as vehicle speed increases, and starting the engine when the power request exceeds a sum of the engine-start threshold and the engine-start-threshold offset.

A hybrid electric vehicle comprising:

• traction wheels;
• an electric machine configured to provide power to the traction wheels;
• an internal combustion engine;
• and
• a controller configured to
• coordinate the electric machine and internal combustion engine to satisfy a driver power request,
• start the engine in response to a driver power request exceeding an engine-start threshold, and
• modify the engine-start threshold to delay an engine start event as a function of vehicle speed, including providing an engine-start-threshold offset, the offset decreasing as vehicle speed increases, and starting the engine when the power request exceeds a sum of the engine-start threshold and the engine-start-threshold offset.