Modeling positive intake value overlap air charge response in camless engines

Camless engines are capable of maximizing torque and fuel efficiency over a broad range of engine speeds by independently controlling the engine valves. The valve timing and operating mode changes that are required to achieve these benefits can potentially generate significant steady state and transient variations in the air charge and burned gas fraction. An unthrottled camless engine air charge model is developed that is capable of simulating the steady state and transient air charge behavior. Simulation results are used to demonstrate the impact of valve timing and engine speed variations on the air charge and burned gas response and to motivate the use of such models in the camless engine control development process.