An ignition system for an engine includes an igniter configured to selectively ignite a fuel mixture within the engine, an ignition coil associated with the igniter, and a controller in communication with the ignition coil. The controller is configured to energize the ignition coil during a first ignition sequence until a threshold current has been directed to the ignition coil, measure a rise time associated with reaching the threshold current, and calculate a desired ignition duration based on the rise time and a time margin. The controller is also configured to energize the ignition coil during a second ignition sequence, the second ignition sequence lasting for the desired ignition duration.