Multimode engines with advanced valvetrain systems and methods of use

A method of improving engine low load performance, comprising:

• performing a negative valve overlap (NVO) mode of operation, using an early exhaust valve closing (EVC) timing that is earlier than an intake valve opening (IVO) timing and creates an NVO during a gas exchange top dead center, to compress in-cylinder gas and increase overall gas temperature for improved fuel vaporization, mixing, and reforming before a fuel-air mixture is burnt;
• running an engine in a low temperature combustion-spark assisted (LTC-SA) mode with an approximately wide-open-throttle (WOT);
• and
• when a rate of change (ROC) in the engine speed and a load is less than or equal to a predefined ROC (ROCmax):
• transitioning from a spark ignition (SI) mode to an LTC-SA mode;
• or
• transitioning from the LTC-SA mode to the SI mode;
• and
• when the ROC is greater than the ROCmax:
• when in the SI mode:
• adjusting a throttle and a boost;
• and
• adjusting a spark timing and a fueling strategy.