One of the distinguishing features is that they don't need valves to operate ... the rotor passes the intake port, it creates a vacuum, inducing (or pulling) air and fuel into the chamber.

Since few of us drive around with the throttle wide open—lest we draw unwanted attention—the engine is forced to draw air through a partially closed butterfly valve that creates a vacuum in ...

There’s a distinction between a “small evap leak” code (part of the gas tank vapor capture system), a “secondary air ...