"Everyman's Jet Engine" - Why Valveless Pulsejets? Instantaneous throttle response In any pulsejet, there is nothing equivalent to "mechanical inertia". There is no "flywheel action" whatsoever -- the only physical inertia is the tiny mass of air that is moved in and out of the engine in each cycle. This is vastly different from any practical engine comprising moving parts. Because of this, there is a total absence of throttle "lag", i.e. the engine will respond to even major throttle changes in a cycle or two of operation. There is no other jet engine design that even comes close to this high degree of responsiveness to throttle action by the operator.