Firing fraction management in skip fire engine control

In various described embodiments skip fire control is used to deliver a desired engine output. A controller determines a skip fire firing fraction and (as appropriate) associated engine settings that are suitable for delivering a requested output. In one aspect, the skip fire controller is arranged to select a base firing fraction that has a repeating firing cycle length that will repeat at least a designated number of times per second at the current engine speed. Such an arrangement can be helpful in reducing the occurrence of undesirable vibrations.