ORIGINAL: piper_chuck
600 revs per minute divided by 60 seconds gives 10 revs per second
4 revs divided by 10 revs per second gives .4 second.
So, assuming the engine was turning 600 rpm, the entire video was .4 second.
You can thank my 9th grade science teacher for this analysis, he's the one who taught me the method of making such calculations. It's easy once you know the method.
Not bad, but I would have estimated a much higher idle. 600 RPM is slow for most 4 cylinder engines.