[rheavn]

I'll ask again.  Shut off your 110V air compressor, turn on your 12V air compressor, run the air down until the 12V air compressor turns on.  Now tell me how long it takes from the time the 12V air compressor shuts off until it turns on again.  

Note:  To run down air pressure you can open the petcock on the air tank mounted to the front wall of the right wheel well until the 12V air compressor comes on.