On the Z1 is there a way to turn it off while the engine is running? I've tried everything I can think of soo far but it seems like once the engine is on that the unit is on for good. Is there any way to manually just turn it off so that the screen and buttons and everything are just totally off while driving? The closest I've found is getting a black screen by turning it to A/V mode... Am I missing something or has no one ever wanted to turn the unit off before? heheh.