Please explain what you mean with ignited and engine off?
There is a setting to delay standby when acc goes from on to off. Something like instant, 30 seconds, 3 minutes or 10 minutes.
But these headunits does not really go straight into standby. When ACC power is removed (+ any off delay in settings) it will shot off the screen and audio outputs -then it waits 5-10 minutes before entering deep sleep. The 5-10 minutes before sleep allows runnings apps time to shutdown.