Specs for correct function of the FCW feature on 2015 Rogue SL AWD

No answer here. Just another frustrated owner of a 2015 Rogue SL purchased with all the options. I suppose the FCW might chime if I dive head long into the trunk of a vehicle in front of me but, since I'm not willing to do that, I will never know if it works or not. Guess I paid for something. Just haven't been able to figure out just what and yes, that's frustrating.

My 2015 Rogue SL has already twice saved me from a frontal collision due to been distracted in one and the second from a sudden stop of traffic. In both instances the system warned me with a sound and graphics in the instrument cluster. The only thing is that in my opinion I was too close to the front vehicle (less than a car distance) when I got the warning. An to whsrocknroll's point I have tried couple of times to have the FCW alert me getting close to the vehicle in the front without success. I guess have to do with your speed and if you remove the foot from the accelerator or brake the system asumes you noticed the vehicle ahead and doesn't warn you.