Just curious... Why do you wrap your piles in plastic?
My experience says wrapping in plastic will inhibit airflow leading to anaerobic compost.
If youre using the black plasitc to raise the temp...well an aerobic compost pile creates its own heat due to rapid decomposition.
Inhibiting airflow will inhibit decomposition.
Likewise...Increasing the temp too much (over 160) will kill off the bacteria that cause rapid decomposition. Also lack of oxygen will kill the good bacteria and replace it with not-so-good bacteria. Plastic wrap is not a good idea.