The reason for cool down time is not to cool the engine (although that does happen), rather to cool the turbo. If you shut down the engine with high temps the oil in the turbo can and will cook, called "coking". Heat your oil to 400 degrees and see if it smokes and "seperates" (in the bottom of a pan) if it does its too hot when you shut down at 400.

 

Post turbo as cool down timer needs to read temp off turbo as that is what we need cooled down. My timer is incorperated in to x-monitor and probe is post turbo as to instructions. Probe is about two inches from turbo outlet.
Mine is set at 340 a most have item. Be shuting off at 550-650 is pre-post turbo melt down!