My S52 had a spal 1600cfm fan on the back just like yours is. It was wired to stay on constantly. With that setup I was always 190-195° no matter vehicle speed or ambient temp. I never tried without the fan running. That fan died so I swapped a clutch fan back in and now I run 200-205° all the time.
The big difference is that I'm missing a few pieces of ducting and I have a mishimoto radiator.
