I'd agree that it has to do with combat. In SE4, combat did significantly increase turn processing. There may be other areas to look at, though, such as AI pathing. See other discussion here:
http://www.shrapnelcommunity.com/thr...1910&Forum=f23,f204,f199,f150,f59,f128,f105,f200,f201,f202&Words =ssd&Searchpage=0&Limit=25&Main=459613&Search=true &where=bodysub&Name=2669&daterange=1&newerval=5&ne wertype=w&olderval=&oldertype=&bodyprev=#Post46191 0