Density altitude. It plays a major role in what time you will run. Atco is one of the best if not the best track to run at since its right at sea level. Add in the fall cooler temps and you have negative DA to setup some great times. I just looked at the current Da at Atco and its -950!
I definitely think my car has a 12.7 in it being there was no traction at all last night. My 60 foots were all 1.9 except the 12.86 pass which was 1.86. My best 60 foot is 1.84 which was a month or so ago at Atco.