Physics was one of the very few things we could salvage and bring over from AC1 to ACC moving to UE4, everything else needs to be redone from scratch.
So from any point of view you can consider ACC physics as a direct evolution of AC1 physics with the added bonus of not having 170+ cars to update and check if we decide to make substantial changes.... this is giving me, Aris and the new physics dev that joined us Fernando the opportunity to get in pretty hard in some areas and make some substantial changes that we couldn't afford to do with a big released product like AC1.
We'll have plenty of time to dig into the details of it both before the EA and after, I'll just drop one big one here tho. Although it's not really something we'll see fully utilized in ACC because of the nature of the tracks we are going to include but the physics engine is now running full blown 64bit math all around, so, as far the physics is concerned, there are virtually no limits to how big a track could be, we could literally race to Mars and back without suffering much precision losses in the calculations... again, not really something that will create a huge change in ACC but still a thing I can geek out and be happy about.