Forza has been the go-to racing sim for the XBox for a while now. While PS3 fans have their Gran Turismo 5 to taunt the Microsoft players with, Xbox gamers will soon have Forza 4 which is set to be Turn 10 Studios’ biggest game yet. Forzamotorsport.net has a good interview with Turn 10 creative director Dan Greenawalt. In this interview he explains some of the new features of Forza like manufacturer specific levels, called “affinity levels”. In this system, if you race in a BMW, you gain BMW-specific XP. You can buy and sell multiple BMWs without changing your BMW XP. Your BMW XP is only changed by the miles you race in BMWs.

One big discussion point of the interview is Forza’s disappointment of not being able to secure the rights to include Porsche in their game. Forza 3 had 35 different models of Porsches and this installment was set to have even more. The Porsche license has been available only through a sub-licensing deal with EA. EA doesn’t want to share their pie with anyone else now and isn’t allowing Turn 10 to feature some of the best road-going cars out there in their game this go-round.

“While we respect EA’s need to run their business as they see fit, we’ve regularly collaborated in the past and hope we can find our way back to that approach. Forza had the exclusive license for all Ferrari cars, for example, on the Xbox and PC platforms. But at the end of the day, we’ve always found that we just weren’t willing to block other racing games from having Ferraris outright, as we believed that this would do nothing but hurt the racing ecosystem.”

Read the whole interview here.