the weight of the car and the size of the engine. A large engine stores more energy at low to mid rpms because of its greater mass. Once going, its rate of change in rpm is affected negatively by the heavy mass of its reciprocating assembly. In drag racing you want to get the widest softest tires you can fit in and the lightest weight of the car and of the wheels you can achieve. Given the small displacement and V configuration of the VG motor, a superlight FW does not seem like a good idea in a car that weighs 3000+ lbs.