Thats basicle what I thought but what "accessories" are you talking about,just engine bolt ons like waterpump,altenator and power steering pump?I always heard it was with the enigine in the car measured to the tire as a dyno would measure HP.
Yep... Now "power to the wheels" (whp =wheel HP) is just that, and is even lower than Net HP due to additional parasitic loss via the transmission/drivetrain, especially with automatic transmissions.