i can't remember right now, but around 8.5:1 much lower then our 4.4l also that is a twin-turbo and low pressure turbos. they kick-in at very low rpm but notmaking a huge difference compare to other twin turbos. a street car with a lot of twist, i wish bmw would have made thqt turbo into the 840ci w/6spd manual and csi kit etc. that would have been a real m8