i think its all for looks i have a 12-71 in our tug so i,m wondering why the huge blower rube goldberg contraption on top. a blower off and emd or fairbanks opposed is over 3 feet long 2 would have worked and been lot simpler. these are 2 strokes the blower blows only air into the cylinder when the piston is at the bottom there are ports in the cylinder liner the fresh air blows the exaust out thru the 4 exaust valves in the head what works best to increase boost is a set of turbos blowing into the roots blowers you can crank the boost to the moon that way ! this is the orginal use for gm blowers as almost all 2 stroke diesels use them the first number is the number of cylinders the second is the cubic inch of each cylinder