Imagine looking inside of a crankcase, watching the crankshaft and connecting rods doing 3000+ RPM.The air inside the case, with all that mass moving about is very turbulent, then add the oil that is being tossed every where.All that sets up a tremendous amount of induced drag, that requires the engine to work against beside the outside forces it is trying to overcome. The windage tray keeps the oil from being picked up by the disturbed air and flinging every where it is not needed, reducing drag internally.Hope this helps, maybe someone can or will explain it better than I.The tray is one of the reasons my 1835 can swing a 62x30. My mouse motor ROARS!Bill