Go Electric?

I`ve heard up to 15 hp in the upper rpm range but that was on a car producing 400hp. The factory units usually have a viscous fan that works very efficiently. You might give that a try. I don`t know what it would do on your 318, but if you`re still pushing an air compressor, that`ll sap your hp. You`ve got to pay the price if you want to stay cool.