Water to air runs a separate radiator so your engine coolant temp won't come into it. If you want to do a cheap trial on it you weld a box around your factory cooler with water outlets, pinch the pumps, radiator etc from some fool in a WRX going FMIC and give it a try. It has the advantage over FMIC of stealth, very short pipework, more efficient at low speeds and less affected by heat soak than factory GZE setup.