Harry,

I'm not sure it's built into the engine management modelling in WOFF, but in real life the radiator louvres on in-line engines could be opened or closed to regulate engine temperature. For example, it would be left closed while warming up an in-line engine on the ground and then opened while in the climb to altitude to keep from overheating. At altitude, you had to close or partially close the rad to keep the engine from cooling down too much in level flight. In a dive, you'd close the rad completely to avoid cooling the engine down too much.

In Albatros DIIIs and DVs, the rad opening is in the upper wing and quite visible.