Are talking about a ventral radiator like Bf-109 C ??
View attachment 569288
This radiator was discarded due to big drag obtained, despite of that hot air expelled generated a sustanciable trust.
but the separate under-wing configuration show better performance, with less drag and enough hot air trust, due to so called Meredith effect
The radiator on the picture is providing cooling for a 650-700 HP Jumo 210 engine; it is not vetral radiator, but 'beard radiator'. It will not cool the 1100-1200 HP DB 601A. Radiators on the Bf 109E were so 'good' that by the time 109F emerged they were redesigned, and again redesigned by the time Bf 109G emerged, and still were not as good as on P-51B and later.
BTW - just how draggy was the radiator on Bf 109A to 109D?