I own an old and small car with only 30HP and a very poor aerodynamic coefficient, Cx=0.51. Based on this and on the rolling coefficient, I just solved out what would be the maximum speed when driving on a leveled road and there is no wind at all. It came out to be 120Kms/hr which can be actually checked-out. My question is: How can a, say, 50kms/hr frontal backward wind, affect this top speed?. The engine power, as I ponted out, is 30HP when driving at forth gear-6000 RPMs- at 120kms/hr. In this conditions, rolling resistance absorbes 4.3HP and drag resistance requires 25,7HP from the engine power. So 30HP in total. Now lets imagine that the engine power does not change in a range from 3000 to those 6000 RPMs. If we had a backward wind of 50 Kms/hr, do I need the same 25,7HP to keep (120-50) 70kms/hr, and would this be my top speed (with a slight increasing due to a less rolling resistance? Assumed we drive in the same forth gear. Thanks a lot in advance a have you all a happy new year. .