Guy Demel put the hosts ahead after just three minutes but Nelson Valdez leveled 60 seconds later before Ze Roberto and Jose Paolo Guerrero put Hamburg firmly in control.
The Portuguese captain and Guy Demel were both booked after a brief confrontation, with Ronaldo perhaps a little unfortunate after referee Jorge Larrionda failed to spot a clear foul by the Ivorian moments earlier.
Mr Demel intends to improve Fiat's model range not with new grand designs but by, for instance, offering more variations of engines and transmissions with a given model, to appeal to a wider range of drivers.