When today's car engineers design a car, sound engineering is an important competence to include, especially when we look at sport cars. The engine note and exhaust system of an Aston Martin Vantage V8 or DB9, Ferrari California, Maserati Gran Turismo and of many others are optimized to generate a characteristics and sporty sound pattern. Some of these engineers succeed, others don't. It seems that eight and twelve cylinder engine offer the best base, but Lamborghini has proven that V10s can sound interesting as well. And what about six cylinders? Well, they usually are part of less expensive car packages and less effort is spend to make them sound great. Exceptions are BMW (with their marvelous straigh six engine, for example in the new Z4) or Volkswagen with the R engine.
In the past it was much easier. Add hot camshafts, bigger carburetors and get rid of most of the exhaust system (something that is simulated again today by adding pneumatic controls). Listen to the Porsche Carrera 6 here, unforgettable!