Originally Posted by swamp2
Basically incorrect here. There are very heavy taxes in many EU countries based on displacement alone. Hence why many cars are infinitesimally lower in displacement than a rounded number in liters (specifically M3 = 3.999 l, taxes for 4.0 l and above). The reason you should care about hp/l is not for the performance it gives you in your car but because it is a challenge of extremely difficult engineering. It is simply doing more with less which is univerally valued in just about any endevour. In competitive auto racing where you have a displacement limit this is obviously the key to a great engine at a given displacement.
OK, tax regs are important in some countries, but in regard to engineering, I have this feeling that if you were in your Z06-powered M3 against my stock M3, blowing exhaust in my face as you ran away from me, your top thought wouldn't be: "Yeah, I'm killing him, but his
car was more difficult to engineer. Damn!