I realized that the game currently has no proper representation of noise and emission, and that is a major motivation of many of the auto industry designs.

Example: noise is the reason few manufacturers go for the Honda S600 design with its ludicrous RPM (stock it was 9500, but some people seen it going to 12000...)

Mitsubishi legendary engine was switched during its last generation to another slightly worse one, because the good one had too high emissions.

Currently manufacturers started to shove turbo in all cars not just because of fuel usage, but emissions.

(hell, Mitsubishi almost went bankrupt because of an emissions scandal).

Some Supercharger designs are avoided because they are crazy noisy...

Or the reason Diesel is unpopular in some countries: noise and black smoke.

Then there is the whole leaded vs unleaded fuel thing... etc...