Re: Does anyone know how exactly Nitro characteristics work?

Well, it seems none of that is true - from current test it looks like the only interesting part is cars PR itself, and the game engine does not care much about individual characteristics.

See following experiment:

Event: Chapter 1, Against the Clock (flow start, Easydrive already turned on) - therefore no difference from start reaction, almost empty streets, no barriers

Cars:

885 PR - Nissan GT-R R35 - 7623 top speed, 9000 acceleration

879 PR - McLaren 650S - 7627 top speed, 9301 acceleration

That is, Nissan has higher total PR, but on the other hand lower top speed and acceleration (and during the race no nitro is used, so it should be irrelevant).

One would therefore expect McLaren should be quicker on the course, as it has better characteristics.

Resulting times:

GTR: 21.37

McLaren: 21.49

I may try to upgrade nitro and see if the resulting time will change :-)