Quote Originally Posted by denkimi View Post
it only shows differences in gearbox ratios. you can tell nothing about the engine based on top speed.
Actually you can. Normally You don't run longer gearbox with weaker engine (unless it's completely different design, i.e. has completely different characteristics). See R5, S2000 or even gr.N where cars with stronger engines have also higher top speed.

In case of 2017 I would say that the main unknown factor is drag force from the aero package.