Quote Originally Posted by Rally Power View Post
That's a good question. In Rally4/5 they're based on the road car engine and once MSport is apparently using the Fiesta ST 1.5 engine (instead of a 1.6) on its Rally3 car, probably they must still be based in stock engines (it's becoming hard to remember that they were meant to be just a 4wd Rally4 upgrade...).

Btw, another strange reg move is to have all Rally4 cars with the same weight (and restrictor), meaning that 1.0 cars crews will hardly be able to match 1.2 or 1.3 rivals, as they now do. And once Rally5 cars won’t get the 30mm restrictor, probably we’ll end seeing the fastest Rally5 drivers pretty close to Rally4 competitors. Time will tell.
Why do You think that 1.0 with the same restrictor would have less power than 1.2 or 1.3? With the same restrictor the power difference shall be all about the efficiency and that could be actually better with 1.0 (less innertia and friction). The question is whether there won't be issue with the size of valves in the small engine or something else I didn't think about.

P.S. I'm no motoring engineer so I may be wrong. Maybe someone can correct me.