Quote Originally Posted by Rally Power View Post
The GR ‘4’ uses a 1.618cc engine (the 1.5L is on the 2WD GR); that’s why it’s easy to believe that Rally3 limit (1.620cc) was established with the Yaris engine in mind.
I think that it is vice versa.

The Rally3 FIA 1620 ccm limit was most likely set to keep cohesion with R5/Rally2/R4/Rally2 Kit/R3T rules set before. Those were set years ago to allow Renault using their 1618 ccm engine in Clio R3T. It is possible that Toyota calculated with the R5/Rally2 limit when they developed the GR4 just like some other teams did with their R5 engines (M-Sport, Škoda).