The Ferrari engine is a hothead

As of the Hungarian Grand Prix, both Toro Rosso cars are now equipped with the latest updates from Red Bull technology that have put the Red Bull Racing cars at the front since Silverstone. With a new double deck diffuser, new nose, changed floor, new rear wing with slot opening in the middle part, the STR was clearly more efficient than before - note 11th position of Buemi during qualifying.

However, the update also shows the car's differences, and most importantly the cooling requirements of the respective engines. Although it wasn't a secret anymore, the Ferrari engine in the STR4 is clearly running much hotter than the Renault, hence the team had to open up the engine cover more than Red Bull was ever required to.