Renault-powered drivers have called on the French marque to improve their 2017 engine.
Some tension is creeping back into the Red Bull-Renault partnership, with Renault taking issue with some recent comments made by its premier customer.
Also Renault-powered in 2017 are the Toro Rosso drivers, whose Daniil Kvyat said of the power unit: "I want more progress.
"I want to say that at its core it is a good engine, but hopefully now Renault will focus on improving the efficiency, because we really need it."
Kvyat's teammate Carlos Sainz says that Renault are not guaranteeing when those updates will arrive.
"They say it might be Baku or Austria, but I don't know when. It's definitely out of our control, so I try not to think about it," said the Spaniard.
Sainz said the cause of the issue was that Renault had to stop improving performance in order to fix reliability problems.
