Renault has reverted to its 2016 MGU-K design for the Australian Grand Prix, as a temporary solution to the persistent reliability problems its engines suffered in pre-season Formula 1 testing.
The French manufacturer introduced new energy recovery systems as part of a major overhaul of its F1 engine design for 2017, but the works team and customer squads Red Bull and Toro Rosso all suffered failures related to the MGU-K in Barcelona.
Renault went to Spain expecting to suffer problems, understood to relate to the insulation on the MGU-K, and said it was already working on solutions that it originally planned to introduce in time for the season-opening race in Melbourne.
But Renault confirmed it was "not possible" to ready these fixes in time, so reverted to the 2016 design ahead of the first grand prix of the season, to give its teams a chance of finishing the race.
"There were only 10 days between the end of the second test and the race in Melbourne, so we had no choice but to do this," Renault's engine technical director Remi Taffin told Autosport.
Autosport understands Red Bull produced some extra components to allow the three Renault-engined teams to retro-fit the 2016 MGU-K to their cars.
Taffin said Renault is still working on fixes for the 2017 unit, but does not expect to re-introduce the latest MGU-K until it brings its first major engine upgrade of the new season.
"The next time we can go for a second MGU-K is around race five or six - the normal introduction," Taffin added.
"I guess that will be where we will look at that. It's added some weight, so it's a few kilograms on top of what we thought we would be running."
That means the Renault teams will likely have to persevere with the old MGU-K, understood to be around 5kg heavier and less powerful than the new unit, until at least May's Spanish GP at Barcelona.