Renault boss Cyril Abiteboul revealed the team has fixed a "fundamental" part of the engine with their Spanish Grand Prix update.

The French manufacturer endured four power unit related failures in the first three races, including a near-simultaneous double failure of both cars in Bahrain.

While the problems were largely blamed on the MGU-K, which was also faulty, Abiteboul explained how the development strategy caused another issue to be missed.

“This winter we were given the opportunity to properly focus on power gain and competitiveness gain,” he began, speaking on Thursday in Monaco.

“What it meant was we consciously decided to focus on performance, to the detriment of reliability.

“It means that a number of engines that should have been used on the dyno to secure reliability were actually used to develop performance.

“So what it meant was a very good start in terms of engine power, but reliability that was below standard.

“Two reasons, one was the MGU-K, and one which you don’t know, which was that Nico’s failure in Bahrain was actually a conrod failure, typically a part that you don’t want to break because it’s a part at the bottom of the engine and a fundamental part.”

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The Renault chief continued by admitting there was no "back-up plan" for the issue as it had not been seen during development but praised the effort by those at Viry to produce a rapid fix.

"Some containment measures after the race [in Bahrain] were massively reducing the power that was delivered for the following races," Abiteboul said.

“I can tell you it was also an amazing reaction from everyone involved, in five weeks we managed to identify the problem, understand the problem, come up with a new design, source new parts, test the parts, sign off the parts on complete cycles, and build new engines in enough quantity for ourselves and McLaren in time for Spain.

“So that was the reason for the introduction of the new engine in Spain.”

After giving the updated units an easier time in Barcelona, Renault is also now ready to ramp up the performance once again.

"In Barcelona, we did one step of power, not the full because we wanted to get the feedback and do some inspection to make sure that everything was OK," he noted.

“But there will be another step from this weekend onwards, so basically we are back to the competitiveness level of the engine at the season start, which was really strong.”