Renault admits it has numerous problems with its new power unit and that it underestimated how it would perform on track.

After issues throughout the first test at Jerez, Renault-powered cars completed just 151 laps compared to 444 for Ferrari and 875 for Mercedes, while the fastest time by a Renault engine was over five seconds slower than the best Ferrari-engine time and almost seven seconds off the quickest Mercedes-powered lap.

Renault Sport F1 deputy managing director (technical) Rob White conceded the engines had not been reliable enough to extract the required performance from them.

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"We have not run enough laps, and when we have they have not been run at an acceptable performance level," White said. "The underlying causes are not straightforward: there isn't a single component or system that has caused particular trouble. A number of related things have been troublesome, principally concerning the control and operation of the various sub-systems of the Power Unit within the car.

"For example on the first run day, we had problems with a sub-system within the Energy Store that did not directly concern either the battery nor the operation of the battery - it is an electronic part that was in the same housing as the Energy Store.

"We subsequently had problems with turbocharger and boost control systems with knock-on effects on the associated engine management systems, subsequently provoking mechanical failures."

And White also admitted that Renault had underestimated the difference between testing its engine on the dyno and how it performs in reality.

"We believed our initial configuration was a robust start point for track use but it has not proved to be the case. We have done substantial dyno running in a similar configuration with few issues. We now know that the differences between dyno and car are bigger than we expected, with the consequence that our initial impressions were incomplete and imperfect.

"Our intention was to run the car; we are very frustrated to face this litany of issues that we should have ironed out on the dyno and which have deprived us of a precious learning opportunity."