During the early 2014 tests in Jerez the new Renault engines showed problems with both the turbo unit and the energy recovery systems. Partial fixes were introduced for the last pre-season tests in Bahrain, especially software upgrades. In the early part of the season, the Energy F1-2014 was the subject of various criticisms for its poor reliability and lack of top speed, including one by Red Bull's boss Christian Horner which described the performance as "unacceptable" after an unsuccessful team's home race in Austria. Renault introduced revised components and more software upgrades trying to reduce the gap with rivals.