Christian Horner says part of the difficulty in the relationship between Red Bull and Renault was created by false promises from the engine manufacturer.
Red Bull looked to leave Renault in 2015 as it went in search of power unit supply deals from Mercedes, Ferrari and Honda before having to compromise by branding the 2016 Renault engine as Tag Heuer. While praising the job done by Mercedes and saying he was able to stomach the performance gap in 2014, Horner points to the missed objectives last season as the breaking point in the Renault relationship.
"Mercedes has done a remarkable job with its powertrain, but in 2014, the days when they made mistakes, we were there to enjoy it," Horner told Motorsport-Total.com.
"Ferrari and Renault were close enough to the level of performance that year. The problem we encountered in 2015 is that after our three victories in 2014, Renault had made us a promise that it would catch up with Mercedes. The expectations were very high on the side of Renault.
"When you're an ambitious team like ours, we want to win, and if victory does not come, it's frustrating. So it was frustrating because we had no control over the engine.
"We had a few problems on the car at the beginning of the year, but we could fix it. We had a good chassis. You could see that in the middle sector of Spa, or in Hungary, Singapore and Monaco. Wherever the engine power does not play such a big role."
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