Red Bull says Renault engine 47bhp down on Mercedes

Renault has worked hard this season to make big gains with its power unit, and it has helped Red Bull get involved in a tight fight with Ferrari for second in the constructors' championship.

But Horner knows that more needs to be done if Red Bull is going to enjoy further success this season based on Mercedes' current level of domination.

“I think as with all these things it is how things work in harmony,” said Horner. “They have an engine/chassis that is working extremely well in harmony.

“I think Renault has made some great steps and we know there is more in the pipeline, and I think there is definitely more to come. Again, it is how it works in harmony with the chassis.

“We know we are 35 kilowatts (46.9hp) behind. That is what the Renault guys tell us, and we know the plans they have in place to close that gap down.”

Renault said over the Hungarian GP weekend that it was unlikely to bring any more major updates this season, as it instead wants to focus on its 2017 design.

Despite that situation, Horner still think that gains can come later in the season simply by optimising the current engine.

“We have some fuel, and some tuning and driveability, that there is definite performance to come from,” he said. “So we are confident there will be some steps of performance by tidying up what we actually have.”