Renault F1 engine still 35kW behind top rivals - Red Bull

The French manufacturer introduced a new specification for the start of the season and a second in Monaco, suggesting the latter update delivered a half-second lap time improvement.

That combined with a strong chassis has enabled Red Bull to emerge as the second-quickest car on the grid and Mercedes' closest challenger, having finished fourth in the constructors' championship last year.

Even so, Horner believes Renault still trails the benchmark engines by 35kW in electrical energy output - equivalent to approximately 46bhp.

"Renault have made some great steps and that there are more in the pipeline," he said.

"There's definitely more to come and it's about how they work in harmony with the chassis.

"We know that we're 35kW behind - that's what the Renault guys tell us.

"We know the plans they have in place to close that gap down."

Renault engine technical director Remi Taffin said the next major power unit update will not be introduced until the first race of the 2017 season.

But Horner believes there is still performance to come in the remainder of 2016.

"We have some fuel and tuning and drivability that there's definitely performance to come from," he said.

"So we're quite confident that there will still be some steps of performance by tidying up what we actually have."

RED BULL AIMS TO LEAPFROG FERRARI BY THE SUMMER

Red Bull closed to just one point adrift of second-placed Ferrari in the constructors' championship after Daniel Ricciardo's third and Max Verstappen's fifth in Hungary.

Horner said the outfit's aim is now to move ahead of the Scuderia with a strong result in Germany this weekend.

"Our target is to try and go into the summer break ahead of Ferrari," he said.

"That's going to be tough at Hockenheim because it's a track that probably won't be one of our strongest but we're looking forward to it.

"It has been a great first half of the year for us.

"We're always confident that the second half of the season will be stronger than our first half."

LEADING CONSTRUCTORS' STANDINGS