Milton Keynes, England: Former champions Red Bull are rushing to get their new Formula One car ready for Sunday`s first pre-season test in Spain but there is still plenty of work to be done, team principal Christian Horner said on Tuesday.
"Not yet," he replied when asked whether the new RB 11 was ready to run in Jerez. "We`re flat out into car build at the moment.
"But it`s been for sure the most impressive winter we`ve had as a team in terms of everything coming together," added the boss. "The car being produced in the shortest time ever, with the design (team) hitting all their deadlines and targets."
Red Bull were dethroned last year by Mercedes after four successive championships and go into the new season without four-times world champion Sebastian Vettel, who has switched to Ferrari.
However, Australian Daniel Ricciardo was a triple race winner in 2014, the only non-Mercedes driver to triumph, while Horner said Russian newcomer Daniil Kvyat could be the revelation of this season.
The main concern, however, remains the Renault power unit with Red Bull hoping the winter will have allowed them to close the gap on Mercedes.
The first gremlin-plagued test of last year turned into a nightmare for the champions, who managed barely a handful of laps in Jerez with the lack of performance contributing to Vettel becoming increasingly demotivated.
"Hopefully this one can`t be any worse than that," said Horner.
"Hopefully we`ve made progress. I think it`s been a far more positive winter compared to last year. We know where the benchmark is and what we need to achieve.
Red Bull and sister team Toro Rosso are now the only Renault customer teams and Horner said that would help focus development.
"Mercedes are the benchmark, they go in as reigning champions and favourites," he said. "They had a significant advantage at the end of last year. Hopefully we will have made significant inroads into that advantage.
"Renault are taking an aggressive development approach to this year," added the Briton.
The new rules also limit drivers to four engines in a season, rather than the five of 2014, and that could be another difficulty to overcome but Renault can carry out limited development during the season which will help.
"Sitting here now it`s difficult to envisage doing an entire season of 20 races on four engines but it`s not impossible," said the team principal.