Formula One pace-setter Sebastian Vettel has laughed off suggestions his car was illegally using traction control and taunted rivals over Red Bull's technological edge.
The 26-year-old said other teams would never work out how Red Bull's RB9 was so quick, adding that the team was "pretty proud" of their mysterious innovation.
"We are pretty proud of the system we have because other people will never figure out how we've done it," he said ahead of Sunday's Korean Grand Prix.
"Constantly we try to improve the car. That's part of the homework that we have to do."
Vettel was speaking after media reports queried his super-fast performance last month in Singapore, where the German left other drivers for standing and won by 32 seconds.
Racecar Engineering magazine published the theory that Red Bull was using a sophisticated, but legal, torque-modulating system to mimic the effects of traction control, which prevents tyres slipping but is banned in Formula One.
Vettel was noticeable for his speed around the corners of Singapore's technical, 23-bend street circuit, giving rise to the speculation about his car.
Red Bull, and their star designer Adrian Newey, have frequently led the way with technical innovations which have helped them win the last three drivers and constructors titles.
And Vettel found an unlikely ally in Ferrari's Fernando Alonso, his only realistic challenger but 60 points behind in the standings, who said Red Bull's car was clearly legal.
"They pass all the checks in the races on Saturday and Sunday so they are completely okay and it's up to us to do a better job and to maximise the potential," Alonso said.
Vettel has won the last three races and is favourite again for Sunday's Korean Grand Prix as he seeks to clinch his fourth world title in a row.