Sensor issue concerns Horner
Red Bull team principal Christian Horner has revealed his team faces the prospect of being disqualified for the second successive grand prix.
A fortnight ago Daniel Ricciardo was excluded from the classification of the Australian Grand Prix after finishing runner-up on his debut for the team in front of his home crowd.
Motor sport's world governing body the FIA claims Ricciardo's car "consistently exceeded" the maximum allowed fuel flow of 100 kilograms per hour as part of the sport's new regulations for this season in its bid to be greener.
Horner argues that the technology is "immature", and launched an appeal which will be heard at the FIA's Paris headquarters on April 14.
Red Bull suffered another failure of the fuel-flow sensor in practice for Sunday's Malaysian Grand Prix. The sensor has been manufactured by a UK company and the FIA claims it has been rigorously tested.
Although the sensor was replaced, Horner was unable to ratify his team's position should there be a repeat this weekend of what unfolded at Albert Park.
"We had a signal failure on Daniel's car on Friday morning, immediately," said Horner.
"We replaced that for the afternoon session, and hopefully it reads as per the fuel rail (a device that delivers fuel to the injectors in an engine), and will behave for the rest of the weekend."
Asked what the plan would be if it did not work, Horner added: "If it doesn't then we will find ourselves in an awkward situation.
"We will try to work with the FIA, but then you are faced with the same dilemma as occurred in Australia a couple of weeks ago.
"We'll have a conversation with (FIA technical director) Charlie (Whiting) beforehand so it will be clear if we do see a variance, 'right, what are we going to do?'
"Hopefully we can agree something that's sensible."
Horner is adamant the appeal Red Bull are making is "not a frivolous claim", citing his confidence that they "have a very strong case".
Horner believes the FIA should scrap the system altogether.
"When you've a variance and an inconsistency in a sensor like this then we need to look at a more robust system," added Horner.
"The biggest thing out of this, irrelevant of the hearing, is we need a better way of measuring and monitoring the fuel, or get rid of it entirely and say 'you've 100 kilos (of fuel) and that's your lot'.
"That would be the easiest thing for the FIA and the teams because the fuel-flow restriction is only really for qualifying as you can't go to stupid revs in the race if you have a limitation on fuel.
"I think it's something that will be discussed with the technical guys."
FIA head of powertrain Fabrice Lom, with the aid of a whiteboard and a felt-tip pin, on Friday provided a debrief as to the workings of the fuel-flow sensor.
Lom claimed the ultrasonic technology was at a level where it is "quite accurate", with 92 per cent of the systems passing muster, with the other eight per cent rejected by the FIA as being deemed not good enough.
"We are working every day to improve the system, with our target to be as fair as possible," said Lom.
"I admit I am a person (who is) not easily satisfied, and this is how you make progress.
"But with this sensor we do a much better job (of monitoring fuel flow) than without it by far.
"I have no question it is more than needed, and much better than anything else I know about, but now we need to improve it."
In practice, Australian GP winner Nico Rosberg emerged quickest, but with Ferrari's Kimi Raikkonen and reigning four-times world champion Sebastian Vettel breathing down his neck.
The early championship pace-setter posted a lap time in his Mercedes of one minute 39.909 seconds, with Raikkonen 0.035secs adrift and Vettel 0.061secs down.
Lewis Hamilton was fastest in first practice for Mercedes but was fourth at the end of FP2, 0.142secs behind Rosberg.
McLaren's Jenson Button was three-quarters of a second down in seventh, with Marussia's Max Chilton 3.7secs back in 18th.