Aleix Espargaro gave Aprilia's new winglet fairing its public debut during day two of MotoGP testing at Phillip Island.

The design, in response to the new ban on external wings, involves aerodynamic devices being integrated into the fairing.

In the case of Yamaha, covered winglets have been added to the sides of the bike, but Aprilia (and later in the day Suzuki) have opted to place their new aerodynamics above the front wheel.

In the case of Aprilia, two distinct nozzle-type channels - rather than traditional winglets - are located above a curved wing-type 'lip'.

"The fairing was not that bad," said Espargaro, who finished the day an impressive sixth quickest courtesy of an earlier lap. "It was interesting the numbers it showed in the wind tunnel this winter in Italy, because we created an interesting amount of downforce without losing top speed. Which is always very important.

"Here the feeling was a little bit strange, because this track is really particular. It has a lot of changes of direction at a really high speed, which makes the bikes a little bit heavier. We will retry in Qatar for sure, because the difference you can feel is quite high. We need to try in a more normal track."

Espargaro reiterated that Aprilia cannot afford to add downforce at the expense of top speed.

"If the fairing gives us a little downforce but without losing top speed, it will great. If we lose just 2-3ks of top speed, I will not use," he warned.

"The most important thing is the top speed and then if we can create - with the same top speed - a little bit of downforce, to use a little bit more power in the exit of the corner, it's is always welcome.

"But again, this track is not really demanding in acceleration, because it's really flowing track."

Espargaro estimates that the RS-GP needs to find 10km/h per hour to match the fastest MotoGP machine, the Ducati.

"If we check what Aprilia did in one year, their improvement has been great. I just wish they can make the same steps this year."

A recent engine upgrade step has not yet brought the expected results, but could be used again for the final day in Australia.

"Today we are working with the old engine. But they are working on [the new engine] in Italy because they found that the dyno results were not the results we had in Malaysia. We had some issues with power delivery. So they are working and maybe tomorrow we will use again the new engine because the power is a little more."

Rookie team-mate Sam Lowes, still testing with last year's machine, improved his lap time by 1.4s to move ahead of KTM's Bradley Smith.

By Peter McLaren