Toro Rosso to race with different aero packages for Kvyat and Sainz

Toro Rosso has struggled to get the most out of an aero package introduced in Germany and hoped to find some answers when it put more downforce on for Singapore's Marina Bay street track this weekend.

But after Friday practice, where Sainz ran the new spec and Kvyat the older version, the numbers suggest the performance is very similar.

"The car is working fine," said Sainz. "It [the new package] hasn't brought the performance, the couple of tenths we were expecting from the upgrade.

"If the team is intending to keep the two packages separate for the weekend, it's because there is not one package which is working better than the other.

"Both packages are working very similarly."

Despite the new aero package not yet delivering the expected gains and the struggles Toro Rosso has had in getting the best out of it, Sainz said he was not concerned about 2017, when new aero regulations are introduced.

"Up until this package, everything we have put on the car has worked," he said.

"All the numbers we have brought to the track have been spot on.

"This is the first time that maybe we didn't accomplish a lot of our expectations.

"It's not ideal but not a disaster because it has worked in 90% of the other cases, so it is not a big concern."

Sainz previously said Singapore represented Toro Rosso's best chance of scoring points before the end of the season and was pleased with its performance with both drivers in the top 10 in practice two.

"It was a better day...finally," he said. "You can see some happy faces around because it is definitely a circuit that is suiting us much more.

"We are using less than half of the lap full throttle so we are losing time in only half of the lap, unlike Monza where we were losing for 80/90% of the lap.

"Q3 is a possibility, but it will be much more difficult than [practice].

"We know we don't have a step on the engine.

"As soon as [Sergio] Perez puts the lap together and as Honda turns the pace up - they were hiding a bit - then a Q3 spot will be very difficult.

"But it's still encouraging, though.

"At least we know we won't be that far off the top 10, even if we don't achieve it.

"If there is a crazy race on Sunday, we'll try and get some points."