McLaren's Eric Boullier says the team's latest aerodynamic updates delivered more performance gains than initially expected in Mexico.
McLaren produced a new front wing which was introduced in Austin on Fernando Alonso's car, and the Spaniard reported back hailing a big step forward which transpired in qualifying last weekend in Mexico.
Alonso went on record saying his McLaren MCL32 was the "best chassis" in the field.
Boullier echoed his driver's positive comments, but admitted the progress was more than what the team had bargained for.
"Let’s say it is a little bit better than we were expecting," Boullier told Motorsport.com.
"It was a surprise. We were not expecting to be that competitive, but if you put everything relative apart, the new full package that we introduced on Fernando’s car last weekend looks like it delivers a little more than expected – which is good news.
"Hopefully Stoffel [Vandoorne] will have it in Brazil as well.
"It is good as a reference as well, because it is part of next year’s car, and it is good to know where we are and what we can do."
Boullier was happy to hear Alonso's ecstatic assessment of the team's car, but the Frenchman was reluctant to follow suit and rank the quality of McLaren's chassis.
"I think every race is a bit different," said Boullier.
"The car characteristics are different between our car and the Red Bull car for example, so we know what is our weakness versus the Red Bull car, and I am sure they know the inverse.
"That means we still have to work. But it is good. And after we reset the car concept three years ago, to have caught up with the top teams is quite an achievement, I would say."