At the recent Austrian and British Grands Prix, McLaren introduced the first two stages of a pivotal three-step update that will mean “pretty much every aerodynamic part on the car changes”.
While the final components originally scheduled for last weekend’s Hungarian GP have been delayed owing to design and production timelines, Norris has finished second in the last two races behind dominant winner Max Verstappen.
With this recent form allowing McLaren to beat Mercedes, team principal of the eight-time constructors’ champions Wolff reckoned his competitors had gained a second per lap.
The Austrian said: “You can see how McLaren has leapfrogged everybody else with an update - they didn't expect to come in that powerful.
“Whatever it was, they gained a second probably. And they leapfrogged Aston Martin and Ferrari, who we've seen as really strong contenders at the beginning of the season, and now they're nowhere.”
While Stella did not publicly declare the lap time found by the revisions to the MCL60, he reckoned Wolff had exaggerated the gains.
Following the most recent Budapest round, in which Oscar Piastri finished fifth after losing out to Norris via a pitstop undercut before sustaining floor damage, Stella said: “In fairness, we haven't done a proper numerical estimate.
“We had our own internal estimate based on what we saw in the aerodynamic maps. And then you simulate these and this gives you a number, which I cannot share really, but it wasn't one second.
“So, I think, somehow the behaviour of your car and the development of your car kind of helps with tyres at the same time. This gives you further lap time benefit.”
While McLaren had played down its hopes for Hungary owing to the lower-speed track nature only to impress, Stella has again moved to check expectations ahead of the Belgian GP this weekend.
He says McLaren must still improve in low-speed corners.
“We certainly come out of this event encouraged that we have made progress in medium speed,” said the Italian.
“That's what we certainly see from comparison with our competition.
“We also see that we do lose time in the three low-speed corners. So confirming that there is still work to do in low speed.”
