Following Friday practice for the Hungarian Grand Prix, Ferrari’s checks in the evening exposed some parameters that the team was not happy with.
The decision was taken for the power unit to be taken out, so it could be shipped back to Ferrari’s Maranello headquarters for further analysis.
The team has elected to fit a fresh unit in its place, which will be the last final one that Sainz can take this season without incurring any penalties.
The extra work required to fit the engine meant Ferrari breached the overnight curfew in place for F1 personnel. This was the first of two exemptions that teams are allowed.
Sainz’s engine switch comes on a weekend where Ferrari is not overly optimistic about its overall form, with the car not as comfortable around the Hungaroring as at other venues.
The Spaniard, who ended second practice one place behind team-mate Charles Leclerc in 12th on the timesheets, said the layout of the track left Ferrari exposed as the run of low and medium speed corners does not especially suit the SF21.
“Unfortunately before coming here, we already knew that we have some weaknesses in our package,” he said.
“In our car we know for some certain corners of this circuit it was not going to be particularly good at and we proved it [on Friday].
Carlos Sainz Jr., Ferrari
Photo by: Andy Hone / Motorsport Images
“In Monaco, we would have never been P11, P10 in a practice session. And unfortunately, as soon as something went in the wrong direction, we found ourselves out of the top 10.
“It shows we are a lot more vulnerable in this sort of track, it’s not a Monaco.
“We’ll kind of hope that we can recover a bit of pace, and at least try and be on top of the midfield.
“But it’s not easy, because the Alpine looks very quick, McLaren looks quick, the Aston Martin was very quick also.
“It looks like a very mixed midfield, and it should be a very interesting battle for Q3.”