Franz Tost has criticised the engineers at AlphaTauri after the team suffered a disappointing start to the 2023 Formula 1 season in Bahrain.
Both drivers finished outside of the top ten, with Yuki Tsunoda pointing out that they were 12kph slower than Williams on the straights due to the amount of drag the AT04 generates.
Tost says the team "expected a much better car" to start off with, criticising the aerodynamic engineers by saying he has lost trust in them.
"Unfortunately I think it's currently the performance level of the car, because we expected a much better car," he told media, including RacingNews365.com.
"We struggled in Bahrain, but it looks a little bit different here. I hope that at least we're with one car in qualifying three, but we have to do a lot of things to make the car faster.
"Especially on the aerodynamics side, there are different programmes going on and the engineers tell me that we make some good progress. But I don't trust them anymore.
"I just want to see the lap time because this is the only thing which counts."
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Tost: Lack of downforce hurting the drivability
Tost points out that the lack of downforce generated by the AT04 severely affects the drivability of the car for both Tsunoda and Nyck de Vries.
"Not enough downforce, therefore the car is unstable under braking, overheating the rear tires, washing out at the apex, traction, everything what you need to do a good lap time," explained Tost.
When asked to elaborate on why he no longer trusts his engineers, Tost said the team told him over the winter that they made "good progress" but ended up struggling at Bahrain.
He added: "During the winter months they [engineers] told me 'car is fantastic, we make it a big progress' then we come to Bahrain we are nowhere. What should I say?"