The car being tested by Toro Rosso this week is a cross between the 2015 and 2016 machines, driver Carlos Sainz has revealed.
The car is being run at Barcelona in an interim plain-blue livery, after the Faenza team ran out of time amid the hurry to switch to Ferrari power.
"The car is a mixture of the 2015 and 2016 cars," Sainz told De Telegraaf. "At the moment we are working on reliability, the speed comes next week. Here, it's a STR10 with STR11 parts that has been made for this test only."
"Knowing how late the engine decision was made last year, I am amazed that the team managed to get the car ready for the first winter test. How they did it is beyond me, but not only did they do it, it is running reliably.
"I don't even know what position I finished today or what compounds the others have used. It is next week that we will see the STR11 in full and I can say something about the performance."
The full STR11 and its livery will be unveiled prior to the second and final Barcelona test next week.
