Antonio Giovinazzi says Ferrari's SF71-H has improved "dramatically" since the Scuderia's junior driver last tested the car in Barcelona back in May.
The Italian set a blistering pace on the first day of Formula 1's in-season test at the Hungaroring, clocking in with a 1m15.648 that represented a new unofficial lap record.
"I had tried the car in the Barcelona test, and I must say it has improved dramatically,” said the 24-year-old Ferrari development driver.
"It’s a big step, last time was in May and now we’re in the end of July. It’s really good to see this improvement from the car.
"It showed the team and drivers are doing a fantastic job to improve the car."
Giovinazzi quickly set a benchmark time and improved throughout the session, achieving his fastest lap on Pirelli's hypersoft tyres.
"My main programme, we did a few long runs in the morning and a quali run in the afternoon," he added.
"The rain was coming and we delayed the end of the programme with a lot of long runs.
“It was a good day, positive for me and for the team and this is really important."
Giovinazzi will switch over to Sauber for Wednesday's second test day.