McLaren-Honda was doing work it "should have been doing" in pre-season Formula 1 testing during last week's Bahrain session, Stoffel Vandoorne admits.
Honda aimed to take a major step with its 2017 engine for its third season back in F1 with McLaren, but was plagued by unreliability during the two weeks of running at Barcelona.
Its fortunes have improved slightly from there, but development driver Oliver Turvey still only managed 17 laps on the first day of the post-Bahrain Grand Prix test due to a water leak in Honda's Energy Recovery System.
Vandoorne took over for the second and final day, turning 81 laps and setting the fourth-fastest time, but the team struggled to explain that trouble-free day.
The rookie said, though, that much of the work was "all things we should have been doing in Barcelona".
"Of course, with all the track time we have missed during winter testing we are catching up on a lot of things," he said.
"There are still things that we are doing during race weekends that should have been done already during testing.
"For me it was nice to just have a normal day, it felt like it was a long time ago that we spent so many laps on track.
"We did a lot of learning that day. It's the first day of the year that we ran without any issues.
"We did a lot of set-up changes and we could understand a lot more about the package that we have.
"It helped us a lot in terms of understanding where the performance of the car comes from."
Vandoorne said changes were "more car" than with Honda's engine, even though he says the team has updates on both fronts for this weekend's Russian Grand Prix.
Having failed to start the race amid a weekend marred by MGU-H failures, Vandoorne hopes the engine changes will mean Honda's testing reliability will continue this weekend in Russia.
"We tried a few new things and settings with the engine and I haven't heard the exact verdict yet on whether that solved the issue 100% but we have a couple of new bits on the car this weekend," he said.
"Hopefully we will be able to say that that particular issue is solved.
"I said afterwards that all our days should be like that, it shouldn't just be a one-off day so hopefully we can carry the learning forward from that and have a smooth weekend."