McLaren ran an updated Honda power unit at the first day of the second test, which is closer to the one the team is hoping to use at the opening race in Melbourne.
Honda has revised much of its power unit over the winter, but has so far has focused on reliability over performance. Despite a software issue that caused the car's telemetry to shut down before lunch, McLaren gathered a total of 93 laps of data on the latest specification of engine.
"After the disappointment of not being able to complete much running at the end of last week's test, it was positive to get so many laps on the board today," Fernando Alonso said. "We tested a number of different configurations and spent a lot of time working on the power unit and collecting data from the aerodynamics.
"It's too early to tell a real difference compared to the engine last week, as we focussed today on shorter runs and adjusting the balance and set-up of the car. However, today's full day of running has been a good start to the second test, and has provided us with lots of useful data that we can analyse overnight before Jenson continues the programme tomorrow."
Engineering director Matt Morris added: "We spent a good chunk of the day evaluating the power unit functionality, although our attention hasn't yet turned to assessing outright performance. The important thing was to get as many miles on this package as possible, so from that point of view and the amount of data we have collected today, it has been very positive.
"We will continue to maximise our track time over the coming days, to work on ironing out reliability niggles and move on to longer runs. We also have some new aero parts arriving overnight, which will be assessed on track tomorrow with Jenson."
Head of Honda's F1 project Yusuke Hasegawa explained the problem: "We had an unexpected control electronics shutdown just before lunch time, believed to be the cause of a software problem. Apart from that, we were able to run a decent amount of laps to finish the first day of the second test in Barcelona.
"On the power unit side, we tested many different modes of running to prepare for the race, so it was a busy day for the system engineers. As a package, we were able to test different balances of the car and tyres together with the power unit. We are looking to perform further detailed checks on the power unit during tomorrow's testing."