Jenson Button says Honda's upgraded engine can take some of the credit for his pace on Friday, which was better than Kimi Raikkonen's Ferrari in FP2's long runs.
Honda spent seven tokens ahead of this weekend's Belgian Grand Prix, a significant upgrade for the race at Spa. Button finished FP2 in ninth, less than 0.2s behind Raikkonen's fastest time in seventh and 1.4s off Max Verstappen's benchmark.
Asked if Honda's new power unit was the reason for his encouraging showing, he replied: "It's definitely some of it. We've made a lot of progress today. We were massively slow in P1, but in P2 we changed a few things.
"Our long run was reasonable as well... I don't know about Sebastian [Vettel], but compared to Kimi our long run on the same tyre was quicker. Compared to the other cars around us, like the Haas, we seem relatively competitive on the long run. So it's going to be an interesting weekend."
Though Button does not expect that pace advantage to continue he is encouraged by the early signs.
"I think [Ferrari] are probably running too little downforce, tomorrow you'll see them more competitive. I'll be surprised if that's the case on Sunday in the race, but I don't think we're in a bad position. There's still a lot of room for improvement."
The encouraging day was overshadowed somewhat by problems for Button's teammate Fernando Alonso, who missed most of FP1 after his new power unit suffered a water leak. However, Button is satisfied Alonso's issues are not related to the upgrade.
"No, it's not a new engine issue -- we had an issue like this in winter testing. It's not just this spec of engine. I think as soon as the engine's running fine you're OK, but it happens very early on, that issue, so this engine should be no problem at all."
Alonso had a new power unit fitted for FP2 -- one which has landed him a grid penalty for Sunday's race -- and recovered from his morning setback to record 30 laps.