Honda's 2016 F1 upgrades building towards big 2017 step - McLaren

Boullier feels although the Japanese manufacturer has the potential to make a significant step during 2016, it is better off biding its time to ensure everything is in place for next year.

Honda is the only manufacturer yet to spend any engine development tokens since the season started, with 14 remaining, and motorsport boss Yusuke Hasegawa is eager for one major development push rather than small steps.

Rival Renault is set to deliver its significantly upgraded package for this weekend's Monaco Grand Prix, with an expected laptime improvement of around 0.4 seconds.

Boullier believes Honda can make a comparable gain during 2016, but that the most important work will be towards '17.

"I think Renault's style [of performance gain] is possible," Boullier told Autosport.

"We will see. They [Honda] are trying as they still have some tokens so they can use them.

"I think there is some learning for 2017 if they can change some stuff in the 2016 engine.

"I would do it this way: to try to improve, but with the bigger picture being to prepare for next year and make a real step up."

The Honda engine is proving far more reliable this season following strenuous efforts to improve in that area, but more power can still be extracted.

"The reliability was important for them obviously," said Boullier.

"We can find more performance, and we're working together on that.

"The complexity is how to improve the harvesting without deteriorating the power. If one goes up, the other goes down. You need to have both together.

"The energy needed to rotate and harvest is higher."

With energy harvesting improving, combustion will be Honda's next focus.

"You have to push for both. It's a bit complicated," added Boullier.

"But it is getting there. It is slow from the outside and slow for us. Obviously we would like to win now, but it is coming."