Honda has revealed plans to debut an upgraded power unit when the Formula 1 season resumes at the Belgian Grand Prix later this month.

The Japanese manufacturer has struggled since returning to F1 as engine supplier to McLaren, but has confirmed it will spend seven engine development tokens to improve the power output of its unit.

Amid the struggles, Honda’s motorsport boss Yasuhisa Arai is confident his team has solved its reliability concerns, which has prompted a push to enhance the performance of its engine.

A selection of new parts are expected to be debuted at Spa from August 21-23.

McLaren has claimed only four points finishes this year, highlighted by two top 10s in Hungary with Fernando Alonso fifth and Jenson Button ninth.

“I am confident that our reliability problems are now behind us which means we can turn our attention to increasing power,” said Arai.

“After the summer shutdown our plan is to apply a new spec engine using some of our remaining seven tokens.

“The most important area for us to concentrate on is the combustion.

“Current regulations require high efficiency of the combustion so we want to change the characteristic with the chamber design and intake and exhaust system layout.

“Another issue we will be addressing is reducing mechanical friction by changing the gear train system along with the combustion.

“Not all of our upgrades will be in place for the Belgian Grand Prix; some parts will be applied for Spa and the rest during the weeks that follow.

“Our plan is to keep improving race-by-race for the remainder of the season.”

Honda has attracted plenty of criticism for its lacklustre return to F1, with Arai now admitting the firm has underestimated challenge.

“The sport has changed immensely since the McLaren-Honda ‘glory days’,” Arai added.

“The current technology is much more sophisticated and it is tough to make a good racing car.

“We knew it wouldn’t be easy, but perhaps we didn’t imagine it would be this hard.

“I certainly didn’t imagine technology-wise what we would be facing, but I have complete confidence in the direction we have taken with our power unit.”