Honda have unveiled the first image of the turbocharged V6 power unit they are developing ahead of their 2015 Formula One return with McLaren.

Progress on the new engine has reached 'prime phase', with the Japanese manufacturer now running full bench tests of the power unit and its connected energy recovery systems.

"At this time, we are unveiling an image of our power unit that is under development - the whole team is concentrating on this development, getting ready for the forthcoming start of F1 participation in six months," said Honda's motorsport chief Yasuhisa Arai, who outlined how Honda hoped to match Mercedes in an exclusive interview with Formula1.com in September.

"Working toward Honda's F1 participation starting in the 2015 season, development of the power unit is entering its prime phase at our R&D facility in Sakura (Tochigi, Japan), where we transferred our automobile motor sports development earlier this year.

"In addition to conducting simulations, we have moved onto the next stage where we conduct full-fledged bench tests of the engine while connecting the turbocharger and energy recovery systems. In the meantime, our racing operation base in Milton Keynes, United Kingdom, has become fully operational."

Honda will offer a sneak preview video of their 2015 power unit - including how it sounds through different rev ranges - from their stand at Suzuka during this weekend's 2014 Formula 1 Japanese Grand Prix.

Honda have not competed in F1 since the end of 2008, but were encouraged to return by the switch to 1.6-litre turbocharged engines. They announced a multi-year technology partnership with McLaren in May last year, reviving one of the most famous technical associations in Formula One history.