Having realizing the tough realities of making its comeback to F1, Honda fixed as many problems from the first year back that it could, and delivered the RA616H to compete in the 2016 season. The major issues were improving reliability, and refining the amount and control of electric regeneration, the key to power units (PUs) under the new regulations.

Through the experience gained in its first year back, Honda determined that the design prioritizing space efficiency would not produce sufficient power, and with McLaren’s understanding, made improvements such as enlarging the turbocharger’s turbine and raising the position of the surge tank, which incorporates a variable intake system, by 30 mm. However, the layout of the MGU-H being housed in the V-bank was retained, and the policy of contributing to “Size Zero” remained unchanged.

As for improvements related to combustion in the internal combustion engine (ICE), the fuel injectors were changed from side injectors (from the intake’s side) to top injectors. This allowed for more optimal fuel/air mixing and increased power output.

The reliability of the RA616H was greatly improved through the hard work of the engineers. The team made every effort to troubleshoot problems based on their experience and data analysis from their first year of competition, and the laps tested in pre-season winter tests saw a remarkable improvement in the amount of regenerative electric energy, which had been an issue, and was highly praised from the team and drivers.

Having secured a certain level of reliability, the next task for the RA616H was to improve its performance. Although the PU was able to run trouble-free from the start of the season, the results showed a large gap between McLaren and the top teams. Improvements were made during the season, and upgrades were applied. In Round 7, Canada, a new version with an improved turbocharger was introduced, and in Round 10, Britain, the “Spec 2” was introduced with an improved intake system and combustion efficiency. In Round 13, Belgium, Honda introduced “Spec 3,” with further improvements to the intake system and turbocharger, as well as a new combustion chamber design. The Spec 3 achieved solid performance improvements, and the results of development were tangible.

The McLaren MP4-31 was also evolved and refined, and McLaren Honda’s position rose to the point where it could compete for the lead in the chasing group, but it was also a season that showed that there was still a large gap between McLaren Honda and the top teams.

In hindsight, the improvements in the RA616H’s reliability led to a significant improvement in the ability to complete races. Of the 21 rounds, Fernando Alonso and Jenson Button retired only ten times, and only three of those retirements were clearly due to the PU. The best results were two fifth-place finishes for Alonso and a sixth-place finish for Button, and although they did not reach their goal of podium finishes, it was a season in which McLaren recovered to sixth place in the constructors’ standings.

Honda’s head of development, Satoshi Tsunoda, looked back on 2016 as “a year of refinement.” The RA616H was the result of troubleshooting and improving the RA615H introduced in Honda’s first year back in F1, but it was also a PU that showed that fundamental changes were needed to join the championship contenders.