Honda’s second F1 era reached the racing stage mid-season in 1983. The 1500cc turbo engine challenge began with the emerging Spirit team, moved on to participation with the powerful Williams team from the final race that season, and its first second-era victory at the 1984 Dallas GP. In 1985, the FW10 was the car raced in the second year of full F1 participation as Williams Honda.

In the 1970s, Williams was an upcoming F1 constructor, but had already established itself as a strong British team through the success of its famous FW07 series cars. (FW was taken from team manager Frank Williams’ initials.) Car development was headed by Patrick Head, close friend of Williams. The team won its first drivers’ and constructors’ titles in 1980, followed by back-to-back constructors' titles in 1981 and another drivers' title in 1982. (Alan Jones was 1980 champion, and Keke Rosberg, Nico’s father, was 1982 champion.)

Yet, because the car continued to be powered by the 3000 cc naturally-aspirated Cosworth DFV engine, Williams fell into a difficult position when the entire F1 world was rapidly shifting toward the 1500 cc turbo engine. Despite Rosberg winning the 1982 title, he had only one win, and in 1983, for the first time in the team’s history, it failed to win either title (1 win throughout the season). Williams was in urgent need of a powerful factory turbo engine, and Honda’s desire to be the engine supplier to a strong team with a proven track record was a perfect match. A powerful tag team was born that would later dominate the F1 world.

All was not smooth sailing for Williams Honda from the beginning. In 1984, their first season of full competition, Williams Honda won one race, but continued to struggle. This was because both the Williams chassis and the Honda engine had issues. In terms of the chassis, the FW09, the first Williams Honda that raced from the final round of the 1983 season to the end of the 1984 season, was built with an aluminum honeycomb monocoque, which was undeniably too fragile to handle the mighty power of Honda’s V6 turbocharged engine. The FW09’s monocoque was said to be the same design as that of the previous FW08s which was designed for a naturally-aspirated V8 engine. It was not a complete Honda-spec Williams, by any means.

The FW10 was Williams’ first carbon composite monocoque. Lightweight and highly rigid, carbon monocoque was a new technology that would become a trend, similar to turbocharging. Although the purpose of using carbon monocoque was not necessarily only to counter turbo power, the FW10 was definitely the first Williams car that was completely developed to accommodate the Honda V6 turbo.

In developing the RA165E for the 1985 season, Honda, of course, had also been studying technologies to improve performance in all aspects, including power output, fuel economy, and reliability. Honda was prepared to take advantage of the lessons learned from the previous year’s struggles, and to make bold policy changes if necessary, and in fact, some major decisions were made. One such change was reducing the bore and lengthening the stroke. The reason was that the conventional 90.0 mm bore / 39.2 mm stroke was problematic for combustion chamber shape, causing abnormal combustion, according to analysis (although the causes and countermeasures were not limited to this).

The new engine, with a bore of 82.0 mm and stroke of 47.3 mm, was introduced in Round 5, Canada. This was a technological departure from the 90.0mm bore tradition (F2’s stroke was 52.3mm) that Honda had followed since it began competing in European F2 as a preparatory step before entering its second F1 era. The introduction of the new engine with a bore of 79.0mm and a stroke of 50.8mm, and further development through 1986, was proven right by winning the title.

In Round 6, Detroit, in the second race with the new engine, Williams Honda claimed its first win of the season. Rosberg was the winner, as in Dallas the previous year, but Nigel Mansell (transferred from Lotus), who had replaced Jacques Laffite, was also fast from the beginning of the year. Between the two, the FW10 qualified in the top 3 in five of the six opening rounds. Following the first victory, Rosberg claimed Honda’s first pole in its second F1 era in the French GP, followed by another pole in Round 8, Britain. The FW10 was gaining momentum. In Round 13, Belgium, Mansell and Rosberg finished 2nd and 4th, respectively, and the team was inching closer to a double-podium finish.

In the 1985 season, McLaren TAG Porsche was as strong as the previous year, but due to the withdrawal of Michelin, their domination had diminished. Compared to the 12 wins in 1984, McLaren won 6 in 1985 on Goodyears, as did Williams. Some other teams wore Pirellis. In the first half of the season, Ferrari threatened McLaren, but they gradually lost ground, and towards the end of the season, Williams Honda played an active role, as if they were declaring themselves to be the next F1 leader.

In Round 14, the European GP at Brands Hatch, Williams Honda introduced the evolved FW10B. With the rear suspension modified, the gearbox casing, Honda engine air chamber, rear fairing, and other modifications, the new FW10, recognized by the B version, and Mansell won for the first time in his home country after 72 grands prix, the slowest record at the time. Rosberg also finished third, for the double podium. Alain Prost of McLaren won his first F1 drivers’ title (the second consecutive title for the team), and although he finished fourth in the race, he was also present at the awards ceremony. Yet, the race seemingly foreshadowed the rise of Williams Honda.

The FW10B is said to have had improved rear aerodynamics. Perhaps it was a good match for Mansell’s driving, as he in return won the next round in South Africa from pole, for his second consecutive victory. Rosberg followed in second place, making it the first 1-2 finish for Williams Honda. In the final round in Australia, Mansell retired from the race, but Rosberg won, giving Williams Honda their third consecutive win. The season came to a close with high expectations for the following year and beyond.

The Williams FW10 (including the FW10B) concluded the season with 4 wins and 3 poles out of the 16 races. In the constructors’ standings, Williams Honda was tied for third with Lotus Renault, behind the reigning champions McLaren TAG Porsche, and Ferrari.

The car’s reliability had improved significantly. 21 retirements from a total of 32 starts in the 16 races during the previous season, had improved to 12 from a total of 31 starts in 16 races. (Mansell was DNS in one race.) Although the FW10 in 1984 boasted superior power, the 1985 version was able to put the performance, and capabilities, on the road. The number of finishes in the top six doubled to 15 in 1985 from seven the previous year. In its second full year of competition, Williams Honda had made great strides in all areas.

This is the FW10B introduced in the 14th round of the European GP at Brands Hatch, with a slightly lower rear cowl.

The FW10 was Williams’ first carbon monocoque car, and Honda’s turbocharged engine was redesigned with a small bore and long stroke. In terms of technology and performance, the FW10 was the car that would usher in the golden age of Williams Honda.