The Honda RA165E was a monumental model in a year that marked another step forward from the 1.5L V6 turbo RA164E engine, which claimed Honda’s first victory in its second F1 era, and dominated the 1985 F1 Grand Prix World Championship.

In its second F1 era that started in 1983, Honda had raced the RA163E and RA164E, both based on an F2 engine, for the first two years. The RA165E, on the other hand, was newly designed for the 1985 season using Honda’s proprietary technology based on the experience gained during these two years, and was often nicknamed “E-spec.”

Until the F1 turbo engine era ended in late 1988, Honda had claimed 36 wins in 64 races over the four years from 1985 to 1988. Honda’s glorious second F1 era began with the RA165E, which recorded an dominating 56% victory rate.

The major difference between the RA165E and RA164E was the basic bore / stroke dimensions. Although the engine remained an 80-degree bank V6, the stroke ratio was dramatically changed from the previous 0.43 short stroke to a 0.57 long stroke. This 82 / 47.3 mm bore / stroke was calculated based on the results of research and development of mass-production engines that had improved combustion efficiency and fuel economy. Of course, the RA165E also incorporated many electronic control technologies cultivated through mass production engine development, such as intake air temperature control and twin injectors. The RA165E was an organic fusion of special technologies for racing engines, and the latest engine mass-production technology with a dominating development objective of improving fuel economy and reducing emissions. From this point on, the goal of Honda’s second F1 era was to aim for victory, while at the same time taking on the challenge of development based on the proprietary technologies that Honda had accumulated as a manufacturer of mass-produced cars.

The RA165E was also designed to fundamentally solve the lack of cooling performance that the previous engines had suffered from: the V6’s cylinders were independently cooled, and aluminum sleeves were used to provide better cooling than steel. The engine was also designed to allow coolant water to flow around the exhaust valves.

The RA165E was also the first racing engine to be equipped with a sensing system that monitored each mechanism and was becoming increasingly intelligent. The analog data measured by sensors placed in various engine components was converted to digital data and recorded onboard. This system was a proprietary development technique that Honda had been researching and developing since the 1950s at the initiative of its founder, Soichiro Honda. This system evolved into the telemetry system the following year, becoming a powerful weapon for Honda, and contributing to the innovative technological evolution of F1 Grand Prix racing as a whole.

The RA165E development plan was delayed until the end of December 1984 due to a fierce technical debates among Honda engineers. The prototype was fervently tested in January 1985, and went into action in June, in Round 6, Canada.

The RA165E finished 4th in its debut race, and won the following round, the Detroit GP, but was plagued by teething problems that could be attributed to the short development period. Once these issues were addressed and the car was able to demonstrate its basic performance, the RA165E proved its high level of competitiveness by winning three consecutive races (rounds 14 to 16) prior to the end of the season. This gave Honda great hope for the following year’s championship.