After witnessing fellow Japanese manufacturers Honda and Yamaha competing in Formula One, Subaru sought to enter the sport as an engine supplier in 1989. The company contracted Italian engineering firm Motori Moderni — which had previously built a turbocharged V6 used by Minardi in the mid-1980s — to design and build a new Formula One engine. Carlo Chiti, Motori Moderni's owner, produced a 3.5-litre, 60-valve flat-twelve engine in the boxer configuration, consistent with Subaru's road car philosophy. Although the flat-twelve layout had served Ferrari well in the mid-to-late 1970s with their 312T series of cars, the wide boxer format had largely fallen out of favour after 1980 due to its incompatibility with ground-effects aerodynamics.
The engine, named the Subaru 1235, first appeared in a Minardi test car at the Misano circuit in May 1989. Dyno tests indicated a maximum power output of approximately 417 kW (559 hp), significantly below contemporaries: even the aging Cosworth DFR V8 produced at least 590 hp, while the dominant Honda RA109E V10 produced at least 660 hp. The engine's weight compounded matters. Although the bare unit weighed 159 kg — only about 10 kg more than a Cosworth DFR — the total assembly including ancillaries was 112 kg heavier than a complete DFR unit. Carlo Chiti publicly targeted a final power output of 447 kW (599 hp), which would have brought it closer to the DFR, but this figure was never achieved in competition.
Rather than supplying the originally intended Minardi team, Subaru opted to partner with Coloni for the 1990 season, purchasing half of the small Italian outfit to form an effective works entry. Bertrand Gachot was retained as the team's sole driver. The existing Coloni C3 chassis, which had raced in 1989 with a Cosworth DFR V8, required extensive modification to accommodate the new engine. The updated machine, designated the C3B, saw its airbox removed and replaced by two sidepod-mounted air ducts, resulting in taller and longer sidepods. The rear weight bias caused by the heavy Subaru engine gave the C3B unpredictable handling characteristics, with balance skewed heavily toward the rear.
The Subaru-Coloni C3B made its debut at the 1990 United States Grand Prix in Phoenix, but Gachot failed to complete even a single lap in pre-qualifying before a gear-linkage failure ended his session. He finished dead last in pre-qualifying. This inauspicious beginning set the tone for the entire campaign.
Over the eight races in which Gachot drove the C3B, the team failed to pre-qualify on every occasion. The Subaru engine was both chronically underpowered relative to the competition and mechanically fragile, often failing before Gachot could complete enough laps to register a meaningful pre-qualifying time. The combination of poor power output, excess weight, and chronic unreliability made the C3B entirely uncompetitive even by the standards of pre-qualifying.
Following a breakdown in relations between Enzo Coloni and Subaru after the 1990 British Grand Prix — just eight races into the engine's Formula One life — the Japanese manufacturer withdrew from the partnership entirely. The team promptly reverted to Cosworth DFR power in a revised chassis designated the C3C. Although Gachot was generally able to pre-qualify the Cosworth-powered C3C, the team never managed to qualify for a race, and Coloni folded at the end of the 1991 season.
The Subaru 1235 engine also appeared in the 1990 World Sportscar Championship, fitted to the Alba AR20 Group C car. Results in sports car racing mirrored Formula One: the car qualified for only one race, the 1990 480 km of Spa, and was unable to start due to engine failure. The engine programme was abandoned mid-season, with Alba switching to a 4.5-litre Buick V6.
The Subaru-Coloni episode stands as one of Formula One's most prominent cautionary tales about the difficulty of entering the sport with an underdeveloped and unconventional engine concept. The flat-twelve configuration — which Chiti believed would offer aerodynamic benefits through a low centre of gravity — proved to be a fundamental liability in the 1990 aerodynamic environment. The project demonstrated that raw engine concept alone was insufficient; weight, power density, and reliability in the context of the complete car assembly were equally critical factors. Subaru did not return to Formula One.