Honda RA121E

The Honda RA121E is the V12 Formula One engine that Honda, through its F1 programme, developed and built for the 1991 season; the article on it also covers the RA122E and RA122E/B that followed in 1992. Honda had raced the V10 RA109E since 1989, but inside the company the V10 was seen as a stopgap and the preferred design was the V12 of its 1960s Formula One tradition, so V12 development began in January 1989 and a prototype was on track at Silverstone by July 1990. The RA121E is a water-cooled 60 degree V12 with DOHC and four valves per cylinder, displacing 3,497 cc with a bore and stroke of 86.5 by 49.6 millimetres, a compression ratio of 12.15 and 735 brake horsepower at 13,500 rpm, and it weighs 150 kilograms. It debuted in the McLaren MP4/6 in 1991, the year Ayrton Senna won the drivers title and McLaren the constructors title. The 1992 versions were redesigned with a 75 degree bank angle and pneumatic valves, yet Williams took both titles. Development ended when Honda left Formula One at the end of its second era in 1992.