HONDA The Power of Dreams

In 1990, the second year of 3.5L naturally-aspirated (NA) engines in Formula 1, Honda supplied McLaren with the RA100E engine, with revised bore x stroke based on the previous year’s RA109E.

The RA109E’s bore x stroke of 91mm x 53.7mm was revised to 93mm x 51.5mm for the RA100E. The expanded bore aimed to stabilize combustion, thus improving fuel efficiency. This means the car can start the race with less fuel, reducing weight and improving dynamic performance in the early stages.

In 1989, a spectacular power war had been raging, but as it died down with the introduction in earnest of NA engines, a fuel economy war, one in which top speed was no longer king, but races were won on fuel economy, took its place. The 1990 Honda RA100E was indeed an engine that competed for the top position in this new war.

There were teething problems with the RA100E, such as the bore x stroke change causing piston pin boss damage through inertia, but necessary measures were rapidly taken.

On the other hand, the RA100E’s throttle system was changed to solve an issue of sluggishness at low revs, which drivers had requested during the 1989 season.

The RA109E used sliding throttle valves, generally considered suitable for racing engines because it does not obstruct the intake air flow when fully open, resulting in less air resistance. However, during throttle operation, an air vortex is generated downstream of the throttle, entraining fuel and causing a delay in fuel supply. Drivers had requested that the sluggishness in acceleration caused by this disadvantage should be eliminated. Poor engine response prevents smooth acceleration, which is a disadvantage in races where every tenth of a second counts. In short, the RA109E’s drivability was not good. In response to the drivers’ demands, the RA100E was improved by changing the throttle system to butterfly valves in order to greatly improve response. In addition, an oil-air separator (OAS) was introduced to ensure sufficient air-liquid separation in the oil tank to minimize problems with the engine’s oil system.

The refined RA100E engine won six of the 16 races in the 1990 season, and earned the Honda the constructors’ and drivers’ titles for the fifth and fourth consecutive seasons, respectively.

In 1991, Honda shifted its main F1 engine to the V12, but continued research and development of the V10 engine, which was supplied to the Tyrrell team as the RA101E engine.