Most of you know the Mazda 787B, the first Japanese car to win Le Mans, the only non-piston-engine car to win the race, and a machine with an unforgettable shriek. You probably know that it had a four-rotor engine, the R26B, but did you know about its variable-length intake system? And have you seen it in action? It’s pretty wild. Mazda is justifiably celebrating the 30th anniversary of that Le Mans win, and it put up a video showing off various bits of the car, including the intakes in action.
The length of an intake runner has a pretty significant effect on the way an engine delivers power. In simple terms, longer runners help generate better low-end torque, short runners provide high-rpm power. Using a variable-length intake system means engineers don’t have to compromise. You get the best of both worlds, and that’s why many road cars have variable-length intake systems.
Rotary engines are notorious for lacking low-end torque, so Mazda engineers used variable-length runners in its racing engines to help them better compete with piston-powered machines. With the 13J four-rotor in the 767, Mazda first used a two-stage intake, before upgrading to a multi-step intake for the R26B. The final iteration of Mazda’s rotary-powered Group C prototypes, the 787B, had the most sophisticated intake system yet. For the full story, check out this article from Road & Track.