MotoGP: You Can Learn A Lot By Listening

How is Honda saving fuel in motorcycle roadracing's premier class?

Honda Racing action shot

At Cycle World's annual Indianapolis Industry Panel this past August, four-time 500cc GP title runner-up Randy Mamola described listening to the Repsol Hondas of Marc Marquez and Dani Pedrosa at one of Catalunya's long 180-degree turns. As soon as one of the machines would reach a steady throttle state, its engine note would switch from the higher pitch of a V-4 to the deeper tone of a triple. When the rider moved the throttle to accelerate, the engine would revert to four cylinders.

This is a fuel-saving scheme. With factory bikes limited to 20 liters of fuel, savings at part throttle can be applied elsewhere to increase acceleration. At small throttle, fuel consumption of spark-ignition engines rises as a result of “pumping loss,” the power required to pull intake vacuum in the cylinders.

Hybrid cars gain mileage by switching to their electric motors at small throttle. Honda achieves a similar result, but switching from four cylinders to three at constant power requires a greater throttle opening, reducing pumping loss. Other savings may be realized because only three piston rings instead of four are sealing pressure.