Adventure bikes keep growing in size and power, with Honda’s Africa Twin growing from 650cc in the late 19080s, up to 1084cc in it’s current iteration. The competition has gone even further, with BMW sporting a 1250, and Ducati offering a 1260 and an upcoming V4. Horsepower wars are not just limited to Superbikes, and Honda is in danger of being left behind in the battle. However, recent Japanese patents show that Big Red might be sharpening a new weapon to battle the Germans and Italians, in the form of crank-driven forced induction.
Adventure Rider has previously reported on Honda supercharging patents, and Kawasaki has shown with their H2 series of sport bikes that supercharging is a viable technology for production motorcycles. Honda is no stranger to forced induction, fielding a production turbocharged CX motorcycle in the early ’80s, and currently relying on turbochargers for many of their production automobiles. But whereas turbochargers use exhaust gas energy to spin a turbine that pressurizes intake air, superchargers use power from the engine’s crankshaft to spin a compressor to provide pressurization, and Honda has not yet produced a supercharged motorcycle or automobile.
Honda’s latest supercharged motorcycle patent appears to show a CRF1100L engine and chassis with a twin-screw supercharger mounted above the gearbox, behind the parallel-twin cylinders. Intake air comes from the airbox on top of the forward part of the frame, around the left side and under the left frame spar, through the supercharger, and into the throttle bodies. The route between the supercharger and throttle bodies is via a fairly long upside-down “U” shaped manifold that also features a bypass tube back to the airbox with a butterfly valve controlling flow.
Notable in the patent is the existence of two sets of injectors, one in the intake tract, and one in the combustion chamber between the intake valves. According to Cycle World, the patent describes a crank-driven, high-pressure pump providing pressure for the direct-injection system, required to finely atomize the injected fuel.
Compared to Kawasaki’s centrifugal supercharger that requires some revs to begin producing boost and power, Honda’s proposed twin-screw setup should make power from low RPM on up, better fitting an adventure bike’s power requirements. The adventure bike horsepower wars might just see a turning of the tides in the near future.