The few cryptic lines about the new engine from Kawasaki are limited to a press release announcing its Tokyo show display, which state: “Kawasaki Heavy Industries, Ltd. also has a long history of developing technologies for turbine engines. The lifeblood of these turbines is their blades, which need to be able to cope with extreme heat and vibration while spinning at high speeds. Know-how from years of designing turbine engine blades was instilled in the first supercharger developed by a motorcycle manufacturer. And of course, designing a motorcycle-use supercharged engine in-house means that maximum efficiency could be pursued.”
Kawasaki currently utilizes superchargered Inline Fours for its personal watercraft in the 1498cc Ultra 310 models. KHI’s last foray into forced induction on a motorcycle was the 750 Turbo, which joined other turbocharged designs by the Big Four Japanese manufacturers in the early ‘80s. The supercharged Kawasaki engine arrives at the same time as another Tokyo show debut, Suzuki’s Recursion concept, which is powered by a turbocharged 558cc Twin.
A Kawasaki patent titled “Motorcycle with Supercharger” is dated November 19, 2013 – with prior publication related to the current patent cited in October 2012. Documentation shows the supercharger engine layout, with the patent-protected part of the invention being the rearward positioning of the air box intake and supercharger.
Patent illustrations show the “air cleaner unit” placed under the seat and fuel tank, directly behind the supercharger, which is in turn behind the engine block. The layout in the patent drawings appear to conform with the lone photo Kawasaki has released of its supercharged Inline Four.
Drawings from Kawasaki’s “Motorcycle with Supercharger” patent show the air cleaner unit (42) positioned rearward of the air
control valve unit (46) and supercharger (44). The supercharged air flows up into the surge tank (46) and through the intake throttle
body (49) where the fuel injectors (78) deliver fuel from the tank (28).
The induction system described in the patent routes air through the air cleaner unit into an air control valve unit. There a butterfly valve controls the intake into the supercharger. Unlike a turbo, which runs off exhaust gas pressure, a supercharger gets rotary power from the engine, and the Kawasaki patent confirms its supercharger is powered via the engine crankshaft “through a chain or a train of gears.” A surge tank positioned atop the supercharger (unseen in the Kawasaki engine photo) channels the supercharged air through to the throttle body and into the engine.
The primary advantage asserted by the patent is the space-saving positioning of the air box intake and supercharger, the close proximity of which eliminates the need for extra piping. Kawasaki also claims the more compact system allows for larger capacities for the surge tank and fuel tank above it.
No official word on whether the shiny Inline Four teased in Tokyo is the same as the one outlined in the patent. However, the patent does state that the “preferred embodiment” of the powerplant for the supercharger system would be “in the form of a parallel multi-cylinder combustion engine, for example, a parallel four-cylinder, four-stroke cycle combustion engine.”
The real fun is figuring out what the new supercharged engine will eventually be powering. The patent drawings show a bike with a profile reminiscent of the ZX-14. Stay tuned.