Kawasaki's patent drawing details a valve actuation system in which both timing and lift c
A new invention or technology can sometimes seem to appear with no precursor or hint of its appearance. But for those trying to foresee new developments, a search through new patent applications can be a kind of crystal ball, revealing images of a breakthrough months or even years before its introduction.
The latest interesting patent application to cross our desks is from Kawasaki, and some observers are already touting it as a sneak preview of the 2011 ZX-10R engine. This describes a valve actuation system that provides both adjustable valve timing and lift.
The Kawasaki Concours14 sport-tourer has had variable valve timing since its introduction in '07, using Mitsubishi automotive technology. But the new system is very different from what we've seen on the Concours, both in its hardware and in the addition of variable lift.
The key can perhaps best be described as a sort of finger follower interposed between the cam and the conventional-looking bucket tappet. The difference is that the dimensions of the follower can be altered to change both valve timing and lift.
The lower part of the follower pivots on a relatively large-diameter shaft, and has a long "shoe" that slides on top of the bucket to operate the valve. Below the bucket, the adjustment shim, keeper, spring and valve are all familiar. Some have suggested that the system uses hairpin-type springs, but I think this is a misinterpretation of the unconventional way the spring is drawn.
The upper part of the follower pivots on the lower part, rotating on another, smaller pivot shaft that's specific to each pair of valves. The position of the upper follower relative to the lower is controlled by a small roller that's eccentrically mounted to the main pivot shaft and which contacts the bottom of the upper follower. A pair of coil springs concentric to the pivot shaft keeps the upper followers of each valve pair in contact with the cam lobe.
The system is controlled by the ECU through a stepper motor that can rotate the pivot shaft a specific amount, changing the position of the upper follower and thus the valve actuation geometry. Separate motors actuate the intake and exhaust valve shafts independently.
It sounds complex, and it is. Let's look at the plusses and minuses, and at some of the hints that the patent application may reveal. First, the date of the application is fairly recent: October 2009. While Kawasaki may have been working on the technology for years without revealing it, the date indicates that it may be pretty new and thus undeveloped. On the other hand, the patent drawings reveal a "real" looking set of parts, including full top views of an inline-four cylinder head. If it was a clean-sheet development, the patent drawings might have shown a single-cylinder conceptual layout.
The plusses of such a system should be a broader spread of power, greater fuel efficiency and cleaner emissions, all especially important in a sport-tourer like the Concours14 and perhaps not as important in a superbike like the ZX-10R.
The minuses of this setup, however, could hurt the superbike. The cylinder head is significantly taller-keep in mind that the cams in a conventional setup contact the bucket tappets directly, and that all this hardware is between the cams and the tappets. That might limit airbox or fuel volumes. Even though the patent application claims improved/reduced valve acceleration forces, there is certainly more reciprocating weight here, which will ultimately limit revs.
Overall weight will increase as well. The follower parts are all steel, as are the pivot shafts and the additional springs. There are more fasteners in the assembly, and the cylinder head, as mentioned, is taller. There may also be increased friction, as the upper follower is held against the cam lobe with springs that look pretty stiff. The patent application goes into great detail about provisions to spray oil on every one of the 16 cam/follower interface surfaces.
Bottom line? I'm not betting on this appearing on the ZX-10R anytime soon. But it may be a different story for the Concours14. The crystal ball of the patent application is still a bit cloudy, but it's definitely interesting and great fun trying to read the signs.