The Evolution of the Modern Camshaft

Usually the front and rear camshaft banks of a engine are mirror images of one another – a design that simplifies production and saves cost. But currently Honda is renowned for bucking convention and the new engine is no exception. The new Honda engine uses a completely different design for each cylinder head.

The front head follows the design cues of the engine of the Honda's CRF450 motocross motorcycle, which saves weight and size on its four-valve single-cylinder engine design by using a single camshaft with three lobes to operate all four valves, marketed under Honda's Unicam trademark. The two outer lobes individually act on the intake valves, with the central lobe moving the exhaust valves via a Y-shaped rocker arm. The new Honda engine does exactly the same thing inside its front cylinder head, but with two cylinders, eight valves and a six-lobe camshaft.

To further cut down on the cylinder head's size, Honda has ditched management (VCM) system from the front head. A development of the Hyper V-Tec in the current VFR, VCM is designed to lock out all four valves to deactivate entire cylinders when they're not needed. However, the system needs lengthened buckets and valve stems, increasing the height of the cylinder head, so Honda engineers have removed it from the front of the new engine, leaving the system to operate only on the cylinders needed.

The cylinders can run on two valves per cylinder, giving better low-end torque; or be shut down completely; leaving just the front cylinders firing; or operate in full power mode with all four valves.