Honda Developing Clutch by Wire for Motorcycles

Perhaps the biggest change to the bikes we ride today compared to their forebears of two decades ago has been the introduction of ride-by-wire throttles—which have in turn enabled all the modern rider-assist systems that have proliferated over the last few years.

Yamaha’s 2006 YZF-R6 was the first production bike to gain a ride-by-wire throttle, eliminating the direct cable control between the twistgrip and butterflies and replacing it with a simulated, servo-based setup. Its greatest initial success was, arguably, the fact that it felt just like a normal throttle; if you weren’t clued up on all the tech details, you’d never know it was anything out of the ordinary. Later on, the same technology was adopted by virtually every manufacturer, to the extent that it’s hard to find a motorcycle on sale today that doesn’t use ride-by-wire.

Initially, ride-by-wire throttles were a boon to engine designers challenged by emissions targets. They allowed the throttle openings to be mapped, along with ignition and injection settings, to provide a smooth, linear response to twistgrip movement, even if the actual butterflies were operating in a quite different, nonlinear way to help reduce emissions and squeeze past legal limits. However, it wasn’t long before manufacturers started to exploit the systems for additional benefits.

Traction control is the most obvious beneficiary. While there had been previous attempts at cutting power in response to wheelspin by altering ignition timing or fuel supply, giving control over the throttle as well offered an extra dimension. Over and above that, in alliance with inertial measurement units, ride-by-wire enables the likes of wheelie control, launch control, and cornering stability control. So what’s the next thing that could offer similar benefits? Honda seems to think that a ride-by-wire clutch might be a significant step and has filed multiple detailed patent applications describing just such a setup.

The Honda design retains the idea of a hydraulically controlled clutch, operated via a bar-mounted lever, but eliminates the direct link between the two. Instead, the lever’s position is electronically monitored, sending information to a hydraulic pressure control unit that in turn engages or disengages the clutch. The main control unit also uses info about throttle position, gear position, speed, revs, and gear lever movement to make sure that every application of the clutch is perfect, regardless how clumsy the rider is.

Unlike a conventional clutch, which allows the transmission and engine to be connected in its resting state and only disengages them when the lever is pulled, the Honda system defaults to a disengaged state. When you release the clutch lever an electric motor moves the piston in the clutch master cylinder, applying hydraulic pressure to the slave cylinder to engage the clutch. It means that the setup is fail-safe, and in the worst-case scenario, drive will be disconnected rather than left impossible to disengage.

With so much extra information going to the clutch-by-wire system, the possibilities for the setup are extensive. The bike could be allowed to operate the clutch completely automatically in some modes, for instance, or to work in harmony with a quickshifter to provide smooth but almost seamless changes without the rider having to think about the clutch. It also opens the door to additional launch control, wheelie control, and traction control strategies, using the clutch as well as the throttle, ignition, and injection to maximize traction and keep the rider in control.

Of course, Honda hasn’t forgotten the fact that riders will still expect a familiar feeling at the lever, even with a futuristic clutch that’s partly computer controlled. The firm’s patents also include a “reactive force generation device” that acts against the lever, giving the sort of feedback that you’re used to, even though there’s no longer a direct connection between your hand and the clutch position.

When you’re riding with the clutch lever released, the bike constantly monitors the pressure in the clutch’s hydraulic system, making sure it stays within limits to keep the clutch engaged. But the system is also capable of deducing when you’re pulling away or coming to a halt, smoothly engaging or disengaging the clutch to suit. So, at the very least, embarrassingly stalling your engine should become a thing of the past.