WHAT NEXT?
So BMW have two distinct optima and Ducati have one full-load cam they vary the position of. The BMW is more involved from a mechanical engineering point of view, but the difficulty of application of the Ducati can’t be overstated with all those control valves and feedback sensors. I can’t split them in terms of being a ‘greater achievement’ – and it’s a short step to realising that what you really want is both. Sooner or later someone will do it.
It’s worth remembering that as far as road-going engines are concerned the first variable examples were two-strokes – Yamaha’s YPVS system had a valve that altered exhaust port height to change timing and crankcase reed valves effectively gave infinite intake timing variation.
Exhaust emission regs aren’t as tight for bikes as cars (yet), and power still sells – people will buy horsepower, but are less willing to pay extra for fuel economy. But you’ll get to the point where you have to use variable timing for emissions, so then you see what else we get can get from it. This is why it’s not come from racing. In racing, you’re almost always at high revs and wide open throttle, and you don’t need it up there. But if you want to bring a race engine to the road – or use power figures to help sell a bike – you have to use this stuff to meet emissions. And to make it usable.
As power has climbed we’ve had to control it more and more. The 1262cc Ducati is remarkably rideable despite big V-twins being inherently lumpy – it’s making a controllable 159bhp thanks to sophisticated engine management (including twin spark plus per cylinder) and dual phasers. The ideal would be a fully variable valve train. 20-odd years ago at Lotus we developed an ‘Active Valve Train’, the research engine programmed for the optimum cam profile for however it was operating, and increased swirl and turbulence for better combustion. Such systems control the exact position of the valves using electrohydraulics, or compressed air, or maybe electro-magnetically. But nobody has ever productionised it because of cost. BMW’S Valvetronic car system continuously varies the valve lift and duration together, and is how they control the engine – it doesn’t have a throttle. That the industry can make a piece of equipment like this, for prices people are quite willing to pay, is remarkable.
Packaging a Valvetronic system on a bike would be difficult. It’s the same for turbochargers, which are now the base technology for car engines. However, direct injection (DI) could be the next step for bike engines, with the air/fuel mixture created in the combustion chamber and giving lower emissions, reduced knock tendency and increased torque.