KTM electric supercharger points to downsized ICE
Smaller, more powerful combustion engines and improved aerodynamics
Whether it’s a pre-war Blower Bentley, a Merlin-powered Supermarine Spitfire or a brand new Kawasaki Ninja H2 there’s no question that forced induction by way of a mechanically-driven supercharger is an effective way to get more performance – and by combining that technology with the latest in electronics and a small, modern motorcycle engine the door could be opened to a generation of bikes that provide more performance with reduced weight and size, all while offering a reduced carbon footprint.
KTM is the latest bike manufacturer to be looking at the idea of supercharging, a new patent application from the company showing a blower powered by both a small electric motor and directly from the engine’s crankshaft to ensure that peak boost is available exactly when it’s needed. It’s a design that appears on the heels of Honda’s proposed V3 E-Compressor engine – shown a year ago at EICMA – and promises the same benefits, with a few more alongside.
The Honda E-Compressor, which is expected to appear in a production bike in the not-too-distant future, addresses the biggest issue that’s stopped supercharging or turbocharging becoming a mainstream motorcycle technology over the last century or so: getting boost at the right time. Exhaust-driven turbos have generally failed on bikes because turbo lag, the delay between opening the throttle and the engine delivering the power you’re asking of it, is much more noticeable on a bike than in a car. Not only are you dealing with a lighter vehicle that’s naturally faster to respond to throttle inputs, but a motorcycle’s hand throttle, rather than the comparatively clumsy foot pedal of a car, means the rider is more acutely aware of how the engine responds. Even a fraction of a second of lag can feel like an eternity.
Superchargers might not lag like turbos, but they still present problems. A centrifugal supercharger, as used on the Kawasaki Ninja H2, needs revs to build up peak boost, while a positive displacement blower like a Roots, screw or scroll-type compressor tends to add more heat and not work as well over a broad RPM range of the sort found in most bikes. The E-Compressor, as proposed by Honda, solves those problems by powering the supercharger using an electric motor rather than the engine, so it can be producing boost even at low RPM and before you open the throttle, maximising its potential.
KTM’s solution is arguably even smarter. It features a scroll-type, positive-displacement blower connected via a belt to the engine’s crankshaft, with the supercharger’s speed multiplied using a planetary gearset so it turns faster than the engine’s revs. But that’s not all. There’s also an electric motor/generator between the supercharger’s input shaft and the compressor, as well as an electrically-operated clutch.
That means the supercharger can be disconnected from the crankshaft at low revs, with the electric motor taking over to spin it faster, building low-end boost and allowing the system to react instantly to throttle inputs. As the engine revs rise, the clutch engages to connect the blower to the crankshaft, so the electric motor isn’t needed anymore and can even switch over to ‘generator’ mode, recharging the small battery used to power the system, all while boost is maintained. The patent includes a chart that illustrates how the supercharger can be spinning at 100,000rpm even when the engine is at idle, rising to 120,000rpm by the time the engine revs hit 8,000rpm, the point at which the ICE takes over driving the supercharger. The chart reveals that maximum engine revs are 12,000rpm, by which time the supercharger is spinning at around 145,000rpm.
The idea of more performance from smaller, lighter engines is an enticing one for motorcycling as a whole, as it introduces the possibility of a virtuous circle – allowing bikes themselves to be made more compact, with the knock-on impact of introducing smaller brakes, lighter suspension components, and more effective aerodynamics.
It’s something that’s been on the radar for White Motorcycle Concepts since our inception. When the patent for our central aerodynamic duct was drawn up, it was initially around a small, forced-induction internal combustion engine, very much like the design that KTM appears to be pursuing in its own new patent applications. We appreciated the benefits that a small, power-dense engine could bring in the form of better aerodynamics and lower weight, but also that one essential element of every motorcycle could not be made smaller: the rider. The introduction of our central duct makes use of the space that a more compact powertrain frees up, slashing drag without forcing the rider into a compromised or uncomfortable crouch, and maximises the aerodynamic potential that the smaller engine introduces.
More recently our work with Pininfarina has illustrated again how a small combustion engine can facilitate the adoption of the WMC duct concept even on an unfaired bike, using the duct itself as a styling feature and a structural chassis component as well as to gain an aerodynamic advantage. The fact that major manufactures like KTM, and of course Honda, are now looking at using downsized, forced-induction combustion engines is an encouraging indication that WMC’s thinking was ahead of the market, and could open substantial opportunities for companies to adopt our aerodynamic duct idea in their future products.