There’s an intrinsic connection between the shape and size of a motorcycle’s powertrain and the bike’s aerodynamic possibilities and recent developments in powertrain tech mean there’s a growing need for innovation in aero to maximise the potential – and the companies that get it right will reap big rewards.
Whether we’re talking about electric motorcycles, future ICE tech like downsized engines and forced induction, or even hybrids, the old conventions of the size, shape and positioning of the powertrain don’t necessarily apply anymore. In some instances the new power units offer opportunities – smaller engines or compact electric motors give more freedom to exploit aero possibilities – in others they’re a hindrance, with additional components and cooling requirements to consider even when the engine or motor itself is more power-dense than earlier designs. In either situation, finding the right packaging solution to balance powertrain and aero performance could be the difference between success and failure.
We can look to history for examples, and Formula 1 is littered with illustrations of successes and failures when it comes to making the powertrain the right shape and size to suit aerodynamic needs. Starting at the dawn of the 1970s when wings really started to come to the forefront, Ferrari’s F1 cars perfectly illustrated how aero and powertrains can be tightly connected. The 1970 312B, for example, replaced Ferrari’s traditional V12 layout for a flat-12, both for a lower centre of gravity and to give a lower profile at the rear of the car so the wing – limited in height by rules introduced the previous year – was exposed to cleaner airflow. But that advantage became a drawback later in the decade as teams followed the lead of Lotus and exploited ground effect, using tunnels under the floors to create low pressure and suck the cars to the tarmac. Suddenly the wide, low flat-12 engines were a hindrance, taking up space that would be better used for underfloor aero and giving the advantage to cars with V-shaped engines.
With more downforce making it possible to exploit higher levels of power, and a tangible advantage to having smaller engines, aero advantages were a key reason behind the adoption of the 1.5 litre turbocharged engines that dominated the 1980s, and McLaren’s Porsche-made TAG V6 turbos were dominant in the middle of that decade having been developed with aerodynamics firmly in mind. In fact, that project was intended to maximise ground effects, with a V6 layout and horizontal exhausts to allow the largest possible underfloor tunnels, but by the time the engines were ready the ground effect era had ended, with F1 imposing flat floor regulations in 1983. Even so, the TAG engine’s narrow-bottomed design was a key reason to a carbon fibre chassis, compensating for the lost torsional rigidity from the structural engine, and its compact dimensions helped give a narrow rear end, taking TAG-powered McLarens to the drivers’ title in 1984, 85 and 86.
Other examples of powertrains assisting aero improvements include the adoption of paddle-shift transmissions, first by Ferrari in 1989, that allowed narrower cockpits by eliminating the gear lever, and slimmer rear ends thanks to the lack of a gear linkage. And more recently Mercedes’ split turbo V6 engines, introduced for the modern turbo era that started in 2014, allowed more compact packing and a smaller intercooler by moving the compressor away from the hot exhaust-driven turbine.
Of course, there are also examples of going too far. Brabham’s attempt to introduced surface cooling via panels on the bodywork instead of conventional radiators with the BT46 in 1978, led to overheating and a compromised car when radiators had to be reintroduced. More recently, McLaren’s attempt to repeat the ‘purpose-made’ powertrain idea that worked so well in the 1980s backfired with its 2015 tie-in with Honda. The resulting engine was impressively small, allowing for ‘size-zero’ bodywork at the back of the car, but the aerodynamic upside didn’t compensate for the compromises in the powertrain.
In motorcycles, the current blanket use of V4 engines in MotoGP is largely down to the powertrain packaging and aero advantage it brings. V4s are narrower than inline fours, and with regulatory limits on the width of bodywork that means it more scope for aerodynamic addenda. At the start of the modern four-stroke era Honda’s dominant RC213V V5 had a similar aero advantage – narrower than an inline four despite an extra cylinder, but more powerful than rival V4s, it was the ideal compromise at the time.
Turning to modern road bikes, the focus on powertrain layouts and density is increasingly clear as companies wrestle with new technologies. Kawasaki, for example, has filed multiple patent applications in recent months showing different layouts for its hybrid models, which combine a 451cc parallel twin with an electric motor and small lithium-ion battery for circa-700cc levels of performance. The extra components – essentially two separate powertrains – make packaging a challenge, and the brand’s patents explore different positions for the batteries, airboxes and fuel tanks to tackle that issue.
Honda’s V3R E-Compressor, without doubt one of the most anticipated new bikes to be due in 2027, has its own aero and packaging issues to combat. The addition of an electric supercharger to a 900cc, 75-degree V3 engine promises performance on a par with a 1200cc four-cylinder bike, but the supercharger and plenum above the engine leave no space for an airbox or air filter in their usual spot. The solution? Honda has shifted the whole airbox outside the bike’s chassis and bodywork, into a bulbous lump on the righthand side of the steering head. Patents as far back as 2020 show the company explored a similar idea for a proposed supercharged version of the two-cylinder Africa Twin. If the V3R achieves showroom success to match the interest shown in the project before its launch, it’s going to open the floodgates to more supercharged machines with downsized engines, and we’ll be looking with interest at the aerodynamic problems and solutions that come from the technological shift.
