Suzuki prepping VVT Hayabusa: System could boost bike’s 187bhp and safeguard against new emissions regs

Suzuki’s R&D department have filed a flurry of patent applications showing a variable valve timing system specifically aimed at the Hayabusa hyper bike – suggesting that even as the Busa hits its 25th anniversary the firm are looking to extend its life while adding even more performance.

Although it won’t be the first bike from the firm to get VVT – that honour goes to the Suzuki GSX-R1000, which gained an oddball, all-mechanical valve-phasing system in 2017 – the new patents specifically relate to the Hayabusa and show a more adaptable, electronically-controlled, hydraulic means to alter the intake cam timing.

It’s a system that should be able to reduce the Hayabusa’s emissions and improve its economy, while simultaneously clawing back the power that was sacrificed when the bike was last revamped and brought into line with Euro5 emissions rules.

The actual VVT system is quite conventional. It features a hydraulic cam phaser on the end of the intake camshaft, between the sprocket and the camshaft itself, that can rotate the camshaft by a few degrees in relation to the sprocket to advance or retard the intake valve timing.

Like many other cam-phasing VVT systems, particularly those used by Ducati and the system on Kawasaki’s old GTR1400, the camshaft is moved in relation to the sprocket using engine oil pressure, controlled by an electronic solenoid. A similar idea has been used on many cars for decades.

Although the GSX-R1000’s mechanical VVT system also changes the intake cam timing by rotating it in relation to the sprocket, it’s aimed at increasing performance rather than giving a substantial improvement in emissions – as witnessed by the fact the GSX-R1000 has now been taken off the market throughout Europe, unable to meet Euro5 limits.

Its system uses metal balls in slightly misaligned radial channels carved into the two halves of the cam phaser – as the camshaft spins faster, the balls are flung outwards by centrifugal force, causing the intake cam timing to be retarded. At lower engine speeds, a spring returns the balls to the centre, advancing the timing.

It’s a solution that sprung from Suzuki’s now-cancelled MotoGP project, because hydraulic and electronic VVT is banned in MotoGP, but it’s less adaptable than the hydraulic kit being developed for the Busa.

With an electric actuator controlling the oil flow to the cam phaser, under the command of the bike’s engine management, the hydraulic VVT can advance and retard the valve timing independently of engine speed, tailoring it to meet the specific demands of emissions rules.

It’s possible, for instance, that the intake timing will be retarded at low revs and low throttle openings, reducing the valve overlap (the period when the intake valves open before the exhaust valves have closed) and helping to prevent unburned fuel entering the exhaust.

On opening the throttle, though, the timing could be advanced to improve torque, before being retarded again at high engine rpm to keep the intake valve open later. All options are open when the VVT is electronically controlled.

Since this is all established tech, particularly in cars, you might wonder what the Suzuki patent applications target. The answer is they’re specific to the positioning of the VVT actuator and the oil channels between it and the cam phaser, which have been cleverly designed to minimise the impact on other elements of the bike’s design.

Suzuki Hayabusa VVT engine – what we know so far

• All about timing: The Suzuki set-up uses an electric actuator to divert oil pressure to four chambers inside the sprocket half of the cam-phaser, each containing vanes that are connected to the camshaft half of the phaser. Direct oil to one side of the vanes and the timing advances, switch the oil pressure to the other side of the vanes and it retards.
• Clever design keeps it neat: Seen from the front, the repositioned actuator, despite being an external addition to an existing engine rather than designed in from day one, doesn’t add any more width to the bike.
• Same bottom end: Oil channels inside the cylinder walls and the cylinder head take the oil to the cam phaser, so those parts need to be changed, but there’s an external pipe taking oil from the oil pump to the actuator, so the engine’s bottom end doesn’t need to be revised.
• No frame mods needed: Normally, the solenoid-based actuator would be mounted on the cylinder head, near the phaser, but Suzuki have shifted it down onto the side of the cylinder. That means there’s no need to modify the Hayabusa’s frame, saving lots of R&D expense.
• Reliability is built-in: Mounting the actuator lower down reduces the vibration it’s subjected to, according to Suzuki’s patents, improving its reliability. The design is also claimed to make the actuator less susceptible to damage if the bike is dropped.