Suzuki applies for a patent for VVT system for light parallel twin

While variable valve timing and lift systems are widely used in the automotive industry, this is highly exceptional in motorcycles. Suzuki has now applied for a patent for a VVT system, which goes far beyond the system of the last generation GSX-R1000.

Variable valve timing on motorcycles has been a thing for a long time since the VFR800 VTEC. The first generation was anything but perfect due to the very abrupt transition zone. With the second generation the wrinkles were ironed out, but the negative image remained attached to VTEC for a long time.

Although still not commonplace, variable valve timing is now increasingly used. BMW used Shiftcam for the first time on the S 1000 RR, Ducati provided the Multistada 1200 with VVT, Kawasaki had a system on the 1400 GTR, while Suzuki also applied variable valve timing for the first time on the 2017 GSX-R1000.

The GSX-R1000’s system uses an unusual all-mechanical camshaft system that relies on centrifugal force to change valve timing as the engine speed increases. It’s a design the company came up with to get around MotoGP rules that ban electronic and hydraulic VVT.

However, Suzuki has also applied for a patent in the past for a more conventional hydraulic system, which would be used in future versions of the Hayabusa, using the same kind of technology as already used by Ducati, among others.

But the aforementioned VVT systems only change the valve timing, by turning the camshaft a few degrees forward or backward, so the benefits are only limited. With more advanced VVT systems, the lift height and lift duration can also be adjusted by switching between two different ridge profiles. BMW’s Shiftcam is one such advanced system.

At the lower end of the market, variable timing and lift systems are also used sporadically, such as Yamaha’s VVA system used on the latest MT-125 and YZF-R125. VVA uses two-piece rocker arms to operate the intake valves, and it’s this design that Suzuki is now working on for a new small parallel twin.

The basic principles of the idea are already well proven in production. The single camshaft has three profiles for each cylinder: one exhaust and two different intakes, one with high lift and long opening duration, the other with low lift and short opening duration.

Either one or the other profile is active via the two-part rocker arm. Oil pressure inserts a steel pin that joins both halves of the rocker arm together when the more extreme profile is needed, then retracts it to return to the milder profile.

Suzuki’s new patent goes into the details of the system and how the pin is operated, with the aim of reducing wear and making it more compact than other designs, but it is essentially the same setup that Yamaha’s VVA engines use.

What the patent shows is that Suzuki is actively developing this type of variable valve timing and lift system, and that it was developed with the 248cc parallel twin in mind. The illustrations show the engine block, which has been used in various models over the years, such as the GW250 Inazuma, the V-Strom 250 and the GSX250R.

The bottom end is unchanged and the cylinder head still features a single camshaft, with central chain drive between the two cylinders, but now with the addition of the VVT ​​system.

The same engine design is also used in 298cc form in several models made by Suzuki’s Chinese partner company, Haojue, which is also responsible for producing the V-Strom 250 and GSX250R for Suzuki.

Currently, the 250 models are no longer sold in Europe due to stricter emissions requirements, but given the enormous growth of the A2 segment, it could certainly be a welcome addition.

– Thanks for information from Motorfreaks.

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