Suzuki’s Parallel-Twin Engine Development Gets New Twist

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Remember the Recursion concept from way back in 2013? Suzuki may still be pursuing the parallel-twin engine design seen in that bike for future models. (Suzuki/)

The drawn-out saga of Suzuki’s efforts to develop a new 700cc parallel twin that will form the basis of next-generation replacements for the SV650 and V-Strom 650 has taken its next step with the publication of a patent that gives a glimpse of another new machine that’s being created around the same engine.

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A new patent shows an SV650-style machine built around a DOHC 700cc engine design. (Japanese Patent Office/)

Parallel twins have been a clear trend in new middleweight bikes over the last few years. Yamaha’s 700cc MT-07, Tracer 7, R7, and Ténéré 700 show how versatile such a platform can be, and we’ve already seen Aprilia follow suit with the RS 660, Tuono 660, and Tuareg 660. Honda is on the bandwagon too, creating the Africa Twin, Rebel 1100, and upcoming NT1100 sport-tourer around its 1,084cc parallel twin, and BMW has opted for the same solution with the F 750 and F 850 GS, the F 900 R, and the F 900 XR. Meanwhile, Kawasaki has always preferred parallel twins, most recently with the Ninja 650, Z650, Versys 650, and now the Z650RS, while KTM has a growing range of parallel twins courtesy of its LC8c engine, used in the 890 Duke and Adventure models.

Related: Is Suzuki Working on a New V-Strom 650?

The normally aspirated engine design locates the airbox under the rider’s seat, where it can also support the battery. (Japanese Patent Office/)

The appeal of the parallel twin is that it offers a cheaper, more compact alternative to both the V-twin layout that Suzuki currently favors with the midsized SV650 and Versys 650, and to the inline four-cylinder alternative. There are fewer components overall, and when compared to V-twins it’s simpler to package the bike, with no rear cylinder to add complexity to things like exhaust routing, cooling, and rear suspension design.

The traditional downsides of the parallel twin—an uninspiring soundtrack and flat power delivery—are easily countered by using a 270-degree crankshaft to give a firing interval that matches a 90-degree V-twin’s. BMW’s F 900 models, Honda’s Africa Twin and NC750-based machines, Triumph’s twins, Yamaha’s 700s, and Aprilia’s 660s all opt for the 270-degree crank for a V-twin-like power delivery and sound. KTM’s LC8c has a 285-degree crank, mimicking a 75-degree V-twin.

Related: Suzuki Parallel Twin Revealed In Patent

That location allows more room for the fuel tank as well, though air intakes would now face rearward. (Japanese Patent Office/)

Suzuki first hinted at its new parallel twin way back in 2013, showing the Recursion concept bike as a turbocharged SOHC parallel twin with a capacity of 588cc. By 2015 the company had rethought that idea, showing its XE7 turbocharged parallel-twin engine—a DOHC design of around 700cc—and it’s this project that has since been pursued by the firm’s R&D department.

Most recently we’ve seen a couple of patents for normally aspirated versions of the engine, and now another has been published that gives a clear look at an SV650-style machine built around the motor.

The latest patent differs from previous ones, showing an unusual arrangement of the airbox to stop it from intruding into the fuel tank area. In previous designs for both the turbocharged and normally aspirated versions of the new engine, the airbox sat above the cylinder head, under the tank, with an intercooler alongside it on the turbo bike. That allowed a very direct route for the air pipework on the turbo version, but clearly restricted the potential size of the tank.

Related: Suzuki Parallel Twin Developing Fast

The engine design is similar to that of Suzuki’s XE7 from 2015, though the new patents show a normally aspirated version. (Suzuki/)

The new design is based around an airbox placed in a new position under the rider’s seat, where it does double duty by also providing a platform for the bike’s battery. Unusually, the layout means that the air intakes face rearward, eliminating any potential “ram air” effect, but the patent points out that the sacrifice is worthwhile as it allows the airbox to be much larger than it would be if mounted under the fuel tank, potentially giving a greater performance advantage than ram air would allow.

With an increasing focus on serviceability, particularly among budget-priced bikes where maintenance costs can be a deal breaker, the underseat airbox design also allows for the air filter to be swapped without removing the tank.

At this stage, with the Suzuki parallel-twin project having been under development for the best part of a decade and still not showing a production version, it’s still unclear how soon we’ll see the engine in showrooms or which bike it will appear in first, though an SV650 replacement seems the most likely initial destination, with adventure bikes and even a full GSX-R-branded sport model potentially following it.

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