Latest patent images reveal that Yamaha may be working on a turbo-charged parallel-twin. While patent applications don't always mean that the technology referred to may reach production, these certainly indicate that Yamaha has spent time and resources on developing a turbo-charged engine for a future model. The patent images reveal the outline of a bike which resembles the Yamaha MT-09, which has a three-cylinder 847 cc, engine, but then the concept in the patents actually is based around a smaller, two-cylinder engine design. And if it's indeed a MT-09 design with one less cylinder, that would put its displacement around 565 cc, smaller than the MT-07's 689 cc engine, but the reduced engine size probably allows space for the piping and turbocharging equipment.
The patent images reveal two distinct layouts of the forced induction motorcycle engine. The first design shows the exhaust headers from two cylinders merging into one shortly after exiting the head, and channeling the gas into a turbocharger mounted low down in front of the cylinders. The second design shows the turbocharger mounted higher up, in front of the cylinder head. The exhaust headers are shorter and feed straight to the turbo. The second layout seems to allow more space for a catalytic converter to be mounted almost vertically ahead of the cylinders rather than underneath the engine. On both the designs, the compressed air from the turbocharger is fed through a water-cooled intercooler before it's fed into the cylinders.
For several years now, manufacturers have been toying with the concept of introducing forced induction engines on motorcycles, as they grapple with challenges of increasing performance while facing ever tightening emission restrictions. Kawasaki has already introduced supercharged engines in the H2 models, while Suzuki has also been toying with the idea of a forced-induction engine for some time now, on the 2013 Suzuki Recursion concept. Now, Yamaha seems to be following a similar path with the patent application images for a turbo-charged engine. All that remains to be seen is when we get to see a production model.