Blowing hot air: Yamaha set to fit turbos across their range

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Yamaha are working on turbocharging for their next range of bikes. This isn’t Yamaha’s first use of the tech as they briefly made an XJ650 Turbo in the early ’80s, however this new system is completely different. So, what exactly is a turbo?

Turbocharging is a forced induction method that uses the engine’s own exhaust gases to force pressurised charge into the combustion chamber. As waste gas passes through the exhaust it spins a turbine at incredibly high speeds – in some cases up to 160,000rpm. This turbine turns a compressor that sucks in air and compresses it before it enters the combustion chamber.

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This increase in pressure enables more fuel and oxygen to be forced into the engine, increasing its explosive power and thus power output. It’s a similar principle to supercharging, as on Kawasaki’s H2, and was originally known as a turbosupercharger; the difference is a supercharger is mechanically driven by the crank, whereas a turbocharger uses the exhaust-driven turbine.

Yamaha filed a patent for a turbocharged bike three years ago. The wastegate (a valve to direct gas away from the turbine to regulate its speed and protect the engine) was an internal type, mounted in the turbo’s housing, and they had two ideas: one locating the turbo within the exhaust, and another where the turbo is incredibly close to the exhaust headers. The latter is the more common application, seen in most modern car engines. 

This is the one Yamaha appear to have used – it means the turbo sees exhaust gas at its highest speed and also leaves room for the essential catalytic convertors. The main  downside is additional heat, which is already a problem with turbos as compressing the air makes it hot – and engines prefer cool, dense air. Yamaha appear to have used an intercooler (a radiator-style heat exchanger) to chill the intake air.

What are the benefits of a turbo?

Turbo cutaway

A turbo typically increases pressure by six to eight pounds-per-square inch (psi), and atmospheric pressure is 14.7psi. That’s an increase of 50% or so. You don’t get 50% more power as there are inefficiencies – the engine has to work harder to push gas out through the turbo, for example – and often the engine will need a lower compression ratio.

However, adding a turbo to an MT-10 could give a 30-40% power boost, taking the 998cc motor from 155bhp to around 200bhp. Enough to rival Kawasaki’s Z H2.

Developing turbos could have financial benefits. To make the new R1 with all its extra catalytic converters create the same power as the outgoing model, Yamaha did a lot of work to the engine. In the future it’s likely they will need to look at variable valve timing, too. However, a turbo on the existing engine could hold back the need for these updates.

There’s also the possibility of sharing this tech across their range. Yamaha’s patent was for a parallel twin based on the MT-09 engine. Lopping a cylinder off the 847cc triple gives a 560cc twin which, when turbocharged, could produce similar power. It would be smaller and lighter, and the reduced capacity could help meet emission targets.

For the time being Yamaha are tight lipped on their use of the tech, but we could see it on a new model later this year if the current Euro5 deadline remains unchanged in the wake of Covid-19.