Yamaha Turbo Triple Project Forges Ahead

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New patents show Yamaha is still heavily involved in its turbocharged triple-cylinder bike project. ( Japanese Patent Office/)

Last year we revealed Yamaha’s turbocharged three-cylinder development project, which featured a machine that’s already reached prototype stage and is helping to develop new ways improving performance, lowering emissions, and helping fuel economy while eliminating the traditional problems of boosted bikes. Now the firm has filed another tranche of patents that give further insight into the thinking behind a design that might well be the template for the next generation of high-performance motorcycles.

The new filings give more detail as to the positioning of the turbocharger, intercooler, and radiator. (Japanese Patent Office/)

To recap, Yamaha confirmed the existence of the project last November, unveiling a prototype that used an MT-10-derived chassis and featured a completely new 847cc, turbocharged three-cylinder engine with direct fuel injection and variable valve timing on both the intake and exhaust camshafts. Despite sharing the same capacity as the MT-09, the engine has vastly different undersquare dimensions—with a 73mm stroke and 67.5mm bore—creating a low-revving, torque-focused motor that hits its 180 hp peak at just 8,500 rpm. More impressive still is the engine’s torque figure of 130 pound-feet, which plateaus from 3,000 to 7,000 rpm. All this is achieved with a 30 percent reduction in CO2 compared with similarly powerful, normally aspirated engines, while NOx and hydrocarbon emissions are at less than 50 percent of the maximums allowed under the latest Euro 5 emissions rules.

The radiator’s unusual location—forward and closer to the ground—takes mass centralization to another level. It even has chamfered corners to aid in ground clearance. (Japanese Patent Office/)

The latest Yamaha patents for the bike focus on a selection of detailed elements of the design, such as the positioning of the turbocharger itself, the intercooler, and the water radiator to package a nearly 1,000cc turbo engine into a machine no larger than a normally aspirated literbike.

By using the existing MT-10 chassis as its starting point, Yamaha had a fixed set of dimensions to work within, but it also had extra components to fit within those boundaries. In the original story last November we pointed out that the prototype’s radiator appeared to be unusually close to the ground as a result of needing to fit the turbo and intercooler into its normal space behind the front wheel. Yamaha’s new patents point out that it’s a feature rather than a glitch, and that the repositioned radiator is intended to allow the wheelbase to be shortened despite the extra parts fitted in its place.

The turbo and intercooler are placed to optimize airflow and reduce turbo lag. (Japanese Patent Office/)

In a side view of the design, the radiator—low down in front of the engine—overlaps with the front wheel. It’s curved to allow either side to sit further forward than the rear edge of the front tire, and compared to a conventional bike, it’s clear this space is usually empty. It shows Yamaha pushing the boundaries of the “mass centralization” concept by fitting even more between the front and rear wheels of the bike.

Angling the radiator to lean it backward means it can be mounted close to the wheel yet still allow the front suspension to compress, while the chamfered lower front corners of the radiator—seen in the front-on view in the patent—allow it to stay clear of the ground even at high angles of lean. By moving the radiator into what’s normally “dead” space on most bikes, Yamaha has effectively cleared room for the turbocharger and intercooler to sit in that previously occupied spot.

Why put the radiator here instead of the smaller intercooler? There are two reasons. One is that airflow from the turbo to the engine needs to pass through the intercooler, and having it go the shortest route possible will help reduce turbo lag, which is one the development team’s key targets. Second, the pipework for the air to run through is much thicker than the water hoses connected to the radiator, so making those pipes any longer vastly increases the overall volume they take up.

Side view shows just how close the backward-angled radiator is positioned to the front wheel, thus opening up space for the other components. ( Japanese Patent Office/)

The vital aspect of throttle response—and the effort to eliminate the turbo lag that dogged the short-lived forced-induction bikes of the mid-1980s—is also addressed by another of Yamaha’s patents. That filing details how the use of a single, large throttle valve leading to a three-way intake manifold improved throttle response when compared to a more conventional system of using individual throttles for each cylinder.

One of the new patents details how during roll-on throttle tests at 3,200 rpm (effectively “off-boost”) with the turbo’s wastegate fixed fully open and the variable valve timing locked, the single-throttle system with relatively long intake runners offered significantly improved response compared to more conventional design with less throttle area and shorter intakes.

Although these patents don’t provide incontrovertible evidence that a turbocharged production bike from Yamaha is imminent, the level of effort going into the project and the seemingly impressive results being achieved mean it’s looking increasingly likely that it will influence future showroom offerings.

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