Yamaha FZ16 – The Midship Muffler Article

It looks like Yamaha is very proactive to market the Yamaha FZ16 bike. This article sourced from Yamaha, focusses on educating the customers about the mid-ship muffler of the FZ16. If you want to read my first article, click on Yamaha FZ16 Review. So lets look into what Yamaha says about the bike’s main feature.

With the release of the new Yamaha FZ16, India is going to see a bike with impressive, macho styling never seen before in the Indian market. It’s a machine packed full of new features that will open the eyes of Indian customers like its sporty mid-ship muffler, a sturdy-looking front fork with extra thick 41mm diameter tubes and India first radial tyre on the rear wheel.

For this article we had a chance to talk with the engineers from Japan who worked on this model. Their design and engineering locus on building a bike that would be Fun to Ride. We begin by reporting what they had to say about the distinctive mid-ship muffler.

The first thing most people will notice when they look at the new FZ16 is its mid-ship muffler. The term mid-ship means of course at the middle of the ship, and in this case, means that the muffler is located closer to the machine’s center of gravity. Is it meant to give the bike an impressive and distinctive exterior design? We asked the engineers about its purpose and its actual benefits for the rider.

As you can see, this muffler has a distinctive look that serves to accentuate the presence of rear tyre and contributes to the machine’s unique exterior styling. But, at the same time it designed to improve exhaust performance and to be a major factor contributing to this models light and natural handling feeling. The muffler is one of the heavier components on a motorcycle. What’s more, it is a weight that is usually positioned far away from the engine and off-center to the right or left of the machine’s center of gravity. So, from the standpoint of an deal concentration of mass at the center of the machine, a mid-ship muffler that moves that weight closer to the machine’s center of gravity makes a big difference. Better concentration of mass means a quicker convergence of motion resulting from reaction to forces from the road, which in turn means quicker, lighter handIing.

Is improving the concentration of mass a new design concept? No, It has long been one of our basic design and engineering ideals. At Yamaha, our basic design and engineering approach is to look at the entire machine, including the engine, chassis and all the components, as a single unit and design it with the aim of achieving a ride that provides the ultimate sense of rider-machine unity. And, to achieve this sense of unity with the machine, concentration of mass is an important key. We have tested mid-ship mufflers on our MotoGP race machines and our European models YZF-R6 and FZ1 have mid-ship mufflers, the engineers told us.

Looking at a mid-ship muffler, however, you might think that it has limited capacity and, thus, limited exhaust performance. And as everyone knows, limited exhaust performance means limited engine performance. We asked the Yamaha engineers to tell us more about the product concepts and the development aims.

The YZF R15 and FZ16 were developed with the aim of going beyond the conventional commuter bike and to achieve true sports bike performance that offers the owner the real fun of riding. With the YZF-R we have achieved performance that can be thoroughly enjoyed not only on the streets but on a race circuit as well, As for the FZ16, it takes the same sporty technical concept of the YZF R15 and translates it into a model with simpler air-cooled engine to create an attractive street machine with something extra to offer riders. That something extra is a wider band of powerful torque for truly dynamic performance plus looks the give the added value of pride of ownership.

Both the FZ16 and YZF-R15 have performance features including a balancer, rocker roller arm and offset crankshaft. Also things like optimized piston rings, all for the purpose of improving the three factors that effect engine performance most: intake/exhaust efficiency, combustion efficiency and reducing the horsepower loss. The major factor contributing to an invigorating acceleration feeling and passing performance in a motorcycle is the optimized inertial mass of the crankshaft. The relationship between the inertial mass of the crankshaft and the engine displacement is called the IV ration, arid it is an important factor effecting drivability. That is why concerted efforts were made to optimize the IV ratio on the FZ16 along with optimizing the cap setting. The combined result is acceleration with a good sense of pulse and strong torque characteristics.

So, what does the mid-ship muffler contribute to the FZ16? It is said that you need plenty of exhaust pipe length and muffler capacity. Can this mid-ship muffler really be effective? The exhaust system is made up of the exhaust pipe, the expansion chamber and the muffler. This mid-ship muffler has 20% more capacity than the unit on the Gladiator to provide plenty of silencing effect and performance. The performance of the exhaust pipe is determined by its diameter, length and curves, the effectiveness of the expansion chamber is determined by its volume and shape, while the performance of the muffler depends on the layout of the pipes and the partitions. Also, since a certain amount of exhaust pipe length is necessary to achieve the desired engine performance, a mid-ship muffler has some disadvantages.

For the FZ16, however, an exhaust system with a mid-ship muffler was chosen in order to help achieve the concentration of mass that would contribute to light, sportier handling. And, to ensure performance the exhaust pipe has been given a full 1,500 mm of length, say the Yamaha engineers. And when you look under the bike you will see that the exhaust pipe passes through the expansion chamber once and then forms a loop before entering the chamber again. This is truly a unique and unprecedented innovation for a model with a single-cylinder engine.

The fact is that there is a pressure pulse created in the exhaust pipe by the high pressure exhaust gases released by the exhaust valve. This rush of pressurized gas reflects back from the end of the exhaust pipe and returns toward the exhaust valve with diminishing strength. The rhythm of this exhaust pressure pulse depends on the length of the exhaust pipe. And, as you know, with a 4-stroke engine there is an overlap in the opening interval of the intake and exhaust valves when both valves are open.

The exhaust system on this model has been designed to use the expansion chamber to minimize the effect of this pulse over a wide rpm range. This increases the intake efficiency, and that ensures plenty of torque over a broad range from low to high speeds, say the engineers. With the combined effects of the 1500mm exhaust pipe and an innovative expansion chamber design, the mid-ship muffler of the Yamaha FZ16 is a part of an exhaust system that contributes to outstanding combustion efficiency.

There are also many measures to ensure greater reliability in the engine. A centrifugal cast Aluminum cylinder has been adopted for the first time on a Yamaha engine. This production method involves making the cast iron sleeve by the centrifugal casting method in order to give it a surface with slight indentations and protrusions that greatly improves the tightness of the fit between the sleeve and the Aluminum cylinder.

The tighter, more complete fit provides excellent heat dissipation. Another thing we did to contribute to improved cooling effect besides simply increasing the size of the cooling fins was to design a package that directs the running air flow so it cools the engine more effectively. This package includes an air scoop which is used to direct air flow more effectively at the cylinder head, the Yamaha Ram-Air Cooling System (YRCS) that sends cooling air to the spark plug area, plus other measures, they say.

In other words, this engine and the mid-ship muffler it is mounted with give this model three strong benefits. The engine is designed to provide plenty of torque from low speeds all the way up to the high-speed range, and the mid-ship muffler improves the concentration of mass to help provide a very high level of handling stability while also giving the bike a very distinctive appearance. There are also several other measures taken in this model’s design to improve the concentration of mass, including adoption of air cooling, adoption of a 20-degree forward-inclined cylinder (25-degree on the Gladiator), adoption of lightweight wheels, lightweight radial tyre, Aluminum handlebar crown, lightweight headlight, plastic resign chain cover and the adoption of a Monocross suspension. ln the next article we will focus on the radial tyre.

I hope you enjoyed the article. It seems the next article will be about the radial tyres of Yamaha FZ16. Will keep you posted. Article, courtesy of Yamaha.

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