Posted 18 June - Expensive indeed! They were selling cc V4 oval street legal bike in Japan. Posted 18 June - NR, that must be it! I don't know why I thought it was the NC30, that must be something else Honda made.
Posted 19 June - Maybe there are benefits in the combusion chamber that help the combustion process, or greater control of the gasflow to benefit combustion. Posted 19 June - There is some inexplicable fascination out there with the Honda NR engines.
Like the Tyrell six-wheeler, they keep popping up on F1 fora. I maintain that the engine and it's derivatives were nothing more than a half-clever workaround of the FIM's 4-cylinder max for the GP class.
Fun and exotic, yes absolutely. But there is nothing inherently superior about non-cylindrical cylinders. Posted 19 June - So true Desmo. If Honda had their druthers they would have built a V6 or V8 to achieve the short stroke and valve area they needed. But because the rules limited them to 4 cylinders they siamesed the cylinders together and in effect produced a 4 cylinder V8. Posted 19 June - I have to agree that it would have been a tricky thing because the piston rings for instance would have been very difficult to make for it.
Posted 19 June - Don't oval shapes have more surface than round ones and therefore cause more ware? Posted 20 June - As far as the regualtions were concetrned, when Honda ran the bike like-for-like, i. I think it was the Bol D'Or endurance race, but I'm not sure. As for wear, if the loads are similar, for more surface area, the pressure is decreased.
Therefore, I would expect wear would be less. Also, the likelihood of gross and total mechanical seizure would be less. The main reason for its ban is its reliability. It is un reliable though its power is high. Also many valves have to be fitted in one cylinder, Firing should be uniform enough in all sparks of same engine.
The reason for its failure in commercial purpose is its cost. It cost a huge to manufacture this type of engine. Also the surface is not cylindrical so there will be uneven stress throughout the oval surface. Another major challenge in this is the manufacturing of piston rings for this type.
At full throttle and rpm, a piston in a gasoline engine is subjected to nearly 10 tons of force every 0. As automakers chase higher efficiency, piston manufacturers are preparing for a future in which the most-potent naturally aspirated gasoline engines produce horsepower per liter, up from today.
With turbocharging and increased outputs come even tougher conditions. In the past decade, piston operating temperatures have climbed degrees, while peak cylinder pressures have swollen from psi to A piston tells a story about the engine in which it resides. The crown can reveal the bore, the number of valves, and whether or not the fuel is directly injected into the cylinder. To coin a maxim: As the automobile goes, so goes the engine; and as the engine goes, so goes the piston.
In the quest for improved fuel economy and lower emissions, automakers are asking for lighter, lower-friction pistons with the stamina to endure tougher operating conditions. In many ways, gasoline-engine development is following the path laid out by diesels 15 years ago. To compensate for the percent increase in peak cylinder pressures, some aluminum pistons now have an iron or steel insert to support the top ring. The squirters shoot oil into a small opening on the bottom of the piston that feeds the gallery.
Creating a hollow passage means casting the piston as two pieces and joining them via friction or laser welding. Friction-reducing, graphite-impregnated resin patches screen-printed onto the skirt are now nearly universal.
Piston supplier Federal-Mogul is experimenting with a tapered face on the oil ring that allows a reduction in the ring tension without increasing oil consumption. The piston pin area is subject to more thermal expansion than other areas of the piston. This occurs from the thermal expansion properties of cast aluminum alloy and the mass in the piston pin area. Some pistons are cast and machined at the factory into a cam ground elliptical shape.
An elliptical shape is an oval shape in which one-half is a mirror image of the other half. These piston shapes provide an advantage in conforming to the ever-changing dimensions of the cylinder bore.
The piston is designed to be an elliptical shape when cold. As the engine reaches operating temperature, the piston pin bore area expands more than other thinner areas of the piston. At operating temperature, the piston shape becomes a circular shape, which matches the cylinder bore for improved sealing and combustion efficiency.
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