TOKYO, Japan, September 26, 2011 - Honda Motor Co., Ltd. has announced the development of a new motorcycle engine with powerful torque in the low- to mid-speed range and top class, fuel-efficient environment performance, along with a second-generation Dual Clutch Transmission. This new engine is a liquid-cooled, 700cc, 4-stroke, in-line, 2-cylinder engine that fits into the mid-class range (displacement between 500 and 750cc) popular in Europe. Fuel economy exceeds 27km/L,*1 best in the mid-class range, and achieves an approximate 40%*2
Newly developed 700cc engine
(Second-generation Dual Clutch Transmission)
Newly developed 700cc engine
(6-speed transmission)
Uniaxial primary balancer Diagrams
The piston uses vertical motion and the crank uses rotary motion. Furthermore, the rotational force working on the crank allows it to move laterally, which generates lateral vibration.
Even if the vibration generated through vertical motion of the piston is cancelled by the crank motion, the lateral vibration of the rotating crank remains. Therefore, a balancer that partitions the crank mass in two is set and rotated in the opposite direction, thus canceling out the lateral vibration of the crank.
In order to achieve a "ride to suit mature tastes," in addition to the combination of a 270º phase crank and uniaxial primary balancer, the team altered the intake-port layout inside the cylinder head to produce precisely calculated combustion timing variations. In-line, 2-cylinder engines have two air intake channels that are adjacent but designed to act independently so that neither channel interferes with the air intake process of the other. In this engine, however, the air intake processes have been intentionally designed to interfere with each other to generate subtle combustion variations, resulting in the "mature taste" called for by the development concept.
This idea of consolidated intake ports inside the cylinder head presented many challenges for the manufacturing process. In particular, how to solve the issue of distortion in the shape of the left and right ports that results from uneven cooling of molten aluminum due to the thickness of the metal around the two "consolidated" ports. Manufacturing precision to eliminate distortion was secured through exhaustive calculation and by adding cooling analysis to cutting-edge CAE mold flow analysis.
To facilitate a subtle interference in air intake volumes and enhance a "ride to suit mature tastes," the optimal open and close timing of the inlet valve is set separately for each cylinder. In-line, multi-cylinder engines do not usually have their valve timing set separately, but the manufacture of different camshafts that change the valve timing for each cylinder does not significantly increase the workload in the machining process of 2-cylinder V-engines with a dedicated camshaft for each cylinder.
In this engine, two kinds of inlet valve timing have been set up for the cam in order to change the reciprocal in-line 2-cylinder valve timing on each camshaft. As explained above, setting up two kinds of inlet valve timing for one camshaft does not create a manufacturing problem. But it does lead to a cost increase because it requires a process that is not normally performed.
Therefore, in order to manufacture the camshaft at an optimal price, various issues including those surrounding cost were successfully resolved by referring to a variety of manufacturing methods, such as those employed in automobiles with a multiple-valve-timing cam and one camshaft.
Honda referred to automobile engine combustion technology, with its complementary focus on the low and middle rpm ranges, to improve fuel efficiency but still deliver a powerful ride through surer combustion. In engines where the aim is to boost output, it has been common practice to prioritize intake efficiency in the high rpm range. In our engine, however, where the non-conventional emphasis was on the low and middle rpm ranges, we focused on low- and mid-range rpm combustion efficiency instead of high-rpm intake efficiency. The result was ɸ73X80mm bore and stroke.
Sure and stable combustion in the low and middle rpm ranges was achieved by marrying this ideal bore and stroke combination with an ideal shape for the combustion chamber and optimal valve timing. Furthermore, core research into idle combustion using a similar engine with the same level of displacement accumulated the basic data required to achieve stable stoichiometric (theoretical air-fuel ratio) combustion. Effecting stoichiometric combustion from idle rpm was a significant contributory factor to the engine's superlative fuel efficiency.
INTEGRA,vehicle equipped with new engine to be unveiled at EICMA 2011 (equipped with options)
improvement over other sports models in its class.
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