According to Honda Press release, Honda has developed a new 700cc engine for motorcycles. The engine has features like 700cc displacement with bore x stroke of 73mm x 80 mm, liquid cooled, 4-stroke in-line two cylinders and second generation Dual Clutch Transmission. The engine has powerful torque in low to mid speed range with top class fuel efficiency that too in most environment friendly manner. Honda claims fuel economy of 27 kilometer per liter (WMTC mode) which is best in 500 and 750cc engines. The engine also claims 40% improvement (according to Honda calculation) in terms of performance compare to other sports model in its class.
This new engine will see its way on three different models based on different concepts which will be showcased in exhibition at EICMA 2011 to be held in November in Milan, Italy. The engine has two types of transmission, a six speed manual transmission and 2nd generation Dual Clutch Transmission. A first generation Dual Clutch Transmission was introduced on Honda’s Flagship model VFR1200F.
Honda claims that the second generation Dual clutch Transmission to be more compact, lightweight and fuel efficient.
The Honda press release has following main features of the new 700cc engine.
1. Higher combustion efficiency and lower friction
A wide variety of low friction technologies that aid better fuel economy are incorporated: To improve fuel efficiency through better-controlled combustion while realizing a powerful ride in the low- to mid-rpm ranges, the bore-stroke ratio is set at 73×80mm. An ideal combustion chamber shape and optimum valve timing also contribute to achieve stable combustion. Resin coating is applied to the pistons, and lightweight aluminum material is employed for the first time in a motorcycle in the friction-reducing roller rocker arm.
2. Uneven-interval firing and uniaxial primary balancer
Adoption of uneven-interval firing with a 270° phase crank and uniaxial primary balancer help realize an engine with a pleasant throbbing feel that also reduces vibration.
3. Branch intake port inside the cylinder head, valve timing
The layout of a branch intake port inside the cylinder head was chosen to have only one intake channel for two cylinders. This design creates deliberate interference between the two cylinders’ intake processes to achieve precisely calculated changes to combustion timing.
In addition, to change the valve timing between the two in-line cylinders with one camshaft, the specifications provide for a cam with two timing routines for the intake valve. Through these measures, subtle combustion changes can be generated to give the engine a delightful, pulsating feel.
4. Exhaust emission purification system
To maximize the efficiency of exhaust emission purification so that the catalyzer, a three-way catalyst, can be started promptly after the engine starts, the catalyzer has been placed directly beneath the exhaust ports. This design lets the combustion gas pass through the catalyst while the gas is still hot. In addition, a combination of measures, including the adoption of an electronically-controlled fuel injection system (PGM-FI)*3 allows the engine to achieve an emission level approximately half the European emission standards (Euro 3)*4 . The resulting environmental performance is ranked among the top in the world without compromising powerful, smooth output.
*3 PGM-FI (Programmed Fuel Injection System) is a Honda registered trademark
*4 Honda calculations
5. Second-generation Dual Clutch Transmission
The Dual Clutch Transmission, developed for the first time by Honda for motorcycles and installed on the VFR1200F, is now lighter and more compact through a simplified hydraulic circuit and other design enhancements. A learning function has been added to each selected running mode to detect a variety of riding environments from city streets to mountain passes and automatically performs the most suitable shift control. Although it is an automatic transmission, the Dual Clutch Transmission delivers fuel economy on a par with manual transmissions as a result of its excellent transmission efficiency.
Seems that Honda is aggressive on its Dual Clutch Transmission technology and in the next phase it will try to incorporate it in smaller capacity engine (250cc-500cc). It may possible that the next generation CBR250R engine will have Dual Clutch Transmission.
– Mahavir Kothari