Honda Develops 63 mpg 700cc Engine

Honda Motorcycle Development

With an aim directly at the middle-class range of motorcycles (500 to 700cc), Honda has developed a 700cc engine that’s reported to get over 63 mpg.

The Japanese Marquee says the new 700cc motorcycle engine will feature “powerful torque in the low- to mid-speed range and top class, fuel-efficient environment performance, along with a second-generation Dual Clutch Transmission.”

The new motor is expected to be unveiled in “three models based on different concepts” at the 69th International Motorcycle Show (EICMA 2011) this November in Milan, Italy. As for what motorcycles, Honda has only released the name of one – the Integra (shown in pic three above).

Honda reports development of the fuel-efficient 700cc engine was performed to meet these requirements:

  • An engine that is easy to handle with plentiful torque in the range normally used, and which also delivers a pleasant, throbbing feel during sporty rides
  • Top-class, fuel-efficient environmental performance best suited for the next-generation mid-class engine
  • A lightweight, compact design that allows more freedom in the body layout and provides highly convenient space

Honda says it “determined the engine layout after examining a variety of engine types from numerous perspectives and decided on an in-line, 700cc, 2-cylinder engine with a 62º forward lean (cylinder assembly angle). To meet a wide variety of uses, two transmissions can be coupled with this engine: the second generation of Honda’s innovative Dual Clutch Transmission, and a 6-speed manual transmission.”

Following are highlights of the 700cc Engine currently being developed:

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.

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.

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.

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),*1 allows the engine to achieve an emission level approximately half the European emission standards (Euro 3).*2 The resulting environmental performance is ranked among the top in the world without compromising powerful, smooth output.

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.

*1 PGM-FI (Programmed Fuel Injection System) is a Honda registered trademark

*2 Honda calculations