New Honda Hybrid System with 3-Stage i-VTEC + IMA


July 14, 2005

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July 15, 2005 Honda will introduce a new Honda Hybrid System in the 2006 Civic Hybrid that features a 3-stage i-VTEC engine that employs Honda’s “intelligent” VTEC (Variable Valve Timing and Lift Electronic Control) system to provide three stages of valve timing (low-rpm, high-rpm and cylinder idle mode), combined with a significantly more compact and efficient Honda IMA (Integrated Motor Assist) system. The new Honda Hybrid System will be introduced in the all-new Civic Hybrid, to be launched Q3, and will offer significantly improved performance and fuel economy over the current system. The new Honda Hybrid System employs intelligent engine functions and a more efficient IMA system to achieve an approximate 20 percent increase in system output over the current system and performance similar to a 1.8-liter engine while improving fuel economy by about 5 percent, reducing the system size by 5 percent and significantly improving emissions performance.

The 3-stage i-VTEC engine employs three hydraulic pathways to couple and uncouple five rocker arm assemblies, providing three stages of valve control depending on the driving conditions to achieve a combination of responsive driving and high fuel economy. During deceleration when the cylinders are idle, combustion in all four cylinders is halted and the cylinders are sealed shut, reducing pumping losses caused by engine aspiration for a 10 percent improvement in recovery of braking energy compared to the current model. To reduce friction, Honda is using aluminum die-cast pistons (which feature low thermal expansion for less friction under high-temperature conditions), ion-plated piston rings and plateau honing of the cylinder walls for a smoother surface.

Honda’s independently developed electric motor employs coils with high-density windings and high-performance magnets to attain output 1.5 times that of the current model while maintaining the same size. The inverter used to control motor speed—also independently developed and manufactured by Honda—is integrated with the motor’s ECU for more precise digital control, contributing to even greater motor efficiency and fuel economy. Battery output power has been increased by around 30 percent over the current model, while a more compact, custom designed battery storage box offers increased cooling performance and vibration resistance for enhanced long-term reliability.

A dynamic regenerative braking system is employed that hydraulically controls the brakes based on the amount of brake regeneration. This permits maximum braking regeneration along with smooth deceleration that conforms to brake-pedal pressure.

The air conditioner features a hybrid compressor unit powered by either the engine, an electric motor, or both. When the engine is in Idle Stop mode, the motor powers a small compressor. If rapid cooling is required, an additional compressor powered by the engine engages also. When the interior temperature is stable, air conditioning is provided by the motor alone for both improved comfort and fuel savings.

About the Author
Mike Hanlon Mike grew up thinking he would become a mathematician, accidentally started motorcycle racing, got a job writing road tests for a motorcycle magazine while at university, and became a writer. As a travelling photojournalist during his early career, his work was published in a dozen languages across 20+ countries. He went on to edit or manage over 50 print publications, with target audiences ranging from pensioners to plumbers, many different sports, many car and motorcycle magazines, with many more in the fields of communication - narrow subject magazines on topics such as advertising, marketing, visual communications, design, presentation and direct marketing. Then came the internet and Mike managed internet projects for Australia's largest multimedia company, (Australia's largest Telco), (Australia's largest employment site),,, and a dozen other internet start-ups before founding Gizmag in 2002. Now he writes and thinks. All articles by Mike Hanlon
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