Honda has improved its IMA system, together with other engine technology advancements, for its Hybrid Civic.

Some people have looked at Honda's figure of 29 km/L (68 MPG) for the hybrid Civic, and mistakenly interpreted this to mean that the hybrid Civic will equal the Insight's fuel efficiency. Their mistake is that Honda Japan's figure (29 km/L) is based on a different test method than is used by the EPA. By the same test procedure, Honda Japan quotes the Insight at 35 km/L, which translates to 82 U.S. MPG

In Honda's U.S. press release, below, they quote a fuel efficiency figure of 50 MPG for the hybrid Civic. The U.S. EPA estimate for various models of the gasoline-only Civics vary from 30-36 MPG in the city, and 37-44 MPG on the highway.

he hybrid Civic is to be available in Japan in December of 2001, and is to be available in the U.S. beginning in March of 2002.

Torrance, CA. 09/05/2001 -- Honda today announced several new technological advancements that further improve the efficiency of its IMA (Integrated Motor Assist) System, a unique hybrid system that combines a small internal combustion engine with an electric motor to provide outstanding performance and fuel economy. The IMA system will be installed in an all-new Civic Hybrid model to be released in December in Japan, and in the U.S. next spring.

The engine in the new IMA System incorporates Honda's state-of-the-art i-DSI (direct and sequential ignition) lean-burn combustion technology, along with a newly-developed cylinder idling system. This system adapts Honda's VTEC variable valve control system to significantly increase the amount of electrical energy recovered during deceleration. These new features contribute significantly to improved fuel economy.

Other technological advances provide improvements to both the motor assist system and Power Control Unit (PCU) efficiency. Combined with Honda's continuously variable transmission (CVT), this new system provides a combination of excellent drivability and superb gas mileage. Expected to achieve about 50 miles per gallon, the Civic Hybrid will rank at the top of its class for mass-produced gasoline-powered vehicles. It is also expected to earn an Ultra Low Emission Vehicle (ULEV) emission rating.

Features of the New IMA System

The new IMA System employs a gasoline engine as its main power source that is assisted by an electric motor as the need arises. It offers improved efficiency compared to the current IMA System used on the Honda Insight, which boasts the highest fuel economy in the world for a production vehicle.

During acceleration and other times of heavy engine load, the electric motor "assists" the gasoline engine by providing additional torque, resulting in both lower fuel consumption and powerful acceleration. At cruising speeds when engine load is lower, the motor assist system shuts down.

During deceleration, the motor converts the energy into electricity (regenerative braking). The cylinder idling system reduces engine friction during deceleration -- greatly improving the vehicle's electrical regenerative efficiency.

The engine also has an idle stop feature. When stopped at traffic light, for example, the engine shuts off automatically, then restarts immediately when the driver steps on the accelerator pedal. This auto idle stop system contributes to both greater fuel efficiency and lower emissions.

New 1.3-liter i-DSI Lean Burn Engine

• The engine features the basic i-DSI configuration of two spark plugs per cylinder. This allows the fuel-air mixture to be made even leaner, for improved fuel economy.
  
• The rocker arms that open and close the intake and exhaust valves are configured for dual operation in either valve-lift mode or idle mode. Normally, they are engaged via a synchronizing piston. During deceleration, the synchro piston is housed inside the idle-mode rocker arm, disengaging the lift-mode rocker arm so that the valve remains at rest, effectively sealing off the cylinder.
  
• Three of the four cylinders can be shut down, achieving 50% less engine friction during deceleration than the present IMA System.
  
• A 900-cell three-stage catalytic converter and a lean burn-compatible absorption-type NOx catalytic converter will help the Civic Hybrid achieve an expected Ultra Low Emission Vehicle (ULEV) rating.

New Motor Assist System

• The motor assist system is composed of an ultra-thin DC brushless motor, a Nickel Metal Hydride battery, and a Power Control Unit (PCU). The new system employs a higher-output motor, a more efficient battery, and a lighter, more compact PCU that results in greater packaging freedom.
  
• Improvements to the internal magnetic coils of the ultra-thin DC brushless motor, which boasts the world's highest output density and overall efficiency, achieves 30 percent greater assisting and regenerative torque than the previous model, without increasing the size
  
• The inverter and the pre-driver have been combined, reducing the weight of the PCU by around 30 percent, and its volume by around 40 percent in comparison to the present system.
  
• The efficiency of the battery modules has been increased, resulting in reduced energy losses. The battery's storage box and peripheral equipment have been made more compact, for an approximate 30 percent reduction in volume.
  
• The lighter, more compact, more efficient PCU and battery have been integrated into a single Intelligent Power Unit (IPU) that can be stored behind the rear seat of a passenger sedan.
  
• Integrating the IPU allows the two cooling circuits previously used to be combined into one. Total volume of the PCU and battery has been reduced by 50 percent.