The big news in the hybrid industry is the introduction of the 2006 Honda Civic IMA (Integrated Motor Assist) hybrid. This vehicle represents Honda’s first full hybrid. Previously, the IMA hybrid system was not able to launch the vehicle on its electric drive alone, which classified Honda’s IMA as a mild system. (See our July eNews article “Introducing Hybrid Technologies” for a complete description.)
With the introduction of the new Civic IMA, this is no longer the case. The new Civic can launch (accelerate from a stop) under three different launch modes. The vehicle can accelerate from a stop using only its 20 hp, 76 ft.lb. electric motor under light throttle. It can continue to accelerate in electric only mode until vehicle speed exceeds 35 MPH, at which time the gasoline engine will also be coupled to the driveline.
Under higher throttle demand, the 1339 cc i-VTEC engine will be started and, operating in normal valve timing and lift mode, will assist the electric motor to accelerate the vehicle.
When full load acceleration is required by the driver, the i-VTEC engine will switch into the high output intake cam map for maximum performance.
Coupling of the gasoline engine to the transmission is accomplished by an electronically controlled multi-plate clutch.
Honda’s i-VTEC engine technology utilizes a single camshaft, two valves per cylinder, and five electro/hydraulic rocker arm/cam assemblies to enable either normal engine operation, an enhanced intake valve operating map for high output, and the ability to deactivate all four cylinders during deceleration.
Regenerative braking is also enhanced in the new Civic compared to previous models. The new Civic will deactivate all four cylinders during deceleration to further reduce pumping losses. When you take your foot off the gas in a conventional vehicle, the fuel supply to the engine is normally cut off, and the vehicle begins to decelerate. During this time, the engine is actually being driven by the momentum of the vehicle. Because the throttle is closed, the engine is acting like a pump and is creating a very high vacuum in the intake manifold. This takes energy, which is why the vehicle will slow down much faster than if you would uncouple the engine by shifting into neutral. The energy being consumed by the engine to help slow the vehicle is known as pumping loss. In a hybrid vehicle with regenerative braking capability, this pumping loss is no longer desirable; it is a waste of energy. Previously only three cylinders were deactivated during this operating mode. The further reduction of pumping loss enables more power to be generated by the IMA motor/generator and stored in the hybrid’s high voltage battery pack.
The other two intake valve strategies are used to operate the engine in a high-efficiency, low-power mode for improved fuel economy as much as possible, yet still provide the different intake valve timing and lift needed when the engine is called on to provide satisfactory power during full load acceleration.
Other changes in the new Civic include use of the improved motor magnet design developed for the hybrid Accord. Even the wire windings in the motor are now made with rectangular shaped wire instead of round wire. This is done to provide a larger wire surface area within the motor.
The dual scroll A/C compressor used in the Accord hybrid is also used in the new Civic. This compressor is basically two compressors in a shared housing. One compressor is driven off the engine drive belt and is utilized whenever the engine is running. The other compressor is driven by an electric motor powered from the IMA battery pack and provides refrigerant flow to the passenger compartment when the gasoline engine is shutdown, such as during idle stop. Many older hybrids, including those made by Honda, Toyota, and Ford do not share this important feature.
The energy density of the Sanyo batteries in the IMA power unit has been increased. Honda claims a 25 percent improvement in energy density. The vehicle carries an EPA city/highway fuel economy rating of 49/51. This is a much narrower city/highway window than many other hybrids.
Honda’s variable ratio transaxle (CVT), which used a steel belt running through variable width pulleys, continues to be used.
Finally, the new Civic IMA carries an AT-PZEV (advanced technology-partial zero emissions vehicle) classification. The PZEV classification comes from the virtual elimination of evaporative emissions, aided by use of a new plastic resin fuel tank and Honda’s 15-year/150,000 mile warranty on all emissions-related equipment.
The 2006 Civic IMA hybrid has a base price of around $22,000.