Honda's Third Hybrid: The Accord

Gary S. Vasilash

Coming soon under the hood of an '05 Honda Accord near you is the third generation of the company's gasoline-electric hybrid system.

Coming soon under the hood of an '05 Honda Accord near you is the third generation of the company's gasoline-electric hybrid system. That's right, Honda is adding another hybrid to its lineup, which, as Dan Bonawitz, American Honda, vp, Corporate Planning & Logistics, points out, makes it the only company offering three hybrid vehicles (the Insight, introduced in '99, and the Civic, introduced in '02).

The Accord Hybrid makes use of a 3-liter V6 i-VTEC engine that is essentially the same as the engine used in the Accord EX. However, the aluminum-block has some additional brackets that permit mounting a magnesium composite head cover for the Variable Cylinder Management (VCM) system that's used for the hybrid, as well as for the Integrated Motor Assist (IMA) electric motor. The VCM is based on the i-VTEC (intelligent Variable Valve-Timing and Lift Electronic Control) system that's used on many Honda vehicles. Ordinary i-VTEC operates at high RPM. In the case of the Accord Hybrid, the three cylinders on the rear bank of the engine are deactivated by a hydraulic circuit, even when operating at low speeds. Among other things, the system controls ignition timing and turns the torque converter lock-up on and off so that there isn't a jolt when switching between three- and six-cylinder operation. Because there are increased vibrations associated with shutting off a bank of cylinders, there is an Active Control Engine Mount (ACM) system that deploys actuators to move in synch with the vibration so as not to transmit vibrations to the vehicle occupants. Additionally, there is an Active Noise Control (ANC) system in the cabin that measures the booming noise from deactivation and emits via the audio system an opposite sound wave to cancel out the booming.

The IMA is a 68-mm wide DC brushless motor that's located between the engine and the five-speed automatic transmission. The transmission is similar to that used for the Acura MDX SUV, but there are differences, like an integrated electric oil pump. This oil pump is important because there is an idle-stop feature of the car, which means that the gasoline engine is off when, say, at a stop light. Consequently, the electric pump is used to pump oil through the transmission's torque converter. The IMA also makes use of an intelligent power unit (IPU), which controls the electricity going to and from the electric motor. There is a bank of Sanyo NiMH batteries (consisting of 120 1.2-V units) that's located in a U-shaped module behind the rear seat; the batteries are charged by the IMA, which acts as a generator when the vehicle is braking or decelerating. The IMA provides up to 16 hp and 100 lb-ft. of torque. Which brings the total to 255 hp (240 from the gas engine) and 232 lb-ft of torque at 5,000 rpm. Unlike the Toyota Prius and the Ford Escape, the Honda system doesn't operate under electric motor power only. Bonawitz insists, "We consider our IMA to be a full hybrid system, one that uses its electric motor for motive power, versus a mild system that uses its electric component for non-motive features, such as idle stop or accessory power. This is an important point. There is nothing inherently more efficient to systems that offer motor-only operation, like the Prius or Escape. Those systems require larger batteries, bigger and heavier motors, and more complex control systems all of which add weight, complexity and cost."

Although not readily discernable, there are some other changes to the basic Accord. For example, aluminum is used for the hood, front and rear bumper beams, and rear suspension knuckle. The objective of these and similar changes (e.g., the magnesium engine head cover) was to reduce the weight of the vehicle because adding the hybrid system to the Accord, naturally, increases overall mass, which decreases efficiency. The engineers were able to reduce the weight of the vehicle by176 lb. so that when the hybrid system was installed, the curbweight of the vehicle was up just 120 lb. (There are visible changes, too: a "Hybrid" badge; integrated rear spoiler; unique aluminum wheels; roof-mounted antenna for AM/FM and XM.)

While the final EPA numbers weren't available at press time, Bonawitz estimates that the Accord Hybrid, thanks to the cylinder deactivation and hybrid system, will provide 30 mpg city/ 37 mpg highway, which represent a 43% and 23%, respectively,increase over the standard Accord V6. Bonawitz says they're planning on a volume of about 20,000 units for the vehicle which will have a price around $30,000. Because of the comparatively low production volume, the Accord Hybrid is being produced in Honda's Sayama, Japan, factory rather than Marysville, OH, where most of the Accords sold in America are built.