Accord Hybrid Takes the Technology to Next Level October 2004

Mention hybrid and eyes begin to glaze over.

It's not a sexy subject, nor is it one that is generally well understood, which probably accounts for the difference between those who say they would consider a hybrid (68 per cent of all buyers) and those who actually buy one. It is, however, an important technology as it represents the bridge between today and the fuel cell age of tomorrow.

The Accord Hybrid is the latest car to put Honda's Integrated Motor Assist hybrid system to use. Where it differs from previous applications is in its focus: The Civic Hybrid was all about economy and lower emissions; the Accord follows this lead but puts an equal emphasis on performance.

The hybrid components are all similar to those employed in the Civic, but with improvements in every area.

For example, the main battery pack delivers the same 144 volts, but it can now satisfy the motor's peak draw of 120 amps (up from 75 amps for the Civic) while being smaller and lighter. Likewise, the electric motor now supplies more horsepower (up from 13 to 16.1), while the torque production more than doubles, rising from 46 to 100 pound-feet. The system is also more efficient, converting 97.5 per cent of the available electricity into productive driving force.

As with its siblings, the Accord sandwiches the electric motor between its gasoline engine (a 3.0-litre V-6 in this case) and transmission (a five-speed automatic).

The gas/electric combination develops 255 horsepower and 232 pound-feet of torque, an increase of 15 and 20 respectively when compared with the regular V-6 Accord.

Significant as these increases are, they pale in comparison with the manner in which the engine/motor reacts when the driver tromps on the gas. As the electric motor develops most of its torque at the bottom of the rev range, it pushes the car off the line with more authority and then maintains this work ethic until the engine comes fully on cam.

In every measurable way, performance takes a significant step forward. Better yet is the giant step forward in fuel economy and reduced emissions.

The secret to the fabulous fuel economy is a combination of the electric motor's assistance, the engine shut-off mode (which kills the engine when the car comes to a standstill and then fires it back to life

using the main electric motor the instant the driver lifts off the brake) and the addition of variable cylinder management (VCM) to the VTEC's variable valve timing and lift control. Simply, VCM reduces fuel consumption by shutting down the three rear cylinders whenever the workload is light.

Each of these strategies helps the overall fuel economy cause, but in different ways. For example, in the city, the electric motor accounts for 60 per cent of the savings, the VCM 15 per cent and the idle stop 25 per cent.

However, on the highway, the roles switch, as the VCM now accounts for 57 per cent of the savings, the motor 38 per cent and aerodynamic improvements five per cent.

On a typical drive, flat-out acceleration sees the engine and motor pull together. Once up to speed, the electric motor shuts off as the VCM kills the cylinders, which leaves just 1.5L of engine to supply the cruising power.

The neat part is, rather than firing the dead cylinders back to life just because the driver encounters a minor incline, it cranks up the electric motor to satisfy the demand, which keeps the engine in its most miserly mode for a longer period. Finally, whenever the driver lifts off the gas or begins braking, the electric motor reverses function to become a massive generator that keeps the main battery topped up. This means there is no need to plug the Accord in to recharge the battery, which eliminates the burden on the hydroelectric grid.

The air-conditioning is another complex piece, as it is both electrically and belt driven. When the car is first started and the cabin needs cooling in a hurry, the compressor is belt driven. However, when just maintaining the temperature (which requires less work), the main battery drives the compressor, removing that load from the engine.

It also means that the system works when the engine shuts down at a stoplight. A small item, perhaps, but one that helps the conservation quest in a meaningful way.

In terms of ride comfort and handling, the extra mass added by the various hybrid bits and pieces has little effect. Large bumps are swallowed in stride and when attacking a faster corner the Accord hunkers down nicely.

Even when the pavement breaks up mid-corner, the suspension keeps its cool, allowing the car to follow the driver's intended line. Part of the reason for the balanced ride and handling is the use of aluminum in the hood, bumper bars, rear suspension, and the sleek, lightweight, 16-inch wheels. Put together, this shaves 76 kilograms off the curb weight and keeps the overall weight increase to just 67 kg when compared with the EX V6 automatic.

The proof of how well the whole lot works is found in the Hybrid's fuel economy numbers - it consumes 8.3 litres per 100 kilometres in the city and 6.1 L/100 km on the highway. This compares well with the conventional Accord V-6's consumption rates of 11.4 and 7.3 respectively. Simply reducing the fuel consumption is an important engineering focus. Dropping it by 28 per cent in the city and 17 per cent on the highway is a massive step in the right direction.

SOURCE: Montreal Gazette

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