Japan’s six major auto makers are divided into two camps on future strategies for stability-enhancing driveline technologies: safety benefits vs. performance improvements. Part 1 of this 6-part series examines Honda’s Super Handling-All-Wheel-Drive technology.

UTSUNOMIYA, Japan – Honda Motor Co. Ltd. is positive about the prospects for so-called torque-vectoring all-wheel-drive systems that more actively influence vehicle handling than current electronic stability-control systems (ESC), which only apply brakes reactively when vehicle stability is in danger.

But increased application of “active” AWD systems, such as Honda’s Super Handling-All-Wheel-Drive (SH-AWD) technology, will depend on the auto maker’s ability to bring down costs. In the future, senior research officials expect the technology to be increasingly introduced into the SUV and upscale sedan segments.

Honda’s SH-AWD system features a rear differential that distributes varying amounts of torque to the left and right rear wheels; directing more torque to the outside rear wheel when cornering, thus, helping the car turn and counteracting the tendency to understeer.

Most other Honda AWD vehicles, conversely, employ a mechanical dual-pump system to distribute drive torque front-to-rear, but not side-to-side.

All of Honda and Acura’s SH-AWD-equipped vehicles also are fitted with antilock braking (along with electronic brake-force distribution and brake assist) and Honda’s Vehicle Stability Assist ESC system, the auto maker says.

Senior Chief Engineer Yasuji Shibahata says Honda’s SH-AWD eventually will be adopted for small and midsize cars such as the Accord and Civic, although the system will not be introduced in Japan’s popular 0.66L minivehicle segment. Shibahata estimates this will take five to 10 years.

“In part, this will be a marketing decision,” he says.

At present, SH-AWD is available only on the Japan-market Honda Legend and the Acura RL sedans and the RDX and MDX cross/utility vehicles sold in North America.

Shibahata declines to comment on whether the SH-AWD system, which centers on the complex torque-directing rear differential, can be modified for rear-wheel-drive vehicles. However, Acura recently showed at the North American International Auto Show its RWD Advanced Sports Car Concept, which features a front-mounted V-10 engine and torque-vectoring technology in its rear axle.

The ASCC is expected to appear in ’09 as the next-generation of the auto maker’s storied NSX sports car.

Regarding future development targets, Shibahata says Honda will attempt to further simplify SH-AWD’s components. For example, the RDX’s torque-biasing differential, introduced in mid-2006 in North America, is simpler, smaller (by 10%) and lighter (by 22 lbs. [10 kg]) than the system launched on the Legend and RL.

By 2010, Honda hopes to reduce SH-AWD’s size and weight by another 50%, which could translate into a 50% cost reduction, Shibahata says, noting Honda’s eventual cost target is just 10% more than conventional 2-wheel-drive layouts.

Torque-vectoring technology (and specifically Honda’s SH-AWD approach) complements brake-based stability-control systems, Shibahata says. However, he insists “fun to drive” is Honda’s primary objective in pursuing the technology. In contrast, Toyota Motor Corp.’s main focus for vehicle stability control is safety.

Shibahata says ESC currently is available on most Honda vehicles, although it is not standard on all models or available in all grades within specific model lines.

In the future, Shibahata expects Honda to integrate active steering and active suspension technology into its stability-control function, but he declines to offer a timeframe.

He also confirms his development team is trying to integrate SH-AWD with the auto maker’s Integrated Motor Assist hybrid-electric drivetrain.

Moreover, he believes SH-AWD can be joined with various other preventive safety technologies.

Although no timeframe is given, other Honda research executives say this “integration” will occur in about 2010. They note, however, that independent electric-drive motors for each wheel, the next stage of driveline development, will not be available until after 2010.

In the past, Honda had been averse to adopting electronic controls in the drivetrain area, but Shibahata says this gradually is changing.

“In the future, we will see greater integration (of electronic drive systems) through use of CAN (controller area networks),” he says.

Meanwhile, Shibahata insists higher gasoline prices will not affect future plans for SH-AWD to be installed in other Honda and Acura vehicles.

“This is mainly because our technology is fun to drive and, specifically, improves high-speed cornering performance,” he says.

While the Honda research executive expects system refinements to slash costs over the next three to five years, he does not foresee any major performance improvements.

“For the moment we’ve reached the technical limit,” he says.

Among Japanese auto makers, Shibahata says Mitsubishi Motor Corp.’s Super All Wheel Control AWD system is the closest to Honda’s in terms of design concept. However, the Mitsubishi Lancer Evolution employs a unique center-differential control, while Honda vehicles do not.

“But the objectives are basically the same: to distribute torque to the vehicle’s four wheels in accordance with driving conditions,” Shibahata says.

Commenting on Toyota’s Vehicle Dynamics Integrated Management brake-based ESC, Shibahata says the concepts are different.

“Of course, Honda is as concerned as Toyota about safety, but (Honda’s) system focus is on fun to drive,” he says.