DETROIT – Sexy sheet metal or the promise of high fuel economy may lure potential buyers into showrooms, but it is the design of the interior and the surprise and delight from features inside that increasingly seal the deal with consumers.

But ask a group of auto designers or engineers to explain what makes an interior irresistible to prospective buyers, and you likely will go through an exercise that sounds like three blind men describing an elephant.

Even so, designers from Toyota Motor Corp. and General Motors Corp., plus a top engineer from Hyundai Motor America, each took a crack at answering that question during the OEM design session at last week’s 2008 Ward’s Auto Interiors Show.

Between them, they found a surprising amount of common ground. Including:

  • The best interiors are collaborative efforts with painstaking attention to detail. They do not simply spring from a brilliant design.
  • Logic-driven engineers, once considered at loggerheads with creative types, now frequently work with designers and make new things possible, rather than telling them what they can’t do.
  • On the flip side, designers no longer simply are artists sketching out new concepts. They must put on a practical hat and look at the big picture. That includes having one eye peeled on improving efficiency and reducing costs – and making a business case for better materials.

Alan Schneider, project chief designer for CALTY Design Research Inc., a subsidiary of Toyota, leads off the discussion emphasizing a car or truck interior must support the vehicle’s overall design theme and message.

For instance, the message from the Toyota A-BAT concept, a hybrid-electric unibody pickup introduced at this year’s North American International Auto Show, is about putting lots of functionality into an environmentally friendly truck with a compact footprint, Schneider says.

The exterior communicates the efficiency theme by adopting the trapezoid silhouette from the side profile of the Toyota Prius hybrid, creating a new type of shape for a pickup truck.

Features such as an expandable pickup bed exemplify the truck’s versatility. Although it is only 4 ft. (1.2 m) long, the bed can be extended by folding down the cabin midgate and opening the tailgate to allow customers to carry a standard 4-by-8-ft. (1.2-by-2.4 m) sheet of plywood.

The A-BAT also features lots of exterior storage spaces outside and underneath the bed, so a buyer can enjoy the flexibility of one day hauling plywood and taking the family on a camping trip the next.

Schneider says the concept truck’s interior, which he designed, reinforces the vehicle’s message about being rugged, efficient and earth-friendly by centering the interior design around an exposed lightweight structure modeled after high-end mountain-bike frames.

Schneider calls the exposed center console a “purposeful, lightweight structure.” It is molded from carbon fiber and aluminum and runs between the two front seats like the vehicle’s spine. It then flows into the instrument panel, which doubles as a structural cross-car beam.

The center console also houses a portable battery pack for both AC and DC current, capable of powering everything from power tools to a laptop computer. And there are numerous seating and interior storage configurations to complement the A-BAT’s exterior storage bins, as well as the requisite port for portable device synching and a hard drive for digital music.

Rounding out the environmental theme, solar panels on the dash help charge the vehicle’s electronics and portable power pack.

Dan Vivian, director of engineering design at Hyundai, surprises show attendees, flatly declaring: “Styling has to be the priority.”

Not long ago, such a statement would have drawn jeers from his colleagues in the engineering community and disbelief from designers. But in recent years, enlightened members of both camps have started working together for the greater good.

Vivian’s rationale for greater collaboration is unassailable: Styling sells a lot more cars than meeting engineering specifications.

Nevertheless, Vivian candidly recalls that until fairly recently, designers used to sketch out their bright new ideas, and then the engineers would come in and tell them all the things they could not do.

Because styling is so important, “engineers have to have a more can-do approach,” he says.

Vivian says engineers too often are happy to settle for fulfilling objective specifications and parameters, rather than going the extra mile to satisfy more difficult-to-quantify subjective measurements.

Design fundamentals ultimately must be judged in the vehicle environment from the layman consumer’s perspective, not from the engineer’s technical perspective, which is highly focused on quantifiable engineering data, Vivian says.

This is a bitter pill for many engineers to swallow, but interior execution has to be judged using the customer’s highly subjective value system, Vivian says. Like it or not, first impressions are crucial, and the customer always is right.

“You may satisfy all specs, but if it does not look right to the customer, you have lost an opportunity,” he sums up.

The strategy appears to be paying off. Vivian spearheaded Hyundai’s redesign of the ’09 Sonata interior, which earned recognition for “Best Redesign” in this year’s Ward’s Interior of the Year awards.

Perhaps the most telling comment comes from panelist Helen Emsley, global director of color and trim for GM, who blithely notes: “I’ve got quite a few friends now who are engineers. I didn’t used to have any.”

Emsley has numerous successful GM designs to her credit, but she spends much of her time speaking about the importance of shortening the development time for color and trim deliverables and championing global workshops to commonize colors and materials.

One of the things Emsley first noticed after being named global director of color was GM had 12 different shades of black for interiors for its global products.

Having so many shades of what should be a simple, basic color was a terrific waste that raised costs and complicated color matching with countless trim pieces around the world. Several years later, Emsley is happy to report there is only one shade of black for interiors across GM.

The auto maker has made huge strides in interior design in recent years and has grown more adventurous in its color schemes as well, allowing even Cadillacs to sport the occasional saffron (yellow) and black interior, Emsley says.

Better quality and more emotionally styled interiors now are beginning to pay dividends, Emsley says, pointing out new GM vehicles such as the Chevy Malibu (also an Interior of the Year winner for 2008), Cadillac CTS and Buick Enclave all are selling far faster and at much higher average transaction prices than their predecessors.

Nevertheless, cultural differences do pose color and trim challenges as GM moves to global architectures and tries to commonize wherever possible, Emsley says.

For instance, she says European and North American consumers see bamboo as an interesting and upscale trim material, while Chinese consumers view it as unacceptably cheap looking, just as Americans would view plywood.

Instead, GM is looking at new materials for the Chinese market. One new design features the use of jade-like trim.