LOS ANGELES – Launched in 2003, the Mazda3 compact car has taken the world by storm, becoming the Japanese auto maker’s best-selling vehicle globally and the recipient of numerous accolades from auto enthusiast magazines.

In the U.S., sales of the Mazda3, which comes in sedan and hatchback body styles and is known as the Axela in some global markets, have surpassed 100,000 units annually in recent years, far above the volume of its predecessor, the Protege.

So when the task of creating a new-generation Mazda3 arose, designers were hesitant to change much about the vehicle’s looks.

“So many people have loved the current 3 that we wanted to make sure we kept achieving their expectations,” Laurens van den Acker, global design chief for Mazda Motor Corp. tells Ward’s of balancing the need for change with a desire to preserve the car’s design language.

“The new Mazda3 is clearly a Mazda3 first,” van den Acker says during a walk-around of the new ’10 model sedan. “(But) then it’s more expressive, it’s (bolder), it’s more aerodynamic.”

Indeed, many of the subtle changes to the sheet metal revolve around improving the car’s aerodynamics, including the new front fascia.

While the current Mazda3 boasts dual grilles, one upper and one lower, van den Acker says the upper grille “wasn’t contributing enough to the airflow management.

“The thing with airflow management is you have to get as little area as possible, but just enough. If you get more air in, it just creates turbulence wherever it comes out,” he says.

To solve that, a single, 20% smaller grille was added to the ’10 Mazda3, and its position was lowered, moving the air intakes to high-pressure areas.

“So even though the area is smaller, it’s actually more effective (in terms of airflow management),” van den Acker says.

Mazda3 chief designer Kunihiko Kurisu says there now is “more air for the radiator, which means it gets (better) in terms of aerodynamics.”

A guide on the front bumper directs air flow through the radiator, and at high speeds a bypass flap opens, lessening cooling fan drag, Mazda says.

The shape of the car also plays a key role in achieving improved aerodynamics from the ’09 to the ’10 model.

While the front end of the vehicle is more rounded, sharp lines and creases in the sheet metal allow air flow to be interrupted at key points.

“It’s important, with aerodynamics, that the air gets cut off,” van den Acker says, adding the new Mazda3 is the slickest car in the global C-segment, with a drag coefficient of 0.29.

Changing the curvature of the windshield, specifically where it meets the A-pillar, reduces the amount of turbulence into the cabin, should the front passenger or driver have the window down, Kurisu says.

Taking this tactic allowed Mazda designers and engineers to lessen noise, vibration and harshness three decibels from levels in the previous-generation Mazda3.

Although the new Mazda3 appears more rounded at its rear corners than the outgoing model, it’s not.

“Physically, it’s actually square,” van den Acker says of the visual trick achieved by using clear glass for the taillamps.

“In the rear, if you make a rounder shape, the aerodynamics gets worse,” Kurisu says.

The improvement in aerodynamics, increased use of lighter-weight materials such as high-strength steel and powertrain changes led to a 10% gain in fuel economy with the 2.0L 4-cyl. engine.

“We managed to get from 30 mpg to 33 mpg ([7.8 to 7.1 L/100 km] highway in 2.0L models) without losing the fun-to-drive attributes or the great driving experience,” van den Acker says.

Perhaps the biggest changes can be found inside, where the previous Mazda3’s hard plastic surfaces and sometimes poor fit-and-finish were targets of critics.

“In the interior, compared to the previous generation, we had the most ground to make up,” van den Acker admits. “Finally, we’ve been able to get what I would call C/D-segment – or even premium-segment – materials into this (car).”

All ’10 Mazda3 trims feature soft-touch skins on the instrument panel. Trim accent pieces come in either a painted silver finish or a textured finish called Curlfit, which is identical to that found on high-end sunglasses.

“It’s the same (technique) as they use for Oakley sunglasses,” van den Acker says. “They dip them into a bath and then they apply the texture to them.”

This finish previously was used in the interior of the ’05 Mazdaspeed MX-5 Miata.

Kurisu says he developed a layered concept for the interior, with a slanted instrument panel that makes it possible for a driver to change settings without taking his eyes off the road.

“You don’t have to move around your eyes so much, (and) you don’t have to move your fingers so much,” he says.

The new ’10 Mazda3 goes on sale in the U.S. late in first-quarter 2009.