Open-air motoring takes a new direction at Bayerische Motoren Werke AG this spring. The air is fresher, the price is lower, and the call of the highway is stronger.

BMW is introducing the 318i convertible. The model supplements the company's 3-Series sedan and coupe, and combines the features of the 318i closed cars with a moveable top. The softtop, which just arrived at the Dreyer and Reinbold BMW dealership in Indianapolis, also considerably lowers the cost of open-air BMW motoring. That is in line with the lowered price threshold that BMW provided a few months ago with its new 318i coupe and sedan.

"The base price is under $30,000, which is almost an entry-level cost for a BMW. The price is $29,060, and there are only three options," said Dennis Reinbold, the dealership's vice president and general manager.

"That's where the 325i (convertible) was introduced three years ago, and we haven't been under $30,000 (for a convertible) since," he said.

Some mechanical features of the 318i softtop are shared with the coupe and sedan.

Power comes via a dual-cam, 16-valve, four-cylinder engine displacing 1.8 liters. The engine produces 134 horsepower from 110 cubic inches of displacement, and propels the car to an electronically limited top speed of 122 mph.

High tech abounds here with four valves per cylinder and a Bosch Motronic engine management system that removes the need for most routine engine maintenance. Even with hydraulic valve lifters, the engine will rev past 6,500 rpm.

In true sports-car tradition, the only transmission offered is a Getrag five-speed manual gearbox. However, all the safety, comfort and convenience features such as anti-lock braking, driver's-side air bag, power accessories, air conditioning and stereo are standard equipment. If you want an automatic, it's necessary to go to the more expensive 325i convertible.

Options consist of heated front seats, a limited-slip differential and metallic paint. Of the three, the limited-slip differential is the most important. The system takes over and drives both rear wheels if there is a loss of traction on one driving wheel.

Convertibles always have been a specialty market. Reinbold said the car is projected to account for 10 percent to 15 percent of 318i sales. "We're coming into the key (selling) season," he said. "But the best month we ever had . . . with a convertible was December.

"Our customers consist of a broad mix. Some people like it as a second car, and a nice weekend fun car. Others drive it every day, including through the winter."

Buyers are expected to be from 25 years old to about 60.

"People that use it for everyday driving probably are going to be a little bit younger," Reinbold said. "They'll probably be in the 25-to-35 age bracket. The people who use it as a second car probably will run from 35 to 60."

A rear drive with a front engine, the softtop adheres to the fundamental design of the automobile that began virtually at Day 1. Add to that the limited-slip rear end, and you have a car in which the gifted can hang the back end out and steer with the throttle.

The 318i has all the facets for those prone to be heavy of foot. There is fast-ratio power steering, 14-by-6-inch cast alloy wheels, and a suspension system that domestic producers still haven't adopted in rear drives except for sports-car application.

This is four-wheel independent suspension in which the rear end forgoes the solid axle housing and uses floating stub axles on both sides of a stationary mounted housing that carries the ring and pinion gears.

The system not only reduces unsprung weight for improved ride, but provides better tire contact with the pavement for improved traction.

The convertible is not only an engineering marvel. Interior styling includes cloth or leatherette upholstery and velour carpeting. Exterior styling is enhanced by body-colored bumpers, free-form headlamps and fog lights, and radial-spoke wheels.

The top also t ucks awa y nicely, although this is a manual operation. "It's a limited-production item," Reinbold said. "We've received just two of them, but I'm not expecting an availability problem. We haven't been informed there will be any restriction in supply, so I believe it will be available, within reason."