When the driver of a Subaru Turbo steps down hard on the gas, odd things begin to happen on the instrument panel.

Directly in front of the driver is an image that resembles a pilot's-eye view of an airport runway. As the Subaru's engine revs up, a tiny car appears on the runway and seems to accelerate forward. Simultaneously, a little turbo fan appears on the screen with blades swirling and "air" blasting from its two outlets. There is also a "varoom-varoom" sound, not from the real car's engine, but from the little car on the screen.

The point of all this: to tell the driver that the engine has reached 3,000 revolutions per minute, and the turbocharger -- a device that pushes fuel and air into the cylinders for extra power -- has kicked in.

While the Subaru goes a bit farther than most, it is but one example of a rapidly spreading phenomenon in automotive technology: the electronic, computer-driven, graphic-digital dashboard.

Not all of the digital dashes, as they are called in the car industry, are as entertaining as the one in the Subaru. But they share a common characteristic: their ability to call up and display information on nearly every automotive function.

There are digital dashes that talk to the driver, telling -- some would say nagging -- him or her to turn on the car's lights, to turn them off, to get more fuel, to slow down.

They are capable of providing far more information than conventional dashboards, and are a far cry from the panels of 20 years ago, which offered nothing more than speed and fuel gauges and a handful of warning lights.

But a number of drivers complain that the data are not presented clearly. Some consumers, for example, have complained to auto makers that they thought they were looking at the speedometer when they actually were looking at the tachometer.

The difference is crucial. The speedometer tells how fast the car is going. The tachometer tells how fast the car's engine is operating. A driver missing the usually small "x 100" notation on the digital tachometer might think that he is going 40 miles per hour when it's the engine that's going 4,000 revolutions per minute and the car is actually moving at between 55 and 60 miles per hour.

But auto makers say that the benefits of the digital dashes far outweigh their problems. Domestic manufacturers and some of their Japanese competitors are spending hundreds of millions of dollars developing digital dashes. Their prime target is a youth market, reared on video games and home computers.

Makers of expensive European performance cars such as Porsche and BMW, however, don't see them as effective marketing tools and look down their noses at the Americans and Japanese for trying them.

"Basically, we don't believe in high technology for high technology's sake," said Martha McKinley, a spokeswoman for Porsche Cars North America, Porsche's marketing arm in the United States. "We'll use high technology only when we feel that it helps the overall performance of the car."

Christopher Cedergren, an automotive industry analyst with California-based J. D. Power & Associates, said the German performance-car manufacturers are right to let the Americans go their own way with the digital dashes.

"The buyers of Porsches and BMWs are usually young, well-educated and affluent. They want a dashboard that is extremely functional. They perceive the digital dashboards as being so much more unnecessary flash, a kind of electronic chrome," Cedergren said.

"For manufacturers like Ford and GM, who are trying to get more young buyers into their luxury-car showroom, I think the digital dash is a big mistake," he added.

Officials at General Motors Corp., Ford Motor Co., Chrysler Corp. and American Motors Corp., all of which offer digital dashes in some car lines, disagree.

"Any motor vehicle manufacturer who ignores the trend" toward electronic instrument panels "will probably have to adjust very quickly to catch up in the future," said Jack Dinan, a spokesman for General Motors's AC Spark Plug Division.

AC Spark Plug and GM's Delco Electronics Division produce electronic dashes and related components for the company's new cars and trucks.

GM, the nation's largest car company, introduced the digital dash to the U.S. market in 1978 as optional equipment on its Cadillac Seville cars. The electronic panels were installed in less than 1 percent of GM's new-car fleet then. But by 1990, digital dashboards will be found in 40 percent of all GM cars sold in the United States, Dinan said.

Ford officials also said that their digital-dash sales are growing rapidly.

Ford introduced the electronic information systems on some of its 1980-model luxury cars, selling 20,000 digital dashes that year. The company sold an estimated 210,000 digital dashes and related systems in 1985, a 600 percent increase from 1980.

"Our surveys find that people like the electronic instrumentation and that they feel it adds value and satisfaction to the car itself," said James Siegl, marketing manager for Ford's electronics equipment division. "But more than that, our surveys show that prospective buyers, young and old, like that equipment, too."

The digital dash is a natural outgrowth of the "hidden computerization" now controlling most new cars' engine and suspension functions, Siegl said. He conceded that some digital dashes can be confusing. "We've heard the stories from owners" who said that they sometimes misread the instrumentation, he said.

"There is a learning curve," Siegl said. The longer customers have the digital dashes, the more they like them, he asserted.

A Ford survey of owner reaction to digital dashes in the company's 1984-1985 Cougar and Thunderbird cars shows that, "After several months of ownership, 96 percent of . . . the owners like their electronic instrumentation as much or more as when they bought their cars.

"In addition, 89 percent said they were happy with the electronic multigauge instrumentation and said that they would buy it in their next car," the Ford survey said.

Reliability of the digital dashes has not proved to be a problem, according to Siegl, Dinan and members of the McLean-based National Automobile Dealers Association, which represents 20,000 auto franchise dealers in the United States.

"You hear all of these comments about how the electronic dashboard is just something else to go wrong in a car. But our experience has been that these systems offer more than the regular mechanical system, and that their reliability is as good as that of the regular system," said David Peacock, general manager of Larry Buick in Arlington.

But when it does malfunction, a driver can be forced to listen to a maddening little voice saying, "your fuel is low . . . your fuel is low" every couple of minutes until the system is repaired or the driver manages to pull the plug on the voice (which can be done on some models).

Still, many people apparently are prepared to run that risk, and pay the $200 to more than $1,000 that digital dashes can add to the price of a car.

"A lot of younger buyers like the high-tech stuff" in late models, including GM's new 1986 Buick Riviera (base price $19,831), which carries a cathode-ray-tube, touch-screen "graphic control center" as standard equipment, Peacock said.

GM, the most aggressive purveyor of digital dashes, is the first company to offer the touch-screen control system in the United States.

The three-by-five-inch video screen in the Riviera allows the driver to get information on all of the car's vital functions by touching the appropriate square on the screen's surface. The driver also can use the screen to estimate the time it would take to get from one city to another if the car is driven at a certain speed, to determine how much further the car can travel with the amount of fuel remaining in the tank, and to control the car's radio and related entertainment functions.

Is any of this really necessary?

"Our feeling is that consumer choice is enhanced by these developments," said J. Ferron, vice president of NADA, the national dealer's group.

"Our dealers tell us that buyers like this technology and that there is a lot of excitement about it," Ferron said. Part of the reason is that buyers believe that the digital dash is more accurate than it mechanical and electro-mechanical counterparts, Ferron said.

"There was an old expression: 'As accurate as a dashboard clock.' Well, that expresion is not accurate any more, because the digital dash clocks are extremely accurate," Ferron said.