Diminutive Audi RS4 has a spectacular engine

Small cars for big bucks is not usually the rule of thumb automobile manufacturers employ to lure customers into their dealers’ showrooms.

But, most rules have their exceptions and German manufacturer Audi has a few of them for sale right now. The car I’m talking about is the Audi RS 4, the most potent offspring of its bread-and-butter A4 sedan.

Most people, understandably, will find it hard to comprehend why anyone would spend $70,000 or more on a car whose usefulness can be duplicated for half that price, or less.

But for a few well-to-do driving enthusiasts with an appreciation of excellence, a need for some real-world practicality and a passion for a world-class driving experience, this Audi might just make the most sense of all. Developed by Audi’s tuning division, the Quattro GmbH is a closer relative to Audi’s exoticar - the voluptuous two-seat R8 coupe - than it is to the look-alike A4 sedans that cart commuters and small families from place to place.

And, “look-alike” should not be confused with “looks the same.” The RS 4 sits 1.2 inches lower than its counterpart, the front wheels are spread 1.5 inches further apart, the rear wheels are nearly two inches further apart, and there are numerous subtle trim differences.

In addition, practically every mechanical part of the RS 4 has been upgraded, strengthened or revised to make it a sports sedan of nearly unparalleled competence.

The RS 4’s kinship to the vaunted R8 is in the engine compartments, where the two seemingly dissimilar vehicles house identical versions of Audi’s most spectacular V-8 engine, An almost completely re-engineered and strengthened version of the 4.2-liter powerplant found in several other Audi models, it features direct fuel injection, two double overhead camshafts and four valves per cylinder.

The result is 420 horsepower, 317 pounds-feet of torque, a redline of 8,250 rpm and 0-60 times of less than five seconds. Sounds like a high-strung, unfriendly brute fit more for the racetrack than the daily commute, right? Wrong!

With maximum torque available throughout most of its power band, this V-8 will pull the two-ton Audi sedan along just as willingly at 25 mph in 6th gear as it will race eagerly to its rev limiter.

From inside the car, it never sounds as if it’s working hard. But, stand by the side of the road as it streaks past in “sport” mode and you’ll hear, even feel, its powerful forces at work. Heck, it’s even able to return 20-plus miles per gallon of premium fuel when handled gently.

For the record, the EPA estimates fuel mileage at 14 per gallon around town and 21 on the highway and that qualifies the RS 4 for a stiff gas-guzzler tax.

A six-speed manual transmission, the only one available, is the perfect partner for the engine, with gears precisely spaced to extract the most the engine has to offer and a short-throw shifter that snicks effortlessly from cog to cog. The clutch, too, is light, with a smooth uptake.

The specially tuned aluminum sport suspension, featuring a four-link setup at the front wheels and double wishbones in back, is primarily responsible for the twin responsibilities of agility and a comfortable ride. But it has help.

With the engine forward of the front axle, the RS4 has a weight bias that would normally give the sedan a fair amount of understeer.

Thanks to Audi’s Dynamic Ride Control, which reduces body roll and pitch, the car handles neutrally in most circumstances.

In addition, Audi’s trademark Quattro all-wheel-drive system directs 40 percent of the power to the front wheels and 60 percent to the rear in normal driving situations to enhance the car’s handling ability. When conditions require, it automatically assigns power to the wheels with the most traction.

The car is also equipped with stability control, which will intervene to help keep it on its intended path if an overzealous driver heads into a corner too fast. Expert drivers who can find a time and a place to explore the RS 4 at its limits can turn the system off.

A powerful car needs powerful brakes, so the engineers have attached pizza-sized discs and cooling ducts to the 19-inch wheels in a system originally developed for race cars.

Finally, the power-assisted steering offers strong directional stability and plenty of feedback.

With all of the emphasis on all-out performance, one might expect the RS 4 to have at least a few rough edges. Not so. It is also a luxury car in the truest sense of the word, with Silk Nappa leathery upholstery and all the comfort and convenience accessories one would expect to find in one of Audi’s limousine-like A8 sedans. It also comes with a full complement of safety features.

You can take mom on a leisurely Sunday drive and she’ll never suspect that you actually spent all of that money to satisfy the wannabe racer that lurks inside all driving enthusiasts.

Audi understands the limited appeal of this high-priced small sedan, no matter how intoxicating its qualities, so it ships them to the United States in extremely limited numbers. Still, for 2008, it is offering an extra treat to about 300 well-to-do Americans - the RS 4 cabriolet.

While the RS 4 comes at a base price of about $70,000, including that $2,100 gas-guzzler tax and $775 destination charge, the convertible arrives fully loaded for $85,500.

If you want one of these cars, you better hurry. The RS 4 will go on vacation for an unspecified amount of time when the redesigned A4 is introduced for the 2009 model year.

Those who can’t quite afford the RS 4 can take heart, too.

Audi also sells an S4. It’s a closer relative to the A4, but it has a spirited, 340-horsepower V-8 engine, is also lots of fun, and comes with a starting price of $48,610 for a manual-transmission model. At $1,700, the gas-guzzler tax is lower, too.

Throw in some extra cash and it can also be purchased in station wagon or convertible form. An automatic transmission is an option.

Not only will the S4 save you up to $20,000, your mom still won’t have to know what you’re really up to.