Honda started its upscale Acura branch 20 years ago. The midsize MDX has been Acura’s only SUV, complementing the entry level RSX sports coupe, TSX compact sports sedan, superb TL, and luxurious RL. The RDX, which first enthralled onlookers as a concept vehicle at the 2002 North American International Auto Show in Detroit, hits showrooms in August.

By then, summer vacations may not have helped heal the large SUV market, which has been stunted by $3 gasoline prices, causing buyers to switch to smaller crossover car-based SUVs. Compact crossover SUVs are virtually certain to zoom right past large SUVs this calendar year.

Honda’s market research predicts the premium crossover segment will expand five times – 500 percent – in the next five years, and tenfold beyond its current size in the next 10 years.

Manager of product planning William Walton said it’s part of a trend of "neo-urbanism," which includes people migrating back from the suburbs to the cities for cultural and entertainment reasons, and with space at a premium in new condos and lofts, and also in parking openings. The ensuing dilemma is that traditional SUV buyers give up sportiness, while sports sedans lack utility and foul-weather capabilities of SUVs.

The RDX offers the solution of combining the best attributes of both, having borrowed and refined the best features from the rest of the Acura fleet. For example: The platform and engine from the hot-performing RSX coupe and TSX sports sedan is jolted to 240 horsepower and 260 foot-pounds of torque by an ingenious variable-flow turbocharger.

The RL’s revolutionary SH-AWD system is adapted for the RDX. Inside, the RDX has utility roots of the larger MDX, and offers the latest version of the unique Panasonic ELS DVD-surround audio system from the TL, which has been my choice as the best audio system ever placed in a vehicle.

The RDX audio is better, with added speakers in the rear doors making a total of 10, dispersing the 410 watts through six channels, in professional sound-engineer Elliot Scheiner’s newest try. Crank up the power on the DVD-surround version of "Money for Nothing" by Dire Straits, and you feel as though Mark Knopfler might be sitting on the dashboard, playing his guitar.

Such a feature can make any trip fly by, and the RDX can do some flying on its own accord, if you can pardon the expression. The whole package is built under Honda’s ultra-safety guidelines to attain best-in-class crash-test ratings. Built entirely at the Marysville, Ohio, assembly plant and the nearby engine facility, the RDX will be priced at about $32,000 base, and up to $37,000 if you add all the Technical Package goodies.

The RDX is more agile than most SUVs, whether zipping through traffic in downtown San Francisco, or carving precise arcs around the hilly switchbacks going north of the Golden Gate Bridge along the coast and then inland to wine country. It definitely lives up to the planned image of a sports-sedan in SUV form, and it is obviously not built as a three-row-seater, or a tow vehicle, although it will tow up to 1,500 pounds.

The assets of being light but still safe are mostly felt in agility and power, but decent fuel-efficiency, with EPA estimates of 19 city, 24 highway, and the ability to meet Level II ultra-low emission standards, are other advantages. The only disadvantage is if a tradition-minded buyer still clings to the idea that the number of cylinders is more important than the performance.

U.S. buyers traditionally insist on a V8 or V6 engine, but Honda solves that with a 4-cylinder that uses technology and sophistication to out-perform V6es. Vice president of corporate planning Dan Bonawitz noted a major shift currently going on, with V6 sales remaining fairly constant, but a large decrease in V8 sales accompanied by a large increase in 4s.

Most likely, most V8 buyers downsized to V6es, and about as many V6 buyers downsized to 4s.

Still, if it seems like a magic trick to make a 4 that offers best-in-class acceleration and fuel economy, the magician is chief engineer Koichi Fujimori. The $50,000 Acura RL has plenty of torque with its 3.5-liter V6, but the RDX’s 260 foot-pounds tops the RL output with a 2.3-liter 4-cylinder. This engine is the latest version of Honda’s "K Series" of 4-cylinders. Koichi Fujimori laughed and denied that the "K" was for his first name.

Through an interpreter, Fujimori gave evidence of Honda’s "unfair" advantage. During an innovative and creative career, Fujimori has worked 20 years on Honda’s superb 4s, such as the over-achieving Civic, Prelude, Accord, S2000, RSX and TSX. And he’s far from finished.

"My goal is to make the K-Series 4 replace the V6," Fujimori said. "The 2.0-liter 4 in the RSX [and TSX, and the new Civic Si] is very good, and conventional thinking is to increase displacement for more power. But we asked if that was the proper evolution path. We have a lot of cars with bigger V6 engines, but our goal is to replace them with smaller 4s that can maintain the same performance."

That makes him my idol. My favorite engines always have been small-displacement over-achievers. Our family’s 1994 Honda Prelude has a 7,500-RPM redline, and I remember how impressed I was at the first S2000 with its redline RPM limit of 9,000. The new Civic Si has an 8,000 redline.

Such capabilities got their start from Honda’s Formula 1 racing technology, but the main reason they work so well on production cars is Fujimori, who presides over "500 to 1,000" other engineers, he said.

"Among engine engineers, others say I’m an oddball," said Fujimori, which prompted a chuckle from the Japanese interpreter. "We have what we call our ‘MM Concept,’ which means ‘Man Maximum, Mechanism Minimum.’ "

Typically, an engineer seeking power would try to improve his engine, then bolt on a turbocharger. Fujimori knows that his engines are so fine, so extremely sophisticated, that it might be a better idea to refine the already excellent Mitsubishi turbocharger. Turbos capture exhaust flow, and channel it to spin a compressor, which spins faster and faster until it has the force to blow a more forceful air-fuel charge back into the engine intake.

Step on the gas abruptly in a turbo engine, and there might be a lag, because at low speeds, less exhaust flow spins the turbo more slowly, so the arrival of engine power must wait for the turbo to "spool up" to adequate spin rate.

As the first production turbocharged engine Honda has made for the U.S., the RDX uses an ingenious variable airflow system to keep the turbo spinning faster, even at low engine speed. Airflow to the turbo is channeled through a smaller path at low RPMs, and being squeezed through a smaller opening causes the flow’s speed to increase, so the turbo spins faster, thus maintaining "spooled up" pressure even at lower engine RPMs, and virtually eliminating turbo lag.

Honda engines have used variable valve-timing technology for superior performance for about the same 20 years that Fujimori has worked for the company. But coordinating the innovative variable turbo with the latest i-VTEC 4 is a feat that should be credited to Fujimori’s fine hand.

Oddball, indeed!

A five-speed automatic works well, and can be manually shifted by steering wheel paddles. Those little thumb switches are showing up more and more, but the RDX has a unique feature. In "S" sport setting, you shift manually, but you can be in "D" for drive, and override the automatic with a left-thumb downshift, say to pass, or go down a grade, and the transmission responds instantly, then reverts back to drive.

Merge all those features with the SH-AWD system, which sends a portion of the engine’s torque from the front to rear axle, apportioned for either slippery driving or the weight shift of hard acceleration.

Up to 70 per cent of the power can shift to the rear axle, and 100 per cent of that torque can go to the outside wheel in hard cornering, which effectively pushes the RDX around the turn. It’s seamless, of course. All you know is you track around the curve as if you were on rails.

In the RL sedan, a variable extra gear can make the outside rear wheel spin faster than the inside, while in the RDX it is it fixed to spin 1.7 percent faster, eliminating the weight and complexity of the extra gear.

The active-lifestyle plan of the RDX may soon make large-SUV owners realize they don’t need girth, heft, and poor fuel-economy to have an SUV. True enough, Honda’s high-tech cars kept its market share growing, and if Honda missed the lucrative large-SUV glut of recent years, the market may now be coming back to Honda.

The RDX body is rigid, with high-strength steel used strategically for maximum stiffness, aiding handling and safety. The rear frame is built in a wave shape for optimum controlled crumple zones in impacts. Any such force is distributed up through the "A" pillar or down through the rocker panels, rather than to the interior.

The instrument panel and interior is well-planned and stylish. You can put two bikes into the rear if you fold the back seats down, or you can haul three friends with ease to a club across town, or a cruise to the north woods. Everything is creature-friendly. And then there’s that sound system. I told Mr. Fujimori that his engine was the quietest I had heard.

He seemed disappointed.

Then I admitted that it only seemed silent because my partner and I kept the ELS audio cranked up so high we couldn’t hear any engine sound.