Just in case you can't decipher Audi's code for naming vehicles, the car I tested was an A4 with the 1.8-liter turbocharged engine and continuously variable transmission. It's a great little sedan, and I use the term a little bit loosely. The four-door sedan has plenty of room up front, the back seat is passable, and the ride is smooth enough. But from the driver's seat, it handles and accelerates like a smaller car, a major plus in my book.

At the heart of this driving machine is a four-cylinder, five-valves-per-cylinder turbocharged engine that measures 1.8 liters, or just 110 in.3 It puts out 170 hp at 5,900 rpm and 166 lb-ft of torque at 1,950 through 5,000 rpm. That's over 1.5 hp/in.3 with a fairly flat torque curve. To get this kind of performance, Audi engineers added double-overhead cams controlling individual valves, variable timing for intake and exhaust valves to boost performance at all points in the rpm range, and an improved fuel-injection system. The engine is also relatively efficient, advertising 20/29 city/highway mileage, and is the first turbocharged engine to meet ULEV (ultralow-emission vehicle) standards.

The engine temporarily transformed me into a speed freak, zooming away from stoplights to be first in line at the next. I also had to continually resist an impulse on the freeway to pass "just one more car."

Helping make the ride more enjoyable and the car more controllable are the "aluminum intensive" four-link suspension up front and trapezoid-link version in the rear, both new this year. Using more aluminum, front and back, reduced weight by 40%, much of it in unsprung mass. (Reducing unsprung mass reduces the energy needed to accelerate and decelerate and improves ride and handling.)

Another feature I wanted to test was the continuously variable transmission (CVT), a "no-charge" option on front-wheel-drive A4s with the 1.8-liter engine. (Other options include a 3.0-liter engine, all-wheel drive, five and six-speed manual transmissions, and a six-speed automatic transmission.) According to the literature, CVT is "as quick as a manual and smoother than an automatic, all with increased efficiency."

It uses a pair of variators connected by a vanadium-plated link-plate drive chain. According to Audi, they act "like split pulleys" with sides that move closer together or farther apart. When they are close, the chain rides on a larger diameter and nearer the outer rim. Conversely, when they are farther apart, the belt rides on a smaller diameter closer to the axis. The variators expand and contract in opposite directions, so the ratio of the drive diameters between the two varies over a wide range (12.7:1 to 2.1:1).

The entire setup is electronically controlled and hydraulically activated and uses accelerator pressure and engine speed to determine the variators' settings. It also has Tiptronic, or clutchless shifting, which lets drivers up or downshift at the flick of a switch or push on the gearshift.

I accelerated several times from a dead stop up to 60, and although Audi says "shifting is imperceptible," you can't help but notice the sound of the engine changing as the CVT does its job. At the very least, CVT acts as an interactive automatic that can be ignored. But perhaps I should attribute some of the quickness and responsiveness to the CVT rather than the engine. Either way, you can't go too far wrong with a no-charge option.

The A4 reconfirms my admiration for German engineering and dedication to the driver. It carried a $29,950 sticker, which included $450 for a metallic paint job; $1,000 for a sunroof; $1,000 for the Sports package (17-in. alloy wheels, sport suspension, and ultrahigh-performance summer wheels); $525 for heated front and rear seats; $350 for a Premium package (autodimming exterior and interior mirror, compass, and the Homelink remote transmitter for garage door openers and such); and a $575 destination charge. Not cheap, but a great way to go for drivers with small families.

The multilink chain at the heart of the CVT is as strong as steel and as flexible as a rubber V belt, letting it handle torque inputs as great as 230 lb-ft, enough for the 1.8 or 3.0-liter engines in the A4 lineup. The chain's flexibility lets Audi eliminate the hydraulic-torque converter, thus avoiding acceleration slippage that cuts performance and fuel economy.