It's a great job, if you like the work. Performance engineer Kevin Zelenka gets paid to drive in what he calls the "nonlinear zone"--a marginal-grip region of time and space where he keeps a car tracing lines he wants it to follow, despite a lack of full friction under the tires. His office sits at the intersection of traction and helpless skid. He goes to work in cars such as the all-new 2013 Cadillac ATS, at places such as the Nordschleife, and occasionally gets himself in YouTube videos.

You must have sufficient car-control skills to apply. You'll need the engineering knowledge to convert sensations under your rear end into the binary code that manages Magnetic Ride Control and antiskid electronics. And you have to bear up under pressure, because there's a lot of it developing an ATS.

The 2013 ATS is Cadillac's first true compact sedan--maybe its most important car--in 32 years. Bring crap to this dance and you'll go home with Cimarron II.

Fortunately for Cadillac, Zelenka and his associates didn't deliver crap. There's Audi/BMW/Mercedes-Benz-grade engineering to the ATS's core-world class, no qualifiers. There's no evidence that Cadillac has taken the easy way or even the most cost-effective way. The ATS is fundamentally solid and inherently balanced. Its three engine options start near the tip in terms of output and technology. The car offers rear- or all-wheel drive out of the box, and its power-to-weight ratios are best in class. With the ATS, Cadillac finally has a second sedan that Audi/BMW/Mercedes drivers (or wannabes) might actually think about buying, in a more lucrative chunk of the market.

Cadillac hasn't been good at small. It tried the compact class only once, with the Cimarron sedan introduced in 1981. The Cimarron was a leather-upholstered, front-drive J-car--just like the Chevrolet Cavalier--driven by new CAFE legislation and dealers clamoring for something to sell. It never came close to sales targets, and it ranks among the historic automotive disasters. Cadillac's market share tumbled 40 percent between the Cimarron's launch and 1997, when it introduced its second smaller car, the Catera.

The Opel-based Catera may or may not have slowed Cadillac's bleeding, but by exterior dimensions and interior volume it was midsize. The Catera gave way to the CTS, which has powered Cadillac's rise back to prosperity and respectability. But like the Catera, the CTS is midsize, matching cars such as the BMW 5-series and the Mercedes-Benz E-class. That has limitations.

The compact class, populated by the BMW 3-series, the Mercedes C-classs and the Lexus IS, is the biggest seller for luxury brands worldwide. "We've been handicapped by not being in this segment," says Don Butler, Cadillac's vice president of marketing. "But it's more than volume. It's the entry point for buyers stepping up into luxury cars, where you draw new buyers to your brand. It tends to be the shaper, the image maker, for your brand as a whole. There's no better example than BMW and the 3-series."

At 182.3 inches long on a 109.3-inch wheelbase, the ATS is almost an identical match to the 3-series and close in dimensions to the C-class, the IS and the Audi A4. It's nine inches shorter than a CTS and 545 pounds lighter. More to the point, it weighs less than just about everything else in the compact-luxury class.

The ATS starts with "all-new rear-drive architecture," says chief engineer David Masch, with one overriding objective: "Light, agile, fun." Weight-saving efforts run "bumper to bumper--engine, body, suspension, audio system." Highlights include an aluminum hood, front suspension and cradle; a half-dozen varieties of sheet and hydroformed steel; smaller fasteners; active magnesium engine mounts; and natural-fiber interior panels. The result is a base rear-drive curb weight of 3,315 pounds--at least 113 pounds less than any A4, 3-series, C-class or IS--and a consistent mass advantage over all equipment configurations. Yet Masch calls Cadillac's effort "smart dieting," because nothing was trimmed if it upset the 50-50 weight balance or significantly increased noise or vibration. The glass could be much thinner than it is. The differential case is cast iron for its better NVH properties and durability in temperature extremes.

The suspension starts with a Mac-Pherson-strut, double-pivot arrangement in front, using a pair of ball joints and lower control links instead of a conventional wishbone at each wheel. The rear applies Cadillac's first five-link arrangement. Both allow what Masch calls "optimal geometry for the best balance" of ride, impact isolation, direct steering feel and quicker lateral response. Tuning will be identical for all world markets.

Cadillac's adaptive suspension will be available on all but the base ATS. Magnetic Ride Control has evolved to Gen III with a faster processor and four smaller magnets in each shock rather than two larger ones. Gen III decreases response time 40 percent, Cadillac says, and pulls electric current out of the shocks when they need to get softer rather than waiting for the current to dissipate. With 18 sensors accounting for steering angle and brake application, MRC adjusts damping rates every inch of travel at 60 mph.

The steering assist is electric, rack-mounted and ZF-supplied, connected to the rack by a belt intended to eliminate lash and improve electric-boost feel. Brakes can be upgraded with a Brembo package featuring 12.6-inch rotors and fixed four-piston calipers, delivering what Cadillac claims is a best-in-class 60-to-0-mph stopping distance of 129 feet. Standard wheels measure 17 inches in diameter, with an 18-inch upgrade.

The top engine is Cadillac's direct-injection 3.6-liter V6, now offered in every Caddy except the Escalade. In the ATS it delivers 321 hp and 275 lb-ft of torque, surpassing similarly sized V6s from Mercedes and Lexus. In the 3.6-liter Premium, the heaviest rear-drive ATS, each pony moves 10.78 pounds of mass. That's best in class, topping both the BMW 335i sedan (11.85) and the supercharged Audi S4 (11.97).

Below the V6 is a pair of inline-fours. While both share bore centers with General Motors' Ecotec engines, Masch says the block and head castings are clean-sheet. Both have direct injection, continuously variable timing for both cams and significant friction reductions, including a variable-displacement oil pump.

The base engine displaces 2.5 liters, generating 202 hp and 191 lb-ft of torque, competitive across the class, before the ATS weight advantage. The volume engine will be the 2.0-liter turbo, which peaks at 272 hp and 260 lb-ft. With 136 hp per liter, it surpasses the 2.0Ts from Audi (105.5 hp/ liter) and BMW (120 hp/liter), yet Cadillac projects EPA ratings of 22 mpg city and 32 mpg highway in rear-drive ATS Turbos.

All ATS variants have a six-speed transmission. The stalwart is the Hydra-Matic 6L45 torque-converter automatic with tap-shift control. Only the 2.0L Turbo will be offered with a manual. A mechanical limited-slip differential comes standard with the turbo and is available with the V6.

The hardware is wrapped in Cadillac's Art & Science design language, 10 years in and proportioned for more compact dimensions. The cues are all here--taut creases, the grille, LED-trimmed vertical headlights. It's unmistakable branding and it's handsome, but the ATS seems more conservative than that first CTS in 2003. Perhaps our sensibilities have adjusted.

Inside, the ATS will feel familiar to CTS owners. There are multiple wood trim choices, aluminum or carbon fiber. You'll get A4 touch points and build quality and better finish than in a 3-series. The cabin's centerpiece is CUE, for Cadillac User Experience, the brand's new capacitive touch-screen control system.

The first thing you notice from the driver's seat is a slight visibility issue. It's becoming a way of life in contemporary automobiles but we don't necessarily like it. The thick, stretched-forward A-pillars and big side mirrors create a triangle of visual obstruction, particularly when you are looking at about 10 and 2 o'clock. It's obvious in the ATS but not horrible and everything gets much better from there.

The steering feels as good as any electric rack we've used, and the ride/handling balance is among the best in class, MRC or not. Everything feels nice, easy and solid-brake pedal, clutch takeup or shifter, which isn't the tightest but it's accurate enough.

The V6 is still the strongest, meatiest, smoothest engine and best with the automatic. There's lots of grunt throughout but it doesn't run out of breath up high and will bounce off the limiter all day.

The 2.0L Turbo is strong and linear, the engineering target for decades. There is no obvious surge point once boost is sufficient, but if you want to have fun you'll keep it at the high end of the rev scale and won't be particularly efficient. The preferred range is 5,000 rpm and up because it's most responsive there with the most satisfying reaction to the throttle and the most engine braking when you lift.

The automatic works better than most in this class even though (or maybe because) it is down a couple of gears to some competitors. It's less busy through the normal routine, but the effect of the downshifts feels like quicker reaction to the throttle. On track in competition mode it's almost as good, with appropriate gear selection and rev-matching downshifts that sound like Fangio. It slips only when you mess up. If you get a corner wrong and have to brake at the wrong time and lose momentum, the automatic can be slow picking the gear you need to get out. That brings us to one of the ATS's real strengths, when you try to imitate Zelenka-excellent balance and chassis tuning.

The ATS will understeer if you go in too hot, braking into an apex, and slide in back if you gas up too aggressively coming out. But that's on the driver, and it's easy to get back on top of the car. It's amazingly immune to sharp lifts that float the body or depressions that slam it down. "Tossable" applies, but the ATS is never mean-spirited, and the data people got the StabiliTrak chassis electronics right. There is more than enough latitude to let the driver screw up. If you want to look fast more than you want to go fast and try to work in the nonlinear zone, StabiliTrak is happy to oblige. But when you fail, the electronics mount a valiantly instantaneous effort to save you.

Short of back-to-back drives, we'll venture this: Measured by "light, nimble, fun" and balance and inherent goodness, the ATS belongs in the same sentence as the BMW 3-series.

The base ATS with the 2.5 four? Its NVH control might fall a bit from the turbo but it's better than the base C-class engine and hardly rough. And it's stout enough to enjoy. The ATS 2.5 is a good, honest and not particularly frilly car, and it might be the bargain of the bunch, if you can live with an automatic.

Cadillac offered no AWD variants for evaluation, but they should be available when the ATS starts landing at dealerships in August. Prices will range from $33,990 to $47,590, with the Turbo starting at $35,795 with destination and the V6 at $42,090. The Sport level adds sport seats and magnesium shift paddles, while the Premium level adds FE3 sport suspension and nav.

Is there an ATS coupe or V-spec in the future? "It's a fair assumption that those are two directions we'd like to take," Butler says with a smile. The more pressing question might be what would power the ATS-V. It almost certainly won't be a small-block.

With the ATS at the bottom and the new, bigger XTS for fogies and Lincoln MKS shoppers, Cadillac is better positioned than it's been in years. Still smiling, Butler notes that his division is "working on more new Cadillacs now than at any point in history."

The important subtlety is that people like Zelenka have been given an important role in developing those cars and are no longer marginalized. He and his peers have delivered a genuine sport sedan in the compact ATS. Now Butler has to sell it.