When engineers at Cadillac built the ATS sedan, they knew that they were competing with some of the best products on the market, such as the BMW 3-series, the Audi A4 and the Mercedes-Benz C-Class. They paid special attention to curb weight to help meet their performance goals. “We designed and engineered the ATS\'s vehicle architecture to deliver quick, nimble and fun-to-drive dynamics,” said David Masch, ATS chief engineer. “We distributed mass to key areas. This enabled the ATS to achieve the performance characteristics that luxury-sport -sedan buyers demand.” What the ATS team came up with was one of the lightest sport luxury sedans on the market, weighing about 3,400 pounds, with a 50:50 weight balance. The 3-series weighs a few pounds more, at 3,406, the A4 weighs in at 3,704 pounds, and the C-class weighs 3,428 pounds. Cadillac minimized weight in the ATS by: 1. Using magnesium engine mounts. 2. Using an aluminum hood instead of a steel one. 3. Using acoustic-laminated glass that is lighter than standard windows and provides more UV protection and better noise reduction. 4. The team cut weight in the rear by using straight steel link with lightening holes instead of aluminum. 5. Using a cast-iron differential that doesn\'t directly reduce weight but whose rigidity helps reduce friction in the driveline for better performance. 6. Using lightweight forged aluminum. So, can it best the stalwarts of the segment? Well, the Audi A4 is the least expensive of the group, while the BMW 3-series has the most power. The ATS is the lightest. Audi is the only one that offers all-wheel drive at this near-35-grand pricing point. For Cadillac, the bottom line is that whether you value a good power-to-weight ratio or a good cost-to-power ratio, the BMW 3-series still reigns supreme--at least in four-cylinder trim on paper. We\'ll check in on the V6s next week. Read more: http://www.autoweek.com/article/20120511/CARNEWS/120519971#ixzz1ugMPTEt6