The performance sedan universe has repopulated several times since the initial generation of BMWs that forged the field in the 1970s. Over these past several decades, there have been many defining examples of the genre, but for now, let's turn to the wallflowers. Those hot four-doors not in your face with monstrous power, enormous bling, bellowing exhausts, or military price tags. The quiet thrillers like the redesigned 2018 Audi S4.

Since the first Audi S4 in 1999, this smallish performance sedan has quietly evolved and matured in the market. In musical terms, it has never been a brass section fanfare, but rather, a distant, subtle and regal French Horn. And there's its true north. Subtlety. It gets the performance sedan job done without fuss. It's no racecar for the street, but it does grip twisty roads with quiet abandon and shortens long straights with Pac-Man voraciousness.

In the world of Audi Sport, the division that gives birth to the S-badged lineup of Audis as well as the even more performance oriented RS models, life in the aspirational automobile jet stream is diversifying. There's business to be had in offering slightly less severe performance hardware to a larger audience.

For Audi, with its RS models coming in as the super heavy-breathers, the conventional S models like the new S4 sedan gain a wider audience.



A turbocharged heart
With regard to supercharging versus turbocharging its sporting cars, Audi has gone back and forth over the years. With the 2018 S4, Audi again turns to turbocharging, the new 3.0-liter V6 engine developing 354 horsepower and 369 lb.-ft. of torque (21 horsepower and 44 lb.-ft. more than last year).

This V6 places its exhaust ports in the valley of the V, enabling the use of a single turbo also located in the V, rather than having two outboard turbos and yards of plumbing to bring the pressurized inlet charge around the engine. It makes a much tidier installation.

This engine, also to be used by corporate brother Porsche, makes more low-rpm torque, at least on paper, and weighs 31 pounds less than the outgoing supercharged engine, which helps improve front-to-rear weight distribution compared to the previous car.

Putting that power down is Audi's Quattro all-wheel-drive system. In the S4, that drive system apportions more power to the rear wheels than the front compared to A4 models, at a 40/60-percent split favoring the rear. Also, the optional Quattro Sport rear differential itself can divert all available power to one rear wheel if it senses undue slip at the opposite side.

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