Aesthetes will be left to debate the success of Hyundai's revamp of its successful Sonata mid-size sedan, as the company opted for a more conservative tack after igniting the company's fortunes with the uniquely styled outgoing model. The new model got its first North American showing at the 2014 New York International Auto Show.
But for engineers the case is closed: the 2015 Sonata boasts so many quantifiable improvements over the current car that its superiority seems beyond debate. Hyundai's engineers started with the car's foundation, boosting the use of high-strength steel to more than 50% and employing hot-stamped steel in the B-pillar for increased strength and crash protection.
The result is an incredible 41% increase in torsional rigidity and a 35% increase in bending rigidity for the unibody. Local strength is also reinforced, with side and crossmembers bracing subframe mounting points. The subframe also mounts on bushings that are 17% stiffer.
To exploit the increased precision made possible by this immensely improved rigidity, the sportier Sonata turbo even has a new rack-mounted dual pinion electric power power steering system said to provide more natural steering feel than the sometimes-numb feel of the outgoing car.
A revised multilink rear suspension is aimed at improving responsiveness, handling, and stability while simultaneously reducing impact harshness. It uses dual lower suspension arms to distribute lateral forces more effectively than the previous single-arm setup. Mando Corp. Dual Flow Damper shocks are used on all trim levels, though the anti-roll bars are 1 mm (0.04 in) thicker on the Sport 2.0T cars.
The company says that the chassis upgrades were proven at Hyundai's Namyang test track, its Mojave, CA, proving grounds, and at the Nurbugring track in Germany.
While the engineering team sought to strengthen the platform, they also sought to tune it for more pleasant NVH characteristics. To that end, they shrunk all apertures in the firewall bulkhead and layered it and the floorpan with extra sound deadening.
The platform encompasses the same 110-in (2794-mm) wheelbase as before, but the car stretches another 2.1 in (53 mm) in overall length to reach 191.1 in (4854 mm). This boosts interior volume from 103.8 to 106.0 ft³ (2939 to 3002 L), promoting the Sonata to the U.S. EPA’s large-car category, making it roomier than any of its competitors. Cargo volume shrinks 0.1 ft³ (3 L) to 16.3 ft³ (462 L), leaving it tied with the Chevrolet Malibu for the largest trunk.
Under the hood, Hyundai has evidently embraced a new philosophy in engine tuning. The 192-hp (143-kW) SAE peak power rating is gone. For 2015, the Sonata’s Theta II 2.4-L four-cylinder engine is tuned for more low-end output, so peak power flattens out at 185 hp SAE (138 kW) now.
The same philosophy is true for the 2.0-L turbocharged engine in the Sport 2.0T model, which sees its peak power sink from 274 hp SAE (204 kW) to 245 hp SAE (183 kW) due to the use of a smaller-diameter twin-scroll turbocharger from Keyang Precision, which offers quicker spool-up for better low-speed response at the expense of peak power.
(Hyundai’s Mike O’Brien details the Sonata’s powertrain engineering in this Automotive Engineering video.)
Hyundai bolstered the available technology in the new Sonata, adding features to its BlueLink infotainment system to let drivers start the car, shut it off, turn on the climate control and activate the rear defroster through their mobile devices. The Sonata also includes Apple’s CarPlay iPhone integration technology, with Siri voice control for 2015.
The result of the many changes is a car that should top its predecessor in many way. The question will be whether customers will embrace its styling as enthusiastically to give the car a chance to show them its upgrades.