2011 Sonata has four-cylinder-only engine lineup

  • 26-Mar-2010 03:31 EDT
aei-sonata210-1a.jpg

Sonata adopts "fluidic" styling, with Cd dropping from 0.32 to 0.28 on the 2011 model.

When product planners for the 2011 Hyundai Sonata sedan made a commitment to limit the transverse front-drive powertrain offerings to a choice of four-cylinder engines, it was the latest step to keep the Korean manufacturer the industry leader in the U.S. fuel economy rankings. Hyundai reached that height last year, with 30.1 mpg, edging No. 2 Honda's 29.7 mpg. Those numbers are based on U.S. EPA tests for the full product lines, adjusted for 55% city/45% highway.

Classified by U.S. EPA as a "large" car, the new Sonata carries a highway economy number of 35 mpg to go with 22 city for the automatic, 24 city for the manual, overall more than 5% better than the 2010 model. That is significant because Hyundai also increased four-cylinder performance. The new model is another step toward the 35.5 mpg required for CAFE (Corporate Average Fuel Economy) by 2016.

The improvements were accomplished with a new platform and powertrain.

Direct-injection engine

The naturally aspirated four-cylinder is based on the "world engine" engineered by Hyundai and shared with Chrysler and Mitsubishi. The Sonata displacement still is 2.4 L, but the engine was extensively reworked, including new cylinder heads and high-pressure fuel system for direct injection. So output is up from 175 hp (130 kW) to 198 hp (148 kW), or 200 p (149 kW) with dual exhaust. The engine is mated to a new Hyundai-developed six-speed automatic.

Yes, the de-listed 3.3 V6 delivered 249 hp (186 kW), but the take rate was only 10%. A turbocharged 2.0-L four-cylinder is coming later this year that will develop "well over 250 horsepower" and "we'll also be trying to get 35 mpg highway with this one," said Hyundai Motor America CEO John Krafcik. In addition, a four-cylinder gasoline-electric hybrid Sonata, using lithium-polymer batteries, is coming later this year, giving Hyundai a competitor to the Fusion hybrid, with fuel economy likely over 40 mpg.

Lower Cd

However, the 2011 Sonata story is much more than its four-cylinder-only lineup. The look now is "fluidic," a sedan with the contemporary coupe-like appearance and a beltline that curves gently down to the headlamps. The car was styled at the Hyundai Design Center in Irvine, CA.

The Sonata's new look also helps lower the Cd to 0.28 vs. 0.32 for the 2010 model. Because the total interior package is at least 120 ft³ (3.4 m³), the Sonata retains an "EPA large car" designation, with an passenger volume of 103.8 ft³ (2.94 m³) and trunk of 16.4 ft³ (0.46 m³). The car grows only an inch to 189.8 in (4821 mm) overall, but wheelbase was lengthened more, growing from 107.4 to 110 in (2728 to 2794 mm).

Significantly, vehicle weight is down. The 2011 Sonata comes in at 3199 lb (1451 kg) with an automatic transmission, a reduction of 128 lb (58 kg) from the 2010. Three major contributors of the reduction were a switch from upper/lower control arm to MacPherson struts for the front suspension; a six-speed automatic that has a mass 26.4 lb (12 kg) less than the previous five-speed unit; and taking out some mass from the front structure that was needed to support the V6.

Although the manual-transmission model is lighter than the automatic, like all competitive manufacturers Hyundai employs it as a price leader of under $20,000 ($19,195). That is a price break category on many Internet car purchase guidance websites, though actual sales below that number are insignificant (typically 2-5%).

Other contributors to fuel economy are a smart alternator (charges the battery primarily during deceleration) and low-rolling-resistance tires. The tires are a new design that maintains good braking performance, with a 70-0 mph (112-0 km/h) distance of 170 ft (52 m).

Despite the lighter weight, the car already has received "good" ratings in the Insurance Institute for Highway Safety dynamic side-impact tests (Federal tests are due in a few months). Compared with the 2010 model, the body-in-white dynamic rigidity numbers are the same (30 Hz in torsion) or higher (52.9 vs. 49.7 Hz in bending, and 45 vs. 42.7 Hz in lateral). In addition to structural benefits from redesign, the new body is made with 62% high-strength steel, including 18% ultra-high and 3% boron super-ultra-high, with the boron used in the B-pillars and roof side outer panels.

A short turning-circle diameter long has been a Sonata characteristic, something Hyundai engineers decided customers would notice even in a brief test drive. The 2011 specification is just 35.8 feet (10.9 m), exactly the same as the 2010 and measurably smaller than all competitors (Toyota Camry, Honda Accord, Nissan Altima, Ford Fusion, and Chevrolet Malibu), except the Mazda6 at 35.4 ft (10.8 m). Sonata also gets column-mount electric power steering, a change primarily for fuel economy.     

There are three models in the Sonata line, GLS (with 16-in wheels), GLS Limited (uplevel trim and 17-in wheels), and the sportier SE (17-in wheels with stiffer suspension, thicker rear sway bar, and monotube rear shock absorbers).

Firmer ride

The ride has been "moved away from the Camry," Hyundai chassis engineer Cameron Kurth said, meaning it is noticeably firmer. The geometry of the MacPherson-strut vs. the previous control-arm front suspension makes a direct numerical comparison of spring rates impractical, but they are an estimated 23% higher. Rear suspension spring rates are up from 43.2 to 48.1 N/mm (247 to 275 lb/in), but because of changes in geometry for the multi-link suspension, this translates to an 8% increase.

Front sway bar thickness is down a bit, from 26 to 24 mm (1.02 to 0.94 in) on all models, because of packaging limitations. The rear is down from 16 to 15 mm (0.63 to 0.59 in) on GLS and Limited, but remains at 17 mm (0.67 in) on the SE. But both sway bars on 2011 models have a ball-joint connection instead of a bushing joint, so the bars respond more directly to cornering force (vs. compression of a bushing joint). Also, the U-clamp bushing contains a pair of curved metal plates that stiffen it, so clamping preload friction can be reduced, also contributing to better response.

Although the cabin noise level on the 2010 was competitive in the class at 63.5 dBA for wind, 70.0 dBA for road, Hyundai took several steps for further reduction, getting the numbers down to 63.1 and 69.5. Driver's side glass is 25% thicker, door frame 12.5% thicker, and the body gaps for the door and between trunk lid and rear glass are tighter. And muffler capacity was increased from 23 to 25 L (1400 to 1525 in³) to lower exhaust noise.

A slimmed-down version of the Sonata platform was used for the recently introduced Tucson small crossover, which previously had been built on the Elantra platform. The platform will be stretched and widened from the Sonata dimensions for the forthcoming Santa Fe mid-size crossover.

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