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The Quickest 2015 Hyundai Sonata on Sale Today is ... the Eco?

Motor Trend logo Motor Trend 12/23/2014 Benson Kong, Motor Trend Staff
The Quickest 2015 Hyundai Sonata on Sale Today is ... the Eco?

"Remarkably, the Eco out-accelerated the Sport 2.0T despite a significant horsepower deficit."

You might find this mini-bombshell in the 2015 Motor Trend Car of the Year Contenders and Finalists article under the section titled "Did He Really Write That?" An allegedly eco-cognizant car out-dragged something with Sport in its name from 0-60 mph and beyond?

'Tis true. When three examples of the 2015 Sonata were put through their paces earlier this year during our annual Car of the Year program, the new Eco model curiously and quickly asserted its place as the top Sonata dragster, as the specs show. Nobody was expecting the base engine in the Sonata Limited (naturally aspirated 2.4-liter I-4) to light up the acceleration scorecard, but we anticipated the Sonata Sport 2.0T would leap to the top.

Instead, when the Vbox data was brought in for analysis, the same results appeared run after run. The 178-hp Eco was consistently faster than the 245-hp Sport 2.0T, and as expected the Sport 2.0T was consistently faster than the 185-hp Limited. That has to be an awkward conversation with a customer who's just laid down extra bucks for the topline Sonata with the red stripe on the engine cover. (Red equals fast.)


2015 Hyundai SonataEcoLimitedSport 2.0T
VEHICLE LAYOUTFront-engine, FWD, 5-pass, 4-door sedanFront-engine, FWD, 5-pass, 4-door sedanFront-engine, FWD, 5-pass, 4-door sedan
ENGINE1.6L/178-hp/195-lb-ft turbo DOHC 16-valve I-42.4L/185-hp/178-lb-ft DOHC 16-valve I-42.0L/245-hp/260-lb-ft turbo DOHC 16-valve I-4
TRANSMISSION7-speed twin-clutch auto. 6-speed automatic6-speed automatic
CURB WEIGHT (F/R DIST)3,307 lb (61/39%)3,488 lb (59/41%)3,605 lb (60/40%)
EPA CITY/HWY/COMB FUEL ECON28/38/32 mpg24/35/28 mpg23/32/26 mpg
TEST DATA
ACCELERATION TO MPH
0-30 3.0 sec3.0 sec2.8 sec
0-404.24.54.2
0-505.96.36.0
0-607.88.48.0
0-7010.111.010.8
0-8013.114.113.7
0-9016.317.716.9
PASSING, 45-65 MPH3.94.34.3
QUARTER MILE16.1 sec @ 89.4 mph16.5 sec @ 86.7 mph16.2 sec @ 88.4 mph

Strange, yes? We also have a few postulations on how this situation came to be.

1) Weight

2015 Hyundai Sonata© Provided by MotorTrend 2015 Hyundai Sonata

True to its trunklid badge, the Sonata Eco placed the least total pressure on Earth of the triplet, weighing in at a comfortably equipped 3,307 pounds (18.6 lb/hp). The Sonata Limited is 181 pounds heavier (18.9 lb/hp), and the Sport 2.0T is 298 pounds heftier than its economical counterpart (14.7 lb/hp). Such dieting works in the Eco's favor, especially if it's realizing a noticeable advantage in the wheels and tires department. The Eco rolls around on 16-inch alloys with 205-wide tires, and the Limited and Sport 2.0T have 17-inch/215-wide and 18-inch/235-wide combos, respectively.

Color us cynical on weight being the chief reason for the Eco being a speedster, though. The powerful Sport 2.0T gets off the line fine, owning a 0.2-second lead (2.8 vs. 3.0) through 30 mph over the Eco and Limited. Then the Eco reels it in by 40 mph as the Limited predictably slips farther and farther back. Unless the Eco is having trouble exercising its power from launch (a possibility, as the acceleration curves demonstrate), the weight difference should exert more influence down low.

2) Aerodynamics

All 2015 Sonatas (excluding the holdover hybrid model) tout a drag coefficient of 0.27. The slight exterior variations (wheel design, front end styling, etc.) between the Eco, Limited, and Sport 2.0T could move the drag count (1 count is worth 0.0001 of the coefficient). Frontal area can be similarly affected (different tire width), and even tiny changes can make their presence felt as a car accelerates to higher speeds.

It's hard to make material statements about aerodynamic impact without the controlled setting a wind tunnel provides. But it remains interesting to see the dip in acceleration the Sport 2.0T experiences once it reaches 60 mph, as if the horsepower on tap is suddenly insufficient for breaking the air's tension at the same rate. It wasn't an anomaly with our acceleration testing, either. All of the Sport 2.0T's runs registered matching drop-offs above 60 mph.

3) Transmission

Optimizing a transmission is as important to a vehicle's driving behavior and performance as it is to make sure the engine has enough power.

From an acceleration standpoint, not taking into account part-throttle shifting and general refinement, the Eco's seven-speed twin-clutch automatic definitely holds an advantage over the Limited and Sport 2.0T's six-speed torque-converter autos. And not just in upshift times. The twin-clutch auto's first gear only has to run to 30 mph before hitting second. It'll shift to third by 50 mph and get into fourth by 77 mph. Such close gearing allows the Eco's less powerful 178-hp 1.6-liter turbo-four to stay near peak power with greater frequency. The Eco's 16.9:1 final-gear ratio in first (39-percent more torque multiplication than Limited, 22-percent more than Sport 2.0T) is a tremendous aid. Although the transmission may initially be protecting itself or waiting for the turbo to spool up, it still helps the Eco make up the speed deficit out of the hole within the first 20 mph.

In contrast, the Sport 2.0T's first gear holds until 36 mph, second through 58 mph, and third is done at 89 mph. The demure Limited is compelled to shift up by the 41, 66, and 96 mph marks before touching fourth gear.

4) Engine

A few decades ago, turbochargers were wear items. (Lasting until 80,000 miles was considered great.) Nowadays, turbos are more smartly designed, manufactured, cooled, and managed, making them the go-to method of forced induction for improving vehicle efficiency, power, fuel economy, and tailpipe emissions. The downside, of course, is that it's difficult for a turbo engine to completely match a naturally breathing engine's linearity in response, particularly in the transient states of operation that dominate our driving experiences.

Even though maximum acceleration is all about mashing the gas pedal, the linearity challenge manifests in the acceleration graph, too. The naturally aspirated Limited's curve progresses relatively smoothly; the pressurized Eco and Sport 2.0T curves flow with more irregularities. It's up to the Eco and Sport 2.0T to determine how much boost it wants, how much ignition timing to advance or retard, and how much power it can safely produce in real time.

Figuring the turbocharged 1.6-liter I-4, 2.4-liter I-4, and turbo 2.0-liter I-4 outputs at the crank is ultimately a job for a dyno. But we're inclined to believe the Eco is a bit more potent and the Sport 2.0T is at more of a disadvantage than the numbers suggest. The all-wheel-drive, 256-hp Subaru Legacy 3.6R trapped 96.5 mph in the quarter mile -- 8.1 mph faster than the 245-hp Sonata Sport 2.0T -- at the same venue.

5) Environmental test conditions

As the Motor Trend test team huddled in the fantastically air-conditioned control room at the Hyundai Motor Group California Proving Grounds during the 2015 Car of the Year event's earliest days, road test editor Scott Mortara commented on the performance-sapping heat searing our brows and any black leather seats. "Hotter than normal," Mortara declared.

And after examining five years of weather for every vehicle tested during a Car of the Year, he's absolutely right. An average high of 90 degrees and barometric pressure of 13.3 psi are the highest documented temp and second-lowest pressure (by 0.01 psi) going back to 2010. Excluding this most recent heat-wave-afflicted program, average conditions are 79 degrees with 13.4-psi air. These temperatures aren't a big deal if you're cruising along, but they matter a lot when an engine is repeatedly asked to make as much power as it can.

Our power correction factor, applied to every vehicle that's been accelerated to ensure comparison consistency, faithfully adjusts times to rectify different qualities of air ingested by everything from a turbo 1.0-liter I-3 to a normally aspirated 8.4-liter V-10. But the factor can't account for heat-induced engine and transmission protection measures that can go into effect subtly (and sometimes not so subtly when turbos are in play).

One thing's for sure: Each Sonata had its work cut out for it, balancing the driver's demand for power with any self-preservation actions. The Eco had it easiest at its 92-degree setting. The Limited and Sport 2.0T logged in at 92.9 and 93.1 degrees.

Conclusion

There are many reasons for considering a 2015 Hyundai Sonata. The exterior sheetmetal has evolved for the better; the interior looks and feels good; it scores well on passive and active safety; it drives well as long as you're not pushing it. However, if straight-line speed is a genuine concern, you may as well (rather unintuitively) hop to the Eco.

We don't know what makes the Eco quicker than the Sport 2.0T. The real answer likely pulls a little bit from each of the above categories.

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