2011 Hyundai Sonata Hybrid First Drive

Finding the White Space in Green

Published: 07/19/2010  - by Jason Kavanagh, Engineering Editor

Just when you thought you've seen every permutation of hybrid, Hyundai goes and tweaks the formula a bit. You know, just a bit.

Fundamentally, the hybrid powertrain in the 2011 Hyundai Sonata Hybrid — Hyundai's first — can deliver that golden moment of silence made possible via electric-only propulsion, which is not so unusual. And during other driving conditions the electric motor's twist can be blended with the gasoline engine or disabled entirely. Again, not unusual.

In ideal conditions — a fully charged battery, no accessories, the right ambient conditions and driven by a totally committed eco-weenie — engineers report that the Sonata Hybrid can briefly touch 62 mph in electric-only mode.

OK, that's a bit unusual. It's also not something that's likely to be replicated in the real world. That's the difficult part.

Mixing the Cutting-Edge and the Familiar
Really, though, Hyundai's hybrid strategy deviates from the norm in its deliberate and strategic combination of the cutting-edge and the familiar.

There's a familiar power plant under the hood of the 2011 Hyundai Sonata Hybrid. You'll find a port-injected version of the 2.4-liter inline-4 from the base-model Sonata, although in hybrid form it's been changed over to the Atkinson cycle in order to boost its efficiency. The engine all by itself generates 169 horsepower at 6,000 rpm and 156 pound-feet of torque at 4,250 rpm. A 30-kilowatt (40 hp) electric motor is sandwiched between the engine and transmission, and when this unit is in play, combined output goes to 209 hp and 195 lb-ft of torque.

The divergence from the typical hybrid path is also where we see more familiarity. Hyundai's hybrid system employs a conventional six-speed automatic transmission rather than a continuously variable transmission (CVT). Using an existing transmission simplifies the system, which both boosts efficiency and lowers cost. Hyundai also reckons that consumers prefer the familiar experience of stepped gearchanges. "A CVT feels like something is slipping," a Hyundai engineer told us.

Because the 2011 Hyundai Sonata Hybrid has fixed gear ratios in the transmission, the speed of the engine and the electric motor must be precisely synchronized when the power of the two devices is being blended. A clutch pack between the engine and the electric motor accomplishes this, acting as a mediator in place of a torque converter. A sophisticated electronic controller manages the activity of the engine and motor to ensure a scrum doesn't ensue.

A 96-pound lithium-polymer (Li-po) battery pack sits just aft of the Sonata's backseat. The primary difference between Li-po and lithium-ion (Li-ion) is the manner in which the lithium electrolyte is suspended — Li-po uses a thin but rugged polymer rather than the organic solvent of Li-ion batteries. This allows for a smaller size and a bit more flexibility in the shape of Li-po batteries, as well as higher power density. It's a technology in which Hyundai is making a large investment and it will find its way into other Hyundai vehicles, like an upcoming hybrid with a dedicated platform and a plug-in hybrid variant.

Today the batteries are sourced from LG, which adds a layer of cost and removes a degree of control. It is this situation that has Hyundai engineers considering taking battery development in-house.

What Say You, Electrons?
Said to accelerate to 100 km/h (62 mph) in 9.2 seconds, the 2011 Hyundai Sonata Hybrid won't be fast, but Hyundai figures it will pip both of its primary competitors, the Ford Fusion Hybrid and Toyota Camry Hybrid. The last examples of the Fusion Hybrid and Camry Hybrid we tested, however, both beat Hyundai's estimate of the Sonata Hybrid's performance by a half-second, and they're both a couple hundred pounds heavier than the grinning Hyundai. So at this point it's probably only safe to say that the Sonata Hybrid at least will be in the same ballpark as those cars.

We briefly drove a preproduction Sonata Hybrid at Hyundai's Namyang Proving Ground in South Korea. Very briefly, as in a few hundred yards in primarily a straight line on flat ground. Still, it was possible to discern what the Hyundai boffins were talking about with that transmission talk. The 2011 Hyundai Sonata Hybrid does indeed deliver its power in a more natural manner than many hybrids thanks to its use of discrete gear ratios. Simply put, the human brain is happy when the engine speed rises in relation to road speed.

The hybrid's zest off the line was about what you'd expect, and the powertrain integrated the activity of the electric motors with the gas engine with less of the abruptness we've observed in other hybrids. The steering and the brakes in particular feel synthetic in the way that the regenerative brakes and electric tillers of most hybrids sometimes are, and are not as refined as they ought to be in production. To be fair, we were not driving the final product.

The Dark Side of Green
Hyundai stylists went to some lengths to visually differentiate the Sonata Hybrid from its non-hybrid brethren.

The hybrid's headlights, rocker sills and wheels are new. Front and rear fascias have been altered to improve the hybrid's ability to slip unfettered through the farts of navel-gazing hybrid-owning tree huggers, improving its drag coefficient from 0.29 to 0.25. The resulting huge gaping maw in the front of this vehicle only needs a few rows of baleen and it could strain the oceans for plankton (better opt for a dark hue to hide it).

The cabin, thankfully, escaped relatively unmolested. There will be a few custom touches like seat fabrics and colors, while the instrument cluster is tweaked to include the de rigueur graphic that depicts where energy is flowing at any given moment.

Fuzzy Future
None of this technological hoop-jumping would be worthwhile if it didn't produce relevant benefits. To hybrid customers, this really boils down to fuel economy and price point.

Unfortunately, there are no official numbers for the 2011 Hyundai Sonata Hybrid on either count. EPA fuel economy figures are yet to be finalized, and Hyundai brass are mum on MSRP. Hyundai's latest preliminary estimates — subject to change slightly, of course — peg the Sonata Hybrid at 37 city/40 highway mpg, or 38 mpg combined. These numbers are better than those of every other midsize hybrid sedan we can think of, save the Ford Fusion Hybrid.

If the past is any indication, Hyundai aims to outperform and out-value Toyota. It's like some kind of corporate mission. So if we had to guess — and we do — we'd say that the 2011 Hyundai Sonata Hybrid will undercut the Toyota Camry Hybrid's base price of $26,400. Say, a nice round number like $24,900.

Sound good to you? It'll hit showrooms just before the turn of the year.

Edmunds attended a manufacturer-sponsored event, to which selected members of the press were invited, to facilitate this report.