Hyundai is expanding its Sonata
lineup seemingly with something for everyone. In honoring this South
Korean company’s press embargo, I cannot share driving impressions just
yet, but I can spill the technical beans. And there are lots of them.
The 2.0T Sonata,
as its name suggests, is powered by a turbocharged 2.0-liter engine.
Hyundai avoided the GDI moniker that could have legitimately been
attached, as this inline-4 also features direct injection of its
gasoline. Now I admit there’s nothing particular novel about having a
turbo-enhanced direct-injected engine of small displacement do the job
of a traditional—and more fuel-consumptive—V-6. But Hyundai engineers
have been busy in perfecting this concept in several distinctly
innovative ways.
For one, the turbo’s compressor housing is actually part of the engine’s
exhaust manifold. What’s more, the casting that integrates these two
elements is of austenite stainless steel. It’s quite a technical
achievement to use this material, but it’s ideal for this application
because of its thermal properties of getting exhaust heat efficiently to
the turbo’s compressor. And, of course, having the two components
integrated into one only enhances this.
Factoid: It’s both the kinetic energy of exhaust flow as well as the
thermal energy of its expanding gases that drive the turbo’s compressor
and its attached forced-induction-producing impeller. Hyundai’s
integrated design enhances both aspects.
The Sonata’s turbo is a twin-scroll type as well. That is, its porting
and vanes are designed to exploit two separate paths of exhaust flow,
from cylinders 1 and 4 and from cylinders 2 and 3. This way, pulses
during inherent four-stroke operation don’t trip over each other. This
twin-scroll idea isn’t unique to Hyundai (the 2.0-liter Buick Regal uses
it as well). But the Sonata’s 274 bhp versus the Regal’s 220 suggests
the other wizardry involved.
Hyundai engineers figure that optimized forced induction plus direct
injection are worth around a 22-percent kick in torque, from 220 to 269
lb.-ft. over a broad rpm range, with the twin scrolls accounting for
perhaps half this. There’s lots of synergy involved here as well: Direct
injection provides a cooler charge of fuel; optimized intercooling does
its magic as well with the forced induction of air. They combine to
produce the 2.0T’s 137 bhp/liter, a figure that’s quite amazing in a car
in the $24K-$29K range. More details on this and my driving impressions
once the embargo has lifted.
The Sonata Hybrid
also carries some very neat tech, specifically in its parallel-hybrid
drivetrain, lithium-polymer battery pack and optimized thermal
management. Hyundai engineers also pointedly used the term “fun to
drive” in describing their hybrid design and development.
Its 2.4-liter gasoline engine operates on an Atkinson Cycle; more
correctly, like other hybrids, on a innovatively valve-timed simulation
of this short-compression/long-expansion concept. A clutch separates
this powerplant from a 41-hp electric motor which resides directly ahead
of a 6-speed automatic transmission eventually sending twist to the
car’s front wheels.
Note the difference between Hyundai’s hybrid layout and those of Toyota Camry, Ford Fusion or Nissan Altima
(these three, certainly technical siblings in more ways than one). The
Hyundai’s 6-speed automatic is in marked contrast to the other’s CVTs,
one claimed benefit being enhanced highway performance. What’s more, as
its operation is integrated with the electric motor’s, this automatic
has no need for an energy-sapping torque converter.
Unlike these other cars’ nickel/metal hydride battery technology, the
Sonata Hybrid’s is lithium-polymer. Newer technology, it offers
improvements in everything from power and energy density to weight to
volume to cycle life to characteristics of state of charge.
This last one, SOC, for short, is particularly interesting in Hyundai’s
optimization of hybrid operation. For reasons of durability, any battery
profits from gentle chemical action—not being discharged too deeply,
not being charged to its full capacity, with SOC being a measure of
this. Typical nickel/metal hydride batteries owe their life-of-the-car
longevity to an SOC window as narrow as 15 percent; e.g., operating no
less than 50 percent SOC, no more than 65 percent SOC. Hyundai engineers
say lithium technology can accept a wider range, say 50 to 75 SOC, with
no degradation of battery durability.
What’s more, innovative thermal management stretches this further: In
cold weather, for example, the Sonata Hybrid’s SOC window can expand to
as wide as 45 percent, from 45 to 90 SOC. One benefit of this is
balancing the inherent loss of battery performance concomitant with
lower ambient temperatures. Despite these exemplary SOC characteristics,
Hyundai engineers expect to confirm battery longevity on the order of
250,000 miles or more.
A last example of Hyundai’s thermal management and efficiency. Compared
with other Sonatas, the Hybrid has a larger air intake; this, to handle
hybrid powertrain cooling in extremes such as Death Valley at summer’s
peak. On the other hand, such a gaping snout is detrimental to
aerodynamics. To optimize matters, the Sonata Hybrid has what engineers
term an Active Air Flap. As its name suggests, this gizmo automatically
adjusts the airflow. It’s wide open at low vehicle speed and high
coolant temperature; it closes as speeds increase or coolant temperature
drops. Engineers figure there’s a 10-percent reduction in CD with this,
all the more impressive when you hear that the car’s inherent drag is
an already low 0.25.
My driving impressions of the Sonata Hybrid can appear on October 18 (one day before my birthday—please, no presents).
Ask David Masch, the chief engineer behind the ATS, why he sees this
sedan as significant, and he’ll cut straight to the chase. Masch says
the compact luxury segment is the most important market for any
automaker that wants to engage the well-monied brands of the world.
Models in this class fall into a certain sweet spot that’s unlike
anything else in the automotive industry, serving as a catchall for
buyers moving up to a luxury purchase for the first time and those
stepping down from a more expensive model for something a little more
engaging to drive. Masch fully expects the ATS to serve as the volume
model for Cadillac moving forward, out pacing the SRX and even the CTS
family in short time.
