Hyundai Sonata Plug-in Stands Out

Last year, Hyundai was the first automaker in the world to sell a vehicle powered by a hydrogen fuel cell. Hyundai Vice Chairman Woong-chul Yang makes it clear the automaker plans to be a trailblazer in hybrids as well as fuel cells.

April 4, 2016

5 Min Read
Hyundai Sonata Plug-in Stands Out

Wards 10 Best Engines competition has recognized outstanding powertrains for 22 years. This installment of the 2016 “Story Behind the 10 Best Engines” series looks at the development of Hyundai’s plug-in hybrid-electric propulsion system.

Creating a hybrid-electric vehicle or plug-in that gets great mileage is one thing. Developing one that consumers actually want to buy in today’s super-competitive marketplace is quite another.

Dozens of affordable, well-engineered HEVs and PHEVs currently are available, yet consumers are shunning them because cheap gas and extremely efficient conventional gasoline powertrains make them less attractive.

Even so, in Wards 10 Best Engines testing last fall, WardsAuto editors found three alternative powertrains that cut through the clutter and found their way onto our list: the Chevrolet Volt extended-range EV, the Toyota Prius hybrid and the Hyundai Sonata plug-in hybrid.

Each has its own special virtues, but the Sonata PHEV, the Korean automaker’s first plug-in hybrid, is the one that created the most buzz in the hallways as editors compared notes about getting 60 mpg (3.9 L/100 km) to 80 mpg (2.9 L/100 km) on their daily commutes, which extended far beyond the car’s all-electric range of 27 miles (43 km).

Officially the car gets 99 MPGe (2.4 L/100 km) combined in all-electric mode and 40 mpg (5.9 L/100 km) combined in HEV mode, but editors found the second number to be conservative. We suspect much of the credit goes to Hyundai’s improved regenerative braking system and enhanced hybrid control software that turns on a high-efficiency on-board charger at strategic moments to add juice even when the car is in EV mode.

Overall, Hyundai’s new HEV architecture represents a big leap from the previous generation, in part because the Korean automaker is obsessed with being recognized as a powertrain leader.

Last year, Hyundai became the first automaker in the world to sell a vehicle powered by a hydrogen fuel cell. Hyundai Vice Chairman Woong-chul Yang, whose responsibilities include overseeing global powertrain development, makes it clear the automaker plans to be a trailblazer in hybrids as well as fuel cells.

“In hybrid technology, we are not looking for a short-term profit,” he tells WardsAuto while visiting Detroit in January with his executive team to pick up the Wards 10 Best Engines trophy for the Sonata plug-in.

A Ph.D. engineer who has been leading development of alternative powertrains at Hyundai for more than a decade, Yang says the company must look 20 to 50 years down the road to keep improving its brands and recognize the needs of consumers and the environment. “We are not just some company selling consumer products,” he says, underscoring the importance of vehicles to society.

Yet despite concerns about pollution and climate change, even the best HEVs and PHEVs are a tough sell in today’s marketplace.

Engine designers recognized the problem even in 2012, when development work began on Hyundai’s latest-generation hybrid architecture, so they set out to make the ’16 Sonata PHEV a “no-compromise” car, says Mike O’Brien, vice president-corporate and product planning at Hyundai Motor America.

It was designed to have a total gasoline and electric range of more than 600 miles (966 km) in order to give drivers the best of both worlds by providing the power delivery of a conventional gasoline engine for long trips or vacations with the additional benefit of environmentally friendly all-electric range for commuting, O’Brien says.

And, to make sure it could be priced attractively, engineers squeezed in the biggest battery in the segment, which allows it to qualify for a $4,919 federal tax credit. That incentive makes it more affordable than many conventional HEVs with fewer features. The base Sonata plug-in starts at $34,600, but when the federal tax incentive is factored in, it’s less than $30,000. “That gives our dealers a real selling advantage,” O’Brien tells WardsAuto.

How Hyundai Sets it Apart  

On paper, the powertrain numbers don’t look that impressive. Engineers switched from a port-injected 2.4L engine making 166 hp and 154 lb.-ft. (209 Nm) of torque to a 2.0L direct-injected 4-cyl. making 154 hp and 140 lb.-ft. (190 Nm).

Total electric output is just 67 hp while plug-ins from Ford and Honda have considerably more.   

But like the other hybrids on the Wards 10 Best Engines list this year, engineers spent a lot of time coaxing more efficiency out of the internal combustion engine part of the equation in addition to numerous system enhancements.

The new engine features a higher compression ratio, an electric water pump instead of a mechanical one, a 2-stage oil pump and cooled exhaust gas recirculation to reduce pumping losses and improve combustion. A high-energy ignition coil also improves combustion stability.

While less powerful than the old, larger engine, the new one has higher specific output, a flatter torque curve and runs on a more-efficient Atkinson cycle.

On the electric side, there is enhanced hybrid control software, a high-voltage electric oil pump for improved efficiency, significantly increased regenerative-energy capture and a 9.8-kWh lithium-polymer battery system five times larger than the standard Sonata HEV’s battery.

And despite being downsized, the new engine still is one of the most powerful in the segment. Most importantly, the car has more all-electric range and better drivability than any comparable plug-in.

Another way the Sonata sets itself apart from the rest of the PHEV pack is that unlike most of the affordable hybrids we test, it uses a 6-speed step transmission instead of a CVT to transmit power to the wheels and an electric motor in place of a torque converter. This is not a new strategy for Hyundai, but it seems especially appropriate for an upscale midsize sedan like the Sonata PHEV.

The transmission layout provides fast and seamless transitions between EV and hybrid modes and a refined transmission shift quality that feels far better than the boring wonkiness of a CVT. This reinforces Hyundai’s contention that Sonata plug-in buyers don’t have to make compromises to buy a roomy family sedan that gets eye-popping mileage on daily commutes.

O’Brien runs another benefit up the flagpole as well. The Sonata PHEV promises to be a better long-term investment than a pure battery-electric vehicle because the duty cycle for BEVs is full of peaks and valleys that shorten battery life, he says.

PHEVs, on the other hand, can manage the state of charge and discharge. “So in terms of total cost of ownership there are some advantages to a plug-in versus a BEV because the duty cycle is so much more extreme,” he says.

However things turn out in the short term, Hyundai executives make it clear that when it comes to plug-in hybrids, they are in for the long haul.

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