MIAMI – Kia Motors America Inc. launches its first turbocharged vehicle, partly to attract buyers who want extra oomph and partly to avoid the cost of developing a V-6 with comparable fuel economy.

The turbocharged 2.0L in the ’11 Optima replaces a bigger V-6 in previous versions of the midsize sedan.

The smaller engine has respectable power but is 15% to 20% more fuel efficient than the V-6 that no longer is available in the Optima.

Keeping a V-6 and equipping it with the technical enhancements needed to cut fuel consumption “would have been very expensive,” says Cory Bruckner, KMA’s powertrain development engineer.

So Kia opted for the Optima to offer the 4-cyl. twin-scroll turbocharged I-4, designed to respond quickly and deliver a fat band of torque, 269 lb.-ft. (364 Nm) sustained between 1,800 and 4,500 rpm.

Helping the power trip is a gasoline direct-injection system that provides more precise firings in the combustion chambers. GDI, combined with the twin scrolling that draws in more air for a potent fuel mix, delivers a higher compression ratio and lower emissions.

Improved thermal efficiency comes from integrating the turbocharger assembly into the exhaust manifold.

The twin-scroll design features two independent exhaust paths between the cylinders and the turbine housing. That prevents cylinder exhaust gas pulses from interfering with each other.

The turbo engine is 0.4L smaller than the Optima’s standard GDI 2.4L, yet delivers more horsepower, 274 compared with 200.

It is a testament to how far turbo technology has come in the last few years, Bruckner tells Ward’s.

Turbo lag, the feeling that the engine is taking a big gulp of air before accelerating, “was a huge issue with the older engines,” he says. “So was engine reliability. With today’s technology, we can deliver precise firing and cleaner burns.

“We are able to predict exactly when the firing takes place in the chamber,” Bruckner adds. “Before it was spray and pray.”

To meet stricter government fuel-economy mandates for the auto industry, “you will see more applications of this technology,” Ralph Tjoa, KMA’s manager-car product planning, tells Ward’s.

’11 Kia Optima Turbo
Vehicle type Front-engine, AWD, 5-passenger sedan
Engine 2.0L turbocharged in-line 4 cyl.with aluminum block and head
Power (SAE net) 274 hp @ 6,000 rpm
Torque 269 lb.-ft. (364 Nm) @ 1,750 rpm
Transmission 6-speed auto
Fuel system Gasoline direct injection (GDI)
Compression ratio 9.5:1
Fuel economy 22/34 mpg (10.7/7 L/100 km)

The 2.0L turbo engine also is offered in the Hyundai Sonata. The Kia’s suspension is tuned for a sportier ride, in keeping with its brand distinction from Hyundai, its South Korean sister.

The turbocharged engine is optional on the Optima EX and standard on the more upscale SX trim level. “The SX turbo appeals to more affluent, educated young males,” Tjoa says. “It appeals to people who want the power and find turbo as acceptable for engine downsizing.”

Kia’s version offers fuel economy of 22/34 mpg (10.7-7 L/100 km). That almost matches the Optima’s naturally aspirated base engine with 37% less horsepower. But it is better fuel efficiency than V-6 engines deliver in Optima competitors such as the Nissan Altima, Honda Accord, Toyota Camry and Ford Fusion, Tjoa says.

The Optima’s base price without the turbo is $18,995. With it, the EX model is priced at $24,495 and the SX at $25,995.

Kia is expecting 20% to 30% of Optima buyers to go for the high-output engine, says Michael Sprague, KMA’s vice president-marketing and communications.

The turbo take-rate will increase as more consumers become aware of its advanced technology, he predicts. “A lot of customers don’t know a lot about it.”

Or, he adds, their perceptions are clouded by memories of previous-generation turbocharged engines’ performance deficiencies.

“Much of today’s turbo audience is made up of people who historically have driven V-6s or V-8s,” Sprague says. “When we told them this delivers the performance of a V-6, they said, ‘Wow.’”

Few Optima buyers have shown an interest in a manual transmission, so the new model doesn’t offer one. “The manual mix was extremely low,” Bruckner says. After all, he adds, “it is a midsize family sedan.”

That didn’t stop KMA from taking auto journalists to a South Florida racetrack to put the turbocharged Optima through the rigors of fast and furious driving, with miles per hour reaching triple digits.

The charged-up engine and tightly tuned suspension system work well together. Turbo lag indeed is a non-issue. The engine obeys when asked to accelerate quickly and without making a fuss.

It’s not the smoothest, most refined turbocharged engine in the world. But it is among the best-priced.

The turbocharged Optima goes on sale this month, initially in selected U.S. markets, then throughout the rest of the country.

The Sportage SUV is the next Kia to get turbocharged, Sprague says.

sfinlay@wardsauto.com