SHAH ALAM (MAlaysia), 1 April 2010 - Hyundai Motor America debuted its 2.0-liter Theta II turbocharged gasoline direct-injection (GDI) engine in the 2011 Sonata at the New York Auto Show today. With the addition of the all-new 2.0-liter Theta II turbocharged GDI engine, the new 2011 Sonata offers an unprecedented combination of segment-leading fuel efficiency and power - with an estimated 34 mpg highway rating, and 274 horsepower. Remarkably, the Sonata 2.0T produces these industry-leading metrics on regular fuel…premium fuel is not required. The new Sonata is the first Hyundai vehicle to have both GDI technology and a turbocharger. By the end of Hyundai’s 24/7 version 2.0 product initiative (seven new models in the next 24 months), four nameplates will be available with GDI or the combination of GDI and a turbocharger. Turbocharging and GDI are part of “Hyundai Blue Drive,” the company’s environmental initiative to continue industry leadership in fuel efficiency and sustainability. “The Sonata 2.0T is a great example of what our Blue Drive product strategy is doing for consumers,” said John Krafcik, Hyundai Motor America president and CEO.
“Think about it - more horsepower than any of our V6 competitors, with better gas mileage than any competitive 4-cylinder model. The 2.0-liter turbocharged GDI four-cylinder engine in the 2011 Sonata produces 274 horsepower at 6,000 rpm and 269 lb-ft of torque from 1800-4500 rpm with regular fuel. The Sonata 2.0T will deliver 22 mpg city and 34 mpg highway (preliminary estimates). Hyundai’s turbocharged engine features a twin-scroll turbocharger that when combined with the GDI system results in instantaneous power delivery. Twin-scroll turbochargers have traditionally been used on more expensive high performance engines, but as with GDI, Hyundai has chosen once again to apply this efficient technology in high volume to its most popular model. Twin-scroll turbocharger designs have two exhaust gas inlets divided by split walls inside the turbine housing, with both gas passages controlled by a waste-gate. A twin-scroll turbo recovers even more energy from the exhaust than a single-scroll turbocharger thanks to a divided manifold.
The twin-scroll design separates the cylinders whose exhaust gas pulses interfere with each other resulting in improved pressure distribution in the exhaust ports and a more efficient delivery of exhaust gas energy to the turbocharger’s turbine. For example, at the start of the intake stroke of cylinder one, and when both the intake and exhaust valves of cylinder one are open (valve overlap period), cylinder three already starts its exhaust stroke with the exhaust valve open. If the exhaust passages of cylinder one and three were connected, the exhaust gas pulse from cylinder three would increase the back pressure of cylinder one. This would reduce the induction of the fresh air and increase the amount of hot residual gases inside the cylinder. However, with the twin-scroll turbocharger setup, this interference is minimized. The result of this superior scavenging effect from a twin-scroll design leads to better pressure distribution in the exhaust ports and a more efficient delivery of exhaust gas energy to the turbocharger's turbine. This in turn allows greater valve overlap, resulting in an improved quality and quantity of the air charge entering each cylinder.
In fact, with more valve overlap, the scavenging effect of the exhaust flow can literally draw more air in on the intake side. At the same time, drawing out the last of the low-pressure exhaust gases help pack each cylinder with a denser and purer air charge. Maximum boost from the turbocharger is 17.4 psi. Essentially, Sonata’s twin-scroll turbo directs even more air into the engine while a compressor increases the pressure entering the cylinder. This allows the air entering the cylinder to be even more densely packed for higher compression and better performance, contributing to a more-efficient burn and fuel efficiency. Thanks to the integrated stainless-steel turbine housing with the exhaust manifold, not only is the weight and cost of the casting dramatically reduced, the durability of the turbine housing is also improved. By adapting the motor-driven electrical waste-gate, the boost pressure is precisely controlled. The back pressure is reduced when turbo boost is not necessary by opening the waste-gate, which improves fuel efficiency.
In addition, during cold starts, the waste-gate remains open which results in faster catalyst light-off for reduced exhaust emissions. A GDI fuel delivery system contributes to improved fuel efficiency and lower emissions. This shorter, more direct path of fuel delivery allows for greater control of the fuel mixture at the optimum moment, thus improving efficiency. The fuel is injected by a camshaft-driven, high pressure pump that operates at pressures up to 2175 psi. Direct injection also utilizes a higher-than-normal 9.5:1 compression ratio while achieving a remarkable 137 horsepower-per-liter. The piston heads are “dished” to increase combustion efficiency in the cylinder. One of the program targets for the 2011 Sonata engineering team was world-class power-to-weight ratio. This philosophy was also applied to the Sonata 2.0T, with the result of a best-in-class power-to-weight ratio of 12.2 horsepower per pound, significantly better than any mid-size sedan competitor, and even better than the performance-focused Chevrolet Camaro V6. Power-to-weight ratio pays dividends in both performance and fuel economy, and is the key to Sonata’s superior performance in both of these areas.
