First direct

With some predicting that Hyundai Kia will be the third biggest car producer by 2013, it’s little wonder that the South Korean OEM is on a powertrain roll. In 2009 the company unveiled its all-new diesel heart, stop/start technology, and six-speed auto transmission.

Image: Hyundai’s 2.4 Theta II GDI engine was created in 46 months

And now there’s more: Hyundai’s first ever direct-injection gasoline engine. Codenamed 2.4 Theta II GDI, the new unit has been created with two things in mind: emissions and fuel economy. The first application of Theta II will be in the new Sonata later this year, and although Hyundai is unwilling to confirm numbers, ETi can reveal that the new Sonata GDI will realize a 10% better fuel economy than a vehicle with a conventional multipoint fuel-injected engine. Expect emissions to be improved by up to 8%.

Featuring a compression ratio of 11.3:1, Theta II generates 198bhp at 6,300rpm and 250Nm of torque at 4,250rpm. Developed within a budget of US$150 million and taking some 46 months to finalize, Theta II is oozing with exciting subsystems. Putting aside the impressive use of GDI, the 2.4-liter engine features a high-pressure fuel pump that injects fuel at pressures of up to 150 bar.

The fuel injection is split into two phases to achieve optimum combustion. In the first phase, the pilot injection and ignition trigger the piston’s downward power stroke. In the main injection phase, during the piston’s descent, more fuel is injected and ignited.

Image: Hyundai will launch the GDI engine in the new Sonata

Such a split-injection setup reduces loading on the catalytic converter and helps to lower emissions. This split-injection arrangement also enables the catalytic converter to reach an optimal operating temperature much more quickly, thus reducing emissions by 25% during cold starts. All this helps the Hyundai engine to meet ULEV-2 and PZEV standards.

Theta II features numerous design enhancements over its predecessor, starting with the application of a three-stage variable induction system that improves breathing by automatically adjusting the volume of the air sucked into the combustion chamber to create the optimal air-to-fuel mix under different engine-load conditions.

Further performance gains were made possible by incorporating dual continuously variable valve timing (DCVVT), which also improves engine breathing on the intake and exhaust sides. Depending on engine load and speed, DCVVT extends or shortens the duration of the valve opening and closing, achieving more power, fewer emissions and better fuel economy. The DCVVT system is governed by a new steel chain with an innovative roller and tooth, specifically designed for silent operation and durability.

Hyundai engineers have also introduced weight-saving innovations on the Theta II. On the bulkhead, reinforcements yielded a stiffer block without a weight penalty, and a redesign of the semi-eight-balance crankshaft led to a weight reduction. The catalytic converter is also lighter due to a new canning process that requires far less welding and uses a thinner gauge stainless steel.