The Hyundai Theta (G4KC) is a gasoline 4-cylinder automobile engine family. The third all-aluminum engine of Hyundai Motor Company debuted in the fourth-generation Hyundai Sonata sedan (codenamed NF), which was unveiled in August 2004 in South Korea.
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It features hollow stainless-steel DOHC with powder-metal cam lobes, pent-roof combustion chamber and shimless bucket tappets in the cylinder head. BorgWarner Morse TEC supplies the complete timing system which uses the company's proprietary silent timing chains. Continuously variable valve timing (CVVT) works on the intake side. The aluminum alloy engine block, which is formed using a high-pressure die-cast method, has a unique Metaldyne-supplied cassette-type balance shaft module with a two-stage oil pump built-in. In the lower-end, the block is reinforced by a ladder frame. Other notable features include fracture-split sinter-forged connecting rods and a stainless-steel exhaust manifold. Theta's EMS (engine management system) software is EMS-II from Siemens VDO and the 32-bit PCM (Powertrain Control Module) calculates the amount of intake air by utilizing a contamination-proof hot-film type MAF (mass air flow) sensor. In the 2011 Hyundai Sonata and Kia Optima, this engine will have Gasoline Direct Injection and produce between 198 hp (148 kW; 201 PS)-200 hp (149 kW; 203 PS) and 184 lb·ft (249 N·m) -186 lb·ft (252 N·m) of torque. MPI version of the 2.4L Theta engine have a 10.5:1 compression ratio and it produces 176 hp (131 kW; 178 PS) at 6000 rpm and 168 lb·ft (228 N·m) of torque at 4000 rpm and is available in the Middle East. MPI version of the 2.0L Theta engine have a 10.5:1 compression ratio and it produces 163 hp (122 kW; 165 PS) at 6200 rpm and 146 lb·ft (198 N·m) of torque at 4600 rpm and is available in the Middle East.
Chrysler Corporation and Mitsubishi Motor began production of a modified version of Theta, dubbed World Engine, in Dundee, Michigan in October 2005. Chrysler engineered their own air intake system and exhaust manifold which is made of gray cast iron. The World Engine also differs in the EMS as it measures the amount of intake air indirectly using a MAP sensor, to lower production costs. Contrary to what Chrysler Corporation has stated, the Theta engine factory in Asan, South Korea is not a part of the Global Engine Manufacturing Alliance. Construction of the Korean factory began in August 2003 and it came on line in April 2004. It is owned and operated by Hyundai Motor Company.
Hyundai Motor Manufacturing Alabama (HMMA) is currently building a Theta II engine shop on the grounds of their Montgomery, Alabama automobile factory. The shop will build only the Theta II engine for both the Hyundai plant and the new Kia Plant in West Point, GA. It was completed in August 2008.
The Theta engine is turbocharged for use in the Genesis Coupe. In this form it produces 210 hp (213 PS) @ 6,000rpm on 87 octane (AKI) gasoline, and 223 hp (226 PS) on 93 AKI. Torque remains the same at 223 lb·ft (302 N·m) @ 2000rpm. The Theta block used is very similar to the Mitsubishi Evolution X 4B11T, but the two engines are not identical. [1]
The turbo used is a Mitsubishi TD04 model. In stock trim this unit pushes a peak of approx. 16-18psi with a sustained 14psi. This value can be changed with a boost controller and tuning.[1]
The 2.0L GDI turbo in 2011 Sonata develops 274 hp (278 PS) and 269 lb·ft (365 N·m) of torque. The fuel economy is rated at 22mpg(10.7L / 100KM) in the city and 34mpg(6.92L / 100KM) on the highway. It comes exclusively with a 6-speed AT. The engine has a maximum boost of 17psi and features twin-scroll turbocharger. [2]