Hyundai Theta engine

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The Hyundai Theta (G4KC) is a gasoline 4-cylinder automobile engine family.

The third all-aluminum engine of Hyundai Motor Company debuted in the fifth-generation Hyundai Sonata sedan, which was unveiled in August 2004 in S. Korea.

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 set of timing system that uses the company's proprietary silent timing chains. CVVT(Continuously-variable valve timing) works on the intake side.

The aluminum alloy engine block, which is formed using 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 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.

Chrysler Corporation produces a modified version of Theta, dubbed World Engine, in Dundee, Michigan. Theta and World Engine share the same basic cylinder head and enigne block design. 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, another cost-saving feature of the Chrysler-modified engine.

Contrary to the official line of Chrysler Corporation, the Theta engine factory in Asan, S. 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.