Hyundai KIA Theta four-cylinder petrol engines

Hyundai / KIA
|
Theta, Theta II, Theta II Turbo,  Theta II GDI, Theta II Turbo GDI  Theta II HEV
Manufacturer:	Hyundai / KIA
Production period:	2004-present
Style:	Line four-cylinder
Engines:	1.8 L (1798 cc)  2.0 L (1998 cc)  2.4 L (2359 cc)
Cylinder firing order:	1-3-4-2
Previous model:	beta
Successor:	Nu

Theta is the name of a series of four-cylinder gasoline engines with two overhead camshafts and four valves per cylinder. The engines are built in Asan ( South Korea ), and from Theta II also in Montgomery (Alabama ), Shandong ( China ) and Hwaseong (South Korea), the development site of the Theta series.

The Theta series comes from the Global Engine Manufacturing Alliance and since 2005 replaces the 1995 released Beta engine series. The engines are built with displacements between 1.8 and 2.4 l and adapted independently by the individual manufacturers in terms of cost, noise and performance. For example, the Chrysler editions since 2004, an adjustment of both camshafts (D-CVVT), at Hyundai / KIA the exhaust side was handed in only in 2008 with the Theta II series. Chrysler, in turn, uses an indirect airflow MAP sensor , while the Theta series uses a direct-measurement, thermal MAF sensorintegrated. The development of the engine block was responsible headed by Hyundai, those of CVVT of Chrysler, the purpose in 2003 at the Mercedes-Benz released, V6 engines implementation related as a basis. The rights to the individual technologies have each contributory companies 2009 Chrysler bought all the shares in 2002 established development company GEMA yet. 

The engine block and cylinder head are in contrast to the predecessor Beta both made of aluminum . The 2.0-liter version (134 kg, Theta II 124 kg ) has a "square engine" cylinder shape: bore and stroke are the same with 86 mm. The 2.4-l variant has a bore of 88 mm and a stroke of 97 mm. This variant without direct predecessor weighs 146 kilograms (Theta II 136 kg) only two more than the 2.0L beta variant. Unlike the predecessor series, the engines were supplemented by a balance shaft for mass balance . This reduces energy losses in the single-digit PS range and the resulting noise. Since the series has more than two liters displacement, a compensation is considered necessary. 

While in the Theta series only the largest variant is controlled by an electronic accelerator , this is standard from Theta II. The idling speed is 650 revolutions per minute. The intake and exhaust camshafts are connected by a timing chain that is driven by a second one of the crankshaft . Thus, the motors do not require a regular replacement of a timing belt as in the predecessor . The valves are actuated by mechanical bucket tappets without overlapping plates They are lighter and cheaper than hydraulic tappets and rely less on good oil viscosity . The surfaces of the plungers and cams wear out, thereby increasing the valve clearance and there may be an audible ticking sound, as the cam hits the tappet somewhat jerkily - the harder emergence produces the ticking noise.  This may disappear by the expansion in the engine is warm, yet the valve clearancewith it too big. Its inspection is scheduled in the maintenance plan of every 95,000 km, but maintenance only on demand. In this, the removed material would be offset by a new, slightly longer tappets. The exchange may possibly be merged with that of the spark plugs (160,000 km).

Theta 

The engine block has "Siamese" cylinders, which means that the cylinders are contiguous and not completely surrounded by cooling water. In addition, they are strengthened by a cast-in lead frame in the lower part of the engine block. Both minimize twisting and vibration. The better thermal conductivity of the aluminum also leads to faster reaching the operating temperature and reduces friction due to unevenly extended cylinder. This design is well prepared for high pressures, such as those found in supercharged and direct injection engines. It was therefore adopted in 2006 with the exception of the "Siamese" cylinder for the gamma series. Both series received since 2009 charged versions and those with direct injection.

Each theta engine has a CVVT ( Continuous Variable Valve Timing ) for intake side camshaft timing . This has only an effect on the overlap of the valve opening from the inlet and outlet side (the opening time on the input side is variable), but not on the valve lift and the opening duration . It is therefore comparable to the BMW single VANOS technology . It causes a higher torque at low speeds and, above all, reduces the emission of nitrogen oxidesby the exhaust gas recirculation effect of a large overlap is used - this already exhaust gas is sucked back into the combustion chamber. The CVVT is supplied by BorgWarner TEC and not always listed because it is standard.The engine control is provided by the EMS-II software from Siemens VDO . 

Theta II 

Mercedes did not use the "world engines" of 2004 in its own products, but asked in 2008 for a joint development. Hyundai, however, did not accept this offer. In the same year, the group released the revision of its "World Motors" series Theta.Theta-II engines have a variable intake manifold (Variable Intake System). This takes into account the pulsation of the air in the intake manifold caused by the opening and closing of the valves. If these waves find a rhythmically adapted path into the cylinder, a resonance charging effect is created.  This opens at low and high speeds suitable for this purpose, short air. At medium speeds, a flap is closed and the air is passed through a longer pipe.The exhaust camshaft also received a CVVT control and thus resembles the BMW double VANOS. The now D (ual) -CVVT named system contributes to improved performance.To reduce friction, the contact surfaces of the tappets were coated with a diamond-like carbon layer. The average real consumption of the series is 9.8 l / 100 km for off-road vehicles and 9.2 l for sedans. 

Theta II Turbo 

In 2009, a turbo version of the 2.0L - Theta II was developed for the Hyundai Genesis Coupe . The used turbocharger is a Mitsubishi TD0. Depending on the octane number , the power is increased to 210 (91) or 223 hp (95 octane). These levels correspond to the American quality levels "Regular" (AKI 87) and "Premium" (AKI 93). As with the later Theta II Turbo GDI, the exhaust manifold is designed for temperatures up to 950 ° C for 200 ° C higher temperatures than the Theta variants without turbocharger. This can be dispensed with a consumption-enhancing, but also cooling enrichment of the mixture . To increase the performance of the cylinder heads were made more compact and introduced two new features, which later found use in the GDI variant: The piston pin is no longer fixed, but flexible (full-floating) stored, which reduces its friction on the cylinder. And at the bottom of the cylinder, a fine oil mist is sprayed, whose cooling effect allows higher speeds and pressures.  Engine and vehicle are offered in Europe since November 2010. 

Theta II GDI 

After four years of development in Hwaseong (South Korea) and 100 million euros in development costs, the 2.4L Theta II GDI appeared in November 2009, the first Hyundai / KIA direct petrol injection. The late 1990s, there was already with the Omega V8 developed by Mitsubishi GDI engine in the Hyundai Equus, which required super-gasoline because of its system-typical high compression. At that time, however, this was rare in South Korea. The resulting drop in performance made the clientele complain. Hyundai responded in 2002 with the changeover to intake manifold injection, while Mitsubishi itself had to stop using the engine due to the crisis, after only 15 months. Despite these initial difficulties Hyundai made him in cooperation with Mitsubishi until 2008 for his top model. 

In the intake manifold injection for gasoline engines, the injection valve is located in the intake manifold in front of the intake valve. In the direct injection is injected directly into the cylinder. The injector is exposed to the high pressures and temperatures in the cylinder. Hyundai used as most GDI competitors for homogeneous stoichiometric mixture formation and dispensed with an inhomogeneous stratified charge (stratified fuel charge).  Stratified charge motors have some disadvantages, such as higher particulate emissions. 

It starts with a pilot injection and ignition to set the piston in motion. During its downward movement follows the thrusting, actual fuel injection and ignition. This more precise direct fuel delivery in-cylinder increased the compression ratio in the cylinder from 10.5 to 11.3 to 1. It leads to an approximately five percent fuel saving And also causes a higher exhaust gas temperature. This benefits the faster heating catalyst, which can reduce emissions by one third during the cold start phase. The higher injection pressure of 150 bar (without GDI about 5 bar) also causes a more homogeneous fuel atomization and thus a cleaner combustion. He goes along with a system-typical ticking noise.Several friction-reducing changes were made, also to allow the higher compression material-friendly. While the contact surfaces of the tappets were already coated with a diamond-like carbon layer since the Theta II series , this is supported in the GDI by a chromium-nitride coating on the piston rings.  As in the Theta II Turbo, the piston pin is no longer fixed, but flexibly (full-floating) mounted, which reduces friction and increases the pressure resistance by 30%. Directly at the bottom of the piston, a fine oil mist is sprayed, whose cooling effect allows higher pressures.The Variable Intake System has been extended by one level to three. 

The adjustable camshafts are powered by a newly developed, quieter and more durable steel chain. In addition, the engine block, catalyst and crankshaft were lighter, the latter by using five instead of the previous eight balancing weights. Overall, the engine now weighs five kilograms less than the non-GDI variant. This should consume 10% less. This is not directly verifiable, since he has not replaced a normal Theta II. 

Theta II Turbo GDI 

A combination of Turbo and GDI was unveiled at the 2010 New York Auto Show . Similar to Volkswagen in 2005, first the introduction is a 2.0L model and the performance-oriented segment.The characteristic of this engine is its twin-scroll turbocharger , which almost completely separates the exhaust gases of the individual cylinders. The resulting turbulences homogenize the exhaust gas flow, which thus drives the turbine with more energy. Because one cylinder is always sucking in air while another is emitting exhaust, its airflows can brake each other. This happens when the inlet valve is already opened in the still ejecting cylinder ( valve overlap ) in order to suck in more fresh air due to the accelerated exhaust gas. At this time, however, another cylinder is already starting to eject, presses its exhaust with the common exhaust duct in the former and brakes its emptying. In addition, the exhaust gas pressure that the turbine requires is reduced. This can normally be counteracted only by the shortest possible valve overlap. However, the lack of suction effect of the exhaust gas reduces the inflowing fresh air quantity and consequently the power due to less combustible oxygen. The separation of the exhaust gas paths in two air channels, however, allows a longer valve overlap with sogigeriger effect. At the same time, the exhaust gas pressure is maintained.

After testing about 30 turbochargers, Hyundai opted for a modification of the Mitsubishi TD04-19T, whose turbine blade count was reduced from 12 to 11 for faster response. The housing of the twin-scroll turbine and the exhaust manifold located in front of it are cast as an austenitic steel component and supplied by BorgWarner. It is designed for exhaust gas temperatures up to 950 ° C. Together with the reinforced valve (seats) in the engine block, as well as the cooling effects of the direct injection and the sprayed oil mist introduced by the GDI, it is possible to dispense with a consumption-enhancing, but also cooling enrichment of the mixture . The pressure relief valve ( Wastegate) is electronically controlled, which compared to mechanical control more precise pressure build-up about to avoid the " turbo lag " allows. To reduce emissions, it is opened during the cold start phase. This reduces the exhaust backpressure and heats the catalyst faster. The same pressure reduction is used to reduce consumption in partial load phases without turbo support. Also counterpressure reducing the catalyst placement acts far behind the turbocharger. This favors the development of power with low-octane regular gasoline , which tends to auto-ignite earlier at high pressure . The seemingly very low compression of 9.5 to 1 is common in turbo engines. The 137 hp per liter of displacement are almost twice as much as the values ​​of the first theta generation of 2004, and the potential of the basic design with particularly pressure-resistant cylinders designed at that time is exploited. In the North American market, the engine for launch has more power than all V6 offers and undercuts the consumption of all four-cylinder mid-range  .Motor was installed among others in Genesis Coupe 2.0T facelift (2012-2016) with a power rating of 202 kW (275 hp) at 6000 / min.

Theta II HEV (hybrid drive)

The first in-house hybrid drive for compact vehicles a Theta II-based for greater followed in January 2011 H YBRID E lectric V ehicles. It is used in two flow-optimized mid-size sedans. Conceptually, he maintains the principle of the first system, but it leads from mild to full hybrids , which means that the vehicle can also be driven purely electrically. According to the manufacturer, this applies up to almost 100 km / h, but in everyday life requires considerable skill for the necessary, gentle acceleration.  The fastest possible acceleration takes 9.2 seconds to 100 km / h. In order to reach the vehicle price of 25,795 US dollars, the electric (40 hp) and gasoline engine (169 hp) work again in parallel, which represents the hybrid form of least complexity and thus minimizes the weight. Both motors can drive the wheels - if necessary also simultaneously, ie parallel. A serial system, on the other hand, directs the gasoline engine energy into the battery. From here, it receives only the electric motor, which is the sole driving force of the wheels - the gasoline engine is thus arranged with the electric motor in series or "serial". The disadvantage, however, is that when storing and retrieving the battery energy due to conversion energy is lost. The Toyota Hybrid Synergy Drivetherefore combines both arrangements. Thus, in addition to driving the wheels, the gasoline engine can simultaneously charge the accumulator. However, working out the operating states where this increases efficiency requires significantly more development time and complexity in the control of each vehicle produced. In forced-sporty city driving consumed by the Toyota system but by three liters less per 100 km than the Theta II HEV with 12 liters. The consumption in normal city driving is in practical North American EPA rating on both between six and seven liters. Here, the Sonata Hybrid saves four liters to the pure gasoline version.

The gasoline and electric engines of the Theta II HEV are connected to a six-speed automatic transmission. This saves about $ 600 and equalizes the acoustics of a conventional automatic vehicle - in contrast to the continuous speed of a CVT transmission of Toyota's Hybrid Synergy Drive. Only the Honda Accord Hybrid had previously this combination, new is the Hyundai / KIA system that the automatic without consumption increasing torque converter gets along. In its place, a clutch is attached. With it, the gasoline engine can be disconnected from the electric motor as in a manual transmission. This saves the electric motor the drive of a permanently coupled Planetary gearbox (Toyota) or torque converter. This is supposed to be effective in constant-speed cruising and, at 5.9 l / 100 km, actually results in highway consumption below the other Sonata engines (6.7 l) and the mid-range Toyota Camry Hybrid (6.9 l) ) and Ford Fusion Hybrid (6.5 l).  The under-consumption of the pure theta gasoline version is low at 0.7 l on long-haul routes.

To reduce costs, they opted for a normal Theta II engine and thus against a direct injection.  Modified but has the opening duration of the intake valve, the engine is now operating in the hybrid typical Atkinson cycle . Here, the intake valve is closed late in the compression stroke, so that the piston pushes a third of the intake air back into the intake. The mixture remaining in the cylinder now has less energy and therefore reduces the power to the level of a smaller engine, here that of a 2L theta II.
The advantage arises in the now following ignition cycle. The larger 2.4-liter engine offers a longer piston stroke (here 11 mm), so that the fuel can convert more of its energy into thrust, as in the shorter-stroke 2-liter engine. Therefore, the Atkinson cycle is more efficient, the lower power more than compensates for an electric motor. The seemingly high compression of 13: 1 arises only from its basis of calculation, the ratio of total cylinder space and remaining space after compression. The smaller amount of mixture fits into a much smaller residual space, but it is not compressed more than in the normal Theta II.The gasoline engine is started as in the Toyota system by a second, smaller electric motor (here "hybrid starter generator"), which works as a starter . Hybrid typical this is about eight times as strong as the starter of a non-hybrid engine and therefore acoustically imperceptible.  The coupling of the engine is only slightly noticeable when driving slowly. 

The manufacturer puts it on a shelf life of 10 years or 240,000 kilometers, which corresponds to the Hyundai drive warranty in the US. For the first-time owners even get an unlimited warranty, which will be replaced by the 10-year standard at the time of sale and will therefore only affect the smallest vehicle quantities. Its capacity is 1.4 kWh at a voltage of 270 V.  This is at the level of Prius, Camry- and Ford fusion batteries, which, however, still in nickel-metal made technique are. Even with the compact 44 kg lithium-ion battery, the vehicle weight of 1550 kg is the lightest of all mid-range hybrids  and is 170 kilograms higher than that of the Toyota compact hybrid Prius and Auris HSD, In South Korea, the Theta II engine is replaced by a 150 hp and 2.0 l Nu .

Technical Data

 Used in.

Listed are the Theta engines installed worldwide for each model, not all countries are offered in all listed configurations.

Hyundai

Hyundai ix35

• ix 35 LM
  • G4KD, G4KE: since 2010
  • G4KJ: since autumn 2010 outside Europe

Hyundai Genesis Coupe

• Genesis Coupe BK
  • G4KF: 2009-2012
  • G4KH: 2012-2016

Hyundai grandeur

• Grandeur TG
  • G4KE: 2008-2010
• Grandeur HG
  • G4KJ: since 2011

Hyundai Sonata

• Sonata NF
  • G4KA, G4KC: 2004-2008
  • G4KD, G4KE: 2008-2010
• Sonata YF
  • G4KD, G4KE: since 2009
  • G4KJ, G4KH: since 2010 outside Europe
  • G4KK: since 2011 in the US and Canada

Hyundai Santa Fe

• Santa Fe CM
  • G4KE: since 2010

Hyundai H-1

• H-1 TQ
  • G4KG: since 2008 (China)

KIA

KIA Carens

• Carens UN
  • G4KA, G4KC: 2006-2009 in the US and Canada
  • G4KG: set since 2009 in Canada, in the US in 2010

KIA Forte

• Forte TD
  • G4KD, G4KE: since 2008

KIA Magentis

• Magentis MG
  • G4KA, G4KB, G4KC: 2005-2008
  • G4KD, G4KE: 2008-2010

KIA Sorento

• Sorento XM
  • G4KE: since 2009

KIA Sportage

• Sportage SL
  • G4KD, G4KE: since 2010
  • G4KJ: since 2011 outside Europe

KIA Optima

• Optima TF
  • G4KD: since 2010 outside Europe
  • G4KJ, G4KH: since 2010 outside Europe
  • G4KK: since early 2011 in the US and Canada
• Optima JF
  • G4KH: since 09/2016 in the GT version