Hyundai KIA Nu four-cylinder G4N petrol engine

Hyundai / KIA
Nu, Nu Hybrid, Nu GDI, Nu CVVL
Manufacturer:	Hyundai / KIA
Production period:	2010-present
Style:	Line four-cylinder
Engines:	1.8 L (1797 cc), 2.0 L (1999 cc)
Cylinder firing order:	1-2-4-3
Previous model:	Hyundai KIA Theta

The Nu series are four-cylinder double overhead camshaft ( DOHC ) gasoline engines with four valves per cylinder (16v). The engines are manufactured in South Korea , for China and North America in Shandong ( China ). 

The engine block and cylinder head are made of aluminum . The 1.8-liter engine weighs 112 kg. weights and dimensions of the other cylinder engines are currently unknown, the same applies to the idle speed of the series.All engines in the Nu range are controlled by an electronic accelerator pedal .The power transmission from the crankshaft to the cylinder head by means of maintenance-free timing chain , the ancillariesare driven by a serpentine belt. For this is from 100,000 km every 25,000 km an inspection provided, an exchange only when determined need.

The valves are actuated in the engines without CVVL via roller rocker arms, which act like a rocker. While one side pushes the valve downwards, the other one is fitted with a built-in spring which rests flush with the valve , valve open (In the CVVL technologythe cam is applied to a rolling wheel, which presses by a low-friction lever on a lever to open the valve. This lever is adjustable and serves to vary the opening duration and valve lift. Both forms of valve clearance compensationare maintenance-free, even an inspection is not provided in the maintenance plan. Wear would be signaled by a ticking noise.

The Nu-Series sums up all the technologies that the manufacturer developed by 2010, apart from direct injection and turbocharger for its gasoline engines. However, none of them made their debut with this series, which is why their presentation was chosen as the highest stage .

Adopted from its predecessor series , a D (ual) -CVVT named camshaft adjustment varies the intake and exhaust side. It has an influence on the timing of the valve opening on both sides, but not on the valve lift and thus the opening time It is therefore comparable to the BMW double-VANOS technology . In addition to a better torque in the lower speed range, it reduces above all the nitrogen oxide values, by the exhaust gas recirculation effect of a large overlap is used - this already sucked exhaust gas is sucked back into the combustion chamber. The D-CVVT is not always listed due to its standardity. 

The air intake is also the variable intake system (Variable Induction System). This takes into account the pulsation of the air in the intake manifold, which is caused by the opening and closing of the valves. If these negative and positive pressure pulses find a rhythmically adapted path into the engine compartment, a slight resonance charging effect is created, similar to a turbocharger . To attain it opens at low and high speeds suitable for this purpose, short air. At medium speeds (3000 to 5500), the longer air flow is used by means of a flap, resulting in consistently high torque and five percent more power. While the technologies listed above appeared on the Theta II series , the offset crankshaft goes back to the 2006 gamma range. The pistons are constantly pressed by the rotational movement of the crankshaft to a cylinder wall. An offset of this position by one centimeter now allows the pistons to slide down more smoothly in the ignition phase. This friction reduction reduces not only the consumption but also the vibrations. The same approach is used by Toyota in the Prius . 

It is not known to use friction-reducing coatings on pistons and valve actuators, which are used in other motor series and are therefore probably unmentioned here.To reduce costs, this expansion stage will remain without adaptation of the ISG automatic start-stop system , which was developed together with Bosch . The real consumption ranges from less than 5 to more than 9 liters, centered in between is the American EPA standard of 7.1 l / 100 km. 

Nu Hybrid

For South Korea the engine in the first full hybrid drive of the manufacturer was exchanged for a 2.0L engine of the Nu series . All other properties were preserved.The composite now delivers 191 hp instead of the previous 209. On the consumption side, the result is not determinable for the time being, since the South Korean consumption assessment differs significantly from the American, with the 209 hp variant was previously measured exclusively. According to figures, fuel consumption dropped from 6.4 to 4.8 liters per 100 km, which is clearly more than the effect of the exchange of two similar engines.

Nu GDI 

Half a year after the Nu series, it was equipped with direct injection (GDI) and used for the market launch of the Hyundai i40 in the summer of 2011 for the first time. Together with the variable valve lift CVVL is G asoline D irect I njection a prerequisite for the next homogeneous engines .In conventional injection for gasoline engines, the injection valve is located in the intake manifold upstream of the intake valve. With increasing speeds, however, the opening time of the valve is always shorter, and thus the time window for introducing the fuel. In the direct injection is therefore injected directly into the cylinder. Hyundai used as most GDI competitors for homogeneous stoichiometricmixture formation and dispensed with an inhomogeneous stratified charge (stratified fuel charge). The latter is associated with systemic disadvantages, such as significantly increased fine dust levels. 

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 fuel delivery, directly in the cylinder, increased the compression rate in the cylinder. This leads to a fuel economy And also causes a higher exhaust gas temperature. This benefits the faster heating catalyst, which can reduce emissions 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.To reduce fuel consumption, the Nu GDI is available with the ISG automatic stop-start system , the effect of which is approximately 0.2 l / 100 km for other vehicles in standard fuel consumption, but can only be checked by manual deactivation due to their standard features on vehicles with Nu GDI engines is.

Nu CVVL 

With the introduction of this variant ended in April 2010, the 44-month development of the Nu series, whose costs of 153 million euros should relate specifically to the CVVL technology. It replaces the dual CVVT technology, but varies only the valves of the inlet side. All other features are identical to the Nu series .In the CVVL system, the cam rests on a rolling wheel, which presses it with little friction on a lever, which then opens the valve. This lever is located on an eccentric shaftso that its fulcrum is adjustable. A servomotor takes over this task and thus changes the rotation deflection. This changes the valve lift (valve lift), the opening time and the opening time. These three effects are interconnected. Because a long stroke means a long opening time, since the strokes must be covered material-friendly with not too fast accelerations. A longer opening period also means that the process begins earlier and ends later. This has also changed the timing. An independent variation of the parameters is only possible with a camshaft-free opening of the valves . In contrast, the CVVL system is similar in design to the BMW Valvetronic.The CVVL eliminates the need for a throttle valve , which reduces the associated throttle losses . These occur on all elements that redirect the air flow, including the valves themselves. However, the throttle that controls the intake air is considered as the main cause. Without them, more air would flow into the cylinder at partial load, which would increase the combustion temperature and thus the amount of nitrogen oxide above the Euro limits as a result of its higher oxygen content . The variable valve lift can now take over the air control itself. This saves him five and a half percent fuel compared to a Nu engine without valve variation, which does not exist.  The effect to the actualBasic tier of the series should be between three and four percent.

Hyundai's vice-development chief explains the Nu series as a link between theta and gamma engines . Especially the former is architecturally not suitable for 1.8 liter capacity. Notwithstanding, however, the leading manufacturer of such a version for years in the theta series. The statement should therefore focus on the sustainability, especially the suitability for homogeneous mixtures (HCCI) . These require very precise valve timing and injection. With CVVL and GDI Nu series meets both conditions, though so far in separate motors. Hyundai / KIA plans its first homogeneous engine for 2012. 

Outlook (Nu HCCI) 

The efficiency expectations of homogeneous engines are based primarily on their higher compression and low-emission combustion. Increasing the compression from today's standard 11: 1 to 15: 1 results in an increase in efficiency of 20%.^,this compression usually produces an uncontrolled auto-ignition of the gasoline. In this " knocking ", the mixture expands too early, that is before the piston has completed its upward stroke. This receives an abrupt braking from above while being pushed further upwards by the crankshaft. Therefore, gasoline engines using knock sensors avoid excessive compression.

To increase the compaction, the mixture must be prepared so that it ignites at the right time and at several points at the same time. The latter, to achieve a residue-free combustion - because unburned fuel is missing in the propulsion. Similar, partially homogeneous combustion has already been achieved with stratified injection gasoline direct injection. However, they emit large amounts of nitrogen oxides and also produce soot during load changes, as they vary the air flow through the valves little or no. Therefore, they need an expensive nitrogen oxide filtration of the exhaust gas, Euro standards since 2009 also limit the soot emissions for petrol engines.Homogenous motors therefore work with variable valve lift. So they suck a larger amount of exhaust back into the cylinder and so regulate the auto-ignition. The lack of oxygen in the exhaust avoids premature ignition, while its heat enables auto-ignition. This requires about 1000 ° K. The combustion takes place at 2000 ° K; due to the low oxygen content around 600 ° cooler than in conventional gasoline engines. The nitrogen oxide levels are thus reduced to a minimum. Nevertheless, the self-ignition at a disadvantage. The problem is the already during partial load range from 24 to 36 bar increasing pressure during ignition, especially its rapid increase and decrease by the eponymous homogeneous, ie simultaneous combustion of the entire fuel. Therefore, homogeneous engines work only in part-load operation with auto-ignition, while they rely on less compression and a spark plug under full load. The same applies at high speeds at which the injection nozzles no longer comply with the homogeneous mixture production. Therefore, the choice of an engine range larger capacity for HCCI development makes sense, since only these give enough power to drive as often as possible in partial load operation . The full-load operation would already lead the materials to their load limit, quite apart from turbocharging with their extra gasoline addition.

CVVL is therefore required to precisely adjust the valves for compression and exhaust gas recirculation rate, especially during load changes. Then the material is also changed from auto-ignition to spark ignition by means of a spark plug with low compression. GDI in turn allows pilot injections. Only so that the gasoline can be added one after the other in the incoming air and thus accurately distributed in the combustion chamber, which is a prerequisite for auto-ignition.The effect of homogeneous operation will not have been named by Hyundai / KIA yet. For the classification of HCCI engines, however, it is worth knowing that the European consumption determination can be almost exclusively carried out in partial load operation.  The first engines with a HCCI-like compression ratio of 14: 1 are the Skyactiv G-drives from Mazda. However, they dispense with the auto-ignition, which means that they can probably maintain the high compression under full load. This engine will be used for the first time from summer 2011 in the Mazda 3 facelift.

Technical Data 

Use 

Hyundai 

Hyundai Elantra

• Elantra UD / MD
  • G4NB (148 hp): 2010-today

Hyundai i40

• i40
  • G4NC (177 hp): 2011-today

Hyundai Sonata

• Sonata YF
  • G4NE (190 hp): 2011-today (only South Korea)

KIA 

Kia Optima

• Optima TF
  • G4NA 2.0 CVVL (170 hp): from 2012

KIA soul

• Soul AM
  • G4NA (164 hp): 2011-today (North America and Canada)