COVER STORY

Engine Technology

The New 1.6 l Diesel Engine Innovations for Hyundai/Kia’s C-Segment Vehicles

A new 1.6 l diesel engine has been launched to enhance the competitive power of Hyundai/Kia Motors’ C-segment vehicles. This engine provides 84.6 kW of maximum power, 255 Nm of torque over a wide engine speed range and has a homologated fuel consumption of 4.7 l/100 km. In parallel to these achievements, noise, vibration and harshness (NVH) characteristics were optimised by both collaborated structural analysis of the powertrain and refined calibration of the injection parameters.

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1 Introduction There is no question that the two biggest concerns in the current automotive world are fuel economy and compliance with tough emission regulations. Since 2000, the oil price has increased sharply and this rise is expected to continue. Considering the rapidly increasing oil demand by developing countries including China, India and South-Eastern Asian countries, the oil price will keep increasing for a substantial period of time. Compliance with stringent emission standards is another challenge, especially for the diesel engine. Current diesel engines complying with the Euro 4 standard are expected to maintain their competitive power compared to petrol engines from the viewpoint of cost of ownership, and this superiority is expected to be maintained for the Euro 5 standard. But for Euro 6 and succeeding emission standards, the application of expensive nitrogen oxide (NOx) aftertreatment systems might be considered for some vehicles, and this will eliminate most of the overall competitive advantage of the diesel engine. A definition of the most cost-efficient systems and refined calibration will decide the competitive power of future diesel engines. These factors were considered and reflected in the development of the new 1.6 l engine.

1.1 Development Concept of the 1.6 l CRDi Engine The main concepts of the development are: – deliver best-in-class power output

– provide best-in-class torque over a wide engine speed range for excellent driveability – reduce fuel consumption to a competitive level – provide optimised NVH characteristics by refined calibration and structural analysis – define a cost-efficient engine system. The 1.6 l CRDi engine has two different engines with displacements of 1.1 l and 1.5 l as a family. The 1.1 l engine, which delivers 55 kW and 152 Nm, was installed in the Kia Picanto and launched in 2005 with Euro 4 certification. The 1.5. l engine with 81 kW and 235 Nm was also launched in the same year.

1.2 Engine Specification The new 1.6 l engine develops a maximum power output of 84.6 kW at 4000 rpm and a maximum torque of 255 Nm over a wide engine speed range from 1900 rpm to 2750 rpm, Table. The second-generation common rail system with a maximum pressure of 1600 bar was implemented together with a variable geometry turbocharger (VGT). The compression ratio was adjusted to 17.3, which was a compromise between two totally opposing requirements towards a better emission potential on the one hand and good startability and combustion stability under cold conditions on the other. A diesel particulate filter (DPF) was provided as an optional package, although this engine has provided enough emission potential for the Euro 4 standard with a diesel oxidation catalyst (DOC) alone for C-segment vehicles even with automatic gearboxes.

The Authors

Ph. D. Yohan Chi is group leader for combustion system and performance development for passenger diesel engines, Hyundai Motor Company, Seoul (Korea).

Juncheol Park is group leader for design and engineering of small displacement passenger diesel engine, Hyundai Motor Company, Seoul (Korea).

Hyeungwoo Lee is deputy manager for combustion system and performance development of small passenger diesel engine, Hyundai Motor Company, Seoul (Korea).

Table: Engine specification Engine Type

–

In-Line 4-Cylinder

Valvetrain

–

4-Valve DOHC

Displacement Volume

cc

1,582

Bore X Stroke

mm

77.2 x 84.5

Power

kW / rpm

84.6 / 4000

Torque

Nm / rpm

255 / 1900 ~ 2750

Compression Ratio

–

17.3 : 1

FIE System

–

BOSCH CRI 2.2

Aftertreatment System

–

DOC (DPF)

Emission

–

EU4 with EOBD

ATZautotechnology 04I2008 Volume 8

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COVER STORY

Engine Technology

Figure 1: Main technical features of 1.6 l CRDi engine

2 Main Features of the Engine 2.1 Engine Hardware Some important technical features were implemented to guarantee sufficient potential for Euro 4 emission compliance and a high power output, low fuel consumption and comfortable acoustics. The 1600 bar second-generation common rail system combined with VGT and refined calibration was one of the main sources of a high power output and low fuel consumption. A cooled exhaust gas recirculation (EGR) system controlled by an electronic EGR valve that is generally accepted as a standard emission package for the Euro 4 standard was also implemented. Other features include the DPF and a variable swirl control system, which was proven to be effective in improving the emission trade-off especially at low speeds and a low-load operating range, Figure 1.

acoustics. As illustrated in the schematics of the injection control strategy, Figure 2, double pilot injection was applied to a wide operating range for improved acoustics. The system’s capability of activating post injections up to two times per cycle was fully utilised for emission reduction and DPF regeneration. Design of Experiment (DoE) technology was introduced to optimise numerous control parameters for the injection quantity and the timing of the pilot, main and post injections from the viewpoint of emissions, fuel consumption and acoustics. One important feature of calibration was that double pilot injection was introduced over a wide operating range covering most of the emission cycle, while single pilot injec-

tion was also extended to its maximum within the limits of system reliability for acoustic reasons. Different injection control strategies were introduced to consider different vehicle and operating range boundary conditions. An example is attached post injection. Attached post injection was applied for heavy vehicles with an automatic transmission, with the aim of compensating for the degradation of particulate matter (PM) emissions, while the combination of only pilot and main injections was applied for relatively light vehicles with a manual transmission. The coordinator for the pilot injection control was carefully calibrated in order to achieve optimum trade-off characteristics between combustion noise, emissions and fuel consumption. Double pilot injection was extended to the maximum operating range for the lower gear group, while the double pilot injection range was reduced for the higher gear group, in which the combustion noise is less noticeable.

2.3 DPF System Although the 1.6 l engine has demonstrated enough emission potential for the Euro 4 standard with an oxidation catalyst alone for C-segment vehicles even with automatic transmissions, the DPF system was also developed and provided as an optional package, thus allowing a reduction in PM emission to below 5 mg/km, which is the proposed Euro 5 standard. A Dura Trap Aluminium-Titanate substrate with a standard

2.2 Fuel Injection System and Calibration Strategy The second-generation common rail system with a system pressure of 1600 bar provided additional potential for emissions, performance and acoustics compared to its predecessor 1350 bar firstgeneration system by providing multiple injection up to five times per cycle and more precise control. The increased system pressure also improves the power output, while flexibility in injection control and refined calibration provide additional potential for emission and 22

ATZautotechnology 04I2008 Volume 8

Figure 2: Schematics of the injection control strategy

design was provided by Corning and was coated with precious metal to enhance the continuously regenerating trap (CRT) effect of the DPF and thus to allow the regeneration of soot trapped inside the DPF under normal operating conditions. The DPF was combined with the DOC in a single can and was located in an underfloor position. However, in the subsequent application, which is aimed at Euro 5, the DPF combined with the DOC will be located in a close-coupled position at the exit of the turbocharger in order to utilise the advantages in favourable regeneration conditions and CRT effects due to the higher exhaust gas temperature, Figure 3.

Figure 3: Layout of the DPF system

2.4 Other Technical Features The intake port design was optimised to comply with two opposing requirements for port performance: a high flow capacity to guarantee a high power output and a high port swirl that is essential for improving the emission potential, especial-

ly for small-bore engines like the 1.6 l engine. The twisted port concept, which is the midway between the tandem and twin port concepts, was selected to satisfy both a high flow coefficient and high port swirl requirements. Swirl chamfer

was applied at the valve seat area to enhance the intake swirl during the low valve lift period. The combustion bowl shape and spray patterns were matched with intake port swirl from the viewpoint of power output and emission po-

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COVER STORY

Engine Technology

engines. However, it should be kept in mind that the operating range of the swirl control valve should be carefully calibrated to minimise the fuel penalty caused by increased pumping losses. The EGR system was upgraded from its preceding non-cooled pneumatically controlled type to an electronically controlled cooled type to comply with Euro 4 emission standard. The EGR rate is controlled by a linear solenoid type EGR valve and is located upstream of the EGR cooler to prevent fouling. A shell and tube type EGR cooler was implemented and the surface of the inner tube was corrugated to enhance the cooling efficiency. The location and shape of the EGR port at which the exhaust gas is introduced into the stream of fresh air was optimised by three-dimensional flow analysis to improve the EGR distribution between each cylinder. For the non-DPF system, in which only an oxidation catalyst was used, the catalyst systems were divided into two parts. A warm-up catalytic converter (WCC) with a smaller volume was located close to the turbocharger exit for fast light-off and the other unit was located in an underfloor position to maintain the overall conversion efficiency.

Figure 4: Power output and torque

Figure 5: Vehicle performance of the i30

3 Engine and Vehicle Performance 3.1 Engine Performance

Figure 6: Comparison of the fuel consumption potential

tential. A wide bowl shape was combined with a relatively large spray angle to fully utilise the improved potential of the fuel injection system. The intake port swirl was optimised by the variable swirl control system installed at the short intake port side. This system is a powerful 24

ATZautotechnology 04I2008 Volume 8

means of improving the NOx-PM tradeoff, especially at low speeds and in the low-load operating range in which the intake swirl is lower than optimum, and it is effective especially for engines with a small bore size in which the swirl requirement is higher than large-bore

Supported by the above-mentioned technical features and refined calibration, the 1.6 l CRDi engine is installed in the Hyundai/Kia Motors’ C-segment vehicles i30 and Cee’d. It delivers a maximum power output of 84.6 kW, corresponding to a specific power output of 53.5 kW/l. It also generates its maximum torque of 255 Nm over a wide engine speed range from 1900 rpm to 2750 rpm. The steadystate brake mean effective pressure (BMEP) at 1000 rpm reaches 11 bar, and more than 90 % of maximum torque is achieved at 1500 rpm. This balance between maximum power output and low-end torque is the main source of the acceleration performance of the two vehicles, Figure 4.

3.2 Vehicle Performance From the certification data of the i30, the maximum speed of 188 km/h, the elapsed times for a dash from a standing start to 100 km/h of 11.6 sec and acceleration

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Figure 7: Sound pressure level inside cabin

from 80 km/h to 120 km/h in top gear of 12.1 sec are competitive figures in the C-segment vehicle class, Figure 5. As illustrated in the figure, where the homologated fuel consumption is plotted against power output, the homologated fuel consumption of the i30 and the Cee’d is 4.7 l/100 km, and is at the lower limit of scattering. The homologation data of the Kia Picanto powered by a 1.1 l engine — another member of the 1.6 l engine family — clearly indicates that the fuel consumption of 4.2 l/100 km is also competitive, with the exception of a few vehicles like the VW Polo Blue Motion and the Smart for Two. Considering the increasing importance of fuel consumption in the future and the fuel consumption potential of a 1.6 l engine, this engine is expected to play an important role in complying with the Euro 5 emission standard for Hyundai / Kia Motors’ C-segment vehicles, Figure 6.

ing device, the chain and cover systems were among the main sources of noise. Structural analysis was performed for design improvement and, based on this, modal analysis reinforcement was performed by applying ribs to the chain and head covers. The shape and structure of the oil pan was also improved, as the oil pan was another major source of noise. Structural analysis was also performed to investigate the effect of the shape and location of ribs on the noise characteristics and to find out the optimum shape of the oil pan. As a result of the competitive dynamic stiffness of the powertrain achieved by the introduction of a bed plate structure and a bell-shaped matching plane between the engine and the gearbox combined with the improved acoustic behaviour of the chain system, the oil pan and other components, a competitive sound pressure level was measured inside the cabin, Figure 7. O

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3.3 NVH Development In parallel with the elaborated calibration of the fuel injection and air handling parameters, the engine hardware was optimised for acoustics. The main sources of noise emission were identified and appropriate measures were implemented. Since the 1.6 l engine is equipped with a chain system for tim-

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