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In a multi-cylinder variable valve lift (VVL) engine, in spite of its high efficiency and low emission performance, operation of the variable valve lift brings about not only variation of the air-fuel ratio at the exhaust manifold, but also individual cylinder air-fuel ratio maldistribution. In this study, in order to reduce the air-fuel ratio variation and maldistribution, we propose an individual cylinder air-fuel ratio estimation algorithm for individual cylinder air-fuel ratio control. For the purpose of the individual cylinder air-fuel ratio estimation, air charging dynamics are modeled according to valve lift conditions. In addition, based on the air charging model, individual cylinder air-fuel ratios are estimated by multi-rate sampling from single universal exhaust gas oxygen (UEGO) sensor located on the exhaust manifold. Estimation results are validated with a one-dimensional engine simulation tool.

End-plates are highly stiff plates that hold together the components composing a fuel cell stack, i.e. Membrane Electrode Assemblies (MEAs), Gas Distribution Layers (GDLs) and bipolar plates, offering sufficient contact pressure between them. The proper contact pressure is required not only to improve energy efficiency of a stack by decreasing ohmic loss but also to prevent leakage of fluids such as hydrogen, air, or coolant. When a fuel cell starts in cold environment, heat generated in a fuel cell stack as a result of electrochemical reactions should not be used much to increase the temperature of endplates but to melt ice inside the stack to prevent ice-blocking and to increase the temperature near the three-phase-boundary on MEAs. However, to satisfy the high stiffness required, massive metallic endplates have been used despite their inferior thermal characteristics: high thermal conductivity and large thermal inertia.

This paper describes the development of THC reduction technologies compliant with SULEV regulations. Technologies embodied by the developmental work include improvement of fuel spay atomization, quick warm-up through coolant control shut off, and acceleration of fuel atomization for the fast rise of cylinder head temp inside the water jacket as well as the improvement of combustion state. The technologies likewise entail reduced HC while operating in lean A/F condition during engine warm-up with the cold lean-burn technology, individual cylinder A/F control for improvement of catalytic converting efficiency, aftertreatment such as thin-wall catalyst, HC absorber and EHC and etc., through vehicle application evaluation in cold start. We carried out an experimental as well as a practical study against SULEV regulations, and the feasibility of adopting these items in vehicle was likewise investigated.

The weight reduction and noise refinement of powertrain has been major concern in automotive industry although they are known as self trade-off. This paper presents various methods to deal with those problems for new Hyundai 1.5 liter powertrain. It was possible to reduce the weight of powertrain by using plastic for both headcover and intake manifold, aluminum for crankshaft damper pulley and stainless steel for exhaust manifold and by reducing the general thickness of cylinder block On the other hand, the noise refinement of vibration in the powertrain was made by optimizing the engine structure and by adapting the hydraulic lash adjuster valve train system, which was proved to be effective in mechanical noise of engine.

It is well known that the EHC (Electrically Heated Catalyst) is very effective for the reduction of cold-start hydrocarbon emissions. To optimize EHC applications for LEVI (Low Emission Vehicle) and ULEV (Ultra Low Emission Vehicle) standards, the effect of heating and secondary air injection on the emission purification efficiency in FTP (Federal Test Procedure) were evaluated with three different EHC system configurations. The exhaust manifold location EHC system in which the EHC with a light-off catalyst is installed near the exhaust manifold, yields 0.038g/mile of THC (Total Hydrocarbon emissions) when the test was performed according to the FFP with an engine-aged condition equivalent to 50,000miles. Therefore, the ULEV standards could be achieved through the system. A new battery system for the EHC and a single battery system for vehicle application were evaluated. Evaluation of the Ni-MH battery for EHC system is included.

A new concept of misfire detection in spark ignition engines using a wide-range oxygen sensor is introduced. A wide-range oxygen sensor, installed at the confluence point of the exhaust manifold, was adopted to measure the variation in oxygen concentration in case of a misfire. The signals of the wide-range oxygen sensor were characterized over the various engine-operating conditions in order to decide the monitoring parameters for the detection of the misfire and the corresponding faulty cylinder. The effect of the sensor position, the transient response characteristics of the sensor and the cyclic variation in the signal fluctuation were also investigated. Limited response time of a commercially available sensor barely allowed to observe misfire. It was found that a misfiring could be distinguished more clearly from normal combustion through the differentiation of the sensor response signal. The differentiated signal has twin peaks for a single misfiring in a cylinder.

To satisfy the global fuel economy restrictions getting stricter, various advanced cooling concepts, like active flow control strategy, cross-flow and fast warm-up, have been applied to the engine. Recently developed Hyundai’s next generation 4-cylinder 2.0L gasoline engine, also adopts several new cooling subsystems. This paper reviews how 3-D CAE analysis has been extensively used to evaluate cooling performance effectively from concept phase to pre-production phase. In the concept stage, the coolant flow in the water jacket of cylinder head and block was investigated to find out the best one among the proposed concepts and the further improvement of flow was also done by optimizing cylinder head gasket holes. Next, 3-D temperature simulation was conducted to satisfy the development criteria in the prototype stage before making initial test engines.

The main contribution of this paper is to employ a sound and vibration theory in order to develop a light and cost effective plastic intercooler pipe. The intercooler pipe was composed of two rubber hoses and one aluminum pipe mounted between an ACV (Air Control Valve) and an intercooler outlet. The engineering design concept is to incorporate low-vibration type bellows and an impedance-mismatched center pipe, which replaces the rubber hoses and aluminum pipe respectively. The bellows were designed to adapt powertrain movement for high vibration transmission loss to the intercooler outlet. Also, the impedance-mismatched center pipe was implemented to increase reflected wave by using relatively higher modulus than bellows part and applying a SeCo (Sequential Coextrusion) processing method.

In order to improve the fuel consumption ratio of the vehicle, a great deal of research is being carried out to improve air-conditioning efficiency. Increasing the efficiency of the condenser is directly connected to the power consumption of the compressor. This paper describes an experimental method of using an additional water-cooled condenser to reduce power consumption and decrease discharge pressure of the air-conditioning system. First, the principle of a combined cooling (water + air) method was evaluated theoretically. Next, experimental proof was conducted with the additional water-cooled condenser. The shape and structure is similar to the plate type of the transmission oil cooler used in a radiator. Through a number of tests, it was found that it is possible is to reduce power consumption of compressor by decreasing discharge pressure.