The Hyundai Powertrain Research and Development Center has produced a fuel efficient and clean burning diesel engine for compact passenger vehicles. The U2 diesel engine is an inline four cylinder 1.6 liter (1,582 cubic inch) engine that utilizes a second generation common rail diesel injection system. Bosch 1,600 bar common rail injection system is capable of delivering up to five injections per cycle.

Hyundai U2 CRDi Diesel engine

Hyundai U2 CRDi Diesel Engine. Photo courtesy of Wikipedia

The engine features a variable geometry turbocharger, a variable swirl control system and an electronically controlled exhaust gas recirculation (EGR) cooling system. Moreover, the diesel engine has a timing chain for improved reliability and valve control. The bed-plate type crankcase reduces noise, vibration, and harshness. The crankcase also improves engine block rigidity. Hyundai claims that the U2 is the quietest engine in its class; the engine measures two decibels lower than leading competitor engines. During the course of development, the main sources of noise were identified and appropriate measures were taken. The chain drive and oil pan were identified as the main sources of noise. Structural analysis was performed on the chain drive and oil pan components. Based on the results of the analysis, the cover for the chain drive was reinforced by ribs. This allowed the cover to absorb vibration coming from the timing chain. The shape and structure of the oil pan was also modified to absorb noise coming from the crankcase.

The U2 engine will be installed in the all-new Hyundai i20. The vehicle scheduled to be launched in Europe in 2009. The vehicle will be produced at Hyundai Motor Company’s Indian subsidiary in Chennai.

The U2 generates a total power output of 126 hp at 4,000rpm, with 192 lb-ft of torque at 1900~2750 rpm. More than 90% of the maximum torque is available at 1,500 rpm. The U2 has a fuel economy rating of 55 miles per gallon and is compliant with the latest European emission standards (Euro 4). An optional particulate filter reduces particulate matter to Euro 5 standards which take effect next year.

The U2 diesel engine is the result of combining engineering knowledge with state-of-the-art technologies. The variable geometry turbocharger, variable swirl control system, and the electronically controlled exhaust gas recirculation cooling system allowed the ports and combustion chambers to be optimized. This allows the U2 to achieve outstanding fuel economy and low emissions.

Following is detailed information to allow a closer look at each component and how each contributes to fuel efficiency, emissions, and power.

Variable geometry turbocharger: A variable geometry turbocharger (VGT) is designed to allow the effective aspect ratio of the turbo to be altered as conditions change. This is necessary because the optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo’s aspect ratio can be maintained at its optimum. Because of this, VGTs are very efficient at higher engine speeds. Aerodynamically-shaped vanes are located in the turbine housing near the turbine inlet. As these vanes move, the area between the tips of them changes, thereby leading to a variable aspect ratio. These actions improve power and fuel economy.

Variable swirl control system: Optimum swirl ratio is necessary for high combustion and emission reduction. A diesel engine needs variable swirl to enhance the combustion according to its operating conditions. For example, at partial load or at low rpm the engine requires stronger swirl. On the other hand, air quantity is more important than the swirl under full load or at high rpm. The swirl and charging quantity can easily be regulated by a variable swirl control system. The variable swirl control system in a diesel engine is designed to meet the combustion needs of swirl in a broad range of operating conditions. The engine can operate under full load or partial load conditions without compromising fuel economy. If a variable swirl system is applied, when a diesel engine works under full load condition, the inlet swirl can be decreased so that the charging efficiency is increased. Under the partial load condition, the inlet swirl can be enhanced at a minimum expense of charge.

Electronically controlled exhaust gas recirculation cooling system: An electronically controlled exhaust gas recirculation cooling system adds exhaust gas back into the engine intake manifold. The turbocharger has to ensure that the pressure difference between the exhaust and inlet manifolds to drive the exhaust system is maintained. Nitrous oxide emissions are reduced at the source of origin by lowering the amount of oxygen in the cylinder and the combustion temperature. The exhaust gas is cooled by recirculation. The cooling of the exhaust gas further reduces NOx emissions.

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