Due to the strict European emission standards and the constant aspiration for the higher power density, turbochargers became essential components of the modern internal combustion engines. Turbochargers are high-speed operating machines thus the design of the rotor and the bearing system requires special attention. The motions of the rotor are affected by several parameters, such as bearing design, clearances, structure of the surface and also the quality and the physical properties of the used lubricant. If the motions of the rotor are intensive in a wide rotational speed range, the bearing load increases, resulting in a reduced lifespan. The motion of the rotor induces vibrations, which leads to audible noise emission to the environment. In this article, the vibrations of a four-cylinder spark ignition engine’s turbocharger are presented, based on component test-bench experiments. Furthermore, the main vibration components and their influencing factors are briefly introduced. During the experiments, the noise and vibrations of the turbocharger have been measured with different viscosity grade oils from 20 °C to 140 °C inlet temperature. The results showed that the amplitudes of both the synchronous and subsynchronous vibrations changed significantly and the volumetric flow is highly dependent on the temperature. The effect of the changing oil temperature will be analyzed with an emphasis on the subsynchronous vibrations and the possible cause of the phenomenon will be presented. Finding the optimal parameters with the lowest possible vibration response could result in an extended lifetime and provides important information for the balancing process during production.

In the scope of this article, the design and testing of a water injection system applicable for a spark ignition engine are presented. Increasingly stringent emission standards within the framework of EURO7 require either directly or indirectly the internal combustion engines to be optimized across the entire field of an engine map, therefore they must comply with the emission standards at each operating point. The greatest challenge is expected to be the Lambda = 1 operation on the full field. The conversion efficiency of the exhaust gas after treatment systems is the highest at this point, therefore it is foreseeable that no deviation can be made. As a result, fuel enrichment for performance enhancement and to protect components against thermal load will not be tolerated, so the resulting thermal loads will need to be reduced in other ways. It is possible to reduce the excess thermal loads by using water injection. Evaporation of water in the intake system and combustion chamber takes off heat and the temperature of the contacting components and fluids decreases. The affected components include pistons, combustion chamber, cylinder head, exhaust valves, exhaust manifold, turbine wheel, turbine housing, and as a medium, the temperature of the intake air. Reducing the temperature of some components is important in the aspect of mechanical strength, while for some components the knock limit can be extended. This article presents the detailed design process and testing phase of a water injection system. An important aspect in system design is compatibility with different engine layouts in a cost-effective manner. Injector nozzle testing also includes analysis of mass flow, dispersion and spray pattern. The scope of the work is the implementation of a water injection system, which is capable of performing measurements in testbench environment at the Department of Internal Combustion Engines and Propulsion Technology of Széchenyi István University. The result of the measurements is the successful cylinder selective application of water injection to the intake system, whereby the addition of water reduces the temperature of the intake air and the exhaust gas, which can be reduced to standard calibration temperature in Lambda 1, without fuel enrichment.