# Kinematic and Dynamic Response of a Novel Engine Mechanism Design Driven by an Oscillation Arm
## 1 Introduction
### Background
The VC-Turbo engine from Nissan uses a multi-link system in place of a traditional connecting rod to rotate the crankshaft, and an actuator motor changes the multi-link system endpoint in order to vary the piston reach to transform the compression ratio. This makes it possible to vary the compression ratio continuously as needed within the range of 8:1 (for high load) to 14:1 (for low load). FEV developed a two-stage VCR engine system that has been proven to be a good concept, considering its low cost to manufacture and the benefit if integration into common engine architectures. The system uses a length-adjustable connecting rod with an eccentric piston pin in the small eye; the compression ratio adjustment is performed through a combination of gas and mass forces [26; 27]. A potential improvement of fuel consumption is 5-7% depending upon drive cycle and vehicle/powertrain combinations [28]. Furthermore, Ford has extensively worked on the development of VCR engines in the last 20 years and a VCR Engine with varying length of piston and connecting rod was developed in 2003 [29]. The research goal is focused to increase engine performance, in which the research-development process has to search for solutions to minimize the expensive costs, by developing and optimizing the end product. This can be achieved by using modern software through computers that can simulate the real process based on experimental data. The use of computer capabilities helps to reduce the experimental tests which means reducing cost for the test itself besides maintenance [30; 31; 32]. There are many domains related to a mechanical system which are analyzed with commercial software in order to reduce the time consuming, providing better/reliable and competitive products on the market. Here, we can name some of these types of domains: MBS (multibody simulation) used for kinematic and dynamic analysis of bodies in motion and FEA (Finite Element Analysis) used for analysis of deformable bodies. There are also other types of analyses developed in the FEA domain: static analysis, vibration analysis, fatigue analysis and CFD (Computed Fluid Dynamics) used for analysis of fluid flows prediction based on some mathematical and numerical methods [33; 34; 35]. Recently, these were extended to some novel challenging domains of interest which start to embed/develop numerical simulations accordingly: electromagnetic field or electrical field [36; 37; 38; 39; 40; 41]. Numerous commercial software programs have been developed in the last two decades with the goal to cover requests coming from customers or market needs [42; 43; 44; 45]. They permit reducing the time to obtain a product to its smaller time limits [22; 23; 46; 47; 48; 49; 50]. Another important goal of using these software programs developed as tools consists the possibility to make a very quick decision on the choice of a viable design solution from a multitude of proposed solutions, based on different virtual analyses processes. In this paper, we discuss the benefits achieved through using the mechanism with an oscillating arm in comparison with a classical mechanism of a conventional engine. To validate the success of the proposed mechanism, we evaluated the kinematic and dynamic parameters such as: piston stroke, compression ratio, torque and power per cycle. To do so, the analyses were performed using analytical calculus and multibody simulation techniques. The results gathered in this survey confirm the achievement of superior engine power parameters (power, torque) and an improvement of eco-parameters of the studied engine (consumption, emission).