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The targets for future gasoline engines in terms of fuel consumption and exhaust gas emissions require the introduction of advanced technologies to increase engine efficiency. The mechanically fully-variable valve train system UniValve is an effective device to reduce fuel consumption through throttle-free load control. This is achieved by the simultaneous variation of valve lift and valve opening event. The method of cylinder deactivation by closing the gas exchange valves is a further approach to increase the efficiency of combustion engines especially at part load. This paper presents the combination of both techniques on a downsized, turbo charged 4-cylinder DI gasoline engine. The mechanical integration of the valve shut-off capability for cylinder deactivation into the Univalve system is explained and strategies for the transition between 2-cylinder and 4-cylinder modus are discussed.

A 2.0 l turbocharged gasoline engine with port injection and a comparable turbocharged gasoline engine with direct injection have been investigated on a test bench at Kaiserslautern Technical University. Both engines were driven with throttle-free load control by fully mechanically variable valve actuation (CVVL). The basic series-production turbocharged engine in this comparison is the version with direct injection without the fully variable valve train. The focuses of the fired tests were investigation of the fuel consumption at part load and of maximum torque behavior at low engine speeds at full load. In both engine modes, use of fully variable valve actuation shows improvements compared with the turbocharged engine versions without CVVL. Better turbocharger response enabled the torque behavior to be optimized.

A 1-cylinder experimental engine with a mechanically fully variable valve train (CVVL) on inlet-and exhaust camshaft and an additional fully variable compression ratio was investigated on a test bed at the Technical University of Kaiserslautern. Up so far only an electro mechanical valve train with similar high valve curve variability has been tested under research conditions. In this paper, the first test results at part load with throttle-free load control are here compared with the results of a 4-cylinder engine. The influence of the charge-cycle-work and the residual gas content concerning fuel consumption is analyzed. Variabilities of the exhaust camshaft, such as the exhaust valve spread phasing for example, are simulated with CFD-methods. Furthermore the influences on fuel consumption and NOx-emissions of the exhaust valve lift height and the duration in a 1-cylinder engine are measured.

A 2.0 l turbo charged gasoline engine with the mechanically fully variable mechanical valve train UniValve has been investigated on a test bed at the University of Kaiserslautern. First results of the mechanical behaviour, full load behaviour and fuel consumption at part load have been measured. These results are compared to the uncharged gasoline engine. In both cases the engines have been driven throttled and throttled free through the variable valve train. The dynamic behaviour of the turbocharger version has been investigated too. The only modification of the engine is the turbo charger, the valve train and the intake manifold hasn't been changed. The results have been compared with GT-Power simulations. The fuel consumption in the turbo charged mode at the map point 2,000 rpm/2bar could be improved up to 14 % through the throttle free load control vs. the throttled mode. The low end torque has been increased by 10 %.

In addition to first test results from a one single-cylinder engine with the UniValve fully variable valve lift and timing system - presented at the 2005 SAE Congress - this paper contains the results of a fired 2.0 I four cylinder gasoline engine [1], [2]. The cylinder head has been replaced with a new cylinder head concept that includes the fully variable valve lift and timing system (VVTL system) UniValve. The other engines parameters and components have not been changed. The intention was to investigate the engine behavior only by exchanging the standard inlet valve train with for the UniValve fully variable valve train. The VVT engine load can be controlled either with a standard throttle or unthrottled, only through the fully variable variation of the valve lift and the valve opening period. The engine has been installed on a dynamic test bench.

So as to fulfill the future requirements regarding fuel consumption and exhaust gas emissions, new technologies have to be adopted in future generations of spark ignition engines. The mechanical fully-variable valve train (MVVT) is one possible technology as BMW has already successfully proven with the Valvetronic-System [1]. At present a large number of such systems is in development. All those systems are alike in terms of their additional variability regarding valve lift and valve opening time by increasing the number of system design units. An increase of the number of design units and the associated increase of the number of the contacts and articulated joints, render such systems softer and dynamically more sensitive than regular types of valve trains, e.g. a roller cam follower or a roller finger follower actuation.

The mechanical fully variable valve lift system UniValve represents one of the new technical solutions for a throttle free load control for combustion engines. The load control is achieved by the variation of the valve lift and the simultaneous variation of the opening and closing time. The design of the system has as result a simple layout with a valve train component assembly that leads to a compact integration into conventional cylinder heads. In addition to the first results presented at the SAE Congress 2004 this paper provides the results of the fired engine and the valve train operation on the component test bench. Furthermore the potentials of the throttle free load control with the UniValve system in comparison to a conventional throttle engine operation with the same engine type are pointed out. Perspectives for the application in an four cylinder engine are given.

This paper provides an up-to-date overview of variable valve control systems that permit valve lift and opening time to be continuously varied, and of the choice of the valve lift function needed for engine load control. In recent years in particular, following the introduction on a volume production scale of a system with continuously variable valve lift, development activity on valve control systems of this kind has been stepped up considerably. This overview refers to the principal systems known to be under development and to recent patent applications. It describes the design criteria and ratings needed for continuously variable valve lift systems, discusses the criteria that are of importance if such valve control systems are to be adopted on production vehicles and indicates the factors that have to be taken into account before the severe requirements imposed by series-production engines can be satisfied.

A fully variable mechanical valve gear has been integrated into an engine with a side-mounted camshaft. The design is specified with the peripheral package terms and the resulting criteria of ratings. The additional costs were analyzed too. The first results obtained from a dynamic simulation of the chosen design are described and assessed. Additionally to this the potential of this type of a mechanical fully-variable valve lift system is evaluated in terms of engine torque, power output and fuel consumption by simulating a cyclic process and the comparison with the potential offered by variable valve timing (VVT).

The ‘UniValve’ fully variable mechanical valve lift system is rated for use at engine speeds up to 8500 rpm. This system varies the valve opening period together with the amount of valve lift. When the engine is idling and valve lift is approximately 0.3 mm, the opening period is about 90 degrees of crankshaft rotation; at the full valve lift of 9 mm, the valve remains open for 320 degrees of crankshaft rotation. Valve lift is adjusted by means of an extremely rigid eccentric shaft rotating in bearings in the cylinder head. The system has been applied to a single-cylinder engine. The valve gear's dynamic behavior at engine speeds up to 8500 rpm the first results are described here, together with the fuel-consumption and torque benefits and the system's influence on emissions. The effects of the new load control system on mixture formation and the resulting nvh of the single-cylinder engine, particularly at low running speeds and loads, are also examined.