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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.