Abstract
This paper presents future plans for the two newly released concept engines, Saab Variable Compression (SVC) and Saab Combustion Control (SCC). Both engines present a major reduction in fuel consumption. However, the members of Association of European Automobile Manufacturers (ACEA) have committed to a reduction of their respective fleet average CO2 emission to reach a value of 140 g/km in the year 2008. This poses a significant challenge to the members of ACEA, especially those who produce relatively heavy vehicles. Due to this challenge the two concept engines have been merged together in an attempt to reach closer to the CO2 emission target. In addition, worldwide emission compliance is regarded to be of utmost importance to Fiat GM Powertrain, Sweden. Thus, this paper presents a solution on how to combine the two concept engines into one with the ambition to further reduce the already low fuel consumption of the SVC engine, and at the same time significantly reduce exhaust gas emissions.
The objectives for the new generation SVC engine is set at a 30% reduction in fuel consumption compared to a naturally aspirated engine of equal performance. The engine shall meet at least the ULEV II emission standards in any passenger car, whilst at the same time offering good driveability as expected of a premium segment car.
This paper briefly presents the SVC and SCC concept engines. With the ambition to successfully meet the objectives of the new generation SVC engine, some limitations of the separate concept engines are pointed out.
The specific limitations of any concept engine are a result of the compromises that had to be made to meet its different objectives. At last, a successful combination of the two separate engines is discussed.
The new generation SVC concept engine is equipped with dual continuously variable camshaft phasers and air-assisted direct injection of fuel into the cylinder. Supercharging is by means of a serial sequential twin turbocharger system. Displacement volume is 1.8 l. The previous SVC generation had a mechanically driven screw-type (Lysholm) compressor and a displacement volume of 1.6 l.
The performance target has been achieved, however an increased response time has to be accepted at positive load changes as a result of exchanging the mechanical supercharger for a twin turbocharger system.