Text by Saab Automobile
New unique engine concept
for high performance and lower fuel consumption. Saab Variable Compression - or SVC for short - is a new engine concept that enables fuel consumption to be radically cut, but without impairing engine performance. The combination of reduced engine displacement, high supercharging pressure and a unique system for varying the compression ratio enables the SVC engine to use the energy in the fuel far more efficiently than today's conventional automotive engines. This offers entirely new scope for combining high performance with low fuel consumption and low exhaust emissions.

Fuel consumption 30 percent lower
The SVC concept enables the fuel consumption of a conventional naturally aspirated engine to be reduced by up to 30 percent without impairing the engine performance. The five-cylinder SVC engine developed by Saab has a displacement of 1.6 litres and is as fuel-efficient under normal conditions as a conventional 1.6-litre engine, but can deliver the power of a 3-litre engine whenever the need arises. The emissions of carbon dioxide (CO2) are reduced proportionately to the fuel consumption, while the CO, HC and NOx emissions will enable the SVC engine to meet all current and proposed future legal requirements.
The unique feature of the SVC engine and the one which is the key to high efficiency is that the engine has a compression ratio which is variable. The fixed compression ratio of a conventional engine is a compromise between the needs in a wide variety of operating conditions - in stop-go city traffic, in highway motoring at constant speed, or in high-speed motorway journeys. As opposed to this, the compression ratio of the SVC engine is continually adjusted to the optimum value for the prevailing conditions.

A platform for continued development
The SVC concept and the 1.6-litre, five-cylinder engine now unveiled represent a surge forward in the development of the Otto engine and provide a totally new platform for further engine development. The fact that the additional compression ratio parameter can now be controlled enables engine operation to be controlled more accurately, and the engine can thus be made more efficient.
SVC can be combined with other engine technologies for improving the performance further, lowering the fuel consumption, and reducing the exhaust emissions.
The SVC engine represents a decisive step in the long-term development work aimed at combining the benefits of the Otto engine and the diesel engine.
This trend is already discernible in engine development. Direct injection will be used on the Otto engine just as it is on the diesel engine, while the diesel engine will have much more electronics. Variable compression has so far been the missing link between the two.

Alternative fuels
The variable compression ratio also gives the engine great fuel flexibility. Since the compression ratio can be varied and adjusted to suit the properties of fuel, the engine will always run at the compression ratio that is best suited to the fuel being used.
Technical data The figures tabulated below relate to the 1.6-litre test engines currently used in the technical development work. The exact technical specifications of future regular production engines will be dependent on this development work and thus cannot be specified before a regular production engine has been presented.