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The “Two-in-One” Engine - Porsche's Variable Valve System (VVS)
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Abstract
Driving fun - one of the major thrills expected by the buyers of high-performance cars - must be absolutely preserved despite all the measures required to further reduce the car's exhaust emissions and fuel consumption.
Powerful engines with high BMEP levels require large unrestricted inlet and outlet valve diameters and lifts as well as a wide camshaft phasing range at least on the intake side. In terms of exhaust emissions and fuel economy such an engine layout is rather unfavourable. Its inherent drawbacks, however, can be compensated by providing for what might be called a “two-in-one” configuration which combines a low-emission concept including intake-valve lift shifting and exhaust-camshaft phasing with a high-performance-engine concept complete with a wide intake camshaft phasing range and large intake valve lifts and a Varioram intake system. With this basic layout, even high-performance sports cars are able of falling below the current ULEV limits.
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Brüstle, C. and Schwarzenthal, D., "The “Two-in-One” Engine - Porsche's Variable Valve System (VVS)," SAE Technical Paper 980766, 1998, https://doi.org/10.4271/980766.Also In
References
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- Porsche ULEV-Konzepte für zukünftige Hochleistungsmotoren 18. Intern. Wiener Motorensymposium Brüstle C. Richter H. Dr. Ruschmann E.
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- High Power Output and low Fuel Consumption - no Self-Contradiction Thanks to the use of Variable Valve Timing Systems Fisita 1996 Brüstle C. Müller S.