One independent laboratory executive says the first commercial applications could be ready by 2010. But a colleague disagrees. "The concept is the holy grail for engine engineers," said Tim Lake, chief engineer for advanced gasoline engines at engineering firm Ricardo Ltd., of Shoreham-by-Sea, England. "But there doesn't seem to be a magic fix for the problems of such a system."
Several carmakers and some independent institutes have taken different approaches to the technology. Nissan, Volvo, PSA/Peugeot-Citroen and Renault each have their own VCR development programs. But General Motors has abandoned VCR research for a cylinder cutoff system called displacement on demand.
Since 2000, independent research company MCE-5, of Lyon, France, has worked on its own VCR system in partnership with PSA and Formula One engine builder Megatron.
Germany's FEV Motorentechnik, a division of Aachen Technical University, is an independent institute that has developed its own system. It receives research cooperation and support partnership from Volvo, Renault, PSA and Le Moteur Moderne, an independent French r&d firm.
FEV tested its VCR engine in an Audi A6. It claims fuel savings of 8 percent on engines where the only alteration is VCR.
"But in combination with downsizing an engine from 3.0-liter capacity to 1.8 liters, we have achieved total savings of 25 to 27 percent," said Knut Habermann, department manager for gasoline engine development.
MCE-5 claims even better savings when VCR is combined with other advanced engine systems, such as Valeo SA's variable valve actuation, turbocharging and gasoline direct injection.
"We claim 27 percent savings at least in combination with (direct injection) and up to 45 percent when all technologies such as direct injection, turbocharging and downsizing are combined in one engine," said Vianney Rabhi, head of development at MCE-5.
But others are more conservative in their fuel saving expectations.
"We ran up to only 14 percent fuel savings with VCR," said Ricardo's Lake. "For us, it seems a lot of effort for too little effect."
Lake also said that the claimed fuel savings are achieved during European Union test-cycle conditions.