|An earlier rendering of the VCR mechanism. Click to enlarge.|
FEV Engine Technology is displaying a developmental gasoline/E85 turbocharged direct injection (GTDI) engine that also features variable compression ratio (VCR) at the 2007 SAE World Congress.
The engine is being developed in-house, in tandem with several other DI engine projects that FEV is working on with various automakers, based on earlier work FEV had done with the VCR platform. While offering the potential to generate V-8 power from a V-6 engine, this concept also provides roughly a 20-25% improvement in fuel consumption.
The VCR system is based upon the concept of an eccentric crankshaft bearing. Rotation of the eccentric bearing leads to a vertical position change of the crank train relative to the cylinder head and thus, a continuous change in the compression ratio. An electric motor controls the adjustment between compression ratios of 8 and 16. FEV has deployed a VCR engine in a demonstration vehicle, and is further optimizing the adjustment mechanism. There is interest in the OEM community in the work, according to Dr.-Ing. Joachim Wolschendorf, Vice President Engineering and Chief Technical Officer.
The VCR element allows the engine to take advantage of the higher octane of ethanol by increasing the compression ratio for higher-level ethanol blends. FEV is currently working to optimize a control strategy for engine management that will take into account the compression ratio as well as load and the fuel mixture.
Although the three principal elements of the engine—VCR, GTDI and Turbocharging—have been tested on the bench and on the road, FEV has not yet put all three together in a vehicle.
Demonstration Vehicle with Continuously Variable Compression Ratio (VCR) (2003)