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May 3, 2007



According to a recent article, FEV Engine Technology, Inc. is continuing its efforts in the development of a variable compression ratio (VCR) system for use with turbocharging and direct gasoline injection. FEV is an independent engine and powertrain systems research, design and development company headquartered in Aachen, Germany. The company’s pursuits are described “as means to exemplify the gasoline engine’s relevance in the face of advancements in alternative powertrains,” according to the article.

At the 2007 SAE World Congress in Detroit, FEV showcased its latest development: a turbocharged four-cylinder engine that has V8 power accompanied by V6 fuel economy. The engine accomplished this by meshing VCR technology with flexible-fuel operation. Robert Last, vice president, operations for FEV, said that the VCR engine will achieve diesel-like efficiency when running on E85.

The article states that the “VCR system operates by actuating an electric motor to move the centerline of the crankshaft up or down about 0.2 inches.” This allows the compression ratio between the pistons and cylinder head to be varied from 8:1 to 16:1. Torque loss at the engine’s output shaft is eliminated due to the placement of couplings at both ends of the crankshaft.

According to Last, the engine’s ability to change the internal operating parameters is what allows for better fuel economy—gains of up to 25% when running on E85. E85 has a higher octane rating than gasoline, allowing for the engine’s compression ratio to increase significantly under full load without any premature combustion, aka “piston knock.” Compression can also be reduced under light-load situation, putting less strain on the engine.

One of the advantages of the engine over alternative fuel powertrains is improved fuel economy. The varying compression range overcomes the lower energy density of E85 and other alternative fuels. Another advantage is the fact that the integrated sensors and controls used for determining the alcohol content of the fuel, as well as the fuel injection and turbocharging systems, are existing technologies. The VCR engine is expected to cost more than a conventional gasoline engine, but less than a diesel.

Robert Last notes that FEV’s efforts do not represent a “war” between gas and diesel engines. Rather, “they both are complementary toward reaching the same goal,” says Last. He also suggests that alternative fuels should be made of biomass that has no other purpose, so that ethanol production does not drive up the cost of corn and potentially contribute to food shortages. “The key to our (energy) sustainability is the conservation of existing fuels,” he states.

Source: Sutton, Mike. (April 25, 2007). “FEV Advances With Variable Compression Ratio Gas Engine.” Retrieved April 25, 2007 from

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