A New Way to Hone Fuel Economy

Researchers in Germany say the adjustable cylinder honing tool they developed can make piston engines 3% more fuel efficient.

The tool contains tiny piezo actuators that can alter its shape and expand its diameter. The resulting adjustments add "imperfections" in the cylinder bore during production to offset distortion that occurs when the engine is assembled and operated.

Researchers at Germany's Fraunhofer Institute for Machine Tools and Forming Technology IWU determine how to guide the tool by first calculating static distortion that occurs when a finished cylinder head is bolted onto the block. Then they estimate the thermal distortion to the cylinder bore that occurs when the engine operates.

Feeding the calculations into the tool enables the bore to be honed to offset both types of distortion simultaneously, according to the Fraunhofer researchers. They developed the prototype honing tool in collaboration with an unnamed carmaker and machine tool producer.

The team expects to complete validation tests by the end of the year to determine how well the honing system reduces internal engine friction, prolongs engine life, improves fuel efficiency and reduces lubrication requirements.