21 June 2016
EPS Diesel is working steadily towards FAA certification for its Graflight 8 engine. Engineers Michael Fuchs and Steven Weinzierl, designers of the engine, say fuel burn has been reduced by by 30 percent and they are expecting a 3,000-hour TBO (Time Before Overhaul).
The liquid-cooled, turbocharged engine is controlled by an electronic engine management system developed with Bosch. EPS also says the engine has passed ground vibration surveys with aluminum, graphite, wood-core, and foam-core composite propellers.
In addition, the Graflight 8 has a unique ferritic crankcase cast from a new steel/carbon alloy developed that is lighter and stronger than anything ever attempted in diesel design before. A key element in the design is the flat-vee construction that minimises the amount of crankcase material necessary (read weight) for stable and reliable engine operation.
EPS has developed and patented a new firing order for the flat-vee that actually allows the engine to run as two four-cylinder engines. Half of the engine could be disabled and the other half would continue to function providing limp-home capability.
The EPS engine uses a ferritic piston and crankcase structure along with the typical steel crankshaft and connecting rods. With this, the piston and crankcase have similar thermal growth, as opposed to a typical aluminum piston which grows at twice the rate of steel. This allows operation with less piston/bore clearance as well as maintaining a more consistently “round” piston. A perfectly round bore with minimal clearance reduces oil consumption by reducing the amount of blow-by gasses that must be accommodated in the engine breather system. At the same time there is a built in scavenge system with a centrifuge that removes “aeration” from the oil before returning it to an integrated dry-sump oil system.
“We didn’t set out to improve on any of the existing technologies,” said Michael Fuchs. “They haven’t worked for the diesel. We synthesised a set of new technologies, based on knowledge gleaned from a wide range of players as well as our own experiences.” The Graflight 8 is expected to complete certification in 2017.
