The Graflight V-8 is an aircraft diesel engine developed by Wisconsin-based Engineered Propulsion Systems
The Graflight V-8 is a liquid-cooled, flat V-8 with steel pistons and compacted graphite iron crankcase for better strength and durability than aluminum at similar weight, increasing time between overhauls to 3,000 hours. It is managed by a Bosch ECU and can run on Jet A, JP-8 or straight diesel fuel. It is intended to be used in general aviation airplanes, small helicopters, military drones, small boats or troop carriers.[1] The engine is specifically targeting the Robinson R44, Beech Bonanza, GippsAero GA8 Airvan, Cessna TTx and Cessna 206 as possible applications.[2]
The design is a, 4.3-liter engine with steel pistons, connecting rods, and crankcase to improve reliability. At, it weighs more than a conventional aircraft engine, not including the radiator for cooling. It should be 30-40% more expensive to purchase than a comparable avgas engine, but with 30-50% better fuel economy. Its low vibration levels allow the use of composite or aluminum propellers.[1]
The engine's 17:1 compression ratio gives it a best brake specific fuel consumption of less than, compared to typical avgas engines with . It is expected that the Graflight V-8 will burn under of fuel at 65% power.[3]
As a direct comparison, the 3500NaN0 version of the Graflight V-8 engine will weigh more than the comparable Lycoming TIO-540-AE2A (dry) or Continental TSIO-550-E (dry). It will cost 30% more, but with a higher time between overhaul and lower fuel burn, it will have lower operating costs.[4] At normal 75% cruise power, the Graflight V-8 consumes of fuel, whereas the Continental TSIO-550-E burns, a reduction of 30%.[5]
EPS set out to certify a new-design flat 8 engine, to replace existing general aviation gasoline engines, with the aim of reducing fuel costs by 45%.[6] EPS started work on the design in 2006, a process that took five years. The engine was first flown in May 2014,[7] first exhibited at the 2017 EAA AirVenture and FAA certification was expected at that time by the end of the year.[2]
Later in 2017 the testing progress was delayed by insufficient funding. By July 2018 it had completed 25 hours of flight testing on a Cirrus Aircraft airplane. At that point the company hoped to attract Fortune 500 investors and planned that a new demonstrator should be ready in the first quarter of 2019.[8] The production version of the engine was shown at AERO Friedrichshafen in April 2019 and work continued on environmental and block testing towards the goal of type certification.[7]
Unable to obtain the needed financing to continue operations, the company filed for Chapter 11 bankruptcy protection in August 2020.[7]