Kit helicopter manufacturer RotorWay is flight testing fuel injectors that will allow piston aero- engines to use unleaded petrol.
The Startube injectors prevent pre-detonation, reducing the fuel octane requirement for a given compression ratio. Developed by Seattle-based Startube, the injector atomises the fuel to produce homogeneous combustion, eliminating pre-ignition, or knock, and either reducing the octane required or increasing the power produced.
"The device reduces the octane needed by 12-14 points," says Startube president Grant Norwitz. An engine designed to use 100-octane low-lead avgas can run without knock on 88- to 92-octane unleaded automotive gasoline, he says. Rotorway is using the injectors to increase the output of its own 162F engine, which is already able to run on 92-octane gasoline, by 12% with the same fuel. In dynamometer tests, the companies have exceeded 170hp (127kW) with the 2.6 litre (160in3) engine, "which is comparable to engines with more than twice the cubic capacity", says Norwitz.
Tests have been performed using 87-octane gasoline diluted with 50% diesel, equivalent to 70-octane, he says. "We ran the engine at full power: with the Startube there was no knock; without, the engine destroyed itself."
Rotorway says the Startube injector is key to the development of a horizontal version of its digitally controlled engine for fixed-wing kitplanes.
Startube is modifying a Continental TSIO-360 for certification flight testing in a Cessna 337, targeting the retrofit market, and is in talks with engine manufacturers on licensing its technology.
The company aims for a price of $100/injector for fuel-injected engines and $700-800 for carburetted powerplants, says Norwitz. "We want this to be a no-brainer. The savings on five tanks of gas are going to pay for one tube."
Source: Flight International
