Photo: BRP Rotax
News Flash! BRP Rotax, in Gunskirchen, Austria, is introducing a computer-controlled, gasoline direct injection engine that promises 38 to 70 pct better fuel efficiency, lower emissions, carefree handling and less maintenance.
Not in the News: Direct injection virtually eliminates harmful preignition or detonation in gasoline fuel piston engines, thereby potentially eliminating the need for leaded AVGAS. At present, legacy piston engines require tetra-ethyl lead to be mixed into aviation gasoline to prevent harmful detonation of the air / fuel mixture that is squeezed and heated during the compression stroke. Direct injection keeps fuel from entering the cylinder until the start of the power stroke, thereby eliminating detonation. This is what potentially allows the use of unleaded AVGAS.
Direct injection isn't a new technology. It was pioneered prior to WW II by the Germans for warbirds and used extensively after the war for some civil aircraft powered by Wright R-3350 duplex-cyclone radials, such as the Lockheed Constellation. The R-3350 could run very economically at super lean air / fuel mixtures with no risk of detonation because of its direct injection. However, heavily leaded fuel still was required because such engines had primitive ignition and fuel delivery systems.
Now BRP Rotax is reintroducing direct injection. New FADEC-controlled ignition and fuel injection systems could eliminate the need for leaded AVGAS. If so, this advance could help reduce general aviation's dependency on fuel with tetra-ethyl lead -- but just by a very small amount.
Want make a big dent in leaded AVGAS consumption? Look to Teledyne-Continental and Textron-Lycoming. The transition to GDI by the two biggest suppliers of high output general aviation piston engines is long, long overdue. GDI also could vastly improve specific fuel consumption, reducing the pain at the pump. It's time for GA piston engines manufacturers to abandon mid 20th century lawnmover-like powerplant designs and step up to 21st century technology like BRP Rotax.