Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL) or certified (A and F) engine and there are four main models (injected too) to date. The original engine is the 80 hp 912, from which the 100 hp 912S was developed and Rotax also has a 115 hp turbocharged 914 engine. In 2015 Rotax announced the 135 hp fuel injected turbocharged 915iS.
Recognizing the different models is easy: the 912 has black cylinder covers, the 912S green/blue (blue for the french market), the 912iS is green but without the carburetors and the 914 has red covers and a turbo. These are the most obvious differences.
As all engines, even the Rotax has its limitations in power, RPM, fuel and other temperatures. Keep in mind that we present this info without any warranty. The manuals from Rotax remain authoritative at any time.
All Rotax four strokes have more or less the same limitations in RPM, temperatures and fuel requirements. Below a quick reference guide. Again, refer to the official manuals for the finer details.
|Take-off RPM (5 min)||5800|
|Max Continuous RPM||5500|
|912 UL/A/F power at 5800||59,6 kW / 81 hp|
|912 UL/A/F power at 5500||58 kW / 79 hp|
|912 ULS/ULSFR/S/iS power at 5800||73,5 kW / 100 hp|
|912 ULS/ULSFR/S/iS power at 5500||69 kW / 95 hp - 72 kW / 98 hp (iS)|
|914 UL/F power at 5800||84,5 kW / 115 hp|
|914 UL/F power at 5500||73,5 kW / 100 hp|
|915 iS power at 5800||100 kW / 135 hp|
|Oil pressure||7 bar max at cold engine start|
|Min Oil pressure||0,8 bar below 3500 RPM (1,5 bar older models)|
|Normal Oil pressure||2 - 5 bar above 3500 RPM (1,5 - 5 bar older models)|
|Max Oil Consumption||0,06 L per hour|
|Max Oil Temperature ULS/S||130°C (ULS/ULSFR/S) 140°C (UL/A/F)|
|Min Oil Temperature||50°C|
|Normal Oil Temperature||90 - 110°C|
|Max Cylinder Head Temperature||135°C (ULS/ULSFR/S) (150°C UL/A/F)|
|Ideal CHT||75 - 110°C|
|Fuel pressure||0,15 - 0,4 bar|
|Hydraulic governor||600 W|
|Vacuum pump||300 W|
The engine is built for lead free mogas, running it on AVGAS (100LL or 100) is possible but do take note of the limitations. Service Instructions SI-18-1997-R5 and SI-912-016-914-019 from Rotax explains it in more detail.
|912 UL / A / F||912 ULS / ULSFR / S|
|min. ROZ 90||min. ROZ 95|
|EN 228 Normal||-------------|
|EN 228 Super||EN 228 Super|
|EN 228 Super Plus||EN 228 Super Plus|
|AVGAS 100LL||AVGAS 100LL|
Make sure to always use clean and fresh fuel from a pump with a high daily volume.