Rotax four stroke aircraft engines have proven themselves as reliable pieces of machinery. They can be bought as experimental (UL), sport (S) or certified (A and F) engine and there are four main models (fuel injected too: i models) 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 BRP-Rotax announced the fuel injected 141 hp turbocharged 915iS. During AERO 2023 we saw the introduction of the successor, the: 160 hp turbocharged 916iS.
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. The 915 is a turbocharged version of the 912iS with blue covers, the 916 has grey covers. These are the most obvious differences.
As all engines, even the Rotax, have limitations in power, RPM, fuel and pressures and 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. Power output and fuel consumption will be different. Below a quick reference guide. Again, refer to the official manuals for the finer details.
| General Operating Limitations | |
| Takeoff RPM (max 5 min) | 5800 |
| Max Continuous RPM | 5500 |
| Idle RPM | 1400 |
| 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 up to 15000 ft |
| 915 iS power at 5800 | 104 kW / 141 hp |
| 915 iS power at 5500 | 99 kW / 135 hp up to 15000 ft |
| 916 iS power at 5800 | 117 kW / 160 hp |
| 916 iS power at 5500 | 101 kW / 137 hp up to 15000 ft |
| Volume Oil Tank | At max: 3,0 l - at min: 2,5 l |
| 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 |
| Alternator | 1200 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.
| Fuel Requirements | |
| 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.
BRP-Rotax introduced a new certified oil alongside the good old AeroShell Sport Plus 4 10W40 we al came to respect and trust. This is the XPS 5W-50 Full Synthetic Aviation Engine oil which is a unique custom engine oil designed specifically for all Rotax aircraft engines using MOGAS or with leaded and unleaded AVGAS.
Read about it on the BRP-Rotax website or download the XPS 5W50 datasheet here.
Written by EAI.
Experimental Aircraft Info
