Rotax 916iS v. 915iS Performance Data

[Matt Ricciardi]

Rotax recently hosted an EAA webinar regarding the new 916iS engine.  The presentation included this power and fuel burn comparison chart.  Some unit conversion and math is required, but the bottom line appears to be that, at maximum continuous power ("Max C"), the 916iS generates about the same power as the 915iS (94.86 kW versus 93.89 kW) but burns about 20% less gas (250 g/kWh v. 315 g/kWh).

EAA members can replay a recording of the entire webinar on the EAA website here: https://www.eaa.org/videos/webinars/engines-and-firewall-forward/6331066065112

[John Crone]

I'm not so sure about this efficiency gain and suspect Rotax are muddying the waters. Some details are missing on the 915 chart above.

My optimum cruise at FL100 is 5000 RPM and 31.5 MAP where I show 24 LTR/hour fuel consumption.

Looking carefully at the charts from the operators manuals this corresponds with 65 kW power on the 915 chart and I reckon EXACTLY the same fuel flow on the 916 chart for the same power/RPM.

I do note the Rotax charts are for FL90, but wouldn't expect too much difference.  However I would expect efficiency gains at higher power settings.