916 upgrade kit?

[Stingy Pilot]

I stand corrected and thank you for pointing this out. I didn't double check my sources.

My concern is whether Rotax intends to ever extend 915 TBO to 2,000. It appears that they used the 915 data to come up with an improved engine model. Interestingly enough, the 916 was directly released with 2,000 hrs TBO, whereas typically Rotax starts with 1,200 hrs on new engines. All that while the 915 is still confined at 1,200 hrs.

An interesting question is, would someone install the 915 risking it will always have a 1,200 hrs TBO or move up with the 916, pay extra upfront but have more peace of mind with 40% longer engine life?

[Magoomba]

An interesting question is, would someone install the 915 risking it will always have a 1,200 hrs TBO or move up with the 916, pay extra upfront but have more peace of mind with 40% longer engine life?

This is exactly what I did, choose the 916 over the 915. My understanding is there are changes integrated into the 916 crank design that enable the 2000 hour TBO. Rumor is that if Rotax incorporates this into the 915, it will increase to 2000 hours, but only from that production run forward. I had already opted to use the MT propeller (with RS FADEC controller) from the start of my build.

Since I'm planning to fly my TSi for the next 25-30 years, I felt the 916 with 2000-hour TBO was worth the up-front investment. Allocating reserves for a new engine, the 916 is cheaper on a per-hour basis with the TBO increase, even though it costs ~$10k more. Per Rotax, the 916 is also more fuel efficient at cruise settings. They claim up to 20%, IIRC from their webinar when the 916 was released. If one plans to keep their Rotax-powered plan for 2000 hours or more, the amortized per-hour cost of 916 is better than 915, unless Rotax increases 915 TBO to 2000 hours. Additional 20 hp for takeoff is just a bonus. Time will tell if there really is improved fuel economy at cruise and/or any increase in cruise speed.