Rotax 915iS in RV9

[airguy]

Way too much for the RV9 airframe - and I'm a proponent of too much horsepower.

[JKevin]

Seems to be an April Fool's Day joke by Kitplanes

[vlittle]

Originally Posted by NordicDave

The new Rotax 918is at 231HP otta get the job done.

"Apparently word of the six-cylinder evolution of the long-running 912-series engines had not yet reached Austria in time for them to actually design and prototype one. We’ll get back to you when we know for sure."

[NordicDave]

I would jump on ordering a 9A if they factory supported the Rotax engine. Exceed VNE is not a problem. Like every other Green/Yellow/Red arc in a plane, limitations must be observed.

Plane going too fast? Pull power.

[Diego9]

...currently busy with a 9 empennage and thinking about engine options (still plenty of time before I decide) and liking very much the 915.
Indeed if a FFW solution was offered I would go for it.
I understand this was evaluated but discarded because, in order to keep the CoG in the right range, the required FW elongation would be too much...
Maybe a combination of moving the engine FW and adding some mass in the engine area would work out (e.g. additional battery, a tool box? Oxygen system (maybe not a good idea close to the engine but not sure)? small luggage area?).
I am sure a solution that makes sense can be worked out by the smart engineering team at Vans...
Cheers
Diego

[ksauce]

I think the 915 is a great engine. Rotax know this and are very proud of it; they want nearly $42k for it.

[NinerBikes]

Originally Posted by 9GT

I think the Rotax would be severely under-powering a -9.

Have a look at a 4 seater Sling TSI with a Rotax 915iS at 141 HP... gross weight is greater than that of a RV-9A 2 seater @2094 #. https://en.wikipedia.org/wiki/Sling_Aircraft_Sling_TSi

So I guess I don't understand how it would be under powered, other than when you're maybe at or below 3000 to 4000 ft ft Density altitude? 3% loss per 1000 ft gain. .03 x 3000 = 0.09 or 9 % loss That's 136.5 HP available on a 320 150 hp engine at 3000 ft density altitude, while the 915 turbo will have the full 141 HP from sea level to well over 12 or 13000 ft of altitude.

Maybe my math needs to be corrected, but that does not sound underpowered, to me. Another aspect is the Rotax engine won't be burning oil at anywhere near the rate a taper bored O-320 will.

Another aspect is that Rotax motors, at least the 912 UL and 912 ULS NA motors, are known to go well, well past 2000 hrs on the motor, if properly serviced, by the books, with regular oil and filter changes on unleaded gas and fully synthetic motor oil. Need to add some weight to the nose? Get a constant speed prop for the 915iS

[NordicDave]

Originally Posted by NinerBikes

Have a look at a 4 seater Sling TSI with a Rotax 915iS at 141 HP... gross weight is greater than that of a RV-9A 2 seater @2094 #. https://en.wikipedia.org/wiki/Sling_Aircraft_Sling_TSi

So I guess I don't understand how it would be under powered, other than when you're maybe at or below 3000 to 4000 ft ft Density altitude? 3% loss per 1000 ft gain. .03 x 3000 = 0.09 or 9 % loss That's 136.5 HP available on a 320 150 hp engine at 3000 ft density altitude, while the 915 turbo will have the full 141 HP from sea level to well over 12 or 13000 ft of altitude.

Maybe my math needs to be corrected, but that does not sound underpowered, to me. Another aspect is the Rotax engine won't be burning oil at anywhere near the rate a taper bored O-320 will.

Another aspect is that Rotax motors, at least the 912 UL and 912 ULS NA motors, are known to go well, well past 2000 hrs on the motor, if properly serviced, by the books, with regular oil and filter changes on unleaded gas and fully synthetic motor oil. Need to add some weight to the nose? Get a constant speed prop for the 915iS

I wish this forum softer had a “like button” I would pump it a few times for the above post.

Adding a constant speed prop and one or two batteries on the firewall along with slowly extending the engine mount forward would be interesting to look at. Since the overall package of the Rotax engines are smaller, there would be space on the firewall for a primary battery and a back up battery for the EFIS.

If we wind the clock back to the middle 90s the Rotax engines had a 600 hour TBO they are now at 2000 hours. Given the factory is finding no wear in the cylinders at 2000 hours, it won’t be long before TBO is lifted even further.

The fact the engine cost $10,000 more is almost no factor, given the overall acquisition cost of the aircraft and the greatly reduced operating cost over the arc of ownership.

[jrock836]

Originally Posted by munbro01

The Rotax from what I’ve read will accept 91+ octane auto fuel. But to be clear Mogas is NOT your everyday automotive gas from your local gas station.

It depends on context and who you're talking to.. In the RV12, Rotax 912ULS world, Mogas is 91+ octane every day automotive gasoline, up to 10% ethanol, found at at any gas station and it burns just fine in a Rotax 912ULS..

Most, if not all of these "mogas" threads are talking about 91+ octane every day automotive gasoline with up to 10% ethanol. https://vansairforce.net/community/s...rchid=49661831

[NordicDave]

Originally Posted by vlittle

"Apparently word of the six-cylinder evolution of the long-running 912-series engines had not yet reached Austria in time for them to actually design and prototype one. We’ll get back to you when we know for sure."

Mike Busch said in one of his EAA webinars Rotax had a 200hp engine, Lycoming bought the rights and buried it,