Lycoming o320 vs. Rotax 915: cost to own

[DMD3.]

There have been some comparisons with these two engines as the o320 is more powerful at lower altitudes, whereas the 915 is more powerful at higher altitudes (10k+ ft). The 915 is also lighter, and you tend to see them on a lot of bush/stol aircraft, such as Zeniths, Kitfox and Rams, but you don’t tend to see them on faster aircraft like the Vans or the single-seat Panther (the VL3 Evolution being an exception).

Being turbocharged, is the 915 a bit more costly to maintain than the o320? And I’m wondering whether or not a fixed-pitch prop could be mounted on a 915 and be practical on performance, also making the o320 less expensive.

I realize the engine price is around $40k for the 915, and $30k for an overhauled o320 but over $50k for a new one. But which one is less costly to maintain (including fuel burn)?

 

[Bathman]

I can’t comment on the O-320 or the 915 but over the last 12 years I have got about 20K hours operating O-200’s and 6K hours operating the Rotax 912.

That 20K hours on the O-200 is over 13 overhauls/factory rebuilt replacement engines and only one made over 2000 hours. All suffered main bearing failure or cracked crankcases. As for the top end I only ever used new cylinders and not a single Continental example made more than 1000 hours before needing work. Exhaust valves even stuck at under 200 hours.

The Superior ones faired better but still needed work at around 1200 hours.

They all have oil filters fitted and get fresh oil every 50 hours.

As for the Rotax well those 6K hours were all flown over 2 engines. The first getting to 5500 hours and it was completely trouble free. Nothing but consumables was replaced. The second has now done 500 hours and has again been trouble free.

So if the 915 is anything like the 912 then it will be a winner with me.

And Cessna choose the O-200 over the 912 in the skycatcher what an earth were then thinking. And vashon for that matter.

 

[FancyG]

915 can do fixed/ground adjustable. Its really nice with the CS MT80 prop. Gets FADEC, single lever and makes your plane Technically Advanced, if that matters to you.

A huge plus with the 915 is it prefers car gas. Take the delta of 93/100LL off your operating cost and save >$20/hour in fuel.

I can report back after more time on the plane, <60 TT now.

 

[Magman]

Based on your concern with maintenance cost you may want to check if there
are folks familiar with the Rotax in your area.

 

[Dave Anderson]

The 916 is coming out soon, the difference is more take-off horses 160HP is my understanding.

 

[TomF]

Maybe they can release the 936 at some point.
https://www.rotax.com/en/100-years/historical-vehicles-engines/detail/type-936.html

 

[German guy]

[...] The 915 is also lighter, and you tend to see them on a lot of bush/stol aircraft, such as Zeniths, Kitfox and Rams, but you don’t tend to see them on faster aircraft like the Vans or the single-seat Panther (the VL3 Evolution being an exception). [...]

I understand that Van's actually built a Rotax 915 powered RV-9 prototype. The problem was however that this engine is so much lighter than the Lycomings / Continentals it was designed for, that they couldn't make the CG work without significant changes to the aircraft.

 

[Kiddo's Driver]

Maybe they can release the 936 at some point.
https://www.rotax.com/en/100-years/historical-vehicles-engines/detail/type-936.html

300 HP!

 

[Eldorado]

O 320 has been around along time with a good reputation. Most A and P’s are well versed in it. That counts for a lot.

 

[Andrew Morris]

There have been some comparisons with these two engines as the o320 is more powerful at lower altitudes, whereas the 915 is more powerful at higher altitudes (10k+ ft). The 915 is also lighter, and you tend to see them on a lot of bush/stol aircraft, such as Zeniths, Kitfox and Rams, but you don’t tend to see them on faster aircraft like the Vans or the single-seat Panther (the VL3 Evolution being an exception).

Being turbocharged, is the 915 a bit more costly to maintain than the o320? And I’m wondering whether or not a fixed-pitch prop could be mounted on a 915 and be practical on performance, also making the o320 less expensive.

I realize the engine price is around $40k for the 915, and $30k for an overhauled o320 but over $50k for a new one. But which one is less costly to maintain (including fuel burn)?

There are actually several manufacturers using the 915 in faster designs. Take a look at the Blackwing 635RG and the Risen. Those are two of the most efficient airplanes that I know of hitting 185 knots on 6GPH with the 915.

Fixed pitch works fine as well but makes more sense on an aircraft that is drag limited otherwise constant speed would be advisable.

The nice thing about the iS engines is there’s not much to do other than changing the oil. As long as care is taken in the operation of the turbo I’d put my money on it being cheaper to operate. If you push the engine for maximum power and efficiency fuel burn is under 8GPH.

 

[DMD3.]

There are actually several manufacturers using the 915 in faster designs. Take a look at the Blackwing 635RG and the Risen. Those are two of the most efficient airplanes that I know of hitting 185 knots on 6GPH with the 915.

Fixed pitch works fine as well but makes more sense on an aircraft that is drag limited otherwise constant speed would be advisable.

The nice thing about the iS engines is there’s not much to do other than changing the oil. As long as care is taken in the operation of the turbo I’d put my money on it being cheaper to operate. If you push the engine for maximum power and efficiency fuel burn is under 8GPH.

Thanks to everyone for all your responses.

I had forgotten that there are several fast aircraft, particularly in the Czech Republic, that are using the 915, such as the Bristell. The Sling also uses it. Though it’s not RV fast, it’s certainly no slowpoke.

 

[DMD3.]

Maybe they can release the 936 at some point.
https://www.rotax.com/en/100-years/historical-vehicles-engines/detail/type-936.html

It doesn’t even say what horsepower it will be rated, but it should be one heck of an engine, especially with turbocharging. There seems to be no info on a 916 engine.

There seems to be a 916 engine, but not necessarily for aircraft. https://www.easa.europa.eu/en/downloads/7633/en

 

[Andrew Morris]

Lightning fast and efficient. This is the definition of optimizing form drag.

 

[DMD3.]

I think I’m moving to the Czech Republic. Though I don’t believe that Italy is actually in the CR, it’s fairly close to it.

 

[Adam Weiss]

I understand that Van's actually built a Rotax 915 powered RV-9 prototype. The problem was however that this engine is so much lighter than the Lycomings / Continentals it was designed for, that they couldn't make the CG work without significant changes to the aircraft.

Untrue. They’re actively flying it. it’s getting fantastic performance from what I see.
My hope is that they have a FWF package soon.
https://flightaware.com/live/flight/N179RV

 

[odie451]

Don't forget about Teal Jenkins and his Yamaha Sidewinder-powered RV-9

 

[NordicDave]

I understand that Van's actually built a Rotax 915 powered RV-9 prototype. The problem was however that this engine is so much lighter than the Lycomings / Continentals it was designed for, that they couldn't make the CG work without significant changes to the aircraft.

Untrue. They’re actively flying it. it’s getting fantastic performance from what I see.
My hope is that they have a FWF package soon.
https://flightaware.com/live/flight/N179RV

If Van's would sell it as a kit... I'd buy one immediately.

 

[Salty]

If Van's would sell it as a kit... I'd buy one immediately.

If Van's would sell it as a kit... You'd buy one in 1.5 to 2 years when your name finally makes it to the top of the list.

 

[Andrew Morris]

VANS RV-4 915 iS. “How brilliant is this Van's RV-4 built to meet the German 600kg UL requirements, powered by a Rotax 915iS? The RV-4/600R has been created by Robert Haag, who runs PlaneWorx.de. Cruise is 160kts (85% @9,000ft) with a 1,800fpm climb rate.”

Source-https://flyer.co.uk/feature/aero-friedrichshafen-2023-around-the-halls/

 

[Lndwarrior]

Rotax has come a long way.

It doesn't seem that many years ago when pretty much everyone on this (and other pilot forums) were saying, "I ain't putting no snowmobile engine in MY airplane!". Me included.

That consensus lasted a long time.

 

[Andrew Morris]

Rotax has come a long way.

It doesn't seem that many years ago when pretty much everyone on this (and other pilot forums) were saying, "I ain't putting no snowmobile engine in MY airplane!".

That consensus lasted a long time.

You’re right. CubCrafters really surprised me this year throwing a 916 iS on a Carbon Cub. I never thought I’d see the day!

 

[wanttaja]

O 320 has been around along time with a good reputation. Most A and P’s are well versed in it. That counts for a lot.

This is from my homebuilt accident database, but is probably indicative of the overall failure rates. The percentage is the percentage of accidents where mechanical failure of the engine was the cause. I've included the Rotax 912 and the VW engine conversions.

Most of these are based on 100 or more accidents. The exception is the Continental IO-550 (64 accidents). The "O-XXX" figures do not include the fuel-injected (IO-XXX) versions of the engine.

Ron Wanttaja

 

[tsts4]

This is from my homebuilt accident database, but is probably indicative of the overall failure rates. The percentage is the percentage of accidents where mechanical failure of the engine was the cause. I've included the Rotax 912 and the VW engine conversions.
View attachment 116850
Most of these are based on 100 or more accidents. The exception is the Continental IO-550 (64 accidents). The "O-XXX" figures do not include the fuel-injected (IO-XXX) versions of the engine.

Ron Wanttaja

Ron, is what you posted an abridged version of the graph from your data? I ask because it doesn't list Lycoming I(O)-540s which I'm pretty sure exist in the experimental fleet in far greater numbers than the Continental 550.

 

[wanttaja]

Ron, is what you posted an abridged version of the graph from your data? I ask because it doesn't list Lycoming I(O)-540s which I'm pretty sure exist in the experimental fleet in far greater numbers than the Continental 550.

Lots of different engines in my ~4600-accident database, including about 125 different engine makes. So, yes, the data was abridged.

Only 28 Lycoming O-540s, not a large enough sample. 143 IO-540s, with about 9.1% of the accidents due to mechanical failure of the engine. Roughly average.

Ron Wanttaja