Rotax 912s versus Rotax 914

What is your plan, aircraft-wise?

that’s the most important question IMHO
wouldn’t consider an engine without the specific airframe and use case

I believe @europaxs flies behind a 914 so maybe he could share his experience. In general, from my experience with other brands of turbo engines I guess turbos themselves do not require scheduled maintenance, or minor like some greasing every now and then (brand dependent), so it’s only a matter of less hours on cylinders for the 914. But I suppose the ops manual will dictate ‘management’ as in making sure you let the turbo cool down properly after landing, failing which you’ll likely get into unscheduled maintenance/replacement.

I’ve been told that the 80hp 912 runs smoother than the 100 hp 912s, and since the 914 is based on the 912 it may run smoother too.

In the MCR4S the Rotax 914 is about 12kts faster and has 70kg more useful load.
It also uses 2 lph more fuel.

That is difficult to answer. We have a few MCR4s in this area. We used to have 2 here at LFFK and they would more than likely have had the 912 ULs engines. I only heard of one problem on both of these and that was that it was using a lot of oil. Turned out to be a blockage in the breather.
Both of these have now moved on.
The aeroclub at Cholet used to have one. IUC it was built by the kids from the local Lycee during their BIA course.
All of these were maintained AFAIK by the owners and aeroclub so it is difficult to comment on maintenance.
One other in the area was or is AIUI used for PPL training and is maintained by part 66 engineers.
I don’t think any of them ran the 914 because their mission didn’t require the more expensive engine. There is also the fact that there are quite a few people in this area and a bit further south at Roysn who have Rotax expertise in both 2 stroke and 4stroke Rotaxes and in particular the 912.
SE aviation are also suggesting a retrofit of the 915iS to the MCR4s.
IMO if you find one you like and the performance is good for you, and the price is right, buy it. You can always change the engine at a future TBO or beyond.
By then the 914 and 915iS will have clocked up many more hours and we will begin to see any downsides with them.
One guy has done 2000hrs on his in 7years but he does have the 912 ULS . He has never flown above FL120
He says the big thing to watch is that in descent, even with only 100/99hp he has to take care not to pass VNE. He does his own maintenance, but he has changed the Ducatti magnetos with Ignitech.
I thought about buying a friend’s who had to stop flying to a serious health problem. He was an ex Jaguar pilot and he loved the MCR4S but he did say he had had the regulateur of tension, also Ducatti,changed for a Schindengen. I asked him what that was and he said “how would I know, I only fly them” 🙂 That’s the problem with these ex military pilots.
We eventually decided that it must have something to do with pressure as having your blood pressure checked in French is ‘controle de la tension artérielle’ but that’s just a guess.🙂

I have a 914 in my Europa. I fly it for more than 600h. A nice engine in my opinion and runs smoothly like the 80 hp engine on which it is based. Troubles I had were very rarely related to the Turbo but rather to the same culprits like with the normally aspirated models (carburetors, ignition boxes). Maintenance is basically the same and same intervals. That said there is of course more complexity in a turbo engine but the TBO for the 914 is 2000 h as with the 912/912 S. Make the 2 minute cooling run before shutdown and you’ll love it for its advantages like plenty of power (not only at high altitude), smooth running, no vapour lock or carburetor icing.

dublinpilot wrote:

but what I’m trying to figure out is my own ‘negative attitude to turbos’, which is based on what I’ve heard about maintenance on Lycoming and Continental turbo charged engines, also applicable to Rotax engines?

I don’t think that’s an apple to apple comparison at all. A turbo in a Lycosaur has only one mission, and that is to enable flying high and fast. In what is (roughly speaking) an identical engine, with identical HP, the one with a turbo will experience considerable higher load at considerable longer time compared with the non turbo. On a Rotax, the turbo is more a method to increase HP (at the deck) with roughly the same engine. This is best seen on the 916. But it is only roughly the same engine. It is beefed up accordingly. Don’t know how much exactly, but apparently enough. Obviously a turbo on a Rotax is more of an integral part of the engine, than merely an “add on” to fly high and fast. Still, adding a turbo makes a much more complex engine. This will create more maintenance, and more complex maintenance.

gallois wrote:

how would I know, I only fly them

This is important to keep in mind. As long as it works, it works. If it doesn’t work, someone has to fix it. That is time and/or money. If you “only fly them”, you don’t see any of that, you only bitch about low availability and insane hour cost

no vapour lock or carburetor icing.

No carburetor icing I can understand, but why no vapour lock?

A turbo in a Lycosaur has only one mission, and that is to enable flying high and fast. In what is (roughly speaking) an identical engine, with identical HP, the one with a turbo will experience considerable higher load at considerable longer time compared with the non turbo. On a Rotax, the turbo is more a method to increase HP (at the deck) with roughly the same engine.

I think this needs research. The mission profile of the turbo Lyco etc community is likely very different from any part of the Rotax community.

@aart – there are 2 electrical fuel pumps at the bottom of the fuselage behind the tank in the Europa (pushing cold fuel from the bottom level of the tank upwards to the fuel pressure regulator). So actually this is just the setup in the Europa which is absolutely not prone to vapour locking. Can’t speak for the 914 installation in the MCR4 though.