What Makes The Rotax 915 Aircraft Engine So Special?

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One of the reasons I chose to build a Sling Tsi is because of the engine it’s built around; a Rotax 915 turbo charged engine. Turbo is not often used for single piston engine aircraft, but when you fly behind one, it’s a great extra boost of power.

The Rotax 915 is not only turbo charged, but it’s also a fully managed engine with an electonic ECU system. Makes this engine a FADEC: full authority digital engine control. Your fuel flow, rpm, engine speed, all managed by a computer.
This engine also takes car gas which is cheaper than 100 ll. Matter of fact, Rotax recommends to use car gas if you can find it.

Maintenance is nothing unusual. You have your oil change at 50 -100 hours, at 200 hours you change the spark plugs and at 600 hours you check your gearbox.

There’s so much to love about the Rotax 915. The video discusses more cool features in detail.

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[TravisB]

Just got a job working on these in sebring fl these engines are impressive they can go 2000 hrs and still have cross hatch on cylinder walls

[FourToedJones]

As a car guy, it's nice to see turbos and computer controls in small aircraft engines. Looking forward to seeing your fuel burn when it's finally flying!

[ndakigeorge]

Wow..I am not an engineer but based on your explanation I think I got a pretty good understanding of how this engine works and If i were to choose an engine, I think I'd be able to make an informed decision...Thanks a lot Mike, keep inspiring us. All the way from Tanzania, East Africa.

[ronblondeau]

The best explaination of how an aircraft engine works I have ever heard Mike. Thank you.

[cyrooski]

Great Video but you left out great things about the rotax engine....

About the Rotax engine:

The case, barrels, heads and pistons are all of the same aluminum metal which contracts and expands uniformly eliminating the problem of shock cooling.

The oil is in a canister and not at the bottom of the engine so it has two traps so that air can never get into the case eliminating condensation and damage from under use.

The carburetors never experience ice so there is no carburetor heat in most planes.

The heads are liquid cooled so the cylinder head temperature does not rise above 230 eliminating the possibility of softening aluminum and giving hot spots. If cooling fluid is lost due to leakage the engine may still be flown.  There is no leaning mixture knob.... it is done automatically. So the pilot cannot damage the engine.

Running at higher RPM you can get the same power as a heavier engine by having the cylinders closer to each other reducing the weight of the entire engine so the weight to power ratio is very good allowing 4+ gallons per hour consumption.  Lycoming and Continental do not want a gear reduction unit so their engines must turn at the rpm they want the prop to turn.  This sacrifice gives us big slow pistons with a lot of bang, not good for longevity. The cylinder attach bolts are computer torqued in the factory in Austria and stabilizing mechanisms are used during the torquing process to ensure balanced forces.  All torque values are saved in the engines computer files at the factory.

The crankshaft is made of five separate pieces not including four piston rods.  If part of the crankshaft is damaged one does not have to buy an entire new one.  The prop also has a breakaway clutch from the crankshaft in case of a prop strike to protect the crankshaft.

Built with very few seals and gaskets, instead they use a paste, leading to less leakage.

No alternator to buy or magnetoes to rebuild.

Mogas ready.  One dollar less per gallon, so effectively a 16:50 fuel cost ratio compared to to an o-360.

[Kennardy]

Extremely well explained! Great channel. I hope Sling is “sponsoring “ (paying) you as you are making a lot of people desire a Sling!

[JonMulveyGuitar]

Go MojoSling Go!! Getting close! Can't wait to see it again! Heading down to Sling in two weeks to fly the TSI. Thanks to you! Very informative content here Mike! Great job!

[OscarDad]

Mojo, Im a newbie just stumbling into the workd of LSA. I live abt 30 min from VANS in Aurora, OR, so spent a lot of time looking at them. Your channel is awesome, thank you, and the SLING is a real eye opener. They look incredible. Thank you again for yr content ! 👍

[Jimidan]

Be like Mike! He knows his stuff. I have been a huge fan of Rotax engines due to them being in my sportbikes. Motorcycle manufacturers using Rotax engines, either Rotax-branded or branded for the OEM, include Aprilia, BMW (F and G series), Buell and KTM. [citation needed] Can-Am resumed motorcycle production with a series of on-road three-wheel motorcycles, starting with the Spyder, using Rotax engines.

[RR-klsl]

Are you going to make one for the 916 also? Should be fairly the same but still nice to have a complete and updated one on that new 916 !

[jhmcglynn]

I sold my turbo charged Mooney 231 in 2010 after flying it over 2000 hours in the previous 15 years. The Continental TSIO 360 produced 210 up to 15, 000’, and gradually less up to its service ceiling of 25, 000’. Likewise I’m sure the 915is will produce much more power than a normally aspirated engine up to its service ceiling. I owned a KITFOX SPEEDSTER running a ROTAX 912. It’s a great engine.

[SalveMonesvol]

I've been looking at Rotax engines, and the only thing I'm not sold about is the high rpm. I'd rather have a somewhat larger engine (2.0L) doing max power at 4.000 rpm. That way it could also be connected to the prop without a gearbox. Is there an engine like that?

[anre]

Great primer on turbocharged engines, ECU power management & power-to-weight ratio dynamics.

Good job Mike

[pierrelaband]

Your best video because each item was explained in understandable detail accompanied by examples in cars, etc.

[ODowney]

Thought I knew it all, well from you I learned something more regarding turbocharging. Thank you

[mcanning]

Thanks Mike for that great 👍 explanation. Good luck with completion of your Sling LSA.

[miguelwall]

The ECU would also monitor density and automatically adjust turbo power output based on throttle position and density altitude. Thats why a turbocharged car for example would perform the same at higher altitude as opposed to sea level level, but a normally aspirated engine would have reduced performance and a carburated engine would need an adjustment the fuel to air ratio (reduce/lean fuel due to less density). In addition to supplying cooler air, the turbo is a compressor, compressing that air before the intercooler to supply both cooler and denser air to the engine. In essence acting as though you're at a higher altitude (requiring leaning/less fuel), but with also the added benefit of more density (even better than at sea level on a standard day), while producing more power. The result is the engine runs more efficiently while using less fuel. That's a wonderful engine! Just wish I could afford a build like this.

[discerningmind]

Very good Mike, thank you. Pump gas is a plus but my thought is to use 93 Octane as I understand the valves run cooler the higher the octane.

[ikay]

Mike i can listen to you talk for hours !! Great videos.

[woodbark]

The normally aspirated engine is only capable of "breathing in" an amount of air relative to its capacity and low restrictive flow capabilities of it's intake passages. as well as atmospheric conditions. So in order to coax more power out of an engine - along comes the Air Boost systems to introduce more air into the combustion chambers. "Ram Air" system - "Turbo Charger" or "Super Charger"