Here are a few shots from the Rotax catalog. Rotax engines can be purchased for items such as ultralights to small four seat planes, and more recently for manufacturing military drones. The 916 is a four stroke turbo. To me they are pieces of art work. Enjoy.
Rotax Aviation Engines
- Thread starter Snagglefoot
- Start date
Our Stemme S10 Motor-glider uses a Stemme specific Rotax 914 turbo/intercooled/115HP.
The engine has been generally reliable, although it hates 100LL, and will foul its tiny motorcycle sized spark plugs quickly with the leaded fuel. The aircraft/engine combo requires either 100LL or 95 RON non ethanol unleaded, which can be difficult to find and expensive. I end up using VP or Sunoco race fuel.
Since this is BITOG, I use Mobil 1, 10W-40 Racing 4t motorcycle oil in the engine. It meets the engine's requirements when operated with unleaded fuels.
Due to the nature of the gear reduction, the engine is a rattling monster at idle, with gear lash and prop v crank inertia adding up to noise. However, once the RPM increases, the operation is quite smooth and pleasant.
One other note, these engines are not more efficient than modern variants of Lycoming or Continental, in fact, only the 916 approaches the BSFC numbers of a 50 year old Lycoming. The reason owners are thrilled with the engines is the low fuel burn, at about 5 gal/hr (or sometimes less) but remember, they are producing very little power at those fuel burn numbers.
Stemme S10, Rotax 914 turbo engine in back. Driveshaft between pilot and pax, fiberglass prop hides behind the the closed dome when not running. 75 foot wingspan.
The engine has been generally reliable, although it hates 100LL, and will foul its tiny motorcycle sized spark plugs quickly with the leaded fuel. The aircraft/engine combo requires either 100LL or 95 RON non ethanol unleaded, which can be difficult to find and expensive. I end up using VP or Sunoco race fuel.
Since this is BITOG, I use Mobil 1, 10W-40 Racing 4t motorcycle oil in the engine. It meets the engine's requirements when operated with unleaded fuels.
Due to the nature of the gear reduction, the engine is a rattling monster at idle, with gear lash and prop v crank inertia adding up to noise. However, once the RPM increases, the operation is quite smooth and pleasant.
One other note, these engines are not more efficient than modern variants of Lycoming or Continental, in fact, only the 916 approaches the BSFC numbers of a 50 year old Lycoming. The reason owners are thrilled with the engines is the low fuel burn, at about 5 gal/hr (or sometimes less) but remember, they are producing very little power at those fuel burn numbers.
Stemme S10, Rotax 914 turbo engine in back. Driveshaft between pilot and pax, fiberglass prop hides behind the the closed dome when not running. 75 foot wingspan.
It is also good to know that the 160HP Rotax 916 sells for $50,000. Which is considerably more than a $37K new Experimental Lycoming 160HP engine, and about the same as the downright epic 215HP IO390 Lyc. But a touch less than the $52K "top of the line" Lycoming 160HP "FADEC" offering.
The reason I bring this up, is that despite the turbocharger's obvious altitude advantages, the Rotax 916 continuous 135HP rating can't really compete with a similarly priced lyc IO390 for its 215 continuous HP output or outright sea level HP. In fact, the 390 can match the Rotax's output all the way to 14,000 feet, at which point the turbocharged Rotax 916 provides a cruise power advantage.
It is nice to have options, but if I were building, say, a Carbon Cub, I'd rather have the extra Sea Level HP of a big Lycoming for options like floats or sandy runways.
The reason I bring this up, is that despite the turbocharger's obvious altitude advantages, the Rotax 916 continuous 135HP rating can't really compete with a similarly priced lyc IO390 for its 215 continuous HP output or outright sea level HP. In fact, the 390 can match the Rotax's output all the way to 14,000 feet, at which point the turbocharged Rotax 916 provides a cruise power advantage.
It is nice to have options, but if I were building, say, a Carbon Cub, I'd rather have the extra Sea Level HP of a big Lycoming for options like floats or sandy runways.
I'm with you on the IO390 bandwagon! I'm 'stuck' with a 400hr IO360, no chance to upgrade for hopefully a long time. The Stemme/Rotax relationship is a strange one. Wonderful flying machine though.
I wish I could replace my O-200 with something more modern. It’s getting to the point it should get overhauled but what they want to rebuild this ancient lawnmower engine is ridiculous.
Is there a significant weight/size difference?
Yes there sure is, and that's a big consideration. The Rotax is 90Kg dry, although when the radiator and water are added, it's not quite as light as it might seem, the O320 is 120Kg and the IO390 is 140Kg. The fact that the lightweight Rotax can compete at all is amazing.
I was comparing a 160HP engine to a 215HP engine by cost. The Rotax is amazingly more complex and "tall" by comparison. Don't forget that the cooling drag caused by a radiator is higher than a typical air cooled engine, as the temp delta is much lower, requiring more airflow.
Compared by Takeoff HP:
160HP Lycoming O320, one of the most reliable and long lasting aircraft engines ever made. Simple, efficient, good power to weight.
And compared by price and high altitude HP, the Lycoming IO390:
True, the O200 in it's original form is quite the old school, and low compression, less efficient design. Although there are any number modifications available.
