With very large volumes in the UL / experimental markets, Rotax has ample funding for R&D. And how they are using it…
The 912 family is a worldwide hit, and this gave Rotax the most critical component of success: a service network.
The humble beginnings with 80 HP should not make us miss the remarkable feat that has already happened and continues to unfold:
The 915 achieved almost miraculous power to weight, breaking the commonly accepted paradigm that power always costs weight.
And they just doubled down with a whopping 160 HP 916 which will keep full take off power to 15’000 ft.
Now wait a minute. Repeat slooowly:
Am I getting over excited or is this finally THE powerplant GA has been waiting for?
Imagine how the above specs would impact performance, handling and useful load of ALL GA planes equipped with one or two Lycosaurs up to 180 HP or CDI / Austro engines. We actually know the impact of extra weight (Austro), so it is easy to imagine the other direction I suppose.
Agreed, and there has to be a market for re-engine in the 135-180hp bracket.
No wonder they keep being knicked … 
I have a Rotax myself, but I also have a ULPower. While Rotax is the VW of (modern) aviation engines, ULPower is the BMW.
A similar 160 HP ULPower, the UL390 i(S)(A) weighs 100 kg. The A version is aerobatics. Direct drive, 6 cylinders, air cooled, normally aspirated, full digital control. Then we have the larger UL520: 180 and 200 hp at 108 kg, also aerobatic version. At the top end the UL520T. Turbo, 220 hp, 120 kg. All are direct drive, air cooled.
The best Rotax is still the original 80 HP 912. Strongly built for the hp, low compression, light and simple. Virtually trouble free (if it wasn’t for the Bings 
). The “larger” ones are almost literally the exact same engine with higher boost (turbo) and/or higher compression ratio and a digital control unit on the newest. 915/916 are probably very good engines, but turbo is IMO an unnecessary and extremely expensive complication when the reason is purely to produce more power at low altitudes (which is what these engines will be used for). Only slightly larger, and at the same installed overall weight, you can get an NA UL520 with 200 HP. Much simpler, much easier to maintain, considerably more HP down low and enough to fly at FL200+
What Rotax should have done is to make a 6 cylinder version of the original NA 912 UL/ULS. They would have had 120/150 HP.
Rotax has had more commercial success than ULPower for sure, but ULPower also sells lots of engines, more and more in fact.
Imagine how the above specs would impact performance, handling and useful load of ALL GA planes equipped with one or two Lycosaurs up to 180 HP or CDI / Austro engines
Hold on your horses, as usual, and the more so in aviation, it ain’t that easy. The dry weight of le O-320 is 122 kg…
I will not list all the problems inherent in a turbo engine, and Rotax installation, but just thinking about the positive (negative in reality ) difference in mass would shift the CG to the rear by some. How, easy, just lengthen the nose… and that is where simplicity ends.
Looking at these fantastic characteristics:
I don’t think performance for Rotax, the simplicity and cost proposition is outstanding to be worth huge shift? it’s getting similar in 100hp-200hp band but not end to end
Can they make 160hp engine at 100kg weight for 30k price and 3k TBO?
How many certified aircraft have the UL Power engine? Is the engine certified?
Note that the MCP of the 916 has not changed vs. the 915, 137 HP. The 916 is basically a 915 that has increased take-off power and also consumes less I believe. MCP up-to critical altitude 137, not 160 HP. So hold these 23 extra horses
Agree @LeSving:
I love the UL Power engines and their very smart engineering and build quality. Didn’t know about their turbo engine, will take a look, thx.
I hope they go certified one day and wish them the best of success. They certainly deserve it.
The one thing that disturbs me about them is the high prop RPM they impose, resulting in shorter blades to prevent tips going into excessive speeds. This in turn means reduced prop efficiency due to smaller prop disc.
This said, in order to achieve worldwide success, ULpower have yet to tick two of the “must have” boxes IMO:
And while we are at the list of criteria: this list was just to highlight that the Rotax 916 ticks all the “must have” boxes.
Of course the Lycosaurs have an even better service network, but what’s relevant is that Rotax have good enough coverage themselves.
Back to the specs: I think we need to recognize Rotax’s achievement in the total installed weight department.
For the sake of the exercise, imagine designing a new plane around this engine.
Knowing the low engine weight, one can reduce structural weight (less material in the airframe and engine mount).
As a matter of fact, the Rotax web site shows an engine frame (?) weighing 2 Kg.
Lower weight for a given power means better take-off and climb performance.
So for a given take-off performance target, the lighter engine will need less wing area, which again saves weight and drag, which again allows the airframe to require less structure etc… You get the idea. This virtuous circle is a fundamental of aircraft design. This is why saving 30 Kg against a Lycosaur is a big deal
As to the turbo and how much power it can make or not:
137 HP continuous is 85% of 160 HP. We would not want to push the engine beyond that in cruise, right?
So let’s see how we can get 137 HP from a normally aspirated engine. which will have 70% power left at 10K feet (ISA). 137 HP / 70% is 195 HP.
So it would take a 195 HP normally aspirated engine to match the Rotax 916 at 10K feet and the higher one goes, the more this is skewed in favor of the turbo Rotax.
And let’s now look at a retrofit case:
There is an STC to retrofit the DA42 with the 155 HP “Thielert”. As Emir said, despite some restrictions imposed by the factory (on the avionics side) this is still the sweetest DA42, simply because it is a balanced package whereas the -VI suffers from excessive empty weight.
Now imagine a DA42 with the -VI aerodynamic tweaks and the Rotax 916. 200 Kg ligher, not even mentionning the 12% weight advantage of Mogas vs JetA.
W&B is easily adjusted in the DA42: its engines sit near CG, and the different existing iterations have already made use of the ability to move ancillaries such as TKS between nose and tail.
I think this DA42"R" would be a wonderful pilot’s plane… Imagine take-off and climb performance of a CDI-155 minus 100 Kg, improved drag in cruise due to the smaller frontal area (especially vs the bulky Austros). Lovely, no?
Yeah, DA42 with R916 would be a sweet airplane. No chance of that happening.
915 has been out for some time … what is the scoop on its reliability? (The turbo ….)
Afaik, 912 is regarded as easy to operate reliable engine.
915/916 is perhaps unnecessarily powerful (and definitively too costly) for 2 seater, and maybe a bit underpowered for 4 seater (at least for the current ones, maybe a clean sheet redesign fully utilizing its lower weight would help).
For the 2 seater market, a lower-weight/lower cost 80-100hp engine would be appreciated, but Rotax has no economic incentives for developing/selling one.
With an IO360, I only use 130hp for cruise (150KTAS) but I wish it has 310hp for 5min during takeoff & climb ? and keep 130hp at FL200?
Rotax seems to know how to build engines that can do these “tricks”
