This small aero engine goes precisely in the opposite direction of the ‘simplicity, practicality, weight and cost sacrificed for efficiency’ paradigm of current turbo diesel initiatives 
Since creativity is looking at things differently than in banal and endlessly repeated propaganda, I found this one interesting…
A side valve engine is intrinsically compact and simple, while typically sacrificing thermal efficiency due to a poorly shaped combustion chamber and thereby limited compression ratio and limited cylinder bore/displacement. Those problems may be less at low rpm, but that also matches the limits of propeller rpm for a light direct drive engine, making the overall package still lighter.
I found it interesting that they supply a fair bit of power and fuel consumption data on the website, not just a single horsepower number and peak fuel efficiency. For instance…
Based on the data, does it make any sense or does it go too far? 
It has often been the way that simple is best, i can think of a number of engines originally intended for mundane tasks that have gone on to greatness due to the rugged simplicity of the design.
It’s very interesting. Extremely light and compact. It is in fact lighter than a Jabiru 2200 and more compact, yet – more HP. Much lighter than the similar powered Rotax 912 ULS. They also make a 6 cylinder engine, but I don’t think it is ready for sale just yet.
I have not seen it in real life, but one guy here talks about replacing his 2 stroke rotax with this one in a microlight Cub kind of plane.
22l/h for 80BHP at 2500RPM is around 34.8lb/h, which results in a BSFC of 0.43lb/BHP/h, which is pretty much the same as a Lycoming, and apparently the old 912 Rotax. The 912iS is said to be more efficient.
I was hoping somebody would calculate the specific fuel consumption for comparison
Other than running at low rpm and presumably using good fuel, I wonder what they might’ve done to preserve efficiency? Typically side valve engines are limited to very low compression ratios and generally throw away a fair bit of heat in exchange for their compactness.
Anyway I’ll be interested to see if they make any progress in the market. The first Continental flat engines were air-cooled side valve designs, replaced by overhead valve designs early on:
Other than running at low rpm and presumably using good fuel, I wonder what they might’ve done to preserve efficiency?
According to specs the compression ratio is 8:1 which is the same as Jabiru engines. And the D-motor has EFI and EI as well as being water cooled, so it probably work just fine even though the basic design is not the most efficient, maybe?
Is this engine still being developed/delivered. It seems to be very quite on their webpage
I talked to the Swedish importer 4-5 months ago. Apparently they are all sold out, but they are making a new batch right now. Seems they are a very small company with limited production facilities.
