915iS High Manifold Temperature

Rotax made the 915 to certified standards (EASA Part E)  I am unaware of any auto engine fuel injected systems, using O2 sensors and auto engine controlers, that can meet the FADEC standards.  For experimental only no problem with your auto engine and Ebay parts, these however cant be certified.  

FAA guidence for FADEC, electronic controlers... https://www.faa.gov/documentLibrary/media/Advisory_Circular/33.28-1.pdf

In the service of bringing this thread back to its intended purpose, it should be noted that in the latest Operating Manual, Revision 2, Rotax increased the Manifold Temperature limit to 80 °C (176 °F). This pretty much makes it a non-issue IMHO, as I don't think anyone will see temps anywhere near that high. 

That is great news! What about the MAT temp of 122F at 15,000ft though? 

High altitude reduces the air efficiency to cool (less dense) and in those cases you normally would fit a larger intercooler.  Drones who operate at very high altitudes usually have much larger intercoolers than the same engine used down low.  I believe most are overthinking the problem as the computer is looking at getting the pressure correct for performance and as long as the temperature does not exceed the limits for the temperature it will be fine.  it is normal when we compress air that it heats, all turbo boosted engines will see this phenomenon.  

Andrew Morris wrote:

That is great news! What about the MAT temp of 122F at 15,000ft though? 

On the section you're referencing, the parameter is Critical Altitude. It's saying the Critical Altitude is 15,000' assuming a max MAT of 50C / 120F. (If your MAT was higher than that you'd have a lower Critical Altitude.) It's not saying that manifold temperature is a maximum operating limitation. 

The subsequent page shows the limitation for the parameter of Manifold Temperature. There, it shows the max is 80C / 176F.