Reduced 912 ULS Performance??

Different altitudes and climates can affect the performance of any internal combustion engine. When considering engine performance, the outside air temperature (OAT) and density altitude are primary factors to be taken into account.

First, thanks for taking the time to respond.  

As I only have ~40 hours on my 912 ULS powered RV-12 I am seeking to gain a better understanding of the 912 ULS engine. 

How sensitive is the 912 ULS to temperature and density altitude changes?

I’m surprised that a 1 degree C increase in temperature combined with a 465 foot increase in density altitude would result in a 80 rpm decrease in climb rpm. But, that is why I asked. 

I think the key summary that you are telling me is that it is normal variation and not to worry about it.  Correct?

Thanks.

Brett

Based on the data you provided, there appears to be a difference of 768 feet in density altitude and a 3-degree temperature change, resulting in an 88 RPM drop. These minor alterations can have an impact on the engine's overall performance. May I ask if your propeller pitch is set to a maximum RPM of 5269?

Additionally, running the engine below 1400 RPM can cause undue stress on the engine. To prevent this, we recommend advancing the throttle to around 2000 RPM after starting the engine. Please note that the choke position (enriching circuit) can also affect the RPM as well as a head or tail wind.

We suggest taking a Rotax service course to improve your familiarity with the engine, as it will provide a comprehensive understanding of its operation. Furthermore, do not hesitate to ask any questions on the forum, as our team is always available to assist you.

https://www.rotax-owner.com/en/education-5/rotax-training

Interesting, there’s always something to learn.  Pray tell, how does a head or tail wind affect engine rpm?

If a pilot is closely monitoring a sensitive digital gauge, they may notice small fluctuations in RPM, even though the impact of winds on RPM is typically minor and may not be noticeable in normal flight operations.