vibrations

The chart two posts above has been replaced by a new one, see SL-912-016R2 dtd Dec 2020 page 7. Note that it is only for the 912S not the 912.

Try this link https://aquila-aviation.de/wp-content/uploads/2021/06/SL_912_016R2_914_014R2_Rotax_Notes_engine_handling.pdf 

According to this, with 98RON fuel (or AVGAS) you can use WOT at 4000rpm and above but with 95RON, not until 5500.

All it says under performance recommendations is "Choose RPM for continuous operation of engine at WOT according to the selected fuel (refer section to 3.4.1)" and don't exceed 5500 for more than 5 minutes.

I can't copy the chart from it unfortunately.

AFAICS it is still the case that nobody can find any official advice from Rotax not to cruise below a particular rpm!

When I had a Kitfox with a 912, it felt very happy at 4800 or even less for economy cruise. Now with a 912S and a CS prop in a Europa, I don't go below 5000, and I don't go above 26" MAP at 5000. It just doesn't feel right. For more power I increase rpm as well as MAP.

It's judgement.

Quite so, no worries above 3500ft anyway :-)

Peter Kl. wrote:

Quite so, no worries above 3500ft anyway :-)

??

There's no mention of that. It's referenced to ISA.

(If there was a limitation like that, shouldn't it be density altitude not pressure altitude?)

Just noticed another point in that service letter - it says after carb synch, adjust the idle mixture. Not seen that before - usually it's just "set it at 1.5 turns".

Well, my perhaps it is  very personal reading that  “up to 3500ft beware…(stick to the frame)” above that “no problem”. If there was another set of parameters to be taken care of above 3500ft Rotax would have stated that. Besides, what level of MAP is realistic at say 5000+ ft?

Interpreting the frame it makes no difference if one flies really or (with WOT) and reduced MAP or reduced MAP with pitched prop.

The different levels of knocking-free engine operation with ROZ98 and ROZ95 (or even less) is not really an update to the chart with the operational frame, is it? I assume it to be a second thread. To me it rather reads like “make sure you use the right fuel for your standard flights” & “gas is not gas”.

This really is an interesting matter…

Regards

Peter

The chart you posted is from rev 1 of the SL.

Rev 2 supersedes rev 1 and the chart in it surely replaces the chart in rev 1? There is no reference to 3500ft in rev 2.

Rev 1 does not differentiate between 95 and 98 so is presumably based on worst case i.e. 95 - which is fine for the 912 but less so for the higher compression 912S.

That's how I see it anyway!