912iS low fuel pressure at altitude

Walt, I had the EXACT issue with my 12iS as you did during my phase 1 testing.  I reached around 7000’ during my climb to 10,000’ before the low-fuel pressure alarm.  To make matters worse, I was using 91 octane, ethanol free in February.  I was completely ignorant to Reid Vapor Pressure and winter vs. summer blend MOGAS.  That experience caused me to get informed.  I’d recommend you at least use a 50% MOGAS/100LL mix, or pure 100LL and I’ll bet your problem goes away. 

Walt,

Are you using a differential type fuel pressure sender referencing air box pressure, or a standard sender which references ambient pressure?

Jeff,

I am using the differential pressure transducer referenced to the air box.

Walt,
Were you able to select your exact sensor part number in the Dynon system, and was that sensor part number (in the Dynon setup) preceded by the word “differential”? Some sensors have two settings in the Dynon system, one for the differential sender and one for the same sensor being uses as a standard gauge pressure sender.  I assume you are using the UMA 0-70PSI differential sender.  

This could be a fuel vaporization problem as Bob suggests, but it being 16-22 deg F. during your flights it does not seem likely unless your fuel was warmed by sitting in the sun before takeoff.  When the injected Rotax engines do have vapor problems, it’s on the suction side of the fuel pump.  

Not only did using AVGAS solve my problem during my phase 1 testing, but at least two times subsequently, as recently as this past February.  To me, it would be worth the maybe $30 incremental cost for 10 gallons of AVGAS to rule out this potential issue.  I'm definitely not a Rotax expert, but this was the experience with my RV-12iS.