---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Sat 07/07/07: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:23 AM - Fuel Octane for 912 Engine (Hugh McKay III) 2. 01:05 PM - Re: Fuel Octane for 912 Engine (Mike Crutchlow) 3. 05:01 PM - Re: Fuel Octane for 912 Engine (Roger Lee) 4. 05:37 PM - Re: Re: Fuel Octane for 912 Engine with Ethanol (Roger Roy) ________________________________ Message 1 _____________________________________ Time: 11:23:51 AM PST US From: "Hugh McKay III" Subject: RotaxEngines-List: Fuel Octane for 912 Engine In a conversation with a friend of mine, who flys an Allegro 2000 with a 912 UL engine, he ask what fuel I used in my Allegro 2000 which also has a 912 UL. I told him I used unleaded 87 Octane (AKI=antiknock index) auto fuel. He was surprised to hear that number, because he was under the understanding that 93 octane (AKI) unleaded auto gas was the lowest octane that should be used. The Rotax 912 Operators Manual states that the minimum RON (Research Octane Number) for the 912 UL fuel is 90. Some time ago I calculated the RON for 87 Octane (AKI) using the formula you see on the pumps at the gas station, (AKI = RON + MON) 2 In the formula, I used a value of 82 for MON (Motor Octane Number), but for the life of me I cannot remember how I got the value of 82 for MON. Anyway using a value of 82 for MON for 87 AKI Octane gasoline in the formula you end up with a RON Value of 92, which is slightly above the minimum of 90. Am I doing this correctly, or am I way off? Does any one know what the real MON number is for 87 AKI unleaded auto gasoline? Where can this number be found? I cant seem to find it. What Octane (AKI) auto fuel are others using in their 912 Uls? Hugh McKay Allegro 2000 Rotax 912 UL N661WW ________________________________ Message 2 _____________________________________ Time: 01:05:58 PM PST US From: "Mike Crutchlow" Subject: RE: RotaxEngines-List: Fuel Octane for 912 Engine The factory Rotax engine brochure calls for a minimum octane rating of MON 83 / RON 91 / AKI 87 to be used in the 912 UL. The operators manual calls for RON 90 in the UL and RON 95 in the ULS. Mike Crutchlow Kitfox II 582 BH ________________________________ Message 3 _____________________________________ Time: 05:01:50 PM PST US Subject: RotaxEngines-List: Re: Fuel Octane for 912 Engine From: "Roger Lee" Hi Hugh, The 80 hp 912 can use 87 octane, but the 100 hp 912 has to have 91 octane or higher, other wise you may be looking for trouble with your engine. -------- Roger Lee Tucson, Az. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=122683#122683 ________________________________ Message 4 _____________________________________ Time: 05:37:52 PM PST US From: "Roger Roy" Subject: Re: RotaxEngines-List: Re: Fuel Octane for 912 Engine with Ethanol I'm flying a Savannah with a Rotax 912S and using Sunoco 93 octane. It seems to be working fine but have some reservations of using it due to 10% Ethanol added. There are some serious debates over this at my flying field which leaves me confused. What say you all about this subject? ----- Original Message ----- aand From: Roger Lee To: rotaxengines-list@matronics.com Sent: Saturday, July 07, 2007 7:59 PM Subject: RotaxEngines-List: Re: Fuel Octane for 912 Engine > Hi Hugh, The 80 hp 912 can use 87 octane, but the 100 hp 912 has to have 91 octane or higher, other wise you may be looking for trouble with your engine. -------- Roger Lee Tucson, Az. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=122683#122683 http://www.matronics.com/Navigator?RotaxEngines-List ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.