---------------------------------------------------------- Stratus-List Digest Archive --- Total Messages Posted Wed 10/03/07: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:42 PM - Stratus Subaru seasonal mixture (LarryMcFarland) ________________________________ Message 1 _____________________________________ Time: 05:42:26 PM PST US From: LarryMcFarland Subject: Stratus-List: Stratus Subaru seasonal mixture Hi guys, Still in test mode, (mentally,) I thought it best to confess my latest flub so others might learn or gain insight. September 29 I was at the airport at 7:00 a.m. Larry Dorgan (a friend and 701 Builder) arrived shortly after and we took off toward Burlington into a decent headwind. A thin overcast with sunshine provided a soft light patchwork of brown and green fields and we had smooth 75-degree air. At 2500 feet and 20 minutes out, water and oil temps crept to my EIS safe set points 220-coolant and 250-oil. We got a warning light. I let off 4900 rpm and temps subsided temporarily. The heat muff was moving cool air, so that wasnt the problem. We were both disappointed, but decided to safely return to MLI and forego this years Open House at Zenith. At home, I re-visited the Bing Manual and realized Id noted 178 and 2.78 jets are for summer. I was still flying with the leaner 176 and 2.76 winter jets. These are intended for a winter-air-soaked engine that could tolerate a warmer mixture. My summer jets should have been 178 and 2.78 for a richer mixture to reduce engine heat so coolant and oil can do their part. After lunch, I drove back to the airport and re-jetted the Bings to 178 and 2.78. Id mixed assumptions about thin hot air versus thick cold air, which are less a concern. The percentage of engine heat output reduced by a richer mixture in summer is important. EGTS reduced from 1425 by 50 degrees should allow coolant and oil temps go lower by similar numbers. The afternoon wind was blowing pretty hard so confirmation of this would be left to the next good day. This good day, I took flying gear to the hangar to check numbers for the 178 and 2.78 jets. I took off from 27, climbed to 4000 ft and maintained 4900 rpm for 15 minutes. This was repeated at 2500 feet. Coolant temperatures never went above 197-deg F, Oil remained at 230-deg F, CHTs read 203-deg F and EGTs stayed under 1380. After the test flight, I landed on 27, taxied back satisfied and reassured by the results. Its true that correct seasonal mixture per one jet size can have everything to do with cooling the Subaru engine. In my haste to be ready for Open Hangar Day, I missed the symptoms of an engine that had been running near safe EIS set points most of the summer. Nothing harmed, but its a point that should be made and will have to be remembered for the next trip. We probably missed a good Saturday too. Larry McFarland 601HDS at www.macsmachine.com ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message stratus-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Stratus-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/stratus-list Browse Digests http://www.matronics.com/digest/stratus-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.