---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Fri 01/13/12: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:44 PM - He assumed I knew what I was =?ISO-8859-1?Q?doing? (henry.voris) ________________________________ Message 1 _____________________________________ Time: 11:44:07 PM PST US Subject: RotaxEngines-List: He assumed I knew what I was =?ISO-8859-1?Q?doing? From: "henry.voris" 13jan12 Gentlemen, My pal Lance asked, So Do you wanna put the big piston in the front or the rear? I assumed he was kidding He assumed I knew what I was doing A train-wreck of assumptions. Deliberating shortly, we figured the larger piston would run hotter and should live closest to the fan. After a couple of hours of swearing, doing-it-again, and fumbling around we got the thundering 447 back together Im sure we got most of those dang needle bearings back in the wristpins Back on the plane, the engine fired right up and ran strong But the cylinder closest to the PTO (#2) was running a bit hotter than the cylinder closest to the alternator (#1). At 5,000 RPM and above, the temperature difference (both CHT and EGT) exceeded the difference allowed by the factory (36 CHT and 45 EGT). I have attached a spreadsheet that reflects the temperatures at different RPMs. I got back to Lance and he said that he had not been kidding about two sizes of pistons I was sick. Purchased a dandy little bore-scope from Aircraft Spruce and with more swearing and fumbling about I could see what I have (done) Cylinder #1, Closest to the alternator, 67.46, green dot Cylinder #2, Closest to the PTO, 67.45, red dot Cylinder #2 is hotter that shoots my theory about the bigger piston running hotter Also the top of piston #2 has accumulated a coating of carbon in only 5 hours of operation, while piston #1 is much cleaner. (Photos attached) I have run only AV-2 two-stroke oil in an effort to minimize carbon build up Im somewhat disappointed. In reviewing the spreadsheet It appears that each piston is operating within the temperature limits set by the factory for operation. The problem is the temperature difference between cylinder #1 and #2. Before installing the digital engine monitor, I only knew the temperatures on one cylinder I would have never have seen this problem and would probably be having a great time out flying, right now. When Rotax sets limits for the difference of temperature allowable between cylinders, Im pretty sure they are figuring on both pistons being the same size (Krauts are like that) A larger than normal temperature difference in an engine with matching pistons could indicate a problem However, in an engine with different sized pistons, perhaps this temperature difference should simply be expected. Comments? -------- Henry Firefly Five-Charlie-Bravo Do Not Archive Read this topic online here: http://forums.matronics.com/viewtopic.php?p=363708#363708 Attachments: http://forums.matronics.com//files/piston_2_pto_6745_red_dot_116.jpg http://forums.matronics.com//files/piston_1_alt_6746_green_dot_514.jpg http://forums.matronics.com//files/cht_egt_run_13jan12_171.xls ------------------------------------------------------------------------------------- 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.