---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Mon 05/26/08: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:25 AM - Baffling for cylinder cooling (carl bertrand) 2. 08:38 AM - 912 engine cases needed (ricklach) 3. 04:09 PM - Re: Baffling for cylinder cooling (Roger Lee) ________________________________ Message 1 _____________________________________ Time: 08:25:56 AM PST US From: "carl bertrand" Subject: RotaxEngines-List: Baffling for cylinder cooling I built my 701 from plans in 1994/95. It is powered by a Rotax 912 covered with a Zenair cowl without any internal baffling as per the Zenair demonstrator and recommendations at the time. The engine now has 490 hrs and is still running smooth and strong; I see no difference in static RPM since first flight. I am concerned about two things however: 1. Front Cylinders head temp is much cooler than the rear; 2. Compression on the front cylinder is 20 lbs less than the rear. 115 vs. 135. This has existed and remained steady since first annual in Nov 1995. I suspect a cause and affect between these to parameters. My questions to the list is: I know of two other 701s that have the same cowl set-up and have never seen a 701/912 with baffles. Is this the norm? I'm considering investigating the reason for the lower compression in the front (vales or cylinders) and designing some baffling to equalize the cooling. If I just correct the cooling could this destabilize an engine that is running well? Any comments appreciated. Carl ________________________________ Message 2 _____________________________________ Time: 08:38:19 AM PST US Subject: RotaxEngines-List: 912 engine cases needed From: "ricklach" I am looking for a pair of 912 engine cases that are JUNK. I need them for a mock-up. They can be crashed, cracked or what ever. The only part that needs to be there is all the mounting bosses on the bottom and the rear of the cases. 80HP, 100HP or 914 for that matter, it doesnt matter to me. I can be reached at: rick@ravengear.us Rick Read this topic online here: http://forums.matronics.com/viewtopic.php?p=184871#184871 ________________________________ Message 3 _____________________________________ Time: 04:09:53 PM PST US Subject: RotaxEngines-List: Re: Baffling for cylinder cooling From: "Roger Lee" Hi Carl, I wouldn't play with the air flow. Zenair spent good money to make sure you had decent airflow under the cowling. I don't personally know of a 701 that has and special cowl for cooling for the engine. If you start to play with it you better have an extremely good working knowledge of baffling and air flow patterns under your cowling. Many people have done this only to cause worse problems. Thinking they are redirecting flow for the better and only hinder it. A CHT difference from the front to the back is normal under a cowling for the 912. You did not say what the difference was? 20-30F is quite normal depending on the installation and maybe even bigger differences in some applications. I see about 12F on my CT CHT's between front and back. I take it 155-135psi is static compression test. What is the differential pressures. This would be more informative. The static compression should be between 174-130 and no more than a 29psi difference between cyl. The differential should be between 87 to 65 psi. Make sure the engine is at operating temps or your readings will be wrong. -------- Roger Lee Tucson, Az. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=184938#184938 ------------------------------------------------------------------------------------- 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.