---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Sat 04/06/13: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:37 AM - Re: Re: Fuel return line (Sacha) 2. 03:19 PM - Re: Fuel return line (Roger Lee) 3. 04:29 PM - Rotax Fly Dat (Alan Carter) ________________________________ Message 1 _____________________________________ Time: 11:37:42 AM PST US From: "Sacha" Subject: RE: RotaxEngines-List: Re: Fuel return line Hi Roger I can see why hot fuel would exacerbate vapor lock problems and this conversation has convinced me to firesleeve my fuel lines. But why does a return line improve the situation. And I would have thought higher fuel pressure would lower the incidence of vapor lock (as it increases the temp at which fuel vaporizes). Can you shed more light on why higher fuel pressure is bad? Regards, Sacha -----Original Message----- From: owner-rotaxengines-list-server@matronics.com [mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Roger Lee Sent: Thursday, 04 April, 2013 19:43 Subject: RotaxEngines-List: Re: Fuel return line --> Hi John, Here's the issues. Many of the planes from yesteryear wasn't a problem. They were open air engines so hot fuel lines weren't an issue and the old style fuel pump didn't have enough excess pressure to be an issue. Come up to date with many of the newer LSA and Experimental aircraft with nice tight cowls and then throw in on top of that too many owners fail to install the fuel and oil lines in fire sleeve then heat inside the cowl makes a night a day difference. Vapor lock. I see it alot now days with tight cowls. Fire sleeve not only protects from fire, but helps with excessive heat too. Now comes along the new Rotax fuel pump that puts out more pressure and then add on top of that someone who likes to run an electric pump all the time which adds .5 -1.0 psi more and the fuel then can't be controlled by the float needle valve and it pukes out the vents all over a hot engine, on hot exhaust manifolds because some didn't bother to install carb drip trays and now we have an issue. Now add that owners haven't rebuilt or replaced an older float needle valve and now we definitely puke fuel and the engine runs rough. Just a side note* Exposed fuel lines outside of fire sleeve tend to deteriorate faster than fire sleeved fuel lines. So the bottom line is application is everything and sooner or later your old pump will die and the new pump is all that is available. It's so easy to add the re-circulation line and never have to look back. On any flight the float needle valve can start leaking then you have the issue too. -------- Roger Lee Tucson, Az. Light Sport Repairman - Maintenance Rated Rotax Repair Center - Heavy Maint. Rated Home 520-574-1080 TRY HOME FIRST Cell 520-349-7056 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397863#397863 ________________________________ Message 2 _____________________________________ Time: 03:19:28 PM PST US Subject: RotaxEngines-List: Re: Fuel return line From: "Roger Lee" Hi Sacha, Higher fuel pressure may lead to flooding of the carbs because we tend to use low pressure to start with. Using a recirculation line keeps cooler fuel moving through the system to help prevent the vapor lock. It keeps cooler fuel within the lines while flying. If your sitting still on the ground with the engine off and it was just shut down then the fuel just sits there and cooks. A re-circulation line moves cooler fuel back up to the carbs much faster after a restart. The re-circulation line also helps keep vapors out of the fuel pump just because the system moves more fuel and it is coming from a cooler point within the system. -------- Roger Lee Tucson, Az. Light Sport Repairman - Maintenance Rated Rotax Repair Center - Heavy Maint. Rated Home 520-574-1080 TRY HOME FIRST Cell 520-349-7056 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397980#397980 ________________________________ Message 3 _____________________________________ Time: 04:29:17 PM PST US Subject: RotaxEngines-List: Rotax Fly Dat From: "Alan Carter" Hello All I have a Rotax FlyDat on my 914, I notice it has a small battery located on the back side. Master switch on, Flydat cycles, shows temp,and hours, turn the key ,Starting the engine and display recycles nothing showing till after its completed its cycle, then come in with all the temps and pressures. But during the vital starting stage I have nothing showing.???? Alan Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397987#397987 ------------------------------------------------------------------------------------- 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.