---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Thu 04/04/13: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:56 AM - Re: fuel return line? (Thom Riddle) 2. 06:49 AM - Re: fuel return line? (Roger Lee) 3. 11:44 AM - Re: Fuel return line (Roger Lee) ________________________________ Message 1 _____________________________________ Time: 05:56:35 AM PST US Subject: RotaxEngines-List: Re: fuel return line? From: "Thom Riddle" The certificated engine installations, like in my Katana, have the return line for the carbureted engines. The primary purpose is to preclude vapor lock. Plumbing back into the supply line is not the same as running the return line back to the gascolator, particularly if you have an electric backup fuel pump between the tank and the "tee". In this case, you will be pressurizing both sides of the fuel system when the electric pump is running. I suppose you could put a check valve in the return line to fix that. Running back to the gascolator returns the excess fuel back to unpressurized ambient pressure location. In experimental or other non-certificated installations, if your operating environment (not high altitude, not intense heat) does not encourage vapor lock, then adding a return line is not absolutely necessary. If you do operate in these potential vapor lock conditions, running your electric fuel pump will help reduce the risk by pressurizing the supply line up to the mechanical pump. Back in the dark ages when I was a drag racer, an electric fuel pump at the tank outlet generally resolved vapor lock issues on hot sunday mornings at the drag strip. -------- Thom Riddle Buffalo, NY (9G0) Kolb Slingshot SS-021 no engine FOR SALE Diamond Katana DA20-A1 Rotax 912 F3 Don't worry about old age... it doesn't last very long. - Anonymous Read this topic online here: http://forums.matronics.com/viewtopic.php?p=397837#397837 ________________________________ Message 2 _____________________________________ Time: 06:49:31 AM PST US Subject: RotaxEngines-List: Re: fuel return line? From: "Roger Lee" Hi Guys, Do not return the fuel re-circulation line back into the fuel feed line. If you are using a new Rotax fuel pump then you will absolutely need the re-circulation line and even if you don't have that pump now your old pump can go at anytime and then you'll be using the new pump. It is easy enough to install the re-circulation line. It helps control vapor lock and over pressure. By the way the new Rotax max fuel pressure is no longer 5.8, but 6.2 psi. If you have a Dynon EMS or some other EMS with fuel pressure limits then it is a good idea to reset the red line fuel pressure to a higher value. -------- 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=397844#397844 ________________________________ Message 3 _____________________________________ Time: 11:44:08 AM PST US Subject: RotaxEngines-List: Re: Fuel return line From: "Roger Lee" 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 ------------------------------------------------------------------------------------- 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.