Moisture problems in unleaded fuel?

There may be other things at work here. Many of us live in the SW US where the day time temps are 105F - 115F and we use 91 Oct. with 10% ethanol without all these issues. Yes some do, but Maybe people should look to see why they are having these issues in much cooler environments and see if there are other contributing causes. Rule some things in or out as contributing. Things like hose routing or no fire sleeve or improper fuel recirculation setup.  Somethings aren't  always cut and dry. Sometimes it's  the aircraft Mfg's fault due to installation and or poor cowl air circulation. 

First off, thanks again to Roger & Rotax wizard for their direct advice to my inquiry. I am new to the forum so forgive me if I "stumble" abit with these inquiries. But a couple other related things with regards to fuel concerns which seem to be always on my mind (oh when will God bless us with Swift 94 or G100UL in Arizona ?!). First off, the 912IS has an exposed bare metal fuel line on top of the engine just beneath the cowling, that runs across the width of the engine that feeds the cylinders on both sides. Being Arizona and all with the potential for very hot days anytime of year, the potential from heat soaking that exposed line (with potentially E10 gas) during a stop, say for lunch, is just asking for a vapor lock issue on departure at some point IMHO. I'm trying to understand why Rotax has left that particular line so exposed in such a vulnerable spot. There are such things as vapor block fuel line covers & that seems like a good bet for the application of that kind of insulation on the exposed metal line but Rotax in their wisdom has obviously thought better of it. Am I just being paranoid or is there some merit to this? What am I missing if anything? Maybe I should post this in the 912IS section?

Hi Mike

Good question.  The line is stainless steel but I don't think you have to much to worry about. The injected engines after the fuel pumps are running 3 bar (about 45psi) and the engine only consumes about ⅓ of the pumps volume.  This was intentional as the pressure is regulated at the end of the circuit and dumps all the extra fuel back to tank.  We need to do this for cooling of the fuel.  The benefit in the case of vapor lock is that under pressure it is much less likely to form bubbles in the system.  As long as you are running the correct MOGAS for the season you should be fine.  The engines that are far more at risk are the low pressure systems as we see on the carb versions. (.5 bar or about 7 psi) 

The idea of putting some insulation on the line is actually a good one.  At the  same time try to not have the full pick up and return line in hard metal. If you are a builder of an experimental and have a choice of where to place the pumps on an injected try to get the pumps as near the source of the fuel as possible.  

Cheers

Are you actually having vapor lock and low fuel pressures while flying or this issue on the ground? As Rotax Wizard said the 912iS recurculates far more fuel than the 912ULS or UL. I have a Flight Design in my hangar with a 912iS. He's flown it all over the country including Alaska twice. We in Tucson have temps close to Phoenix. He flys at all altitudes and never has any vapor lock issues. With the pressure in the fuel system and the amount of recirculated fuel you should be okay. Plus as RW said if you want to insulate those lines it won't  hurt.

Sometimes if you can increase in cowl air flow then other issues can be reduced.

Thanks again, my plane is an SLSA so I cant be messing with modifications but I keep thinking I could maybe get away with insulating that crossover line. On the other hand I just started wondering if by covering fuel line if I might be preventing necessary cooling from airflow blowing across  it from the cowling vents. Kind of a catch 22 I guess. I suppose I'm just being paranoid from reading quite a few articles concerning 912IS cavitating fuel pumps/varying degrees of vapor lock, especially at higher altitudes when running mogas & during the winter/summer blend transition time when there's always some question mark about what you're fueling with. I know I can alleviate my concern I guess by blending some avgas in the mix, at least during those transition months. This plane is new & I just hate the idea of leaded fuel. I have friends in the midwest area and they keep taunting me "no worries mate, we just run Swift 94! Lucky you I tell them......?.