Maaaaaate!
You should understand that this Forum is international.
Your statement “Most auto fuel has ethanol in it” is just wrong.
Here in Australia the only “autofuel” that has ethanol in it is E10 (10%). We have 91, 95 & 98 RON, with no ethanol.
Rotax 9’s 80 hp will run on 91 RON, 100 & 115 hp on 95 RON but prefer 98 RON.
Also your statemnt “The vapor pressure of ethanol fuel causes vapor lock.” is incorrect. Ethanol blended petrol, in certain climatic conditions and most importantly fuel reticulation systems, may have issues with vapour lock / fuel vaporization (FV). ie its extraneous factors which cause FV in fuel.
Rotax engined will run quite happily on E10, subject to the fuel storage & delivery system being ethanol tolerant.
Users of E10, need to design their fuel reticulation system & adjust their management of this fuel, to minimise the potential for FV, water build up and due to lower energy , redused power & possibly duration.. 
I do understand this forum is international. That is why I mentioned that here in CANADA, all auto fuel contains ethanol. I’m not sure about the US as it probably varies by state. Gasoline blended with ethanol has a higher vapor pressure leading to vapor lock. Everywhere. Here in Canada it is illegal to fly with fuel containing ethanol.
No offense Chrisqb -
“Most auto fuel has ethanol in it”. This is your stand alone statement. The next sentence, dose not limit it to Canada. In fact it emphasis your first statement by using the word “all”
Ethanol blended into petrol, does not cause / lead to vapour lock.
It may be more prone to FV, than straight petrol, but it does not CAUSE it.
As stated, there has to be another additional factor(s) to cause the FV.
I have no idea why Canada has made it illegal to use in aircraft - it’s used in other countries.
I don’t use E10, simply because reduces my engines performance/false economy and would require me to be even more vigilant than I already am, about the potential for water in fuel.
At a pinch (no other suitable fuel available) I would not hesitate to use it .
I had multiple occasions of fuel vapor in the lines. Fuel lines run as per plans. Tried cooling changes with almost effect. Insulated fuel lines in the engine/exhaust areas. Ended up eliminating the gascolator and running direct to the engine through an inline filter. Problem solved. Talked to factory and was told none of the factory aircraft use gascolators.
Thank you for your thought provoking comments.
You don’t say what engine. Mine is a Rotax 912ULS.
I have never had FV in the Sonex but did on several occasion, in my last 912ULS powered aircraft.
What I do get is weird fuel pressure fluctuations. I have put this down to a complex fuel delivery system (3 fuel tanks, two selector valves , transfer and boost pumps.) causing reduced flow/pressure, which may increase the chances of FV.
My fuel filtration is , like yours , through a gascolator.
Your solution (removing the gascolator) has got me thinking.
You are correct, I failed to supply some important information.
AeroVee engine from Sonex, Aeroinjector from Sonex.
Without a fuel bowl to buffer fluctuations in fuel flow and vapors in the feed lines the Aeroinjector seems sensitive to fuel vapors caused by hot fuel lines feeding it. After a few attempts of shielding the lines from heat with unacceptable results I ran straight from the tank thru the firewall then an inline filter to the Aeroinjector. The fuel flow issue seems to be resolved. Now I am dealing with a burned up stator situation and broken secondary ignition module replacement (probably caused from the stator melt down heat). Now testing the new B&C voltage regulator installation.
Does your fuel supply system have a fuel return to tank ?
No it does not. If you are not familiar with the Aeroinjector, it’s basically a metered orfice into the air induction.
A fuel return system is a recognised system that may assist in the prevention of FV.
Basically it does two things;
- Draws of any existing vapour before it reaches the carburettor float chamber or in your case the Aeroinjector. The vapour and hot fuel returns to the tank where it is cooled by the greater mass of the tank content (vapour returns to liquid state).
- Maintains a continuouse flow of cooler fuel from the tank, thus reducing the chance of the inline fuel becoming heated to the point of vapourising.
I have no knowledge of your engine or its fuel system, so do not know if fitting a fuel return would be possible or beneficial.
UL Power engines do have a return to tank fuel line from fuel pressure regulator on the engine. My plan at the moment is to add fire sleeve insulation to fuel pumps, fuel filters and all fuel lines forward of the fire wall, and add Aux temperature sensors on the fuel pump and pre-pump filter. May also wrap the muffler with insulating sleeve.
Steve, curious how you insulated your gascolator. I am pretty sure I am getting vaporization (hotter than hades here in Texas, makes me too nervous to fly it at the moment) and while I have some new insulation for the fuel lines going on at conditional this month, I’m at a loss for a neat and serviceable way to insulate the gascolator. Curious as to your solution.
As a general rule, the return line should be as close to the delivery end (carburettor(s) /injector(s)) of the fuel supply as practical. The reason is quite simple;
Any fuel hose/line, after the return, that is exposed to engine heat, will have the potential to develop FV.
Not a question to me however I have attempted this;
My gascolator is very close to the bottom of the firewall. I used light weight aluminium to shield, rather than wrap the gascolator. My hope is that being low down, the convection heating is minimal and the aluminium shield is reducing radiant heat.
All my engine bay fuel lines are insulated with firesleeve. Those that are particularly vulnerable to heating have an additional wrap of air-conditioning reflective foil.
My exhaust pipes have shielding, where they pass close to vulnerable componenets.
My muffler is completely shielded, with opening for cooling air flow on each end.
I have progressively enlarged my exit air vent, to reduce under cowl temperatures. Progress monitored by temperature sensors. I am now happy with a pretty constant in flight +10C above ambient.
I run the gascolator with my revmaster 2300 VW and have had no FV issues. Insulate all fuel lines and gascolator
The performance auto shops sell the hose wrap and also larger pieces that can bet cut and wrapped around the gascolator using tie wraps. Cut a small slit so you can still sump fuel prior to flying. The material is fiberglass on the inside and foil on the outside. My friend built a small box around his gascolator using some foam and wrap. Whatever works for you and your space
I did even ‘worse’ on my gascolator, with a removable box for servicing, and a 1 in dia blast tube fron the center portion of engine baffle as source of cooler air. also double wrapped exhaust fron heads to nearly outside, fuel line heat shields, as well as oil line heat shields. no burps, FV problems, overheated oil (also 2x size oil cooler on bottom), oil filter, and a 25% larger exit, and taller seaplane lip on bottom of cowling. so far no problems! also, same cooling 1" tube for both coils, and regulator mounted on big heat sink.