FlyingMonkey

I didn’t want to turn this into a Mogas v. Avgas argument. I don’t have anything against Mogas and ran it with ethanol trouble-free in hot Georgia Summers for a decade. But something has changed and I need to change with the situation. Fred I don’t think the new lines are poorer at insulating the fuel from heat. What I suspect is that the stainless steel braiding absorbs and retains heat, and potentially transfers it to the fuel and leads to higher chances of vapor formation. It’s maybe a distinction without a practical difference, but I just want to be clear about what I think is occurring.

I have tested my gas in the past and it was around 5% ethanol, I have not tested recently. I don't really want to run a fuel mixture because you then get all the hassles of avgas AND all the hassles of mogas, and save hardly any money on fuel. I'm only saving about 50 cents a gallon between 100LL and mogas as it is.

I imagine if I had a restriction, blockage, or wrong size orifice I would have the issue with both mogas and 100LL, right?

Running 93 octane ethanol pump mogas I have been struggling with vapor issues in my CTSW for a while now, but I wanted to work through them as far as I could without asking for help. I ran this same fuel for ten years with no issues, and it came up after I changed my fuel system to include teflon-lined hoses. The symptom has been pretty consistent: intermittent power loss when the engine is hot and the deck angle is high. This means I most often saw it on takeoff and climb out, sometimes at very low altitudes (not fun!). The RPM would drop from WOT RPM (5200-5500 with the eProp) down to about 4000rpm, often surging up and down in 2-5sec pulses. Reducing throttle and deck angle usually allows me to fly at 4000-5000rpm and land. After this first happened I re-routed a fuel line to remove a potential vapor trap and the issue went away and was gone all Summer when it was hot so I assumed it was solved. Then I went to Tampa last fall to visit Bill Ince, and we were two up departing St. Petersburg and the issue happened again out over the water, two quick pulses and then it smoothed back out but we were both a little puckered up! The problem did not recur and we continued on the 15-20 miles back to Clearwater. Before I went back to Georgia I topped off with 100LL and had no issues going back home. After I got back home I went back to mogas and had no issues all winter, so I thought maybe a difference in Florida fuel blends vs Georgia could have been the cause, or just some bad gas in Florida. Carbs were rebuilt in March, and I flew until mid-April with no issues. The last few weeks it got warmer, but only in the 70s or so. Quite suddenly I started getting the vapor issue on every flight. I tried insulating all the AN connections on my fuel lines in case they were getting hot, but no joy. Finally I switched to 100% 100LL fuel and the problem ceased immediately and has been gone for several flights. I'm fine with running avgas if necessary, but I'm still a little confused over what exactly happened or changed. I checked my gascolator screen and did a fuel flow test draining out the tanks completely and there were no issues. My ideas are: 1) The new fuel lines are teflon, stainless braided, and with integral silicone firesleeve. It's possible the new lines retain more heat than rubber hoses and lead to increased chance of vaporization of ethanol. 2) Fuel blends have changed. I read that the EPA is working on changing the max ethanol in standard fuel from 10% to 15%...I'm wondering if suppliers have begun a stealth creep up of ethanol content or other additives. 3) I changed out my fuel pump when I did the hose change...perhaps my new pump is weaker than the old one? The old one was well past replacement age and was an older revision pump, but I never had this issue until after it got changed out. Maybe the new one is just a factory dud. 4) I had to make a new heat shield for my gascolator during the fuel system changes, but it's pretty much the same thickness aluminum material and the exact same shape as the old one if not slightly larger, plus it's more reflective so should bounce more heat. I guess I could beef that up or add additional insulation. Here's what it looks like: I'm certainly open to other ideas, recommendations, or wild speculation. I know Corey recommends a boost pump installation, and I'd do that if 100LL ends up not totally curing the issue, but so far so good. I miss the cheaper fuel, but it is more convenient to just pull up to the pump.

You might be able to, but it's far easier to at least swing the engine away from the firewall. During a rubber change you should be changing the engine mount isolators anyway, which requires disconnecting the ring mount from the firewall mount.

I use this one, you can get forecasts by airport identifier, I find them to be accurate about 90% of the time. https://www.usairnet.com/cgi-bin/launch/code.cgi

I had to do a double-take on that airplane, outwardly it looks *exactly* like mine (N509CT)...same livery, prop & spinner, wheel pants (small)...everything! Though I only have a single Dynon in my cockpit.

I typically just fill the left wing tank, and let them balance out as it sits on the ground. I only crack open the right tank if I'm taking a long flight and want to start out with both tanks topped off. My right wingtip is an inch or so lower then the left so the fuel tends to flow toward the right tank on the ground.

Sure don't get me wrong, I like the Jabiru, I was planning to put one on the Sonex I was building. They just have had a fussy history with some teething pains.

My friend determined it was run out at 1000hrs, not just in need of a top. This was an early 3300, I'm sure the newer ones are better.

That's a fact. I'm guessing China's quality is coming up while the West's quality is declining. At some point it will all meet in the middle. I have a buddy who just bought a new latest-rev Jabiru 3300, his previous one was very reliable and he was a sticker on maintenance, but it still only lasted 1000hrs. That's not much time on a $20k engine.

Really? Wow! Turbos add a lot of heat and stress to an engine. I guess the good news is they have a 500hr warranty.

If it's just an engineering copy of dimensions and specs, I don't think there is any legal liability. I think the problem arises where there are patents. The Rotax engine is pretty conventional, I don't know how many patents are involved. Even if the engine is not as good as a Rotax, I think it will find a home among E-AB builders and some value-priced factory aircraft. Since it's ASTM compliant it can be used in S-LSA. If enough of them get used it will provide competition and downward price pressure on Rotax, which can only benefit us. I hope they succeed. I wouldn't use one for an engine swap right now, but in 5 years if they have a good track record and a lot of flight hours on them... Who knows? Remember Rotax was once looked down on by all the Ly/Con owners as "snowmobile engines" ( I still hear that!)...and now 80% of new aircraft engines sold are Rotax.

Why is that?

Drop in 912 ULS clone from China with a lower price and better warranty than Rotax. According to the Website it's about ~$15k.