Burp tubes

[XenosPilot]

Thanks. Mine began yesterday on climb out at about 1500 AGL. Once it begins, it just gets worse, unless I pick up the speed quite a bit, then it seems to help maintain, but not eliminate. The other day, they got worse on final, then almost unmanageable on taxi.

[fastj22]

Thanks. Mine began yesterday on climb out at about 1500 AGL. Once it begins, it just gets worse, unless I pick up the speed quite a bit, then it seems to help maintain, but not eliminate. The other day, they got worse on final, then almost unmanageable on taxi.

Couple of questions...

MoGAS w/ethanol? Burps seem to be the worst with this.
Did you heat soak the engine/cowl prior to the burps? (after landing, leaving the cowl buttoned up while sitting in the sun?)

Three of us Sonex flew up to KBJC last summer for an airshow. The planes heat soaked all day in 100 degree sun. I was the only one who opened up my cowl to vent the hot air out during the day. All three of us experienced the burps on takeoff, mine stopped burping by the end of the runway, one continued burping for a few miles, one aborted departure returned to the airport due to burps. The one who aborted had MoGAS and no burp tube.

[XenosPilot]

Fuel is 100LL. My first experience was a few weeks ago after flying to a nearby airport to fuel up. I parked facing away from the wind, then talked to a guy on the ramp for 40 mins or so. I noticed my cowl was VERY hot to the touch when I got ready to leave. About 1 minute into my taxi, it started surging really bad, then dying. I thought I got water in my fuel, since I had just fueled up. Eventually, I got to the hold short line, got out, and drained fuel from the gascolator (tank valve shut off). I was surprised how hot the fuel was when it started burning my finger! That was the first time I considered that it might be a heat issue in the fuel line.

Lately however, the outside temp has been higher and it is happening in the air. This is concerning to me, because I am led to believe that it is hot air coming from the engine that is causing the fuel temp to increase and vaporize. If I insulate the fuel line, it may eventually warm up to the same temp, it will just take longer to get there. Once it is there, it will be hard to cool off again. This is not necessarily true, since flowing fuel will cool off the line too.

[fastj22]

Your first experience is classic heat soak/burp issues.

But if you are burping after flowing fuel through the line, I suspect if you insulate and perhaps put a blast tube on the gascolator (or remove it) the inflight burps will go away. But the heat soak ones will still haunt you. What size fuel line are you using? AN6? I think the bigger the line, the less vaporization you will have.

I changed out to a Rotec TBI with a pressure regulator built in last fall. I removed my burp tube during the install as we were going into the fall flying weather. Never had a burp yet. But its getting hot here too. If I start burping, I already have a plan to put in an electric pump to pressurize the fuel line and create a return circuit to the tank. But I'm waiting to add the complexity.

[vwglenn]

I had burp issues. Removed the gacolator, installed a deflector plate behind the oil cooler, inline AN fuel filter, and insulated the lines with reflective sheilding. So far I haven't had any issues. Outside temp has been hot enough to shutdown my iPad but no burps...yet.

[LarryEWaiex121]

On my Waiex, with plans built fuel system (meaning gascolator plus Dynon fuel cube, AN6 line, firesleeve) and Aero-Injector, I had burps until I modified with a burp tube and some reflective tape on the fuel lines. My line is capped off instead of tied into the vent system.
I've never burped on the ground but have in extreme heat in the air and especially at high altitudes.
Normally, if I get some occasional burps, I simply enrichen the mixture a touch and that will stop them.
All this was with the Jab3300. Now, I've switched to the Camit and have just begun flight tests/break in on the Camit.
I didn't change a thing on the Aero-Injector and already, I'm getting better fuel distribution on the Camit. I believe the plenum on the Camit has been modified somewhat? I'm seeing no lean condition on the rear 5 and 6 cylinders that I used to see on the Jabiru on the first flight of the day. After the engine was thoroughly warmed through and through it was less a factor.
My method for compensation was to simply pull about a half inch off the throttle and the rear egts would fall right in line.
I sure love taxiing with lights and radios working and no drop out do low voltage like the AC generator of the Jabiru. The alternator on this thing bumps the battery back up to full voltage in about 2-3 minutes of 1000rpm running.
I hope as time goes by I find even more things I like about this Camit engine.

Larry
Waiex121YX, Camit 3300, Skyview

[Fastcapy]

Like John, after switching to the Rotec I have not had a single issue of the burps without changing a thing.

I do however still have an issue with the heatsoak causing my idle mixture to go rich when I am taxiing back after landing which makes for some rough running.

I am still trying to sort that out and I do wish that I could control the mixture at idle rpms from the cockpit on the Rotec like you can do with the Aerocarb but at least I am not getting the burps like I was with the Aerocarb.

[XenosPilot]

I took a closer look at my setup yesterday, and saw some glaring needs. None of this had occurred to me before, since I wasn't having problems with it (throughout the winter). Attached is a picture that shows my current arrangement. The 90 degree elbow that ties to the throttle body is less than 2 inches from the exposed portion of the exhaust pipe. Tonight I plan on shielding the fuel line from firewall to throttle body, and the exhaust pipe as well if I can come up with some material (temporary).

Has anyone with the 'burps' determined the primary source of heat influx to the fuel? I am thinking about buying some thermocouples and strapping them to various spots on the fuel lines (gascolator, aluminum line, connection at throttle body, throttle body itself) and monitoring the temps to see if there is a glaring issue in any one place. Not only would that be educational, but it also tells me where to spend more effort and money to resolve the issue. I'm willing to, but highly resistant to simply changing parts or adding items without knowing why. I am thinking that in my case, the elbow next to the exposed exhaust pipe is probably where the fuel is vaporizing.

[kmwoody]

Start with the simple things first. I started with a cut to fit reflective 700 degree interior insulation, that I had left over from my 68 Mustang restoration, covering the gascolator and the flow meter, wire tied. Firesleve covering all fuel lines and elbows, aluminum tape insulation wrapped around the inlet side of the aerocarb and exhaust wrap, at least where the exhaust is close to the fuel line.
Ok maybe not real simple but I would do these before fabricating items.
JMHO

Ken W
Ex-Aerovee owner
Sonex 959 374 hrs
Camit 3300 44 hrs

[Sonex1517]

If anyone has installed a burp tube on an AeroInjector, and has e part numbers they used for the AN6 tee fitting I would appreciate knowing what the part numbers are. Thanks.


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