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Hi all,

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You could use any carb you want with the VW motor. There isn't anything special about them. The trick would be finding adaptors to make the carb an updraft. You may also run into a problem with getting enough space between the intake tube and the cowel to fit alot of carbs. Finally, you will also have to put in some sort of carb heat since you now have a carb with venturi's that are prone to icing. In short, it can be done but is the complexity of doing it going to give you less risk than trying to eliminate the burps on the aerocarb?

Keith
#554

Call me skeptical but fuel injection from Simple Digital Systems is starting to look real good.An engine that hesitates when I need it most is not my idea of safe flying.
This just goes to show how many people were having this issue but chose to keep quiet about it until someone actually brought it up in the forum,then everyone who has the issue is adding their 2 cents as to how they have dealt with it.For some it just seems to be an ongoing issue that they solve by playing with the mixture at the appropriate time.Good grief. :?

Seems to me the proper solution would be to add a bowl/expansion chamber just in front of the aerocarb. This would be a fitting attached to the fuel input of the aerocarb that would be cylindrical and say 2 inches in diameter holding a couple ounces of fuel, with the low point at the carb, the high point at the input to the chamber. Fuel would gravity feed into the chamber and fill the chamber normally.
Any bubbles or vaporization up stream would be absorbed by the bowl giving the carb constant liquid fuel, vapor would gather at the top of the chamber and escape back up the fuel line or through a vent from the top of the chamber. Attaching the chamber directly to the aerocarb would minimize any further vaporization/bubbles in the short distance through the carb. This would provide the same benefit of having a float/carb like the Bing but wouldn't rely on a float to meter fuel into a bowl or a fuel pump to pressurize the line. Just my thoughts, and take it with what its worth.

Mike53 wrote:Call me skeptical but fuel injection from Simple Digital Systems is starting to look real good.An engine that hesitates when I need it most is not my idea of safe flying.
This just goes to show how many people were having this issue but chose to keep quiet about it until someone actually brought it up in the forum,then everyone who has the issue is adding their 2 cents as to how they have dealt with it.For some it just seems to be an ongoing issue that they solve by playing with the mixture at the appropriate time.Good grief. :?

A lot of people write it off as a non-issue, "ok it burps from time to time but has never affected anyone's safety".

Well even if that is true, here you are having just completed a beautiful airplane and you want to take your pilot buddies up to show it off, the last thing you want to show them is an engine burping and hesitating as you climb out, trying to convince them it's not a problem, that's just what it does...

fastj22 wrote:Seems to me the proper solution would be to add a bowl/expansion chamber just in front of the aerocarb.

Several guys are doing that very thing. They are calling it a "burp tube", but its essentially a chamber in front of the carb that allows bubbles to escape before entering the carb.

My impression of the burp tube was just a relief vent right before the carb. Not much chance of trapping vapor especially at higher fuel rates. My idea is an expansion chamber to allow the gases to gather at the top while liquid keeps feeding the carb. Without the expansion, the gasses could still get sucked into the carb and create a burp. Basically serves the same purpose as a bowl on a conventional carburator. Heck one could put some sort of float/bowl in stream and use a fuel pump to pressurize the intake just like a VW Bug. As the bowl drains, the float opens the valve and pressurized fuel squirts into the bowl until the float closes the valve. The carb still gets gravity fed from the bowl. No chance of vapors entering the carb. Just liquid fuel.

fastj22 wrote:My impression of the burp tube was just a relief vent right before the carb.

At least one guy started with a vent tube and then capped it to make a chamber. He said it worked.

I wonder if the issue will get better or worse with the aerocarb mounted on the turbo.
will the pressurized air into the carb actually improve or worsen a burpy aerocarb setup?

I doubt the turbo would make the situation better, maybe worse. The turbo configuration I saw was the aeroinjector was before the turbo. Even if it was after, the leaning caused by the vapors would still exist. In a turbo, temps would be elevated, possibly creating more vapors. What is needed is pressurization of the fuel, but that is unacceptable in the aerocarb. It would simply push more fuel into the carb instead of metering it. Pressurizing the fuel would lower the vapor temp and keep the fuel liquid at higher temps. But it would require a bowl with a float valve to meter the fuel.