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If you're going to stay with the AeroInjector/AeroCarb, a fuel pump is generally a bad idea. Even a low boost setup still pushes too much fuel through the system (so I've been told), making it hard to tune and run well. The gravity feed is all you really need and want for the AeroCarbs.

Again, this is just what i've been told. If someone out there has better knowledge I'd love to hear about it!

Short fuel line runs, as few bends and 90 degree fittings as possible in those lines, and well-insulated/shielded fuel components will drastically cut down on the vapor lock issue. I've heard of a few guys deleting the gascolator, adding an in-line filter and installing fresh air blast tubes to keep the fuel system components cool since the Sonex engine compartment space is small.

Like Mike said, I'd be very leary of putting any type of pump in the system if you are going with the Aerocarb.

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Those are certainly valid points. The question I would have is what reliable carbs are available for the VW? I haven't heard of a Marvel Schebler being used on one (not sure why...maybe the VW is too low powered for it)....so maybe the carbs available for the VW aren't any more reliable than the AeroCarb. I think GP sells the Zenith carb for the VW but I've heard enough issue with it to doubt its better than an AeroCarb.

Anyone know of what other carbs are available for the VW?

I have an AeroCarb, but I'm always looking to improve on engine reliability if I can.

daleandee wrote:
the Aerocarb don't tolerate a fuel pump very well, if at all,

they are quite sensitive to fuel flow bubbles,

the slide (at least on some of the older models) can stick or jam,

they pour fuel out whenever the mixture control is open,

they cannot be fed with ram air,

are they really worth the hassle?

Some argue they don't require carb heat. That's good but may not be totally true.

They are light weight. Yes but if you have to add 2 lbs of insulation and blast hoses you've lost that advantage.

They are reliably simple. This is true but so is a Marvel Schebler.

They are low cost. That really should not be a factor when considering your safety.

Absolutely no ill intent is meant.

All very good points Dale. I've not personally run the Aerocarb, but it's good to understand the pros and cons of each setup!

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There is the Rotec TBI. http://www.rotectbi.com/index.html It looks like any other slide carburetor, but is a very different design with real metering of fuel with a regulator and spray nozzles. It looks similar to the Ellison TBIs.

Running auto fuel without a fuel pump is generally not such a good idea in any case due to the vapor problem regardless of type of carb. The clue is of course to minimize losses by minimizing bends and fittings and/or have a way for vapor to escape.

A mechanical engine pump and an electrical backup/boost is what every Rotax 912 have and there are tens of thousands of them running flawlessly on auto fuel.

SvingenB wrote:Running auto fuel without a fuel pump is generally not such a good idea in any case due to the vapor problem regardless of type of carb. The clue is of course to minimize losses by minimizing bends and fittings and/or have a way for vapor to escape.

There are challenges to using auto fuel in a gravity flow system like the Aerocarb. I seem to have solved any issues with my setup. I use gas that has no alcohol and I insulated all my fuel lines and the gascolator.

One thing to watch for is the difference between "winter" and "summer" blend gas. http://www.popularmechanics.com/cars/ne ... e-13747431

Winter blend gas is more likely to cause vapor lock in warm conditions. I once had a serious problem due to this issue. I had fueled my plane over the winter and didn't fly until a warm spring day. After the engine and cowl got hot I started having rough running that eventually reached the point that the engine would not maintain enough power to fly. Luckily I was near the airport when this happened. This incident prompted me to fully insulate all the lines in the cowl and I've not had a problem since.

After talking with a few people who have ran the Rotec on their Aerovee and other VW conversions I am planning on buying one. Everyone I have talked to about it loves it so much more than the aerocarb/injector (which has the nickname "the red menace" in the VW conversion world). A pilot I know who flys for Fedex and competes in unlimited acro has flown behind a aerovee powered Sonex doing the sportsman routine. I was talking to him about my mixture problems and he outright told me, "the aerovee is a decent motor, but the carb is junk, it is simple, too simple. Put a rotec on it and get rid of the headaches" He has no affiliation with Rotec and I value his opinion as a pilot and as a builder of numerous aircraft including unlimited acro planes. So after hearing a bunch of the same from others and then him I plan on buying one for my aerovee.

There are plenty of people in the Sonex world and other happily flying behind their AeroInjector/AeroCarbs, but the joy of experimental aviation is that you can do whatever you want! The Rotec TBI looks like an interesting unit, but I have some reservations. First, it looks like you need to add a dedicated primer control line for the thing to work. Second, you have to add that little saucer shaped fuel regulator and it must be mounted very specifically in the relation to the carb for the thing to work properly. Rotec also requires carb heat in their setups. The AeroInjector doesn't have any of these limitations. Finally, I don't see any versions that would easily mount to the AeroVee intake system. Their Jabiru unit may, but most are flange mounted systems. What does your friend have?

Have you been able to find any discussions on the web that talks about the Rotec? It is true..the AeroInjector is very simple, but once you get it dialed up right, I think it works just fine. On the other hand, if there is a truly superior product I'd be interested in hearing more about it.

Thanks!