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Initially I had purchased a new BING Type 94 carburettor. Shortly after I also got two used BING Type 64 carburettors.
Type 94 has a 40 mm throat; Type 64 has a 32 mm throat.
Using two 32mm carbs provides a 20% increase in carburettor throat surface over a single 40mm carb, which theoretically could lead to a better volumetric efficiency.
But does it? NOT at the RPM's we operate our aero engines on.
For street modding or track racing

BING Type 94 - 40 mm carburettor

- where you'd be going for double the RPM or even higher - it would work, but not in our neck of the aviation woods. So out went the double 32mm carbs, the single 40mm carb is for keeps.
Incidentely: quite a few IBIS'es are equipped with double barrel Weber DCOE-40 carbs. These are very good carbs indeed, especially so if you'd want to race your VW on a track. On an aircraft, during take off, a VW engine sees no more than around 3400-3600 RPM and only so for a few minutes. A naturally aspirated engine can pump only so much air at that RPM and only needs so much fuel metered in. You'll never be able to use twin 32mm carbs or a double barrel 40mm carb to the max at those low RPM's.


Then again, I haven't completely given up on electronic fuel injection either.
One significant advantage would be a much more even fuel metering across all cylinders which would ensure a much more even thermo-dynamic balance across the board. Another siginificant advantage is that iced carbs are a thing of the past. Lastly, fuel economy would be slightly improved, which should count for something as well.

I'd have to pay for these advantages, though: increased costs and complexity and I'd have to install a starter on my engine.

Conclusion: for now I stick with my single BING Type-94 altitude compensating carburettor, as used on Limbach, Sauer and Jabiru aero engines.
Should someone come up with a tried and tested fuel injection system I might listen up and adapt my engine at some point in time. Most certainly I will not be doing the engineering and testing for that.

Also check out: VW-derived Aero Engine >> Pistons & Cylinders