Hello together,
I spent some time thinking over the “classic” twin-flap-automixer (see here: Vacuum Automixer project) and Tone’s automixer. Let me write down the pros and cons of both, which came to my mind.
Tone’s automixer:
Pros: Less parts, gas-air-relation “programmable”, insensitive to vaccuum fluctuations in the gas-pipe, good mixture from start, good gas-air-mixing due to venturi-effect, blocks off gas and air pipe when engine is stopped (valve seated in the venturi restriction)
Cons: probably higher flow resistance at WOT, prone to gum up with poor filtrated woodgas, no pressure compensation in the air-pipe (dirty air filter).
Classic twin flap automixer:
Pros: Lower flow resistance at WOT, compensates pressure variations of both air and gas pipe
Cons: More moving parts, needs some turbulence after the flaps for good mixing of gas and air, fixed 50/50 mixture.
I thought about "fine-tuning"of the mixture. This may be sometimes needed due to fluctuations in gas quality.
My idea, if don’t want to move too far away from 50/50 with the classic automixer: With a tiny three-way-valve you could lower the vacuum on one side of the membrane for a leaner or the other side to get a richer mixture. (Sketch from Max: Vacuum Automixer project - #145 by gasman)
For Tone’s mixer, it could be possible to adjust the basic mixture on the rich side and then blend some air in the woodgas pipe before the mixer to make it leaner.
Advantage: With the automixer you get a quite good mixture to start with and then you can do some fine-tuning with the air valve while running to find the sweet spot.