Notes on mixer design: a gas mixer is supposed to cause a vacuum in the lpg supply hose proportional to the air flow through it. Air flow over a hole perpendicular to the flow will create a vacuum (Bernoulli's principle I believe) Now an efficient mixer will create a vacuum signal for the lowest pressure drop across the mixer. To do that the air flow at the gas outlet must be faster than the average air speed through the mixer. A traditional venturi shape mixer is good at that, providing the gas outlet is a continuous slot right around the mixer, at the point of minimum diameter. Many venturi mixers feed gas through a series of holes and are not as efficient as the air flow across bare metal provides no vacuum.

The AMOS mixer is not bad as the nozzle jutting out into the air stream creates a local zone of higher air speed. But they are a bit asymmetric and can cause mixture imbalance when too close to the cylinders, ie not enough flow length to properly mix the gas/air. Some EFI engines are not suitable for them. They work best through carbies which help mixing.

The new gen mixer has a series of holes spaced apart so that only 1/3rd of the air flow produces a vacuum. Poor design. To fix this issue I get a thin steel ring cut out and fasten it over the ring of holes. This joins all the holes together and faces the gas outlet towards the engine. I can then raise the air plate 1-2mm and get better performance right across the range.

Now another thing about mixers. The gas flow is about 1/15th of the air flow, so there must be an immediate increase in diameter of the venturi downstream of the gas inlet. Otherwise the gas entering the air flow caused a pressure wave that effectively reduces the venturi diameter. Sometimes I can modify a poor design mixer in the lathe to improve it by creating a step at the gas outlet, usually 1 to 2mm deep.

I actually designed and patented a new type of efficient mixer years ago, but nowadays gas injection is where the action is so it doesn't matter anymore.