Abstract: The current application is directed to mechanical devices that mix gasses, including an end section of a split cycle engine crossover passage. The end section forms, using high-pressure air from the crossover passage and fuel from the injector, a swirling, entwined mixture on multiple axes with distributed rotational frequencies that results in a superior air/fuel mixture. Additionally, by appropriately dividing the air and geometrically entwining the mixture from each of the parallel stages, the end section provides for geometric dilution of the air/fuel mixture.