Nakamura, H., Ohinouye, T., Hori, K., Kiyota, Y. et al., "Development of a New Combustion System (MCA-JET) in Gasoline Engine," SAE Technical Paper 780007, 1978, doi:10.4271/780007.
A new combustion system - called MCA-JET- has been developed to improve combustion under the low speed, low load conditions typical of urban driving. Engines with this new system incorporate a special “jet valve”, in addition to the inlet and exhaust valves of the conventional combustion chamber, which directs air or a super-lean mixture towards the spark plug, and induces a strong swirling flow in the cylinder. This swirl persists during the compression and expansion processes, moves the mixture spirally and helps the flame to propagate. As a result, the combustion of lean mixtures, including those with exhaust gas recirculation, can be carried out rapidly and thus the fuel economy improved.