Socièté Sebia studied an engine that, instead of performing normal compression, it did it in stages to make it isothermal.

-It required a double compressor with cooling between them.

-There was a second version on a classic engine, with a tubular cooling system before entering the cylinder, modifying the timing or opening adjustment of the valves depending on whether the cycle was aspirated or supercharged, it was previously cooled in the aforementioned tubulars.

-This compression in two stages, normal and refrigerated, allowed - in theory - to reach higher final pressures without causing excessive fatigue.

-Although we do not have sufficient information or any illustration, it is clear that the tests did not provide data to establish the real value of the device.