injector 38 channel 39 permits flow bypassing the piston 33 non return valve 44 enables recharging of the tank 45 fig4 shows the cross section of the channel 39 which is adapted to fast valving action by the piston 33 referring to fig5 arrow 53 represents the starting pressurization of the receivers 36 and 37 the initial inward movement of the pistons which compresses 55 air between the pistons continues till the channel 39 opens when air flows around piston 33 through the channel 39 the channel 39 is open for flow when the volume between pistons is between the dotted lines 61 this flow is represented by curve 56 which inertially continues below p out the pressure of receiver 37 utilizing the kinetic energy of the flow this spill 56 of gas from the combustion chamber 49 serves to stabilize the quantity of gas compressed for combustion the momentum of the pistons continues the compression 57 fuel is injected at 58 from the injector 38 combustion further increasing the pressure the pressure due to compression and combustion stops and turn the pistons into the initial expansion 59 which continues until the channel 39 opens and blowdown scavenge 60 results the outward momentum of the piston continues 61 piston 32 uncovers the intake 34 at 63 and air is drawn in when the pressure between the pistons goes below p in 62 this intaking continues until the outward momentum of the pistons.