An improved system for total cylinder sampling from an indirect injection passenger car type diesel engine has been developed. The system utilizes explosively actuated cutters which cut aluminum diaphragms in both the main combustion chamber and precombustion chamber at a predetermined time. The cylinder charge is rapidly cooled and diluted as it flows from the chambers into the sampling system. When sampling from near top dead center, cylinder pressure decay half times of about 0.5 ms have been achieved. The system has been used to determine NOx concentrations in the cylinder as a function of crankangle position at 1000 rpm with equivalence ratios of 0.32, 0.52, and 0.60. NOx concentrations rise rapidly shortly after the onset of combustion, attain maxima which are 2 to 10% higher than corresponding exhaust concentrations at about 5-10 crankangle degrees after the end of the fuel injection process and then slowly decay to exhaust levels.