... . Special Design and Treatment for Dedicated CNG/LPG Engines:Engine pistons,valves,valve seats,valve guides,ignition systems,high voltage cables ... ) is normally 10.5:1-12:1 for CNG and 9:1-10:1 for LPG. Also shapes of pistons are specially designed for gas ... include Isuzu 4JA1, 4JB1 and some Chinese gas engines)Engine pistons, valves, valve seats, ignition systems, high voltage cables, spark plugs ...