suction tube with respect to the open cross section the variation of this resultant curve and thus the fuel air ratio of the mixture may be predetermined the dashed lines show the variation of the resultant which may be produced for example when the kinematic pivot point of the auxiliary valve according to fig4 is altered by virtue of a change in the composition of the exhaust gas the moment variation a a 39 can be altered by displacing the suspension point 28 as a result of which the resultant then changes to r 39 in any event the subject of the present invention ensures that at full load the charging deficiencies are kept to a minimum as in this speed range the air measuring valve is not adjusted according to the impedance principle but according to the airfoil principle which operates with substantially lower flow losses as shown in fig7 the pin 3 can be displaced axially and rotatably against bushing 36 by means of a button 50 in order to lock the adjusted position a screw 51 is provided these provisions allow fuel flow corrections and in turn accurate adjustment of the fuel air ratio in fig9 a possibility is shown as to how the mounting pin 28 of the rod 26 can be adjusted in horizontal and vertical direction pin 28 is connected by means of part 39 with a threaded rod 40 this rod is put through vertical slots 41 42 of adapter 43 fixed on the suction tube 1 a nut 44 is located between the two vertical.