in fig1 , an internal combustion engine is denoted in its entirety by reference numeral 10 . it is used to drive a motor vehicle , which is not shown , and includes an engine block 12 having a plurality of combustion chambers , of which only one in the present case is denoted by reference numeral 14 . combustion air enters combustion chamber 14 through , among other things , a charge motion channel 16 in which a charge motion flap 18 is situated as an actuator . charge motion channel 16 and charge motion flap 18 are used to produce the greatest possible turbulence (“ charge motion ”) and thus convert the injected fuel into mechanical energy in as optimal a manner as possible . this favorably influences the fuel consumption and emissions characteristics of internal combustion engine 10 . to this end , it is possible to change the position of charge motion flap 18 based on a corresponding control signal u_lbk . this is provided by a control and regulating device 20 . for the control and regulation of internal combustion engine 10 , control and regulating device 20 receives numerous input signals , as well as from an hfm sensor 22 , which detects the air mass flowing to combustion chamber 14 , from which a corresponding air charge rl is determined in control and regulating device 20 . control and regulating device 20 also receives signals from pressure sensors , of which only one is provided with a reference numeral 24 in fig1 , specifically the one which detects the pressure in combustion chamber 14 . the curve of the pressure in combustion chamber 14 and variables derived from it are used as input signals for various control and regulating functions . additional output signals of control and regulating device 20 are , for example , activation signals for fuel metering and control of the ignition of the air - fuel mixture located in combustion chamber 14 . for the correct operation of internal combustion engine 10 , it is important to know if charge motion flap 18 functions properly , i . e ., its actual position corresponds with a setpoint position . if this is not the case , allowable limiting values for exhaust gas emissions are exceeded and control and regulating device 20 determines non - optimal control signals ( for example , ignition points ). for monitoring of the correct function of charge motion flap 18 , a procedure is followed , which is stored as a computer program in a memory of control and regulating device 20 . this method will now be explained with reference to fig2 and 3 . in 26 , it is queried whether a combustion cycle starts within a working cycle . if the answer is yes , a pressure p i is detected in 28 . the corresponding signal is provided by pressure sensor 24 . pressure p i is detected repetitively in discrete time steps i = 1 to m by incrementing a time step index i in 29 . the corresponding values p i are stored for the individual time steps i ( or crank angle kw of a crankshaft of internal combustion engine 10 which is not shown in fig1 ) in 30 . in 32 it is queried whether the combustion cycle has ended . if the answer is yes , an actual value bd_actual of a variable characterizing the combustion in combustion chamber 14 is determined in 34 from stored pressure values p i . physically , this variable represents a combustion duration , which is determined in turn from the heating characteristic . this is a thermodynamic parameter which describes the chronological sequence of the combustion . the use of the heating characteristic in the present method has the advantage that it is comparatively simple to calculate because wall heat losses are not taken into consideration . the following relation applies : where dqh is the quantity of heat supplied , du is the increase of the internal energy of the gas , and p * dv is the delivered mechanical work . through integration across the crank angle , the percentage share of energy conversion qh across the crank angle is determined from variable dqh in 34 . fig3 shows a typical curve of such an integral across crank angle kw . a value in ° kw between two percentage values of energy conversion qh is understood to be combustion duration bd_actual . in the present case , as actual combustion duration bd_actual , the crank angle is understood to be between an energy conversion qh of 10 % and an energy conversion qh of 90 %. a simple possibility for calculating the heating characteristic necessary for determining combustion duration bd_actual from pressure values p i stored in 30 is to use the following polytropic state equation : δ ⁢ ⁢ q i = n n - 1 * p i * ( v i + 1 - v i - 1 ) + 1 n - 1 * v i * ( p i + 1 - p i - 1 ) ( 2 ) where i is the running index of cylinder pressure p i used in 28 and also stored in 30 from the start to the end of the calculation interval ; n is the polytrope exponent . it should be pointed out here that the calculation interval does not necessarily have to include the entire combustion cycle . in order to save computing capacity , it is also possible to limit the calculation to the relevant portion of the combustion cycle in which the energy is liberated from the fuel . δqi is the energy conversion at time step i . energy conversion qh over crank angle kw is now determined by summation or integration corresponding to the following formula : qh m = ∑ i = 1 m ⁢ δ ⁢ ⁢ q i ( 3 ) after integration across the complete combustion cycle , i . e ., the determination of the 100 % value , crank angle kw is determined for 10 % or 90 % of the 100 % value of energy conversion qh . the difference between these two crank angles kw produces combustion duration bd_actual . in 36 , the setpoint value for the variable characterizing the combustion is determined , i . e ., a setpoint combustion duration bd_setpoint . this setpoint value bd_setpoint is based on control variable u_lbk used to actuate charge motion flap 18 . this control variable u_lbk is thus a setpoint operating position of the variable characterizing charge motion flap 18 . furthermore , a rotational speed nmot of the crankshaft of internal combustion engine 10 , an air charge rl ( based on the signal of hfm sensor 22 ) and a set rate agr of an exhaust gas recirculation are also taken into consideration for the determination of setpoint value bd_setpoint . corresponding characteristic maps and characteristic functions are used for this purpose in 38 . additional operating parameters of internal combustion engine 10 may also be used for the most exact determination possible of setpoint value bd_setpoint . for example , the data of these characteristic maps and characteristic functions have been determined in advance on a test bench for the particular internal combustion engine type for various positions of charge motion flap 18 and at the operating points of internal combustion engine 10 to be expected for monitoring . in 40 , the difference between setpoint value bd_setpoint and actual value bd_actual is formed and it is checked if this difference is greater than a limiting value g 1 . if this is not the case , it is checked in 42 if the same difference is smaller than a second limiting value g 2 . if the answer in 40 or 42 is yes , an action is performed in 44 . this action may be that information concerning a deviation of the present charge motion in combustion chamber 14 from a desired charge motion is stored in control and regulating device 20 so that it can be retrieved in a later servicing of internal combustion engine 10 . however , the exceeding of one of the two limiting values g 1 and g 2 may also be displayed immediately . in order to avoid incorrect indications , it is provided that the display in 44 or the storage of a deviation only occurs if one of limiting values g 1 and g 2 was exceeded during a plurality of successive working cycles or combustion cycles of internal combustion engine 10 . the procedure ends in 46 . physically , the method shown in fig2 is based on the fact that if charge motion flap 18 does not assume a desired position , the charge motion or turbulence in combustion chamber 14 is not as desired . accordingly , the heating characteristic also deviates from a desired heating characteristic , which is determined by comparing desired combustion duration bd_setpoint with actual combustion duration bd_actual . such a deviation is therefore an indication and if necessary also a measure of a deviation of the actual position of charge motion flap 18 from a desired position . however , actual value bd_actual and setpoint value bd_setpoint may also be used in 48 for regulating charge motion flap 18 . this means that the deviation between setpoint value bd_setpoint and actual value bd_actual is regulated . in an exemplary embodiment which is not shown , charge motion flap 18 is actuated in such a way that no change of the torque of internal combustion engine 10 or similar changes in the behavior of internal combustion engine 10 are noticeable to its user . if , however , the expected change of actual value bd_actual occurs , charge motion flap 18 is functional . this version of the method has the advantage that specific influencing variables that also influence the combustion duration and accordingly actual value bd_actual are decoupled from the function test of charge motion flap 18 .