To provide a method of processing intake air pressure signals for accurately
detecting
the engine load including the accelerating state and the intake air flow rate from
the intake air pressure.
Intake air pressure signals detected with an intake air pressure sensor 15
are processed with a low-pass filter. The low-pass filter is set to cut off
frequencies that are not higher than the frequency corresponding to the wavelength
that is four times the length of a pressure guide pipe 23 leading to the
pressure sensor 15 and to cut off frequencies that are not lower than the
driving frequency of the intake valve, which eliminates electric noises and air
column vibration occurring in the pressure guide pipe 23 and makes it possible
to obtain smooth and real changes in the intake air pressure commensurate with
the strokes.
