Signal generating process for use in engine control

Claim 1

A process for generating a signal for use in the control of a spark ignition internal combustion engine having at least one combustion chamber and having a conduit for conveying air to said combustion chamber, said process comprising the steps of: partially obstructing the flow of air through said conduit to said combustion chamber during the operation of said engine thereby causing the formation of vortices in the air flowing through said conduit; generating a first electrical signal which has an amplitude which varies with the rate at which said vortices are formed, said amplitude of said first electrical signal being proportional to the volumetric flow of air through said conduit; applying said first electrical signal to one input to an electronic multiplier; generating a second electrical signal having an amplitude proportional to the ratio of the pressure of air flowing through said conduit to the pressure of air at standard conditions (14.7 psia); applying said second electrical signal to another input to said electronic multiplier to produce a third electrical signal at the output of said multiplier, said third electrical signal having an amplitude proportional to the product of said first and second electrical signals; applying said third electrical signal to the input of an operational amplifier, said operational amplifier having a feedback resistance which varies as a function of the temperature of air flowing through said conduit to produce a fourth electrical signal at the output of said operational amplifier, said fourth electrical signal being proportional to the mass of air flowing through said conduit; and applying said fourth electrical signal or a signal derived therefrom to a device for controlling the amount of fuel metered to said engine.