Electronic fuel injection is a big step forward in engine control. However, early implementations often left something to be desired.this is [Rob] And his Porsche 944 relied on an outdated mechanical airflow meter (AFM). He decided to replace it with a modern air flow (MAF) sensor. I have documented the process online.
AFMs are often the target of replacement for older cars. They are usually based on flaps that move potentiometer wipers across carbon traces that wear out over the years. Instead, the MAF sensor measures the amount of air flowing over the hot wire. The amount of current required to maintain the temperature of the wire indicates the amount of air flowing through the sensor. It’s used in many cars today, so it’s less restrictive and readily available.
To run MAF instead of AFM, we need a circuit that emulates the AFM’s output. [Rob] An STM32 Cortex-M0 was used to read the MAF and output the relevant voltages through PWM and low-pass filters to the Porsche’s engine computer. To understand how to map the output of MAF to match AFM, [Rob] made a rig Blow air through both devices in series and measure the output with an oscilloscope. This data is Program the STM32 Output emulated AFM voltages appropriate for a given MAF signal.
A great work from [Rob] His Porsche is running happily with new parts. I’ve seen similar hacks done to other cars before, just like! Video after break.
