What’s Old Is New

Recently, I’ve been working on an engine swap in my mom’s 1980 Volkswagen Scirocco. Originally, it came with a ~75 horsepower, 1.6 liter 4 cylinder engine. Despite its lack of power, the car was known for its light weight and great handling. To bring it up to today’s standards, we decided to throw in a modern 2.5 liter 5 cylinder engine making roughly 170 to 200 horsepower. Naturally, when replacing the entire engine, some things might not work as originally intended. One such piece is the tachometer. Originally driven by a noisy high negative voltage signal from the ignition coil, I decided that it was too much work to adapt the signal from the modern engine computer to the gauge. With the power of parts available at M5, I was able to get the tachometer to function with nothing but an Arduino Uno, a voltage regulator, and some MOSFETs! Currently, I have it functioning so I can read signals from the CAN bus to the Arduino, which is then able to decode them and drive the tachometer, fuel gauge, and coolant temperature gauge. Ultimately, I’d like to integrate this into a PCB that’s plug and play with the original tachometer for a factory fit and finish. I’d also like to integrate outputs for warning lights and things like that. Being able to preserve the main informational display from the car instead of replacing it with a screen is one of the largest parts of making this swap feel authentic, and I’m proud to have done it at M5!