Back in Oct. 2013, I joined a racing team for 24 Hours of LeMons and other junker leagues. The team had an ‘86 Honda Prelude 1.8L with an engine that blew 3 laps into practice at their first race. I decided that the first project I should take on would be a digital dashboard to replace the simple displays on the factory dash and try to prevent another disaster.

Research

I was lucky to find Honda service manuals online for the car, as well as a used Haynes manual on Amazon. These books, combined with info from preludepower.com and other forums, gave me a good view into the electrical systems of the car.

I discovered the ECU was a simple analog state-machine, and had been practically disconnected from the engine by my team. The ECU mostly controlled the carbs, choke, and spark advance for emissions control, which is not needed in a race car. Deprecating the onboard electronics gave me full access to the sensors on the engine. Some more research and measurements of parts gave me the specs of all the factory sensors.

The Data

While I was learning about the operation of the engine, I started sketching out requirements for the data I would like to collect. I wound up with the following list.

• Tach
• Speed
• Water Temp
• Fuel Level
• Volts
• Oil pressure
• Brake fluid low
• Accelerometer
• GPS

The Work

I also started sketching out the functionality I needed.

• Data Collection
• Logging
• Dash display w/values, gauges, and alerts
• Lap counter
• Lap/split timing
• Wireless link to pit
• Multi-stage shift light

The Hardware

I needed a hardware target to aim at while I sketched, so I tentatively chose an AVR for data collection and a Raspberry Pi for the heavy lifting. I’m familiar with both and had the hardware on hand so it was an easy choice. I grabbed a cheap 7” LCD off Amazon to use as my dash display, along with a standalone tachometer in case our computer crashes.