It's Over (A New Tack).

I have given up on building a standalone engine monitor. Several reasons, but the biggest, I can buy basically the basis for $200. Once I started looking at part prices, and all, I decided to look at what is out there. I looked at Dynon, GRT and MGL. 

MGL has a remote data acquisition computer (RDAC) for 4 cylinder engines for about $200. The RDAC XG supports both CAN and RS-232 communication. The CAN bus is the most interesting, since that is how most modern cars talk to their instruments. The device can monitor 4 CHTs, 4 EGTs, Oil Pressure, Oil Temperature, Current, Volts, Tachometer, Fuel Flow, Coolant, and two aux inputs. 

MGL doesn't have the best reputation, but I am sure it is quite reliable compared to anything I can put together, and will be considerably cheaper than the prototype. This unit seems to be the quite capable for what I want. I could still use the phone or tablet as a display. The CAN or RS-232 bus could be converted to USB, Bluetooth, or WiFi. 

There you go. Why would I build something when I could buy it for less. 

So what is my plan? 

Modules! Well, node-red or MQTT modules that can be put anywhere, airplane, tractor, scooter, etc. The RaspberryPI as the hub can allow all kinds of configurations, displays, inputs. These modules can be temperature sensors, pressure sensors, GPSs, IMUs, etc.