Originally Posted by BarbyCar
I'd like to hear more about how you dropped this 6P3T into your project.
Thanks for asking. Here are a couple of pics. The person I bought it from claimed it was a surplus switch from a MIG jet. I don't know, but it certainly is sturdy - it has an action like a rifle bolt. It is all metal and ceramic, and, as you can see from the pics, it is pretty large. I put it in an enclosure and tucked it behind the hood release.
The way I have it working is to switch all the injector and spark outputs to the engine simultaneously from one ECU to another. It is a three position, six pole switch. Each pole is used for one of the injector or spark wires. The two injector banks have two wires each, and each coil has one wire, coming from the engine. So, you need six poles. The way I wired it, the first position is the Mazda ECU, the second is null (no output), and the third is the Megasquirt. The ECUs share all other sensor inputs. I don't have a ****, because I was afraid of kicking it and switching while driving.
It has been very useful. For example you can take the back off and tie in an oscilloscope to the contacts to compare the performance of the MS to the factory ECU while the engine is running. Also, if the MS floods the engine for example, I just switch over to the factory ECU to clear the flood.
I imagine for the track, a similar setup could be used to have a back up ECU, or switch between ECUs running different code.