I know stock NAV isn't a very common feature, but still hopefully this helps anyone interested. I have no idea if anyone sells AV Switchers for RX-8 anymore, but even if they do, they only accept RCA or S-Video input at best, which is pretty crappy.

I'm attaching a picture of a switching system of my own design that takes 3 inputs: 2 VGA inputs plus the stock navigation input. In the past, I've seen an in-depth thread on here devoted to figuring out the OEM nav screen's sync/refresh rate and that was a huge barrier. I wasted a lot of money on some pretty robust video scaler equipment, which didn't work. I forget how I eventually figured this out, but at some point I came to realize that the stock nav screen simply uses CGA format, which is the old school low resolution format that cabinet arcade games use. As such, there are plenty of VGA to CGA converters out there, so people can retrofit a computer and bypass the guts of a broken arcade game, and transparently end up with exactly the same look and feel of the original.

So I have three inputs I want to show up on the screen: One VGA input for my CarPC (you can use raspberry pi, android auto, tablet etc.). A second VGA input for reverse backup camera. The third input is again, the stock navigation.

To accomplish, I bought 2 VGA to CGA converters.

Then, I needed a way to switch between the inputs, which is easy and cheap to do with 12V 4-pole double throw relays. These toggle between two settings when when energized with 12V DC. I bought 2 of these.

Then it was time to wire this up. I hooked up the carPC's CGA converted signal to the default input of the relay #1, and then the OEM nav output to the other input. I hooked up the 12V power to the accessory line, and then the ground to a push button toggle switch. This switch allows for switching between the carPC and stock NAV on the screen.

Next, we need the second relay, to allow the reverse camera to come on regardless of whether the OEM nav or the CarPC is on the screen.

The output of relay#1 goes into the default input of relay #2. The output of relay #2 goes straight out to the screen. The second input is connected to my reverse camera. Relay #2 is grounded directly without a switch. The 12V DC power comes from the taillight's reverse light. So anytime the reverse gear is engaged, the relay closes and the camera input shows up.

What else was needed? Reverse cameras tend to come only in RCA. So I bought a cheap little RCA to VGA converter. Then the VGA converted signal goes to the CGA converter. The RCA to VGA converter and the VGA to CGA converters all run on 5V DC. So I bought a 12V to 5V step down converter, and spliced that into the accessory line too, and powered these little devices with the 5V output.

That's it!

Parts breakdown was:

2 VGA - CGA converters - $23 each
2 12V 4P DPDT relays - $12 for both
1 RCA - VGA converter - $18
1 12V-5V step down converter- $10
1 latching push button - $8

Total: $94

I have 18 gauge wire and heatshrink but otherwise you'll need to spend another 15 bucks there or so.
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If anyone is interested, here's the CarPC setup I have -- 10 years old now!!

​​​​​​​https://www.rx8club.com/series-i-int...ck-nav-188843/

This was built using an off the shelf AV switcher. I unfortunately wrecked this 8 a few years ago and finally got around to pulling everything out of it. I am doing a hardware refresh and it's becoming increasingly difficult to find computers with RCA output, so I devised the solution above. I've also since added a capacitive touchscreen overlay instead of the resistive one. Any questions, just holler!