I realize this probably should be one of the last things on my list, as I'm still troubleshooting a turbo issue, but nonetheless, it's been on my mind for quite awhile. As I was doing the Android Auto retrofit on the Mazda 3 a few months back, an idea popped into my head.

Would it be possible to retrofit the Mazda infotainment system from a 2015-2019 era 3/6/Miata into the RX-7? Theoretically the armrest/ashtray could fit the dial/control ****, and the screen itself could mount right in front of the center speaker without obstructing too much visibility. However, obviously wiring would be the biggest issue. This came to mind because I thought of installing a 1,000$+ wireless android auto headunit in the car, but anytime I'd be using it in 5th gear, the shifter would be in the way I feel, which led me to think of retrofitting the Mazda Infotainment system.

Now obviously there are going to be some issues, as it won't connect to the non existent CANbus, so many features won't be available, but in terms of the core abilities to use the radio/android auto, etc, that has me thinking. Theoretically I would just need to harvest the connections and components, and run the wires independently and tap into the respective power sources in the car. What I'm not sure of is, would tapping into the regular speaker wires on the car to the infotainment work, i.e. will it see that signal as an output, or is it looking specifically for a can signal for the audio? Could do the same with the reverse camera.

Anyway, just putting some thoughts into text, if anyone has any ideas on whether this is actually do-able, I'd like to discuss.

 

Possible…yes…speakers are analog devices so they need an analog signal. The head unit might go to a separate processing unit/amp.
As for as CAN, nothing magical here either except it’s digital. Of course as you mentioned our cars aren’t CAN based, but that doesn’t mean it couldn’t work…however the CAN signal is probably processing back at the car specific ECU …you’d have to decode the signals and build a device to process the signals. Could it work without the CAN interface…not sure. What’s your current ability with circuits and wiring skills??
I’d love to modernize the FD…almost 30 years of car technology has past…but this would require lots of time, energy, and money. But at the same time I also love the simpler bits too and want to enjoy the car for what it is…a great Japanese car from the 90s.

In the end, unless you plan on spending a lot of time experimenting, just go with a good ol DIN head unit and fix your turbo issues.

 

Also, keep in mind a 2015 infotainment system was likely designed in 2010, so it's really outdated vs what's available today.

 

If android auto is what you want there's plenty of aftermarket head units to choose from. I'd just get one of those and be done with it.

 

Maybe the best way to research would be to track down a written off model at a Pick-a-Part and try to pull the speakers, unit and loom or ask a dealer if you can have a copy of the wiring or infotainment diagrams of a 3/6/MX5 or which ever model could be available for salvage?

Most of the components are integrated, usually with some form of anti-theft which can be tied to the ECU. It may turn out that you need the whole body loom and modules that won't fit behind the dash along side the existing wiring.

Or, if you can find an MX5, Maybe the Dash could be retro fitted? Not sure on the dimensions though, I think the MX5 is a fair bit wider.

I thought on this one as well, but already dropping cash into parts during my build, I decided to go with an Eonon Android Double DIN and be done with it for around $200. Android Auto, Apple Car Play, GPS, Bluetooth, Hands Free and WiFi out the box. Tidy up the factory body speaker loom, and done.

But I have to admit, it still pales in comparison to the Bose system in my 2019 Mazda6.

 

I have a wireless Apple Carplay Mazda infotainment system in my 2021 Miata grand touring. It uses the vehicle speed signal to control access to the touch screen (moving car --> touch screen lockout, must use the BMW iDrive style rotary thing). it needs an SD card for the built in navigation to work, and of course there's all the wiring specific to all the speakers. It's mounted on top of the dash and sort of sticks out; a lot of newer infotainment systems are like that (like from say an Accord)

I think you'd just be better off with an aftermarket unit. Just bite the bullet and pay up, this stuff is expensive right now due to the chip shortage.