After getting my 2009 RX-8 R3, I very soon realised the limitations of the stock radio, and while it does have an AUX, I was left wanting more, so it’s been a bit of a bumpy ride getting here, but I’ve installed a Sony XAV AX100 head unit into my rex, and after taking more detailed photos (which have a red usb cable in - ignore that hah!), here is my guide and tips/tricks to installing a head unit into your Series 2 (R3). I believe some of this can apply to the Series 1’s also, however will require an interface box (such as the Metra Axxess) to retain A/C controls, as they are integrated into the stock HU, unlike the S2 where it is a seperate control unit.
(Buckle up, this may be a bit long winded and some of the ordering may not make sense as I’ll be adding bits of info here and there (so please read it all through before attempting) but I’ll try my best and hope it helps you guys out! Also, if anyone wants to link or post this elsewhere for others to use, be that inside or outside the OC, please feel free – the more people it helps, the better
)This guide is mostly based on my installation and something similar, so if you are planning to do a different configuration, you will have to adapt the parts that don’t apply to you. I’ll try and cover most bases. I installed an aftermarket head unit but kept the audio system stock – so no changing of amplifiers or speakers, I only changed the head unit.
Items to buy or to look into:
Dash fascia replacement
This is different depending on your tastes, there are two for the S2 from Metra, and also from Connects2. The Metra kits come with an additional tray for the bottom segment if only a single DIN slot is required (unsure if Connects2 do the same). The model numbers are as follows:
Metra 99-7515 (matte black)
Metra 99-7515HG (gloss black)
Connects2 CT24MZ17 (matte black)
Connects2 CT24MZ16 (gloss black)
These above are only for the plastic fascia, no wiring included. – the S1 kits from Metra include the wiring and axxess box too, and model numbers are as follows:
Metra 95-7510 (double DIN matte black)
Metra 95-7510HG (double DIN gloss black)
Metra 99-7510 (single DIN matte black)
Metra 99-7510HG (single DIN gloss black)
There may be others, but these are the ones that I know of and the most common ones. I personally purchased the Metra 99-7515HG (gloss black) for my R3. Sold by CISCAR EXPORT on amazon, total £24.47 at time of writing.
Wiring harness
Tthe harness that I opted for was the Autoleads 53629E SOT-077 harness, as it has every pin terminated on the connector. I did not use most of them as they weren’t needed, however if they are needed in future, they are there to be used and I will not have to get another harness. There are pins missing on most harnesses out there and they’re the same price most times, so for peace of mind I went for this for the base of my custom harness (around £5-10 normally)
Head Unit
Now this one is completely personal preference. Whatever features or price range you require is what you should base this on. I wanted android auto with a volume button, pre-outs and the ability to remove the warning screen on boot, and the AX100 fit the bill. I would recommend getting a head unit with pre-outs. (mostly come in the form of RCA connectors, but some manufacturers may have wires dedicated to pre-outs in their harness? Not sure on that one.) Having pre-outs means that the signal is not amplified by the head unit, allowing for an amp in the car. All rx-8s with a BOSE amplifier will need to use pre-outs, OR a line out converter (often called an LOC) can be used to bring back down a line level (aka amplified by the head unit) output signal, however this will mean more cost and more bulk behind the HU. I believe NewDuke here on the RX8OC used an LOC, and has the InCarTec LOC, and it seems to work well. I’d advise doing a bit of research into which are best if you’re going this route.
Optionals:
Radio replacement interface (S2) - On the S2, this is an optional. These are the likes of the PAC Audio RP4-MZ11. The main features of this, is editing the time without having to plug in the stock HU, make a user customisable message during normal operation and retains steering wheel controls all in one unit. I believe it does a few other things but these are the main. It's plug and play so that may be a plus, but it isn't a cheap option but should mean no soldering or messing about like I have done below making my own harness.
Steering wheel controls – I might plan to do these in future, as I would like to get a close to OEM finish, but to use them on an aftermarket HU, an adapter is needed. The most common is the Axxess ASWC-1, and should work well. I am still to pull the trigger on this though, as i might just get used to using the volume knob.
Tessa tape – for tidying your harness when done! Only fools don’t wrap their tools
Heatshrink/Electrical tape – both can be used; however I’d strongly suggest using shrink as it is more secure.
Aerial extension - as the aerial connection is on the left of the HU, it will be short if your new head unit has the aerial in any other location. I just picked up a no-name 30cm ISO aerial extension from eBay for a pound and some change. Just a heads up if needed.
Soldering vs crimping – again I strongly suggest soldering. It is a very secure connection and is much less likely to come apart or become loose, meaning no pulling apart the dash again!
Both can be used though if you aren’t comfortable with soldering. If unsure, take a look at soldering videos on youtube like Car Audio Fabrications. There are a few good videos around that are a few clicks away and can explain much better than I ever can.Removing the stock head unit:
Step 1
Starting off at the beginning. A long time ago, in a land far far away, there once was a gear knob that was right in the damn way. This is threaded on to the gear stick, so unscrew it counter-clockwise (all that lefty loosey, righty tighty gubbins). It may be a little stiff if it is on tight and hasn’t been removed in a while or at all, so it may take some oomph to get it started, but don’t worry. (Please note: if you have an illuminated gear knob, please reverse this step with step 2, as the cable will be damaged or snapped by unscrewing the knob first. There are sooooooo many horror stories of mazda techs and owners alike damaging it in this way, so I would advise caution with this step.)
Step 2
Removing the trim around the handbrake and gear knob. There are 6 retention clips in this trim, positions shown in the photo. The way that I removed this was by having the handbrake up, gripping under the trim with my finger and carefully pulling up on it. This did take a fair bit of force the first time I did it, and the clips came with a substantial snap sound, but that wasn’t them breaking, it was just well secured hah! Another way I have heard to do this is to pull up on the shift boot material, meaning that the force is in the centre of the trim clips. Either way should work though
This is best done with the armrest and the cigarette lighter cubby open too.Step 3
Removing the two screws holding down the cigarette lighter cubby. After these are out, the assembly can be pulled out gently, as there are two cables behind, one to the cig lighter, and one to the lamp inside the compartment. Both of these have small clips on the cables to be removed and the cables detached
Step 4
There are now two more screws that are holding in the bottom of the head unit, and one 10mm bolt into the side. To access the bolt, you’ll need a 10mm socket and extension. Now this is where being a contortionist would be really useful. While getting yourself cosy and acquainted with the floor mat in the driver’s footwell, remove the trim below the steering wheel (It hinges down and is held in place by two small clips towards the pedals side) and then peer into the abyss that is inside the dash. The one bolt is located up and to the left, and needs to be removed (and hopefully not dropped inside the dash where it needed to be fished out, unlike me whoops!) After that wretched bolt is removed, onto the next step!
I pinched this of RX8club.com 
)Step 5
Now all that is holding the stock HU in will be the plastic clips, 3 at the top and two at the middle. Grab the bottom edge of the head unit and pull outwards – this should release the two middle clips which then allows you to grip the top below the hazards button and pull the top of the head unit outwards to release the final three clips. If you cannot grip the top, then pulling from the bottom again should still work, although avoid pulling upwards as this may damage the top clips. These clips are a similar story to the gear knob surround, they were very tight for me, so it may require quite a substantial amount of force.
EDIT - Whilst doing this myself, I didn't remove the vents above thew HU, however it has been brought to my attention that it may help with getting a bit more space and room to get hands in and help with the connectors. This is removed by taking out the three screws marked below on the next photo)
Step 6
Ahhh yes. This part. I’m not going to sugar coat it, this is probably where your hands and fingers cramp or end up cut (or if you’re me it is hah!). It’s connector pulling time. But hopefully this should work ok for you!
The radio harness on the rx-8 is very tight, both S1&2. Once step 5 is done and the clips are released, the HU will be free to slide out of the dash, although likely only 5-10cm. Shown below are images of the positions for the connections on both S1&S2 HUs and the position of where the harness sits when plugged in, hopefully it will make it easier to feel behind the radio and try to disconnect them. Now, here I really recommend going and finding some good padding or soft furnishing, like a thick blanket or duvet level of padding, because it is very easy to tip the HU to the side and mark the dash, I did this on mine and it’s not great (you’ll see the aftermath in the photo below). Putting a blanket between the metal of the sides of the HU and the plastic dash pillars, maybe using some clothes pegs to hold it or something to that effect - it will save your dash from scratch heaven! Please don't make the same mistake I did here!!
Step 6.1
Now now now, the first connector up on the chopping block is the A/C cable. For this one and the next two after, it is best to hold the HU as far out of the dash as possible while holding from the top with one hand, and reaching under to the rear from where the cigarette lighter was (or even getting someone to sit in the passenger seat and hold the HU out might be easier, but its do-able without
). This cable is low down in the centre, directly behind the controls for A/C. The connector is as shown below and has a small release tab in the centre to be pressed while pulling out. Should be a simple one to remove.Step 6.2
The second one to try and remove is the big one on the right hand side (as looking from the driver's seat). In my car, this big cable was held to the HU by a cable tie right where the cut black plastic is on the middle of the rear R3 HU photo - above the centre screw (shown circled above). This will have to be cut away from the HU. I used a small set of side cutters and felt for it when cutting, but doing this releases a lot more cable length to play with, and will make removing these last two much easier (this may not be tied in your car, but from my sample size of one, it may be
). After this is cut, it will allow more leverage on the big connector - the release tab is easier to feel on this big connection, and it doesn't take much force on the release, but does take force to remove out of the HU plug (or mine did hah, it got my knuckle here ](./images/smilies/eusa_wall.gif "Brick wall"){kind=small}
)Step 6.3
These next photos show first, the position of the last two connectors and cables by default when plugged in with the radio removed, and second shows where the harness can (hopefully) be manipulated to above the plastic trim. (Note: this may be possible at 6.2 with the big connector after the cable tie is cut, so it may be worth a shot there to get more room). As this trim above doesn’t go as far back as the trim where they are normally placed, it allows the HU to move further out of the dash.
This is likely the easiest way (in my opinion) as it will allow more length on the last connector that’s on the left hand side at the top (the release catch for this one is a PITA though). If the harness is above that plastic, the HU will slide out enough that it can be rotated carefully through 90 degrees clockwise, and I could just get my hand and pliers in to compress the release catch on the last connector and pull the HU out with my other hand. This is the way I did it and managed just about with my hands intact.
The aerial wire is also just next to this final connector, and in mine just stayed in line with the harness on the last connector, so was easy to just gently pull out and the HU is now free of all cables and can be removed from the dash! (WooHoo!) "Cool & The Gang - Celebration" plays in the backgroundWiring the custom harness:
Now for the harness, I used an Autoleads 53629E SOT-077 as my start point. This already has the power and audio cables routed to the correct two ISO connector layouts ready to use with most devices, but with the Bose amp in the RX-8, the speaker outputs in the main car harness are low level signals. A majority of aftermarket HUs will have their ISO harness adapters wired so that the signals to these wires are amplified, which is not a fun scenario when your new HU is amplifying the sound, and then your car amp is doing the same.
Damage will likely occur SO! This is where the recommendation for the RCA outputs on the HU come into play. (unless you are performing a bose-ectomy and removing the amp, or have chosen a head unit with a different audio output, then feel free to ignore me and follow the correct steps for your wiring needs 
)First things first is to find some sacrificial RCA connectors. This can be from any sort of cable that you don't mind chopping up, or to a small RCA to AUX adapter, anything works as long as its got a decent bit of length behind the connector. The insulation on the end of these cables will have to be stripped back. 4 RCAs will be needed.
Now, RCA connectors have different colours, with red meaning right channel and black or white meaning left channel. Inside a single RCA cable is two wires - one is a positive inner wire in the centre (which will have insulation) and the other is the outer wire braiding, which is negative (without insulation after the outer is removed). This means that using the colour coding for the ISO speaker connections, the wires will need to be connected as follows:
Purple = Right rear speaker +
Purple = Right rear speaker -
Grey = Right front speaker +
Grey = Right front speaker -
White = Left front speaker +
White = Left front speaker -
Green = Left rear speaker +
Green = Left rear speaker -
Purple = Right rear speaker -
Grey = Right front speaker +
Grey = Right front speaker -
White = Left front speaker +
White = Left front speaker -
Green = Left rear speaker +
Green = Left rear speaker -
So, The grey, green, white and purple wires all need to be cut from the harness, shown below. To solder these connections, I twisted the strands together, bent it back to form a hook and then wrapped them around each other as many times as I could back along the length their respective wire. After the wires are soldered, it makes a tight bond. Make sure to slide heatshrink on to the wires first and then slide it into place after soldered and gun it down with a heat gun
(or a hairdryer... that works too )Now after wiring the audio wires into the RCA connectors, there may be a few more wires to solder and connect depending on your head unit. If your head unit has a handbrake cable (used to identify when the handbrake is active for showing video etc) you can either extend the wire and take it to the handbrake, or you can connect it to the ground in the harness and be done with it. Doing this may need a mid cable splice along with some other connections further down in the guide, bit it means the original cable you are connecting to will not be affected by your joint, in essence meaning it stays as close to a factory connection without a cut and rejoint - this just requires removing a small amount of insulation in the centre of the cable and then twisting the joining cable around it and soldering it. If you do it this way and don't cut it, the heatshrink will either need to be sliced down the side or use electrical tape to cover it (although it can be cut if it's easier for you, it's not the end of the world, but just make sure it's a good connection after
.The 1J pin as shown on the connector pinout in the bottom left is the amp trigger wire, and so can be wired to the 12v switched wire to the HU (1R is the 12V accessory relay feed), as it will then be turned on whenever the HU is turned on - an ideal situation if you would like to listen to what's coming out of the HU
(Note: all wiring diagrams for the S2 are available - including the other ones for the audio system - here for members of the OC) Note: The connector or pinout may be different for the Series 1, so please use the appropriate wiring diagrams for your model and spec of RX-8 Orientation of the mazda harness connector in diagrams can be figured out by looking at the three large pins on the left and right, one side has two and the other has one. Positions of the desired pin you want can be found in relation to those. (or that's how I did it as I was looking at multiple different diagrams at the same time which were shown opposite ways)
Now with the harness wiring done, slide some heatshrink over all of the cut ends that are not in use so that they cannot be shorted or come into contact with anything. After this, give it a test and make sure that everything is working as intended and then after all is working well, use some tessa tape to wrap up the harness nice and neat to keep all the cables secure and together so they can't get caught or snagged inside the dash once installed
Fitting the head unit into the fascia:
Now, for fitting the HU into the fascia you have depends on the size of your HU. For the single DIN people out there, it's quite simple for you - insert the tray into the bottom section and clip the side supports into the sides of the front face until they are flush and then insert and screw in the HU to secure it. For the double DINs out there, there is some cutting and some filing involved. The horizontal centre plastic bar needs to be removed, but on both sides it needs to be cut perfectly flush, or the side supports will not slot in properly and the HU will not have enough room to slide in. See below for a front and rear shot of how it should end up.
The fascia also requires that you use the included bezel surround, as the one that may come with your radio will likely not be the right size (mine was too big) I found it easier to slide the HU into the fascia from the back, as the side supports can be bent out slightly and then the HU slides in, rather than fighting with the small tolerances on the front opening.
There will be some small white clip on pieces in the bag with the fascia kit, and these need to be placed onto the clip positions where it will be held into the dash. The A/C assembly also needs to be moved over to the new fascia, but this is just a drag and drop, nothing different here between the two.
Now follow reverse of disassembly Steps 1-5 (apart from that wretched 10mm side bolt, take a victory lap and throw that thing as far away as possible. Or keep it with your stock head unit, whichever you feel like
)So that’s it! I hope this helps or was at least an entertaining essay guide to read. As always, I’ll be happy to try and answer any questions or help as best I can! Let me know if there is anything I can edit to make it a better or easier guide to read too! If I don't reply very fast, i'll probably be busy pulling apart my dash again because looking at these photos makes me realise it all needs a damn good clean hah!
Oh, and enjoy your new head unit!
