Turns out Size Matters.... Head Unit Size ...

Old 12-04-2018, 07:26 PM
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Turns out Size Matters.... Head Unit Size ...

Started Research for a 2 DIN Head Unit. Will share details on the buy after Christmas. But, along the way I found some gaps. Head unit size is not mentioned, just references to cutting the Metra Kit.. This is for the head units that are supposed to be Double DIN, not the oversize ones.

So, Data on how Size Matters, At least related to the size of the hole in dash kits.

According to, US Double DIN is 173.5mm x 101.6 mm. European (and I think rest of the planet) Double DIN is 180 mm x 100.3 mm. In the US, we use inches, so it is about 7 inchs x 4 inches, or 178mm x 102 mm (this is important later). So, 2 standards. Also, this refers to the hole the radio goes in, not the panel in the dash. The standard is based on a panel mount, shove it in from the front. That does not apply here. The radio mounts in the "panel", or hole, and the front of the radio goes through an opening in the pretty part. The opening in the pretty part is the common issue. Our pretty part hole does not match up with the majority of the head units out there. The Metra unit you get from Amazon has the precise US size hole, 173 mm wide. The vast majority of the head units I found on Amazon (several hundred looked at) take the easy way out and go with a 7" x 4" hole, or 178mm wide. The 178mm is why people have to cut the Metra Kit most of the time. The smart manufacturers seem to make the radio face match the 173mm spec, then add a bezel for the head unit to get to either 178 mm or 180 mm. Some even say "works with Metra or Scosche kits". The more thought out ones have 2 or 3 different size bezels. Most of the non smart manufacturers build for the non-US world and do NOT list size. They say "check the dash for fit". When you dig into it, or look closely at the chassis measurements, they are all around the 178mm (7") size with a bezel to get to 180 or larger. You have to cut things for this to work. I guess they figure you will cut things over sending the radio back for not reading the fine print.

I did find some 178 mm and 180 mm kits for for RX8, on ebay, but they were only the face plate. And, they were in Europe or Asia with **** poor reviews and extra shipping. So, the idea here is to think about radio face size before you buy a radio. I can share that the KURATU and ATOTO radios all declare 173mm, others were in the Metra and Scoche compatible category, but I could not find them again for this post.

More Data.. Depth seems is important too..

The depth of the radio, how far it sticks out from the box towards the dash, is another potential issue. I will know more about that after Christmas. I expect I will want to bring the radio forward a bit. But, this is a mod to the depth of the kit, and a cut that will not be seen (unless I really screw up) as opposed to shaving things down and trying to butt up against the radio face, where a 1 mm difference will show.

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Old 12-04-2018, 08:13 PM
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Old 12-05-2018, 10:41 AM
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No idea, the goal here is to provide data on fitting inside the hole. Now, with one like that, you can do whatever you want to the faceplace. But, you may block AC ducts, hazards and AC controls.

And, there are good threads on the units, I was just trying to share why stuff does not fit in time for Christmas. Although, you bring up a good point. It might be nice to have a list of 173mm head units someplace. If traffic shows up, I can do it here. I listed the two that made the cut. There are more out there, but many had 1 and 2 start reviews.
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Old 01-06-2019, 07:45 PM
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The end state..

Journey is complete. And, size did matter!

The Car – 2004 RX8, Jessica (RIP Brandy) with BOSE system.

The Goal – All of this (Hands Free, Blue Tooth, Backup Camera, Front Camera, Android Integration, Torque App, ODBII, Pandora, EQ to match old ears and a platform to build on).

In Here

(And, yeah, I cleaned everything before I put it back together)

I bought everything through Amazon. The 173 vs 177 vs 180 mm discussion is in the initial post. There were only a few 173 mm listed head units (KURATU and ATOTO). I chose KURATU. I can save a few bucks with ATOTO, but with all the other costs, a few dollars more here seemed prudent based on the reviews. A great help with Firebirdude’s post on why BOSE is a PITA to deal with. If I had to do it again (someone brought a lot of beer buy on a slow weekend) I would pretty much do it this way again.


1. Put a big towel on the roof of the car

2. Thread off sift ****, keep close

3. Lift out the panel with shift boot, 2 clips at rear first, then clips in front, disconnect cables if heated seats, reach outside and lay panel gently on the roof

4. There are 2 screws, going down, for the ash tray, pull them, lift slightly, pull out ash tray a bit, disconnect wires, set screws in the cup holder and lay ash tray gently on the roof

5. Screw the **** **** back on, just a bit. That removes a sharp edge that will try to scratch most of what you are going to install, put it in 4th gear

6. There are now 4 screws visible, the two inner ones are next. Leave the outer ones alone. Put screws in the cup holder. The entire panel is now held in by clips and cables.

7. Pull forward on the bottom, near AC controls to pop out clips. Do the same at the top. Radio will slide out.

8. Disconnect all the cables being very careful with the AC control ones, you need those parts. They are a PITA, a small screwdriver can make life easier pushing down the clip. This is all best done from the right seat with the radio shifted over to the left side. This will give you more room. The radio antenna wire is the shortest one, it is on the left side, pulling it first will give you more room to work on the rest of it all.

9. Pull the radio the rest of the way out, set it on the bench.

10. Remove the 2 screws holding the center AC vent in and gently pull it out. Set it on the roof and put the screws (different ones in my case) in the cup holder.

11. Beer 1 has been earned.


Follow whatever directions exist for the installation kit. I used Metra. Whatever the kit says DO NOT install the little white plastic clips yet. These are for locking the kit in, you will be doing multiple fit checks and each one is a chance to break something.

1. Regarding wiring, I did all of mine on the bench, before the project started, with solder and heat shrink, following the kit directions. I have an Amazon assortment of heat shrink bits that this barely made a dent in. An option is crimp connections, make sure you have little ones. The kind that will then heat shrink around the wire are great. I also left the screen protector on the display.

2. For BOSE, you need an extra part (again, thanks Firebirdude), a Line Out Converter. This is because BOSE is not positive – negative but is a differential signal. I never found the one he referenced so I bought the PAC one. It needs to be installed per the directions on the SPEAKER side, this one attenuates too much for use on the line outputs. Mine is in the trunk, spliced in right before the amp. This leaves the levels high until right before they are used, makes any noise less of an issue and means less surgery on the head unit wiring harness. You could set it up for in the dash but it is kind of tight with the metra box and the new radio in there . It might go under the ashtray with lengthened wires. Looking at the wiring diagrams the connections go like this:

a. Front Left – Pos is Red with Blue stripe, Neg is Light Green with Red stripe

b. Front Right – Pos is Blue with White stripe, Neg is Yellow with Green stripe

c. Rear Left – Pos is Green with Orange stripe, Neg is Blue with Orange stripe

d. Rear Right – Pos is Grey with Red stripe, Neg is Brown with Red stripe.

You should find these grouped together in pairs in the harness near the amp. If you are going for under the dash, just put it in line with the speaker wires from the adapter kit.

3. For non BOSE, just wire up the speakers.

4. I used the power antenna turn on line to run the front camera, rear camera runs off back up light. Both are attached with spade connectors. I attached the back up light to the lens of the license plate light. The one I picked routes the signal from the back up light forward to the sensor line on the radio.

5. The ODBII / CAN bus mods require you to get under the dash to get to the connector. The panel under the steering wheel pulls out from the bottom IIRC, and then the steel panel can be removed. This give you a bit more access. I think all this does it let Metra display outside temp, smarter people will have to share what else is provided.

6. Finish all harness mods as well as the AC control mods.

7. The rear mount slips in a hole in the back of the dash. You need this with the metra kit since the side plates are plastic. Probably need it for steel side plates as well. The pick up is in the middle for the 8. I had to attach it with a small piece of double back tape on the bottom and a mounting screw through the hole and threaded in between the fins of the heat sink. My buddy came up with the idea. Side to side can be off a tad, but and down is important. I used trim tape, but very thin foam tape should work.

8. I forgot to take a picture of the holes used to attach the side plates, but I can share that the front of the plate left a 2mm or so silver gap between the black of the face plate and the black of the side plate. I also got 3 screws in each side.

9. I removed the lighter and installed the USB panel mount kit there. Worked way better than expected.

10. Beer 2 has been earned.

(EDIT, not all METRA fault)
Installation: Warning, the connectors on my METRA kit were the biggest source of problems for the entire project, the ones on the ACCESS box, especially the ones for the AC, require a significant amount of force to seat. More than I wanted to provide the first time around. The other end of the extension cable is very easy to install. I suggest tie wrapping that one to keep it from coming loose.

1. Run all the external device wires through the back of the dash and bring them out the front (external GPS antenna, Wifi antenna, Front camera, Rear camera, USB ports, anything else).

2. Attach all the wires to the Metra box, make sure the flasher wire goes up high and the ac control ones go low. I ran the high power USB and a regular one down to the lighter, left the short one hanging and ran the 4th to the glove box.

3. Hook up all the radio related stuff, verify as much as you can. Specifically, that you remembered to hook up the radio antenna, all the speakers work, all the speakers are in the right spot (left front is left front, …). This is the time to fix any issues. Backup camera and front camera should work as well.

4. Take a piece of string or paracord and wrap it under all the wires, except the Metra AC control wires, and run both ends over the top of the head unit. You will use this to gently pull them up into the recess in the back of the dash when you slide the radio in (you can see recess in the "In There" photo). Make sure the flasher cable is on top.

5. Work the radio in the hole, use tension on the string over the top to lift the wires, the pin should seat in the back and it should slide all the way in. Put the 2 screws in.

6. Test fit the face place without the white clips installed to make sure it goes in and the head unit comes through the hole. This is where you find out exactly where the head unit needs to be. I had to apply a touch of force, the fit was snug.

7. Attach the wires for the AC controls. Tune on the key, test the radio function, the hazard lights and all the AC controls. I kept seeing issues where recirculation did not work if the defroster was on. But I think this is normal. All my connection issues were with the connector on the right side. I threaded a tie wrap through the connectors to hold them together.

8. If everything fits, pull the face plate out, take the radio screws out and install the vent. Then put the radio back in with the tabs sandwiched between the vent tabs and the dash, put it in the same location and screw it back in. Make sure the face plate still matches up. Install the white clips and test everything one more time. If all is good, re-install the face place, attach the screws at the bottom, and test one more time.

9. I attached the rear camera to the lens for the license plate light. The one I used took power from the backup light as well as used the backup light to trigger the head unit to switch. I am still working on the location for the front camera. As of this writing, it may be the same camera used in the back, mounted inside, around the rear-view mirror. All my front locations are too low to be of much use.

10. Beer 3 has been earned.

It looks like this:

The rest is just pairing phones, adjusting levels, installing apps (TORQUE is on the list). I also had a bit of trouble with time zone. It seems there are 2 places to set it. I forgot which one worked. The GPS is impressive with the external antenna. I ran it up on the dash, on the driver side, behind my ultra gauge. I think it grabs almost a dozen satellites and tracks movement across the parking lot.

Sources – Internet, this Forum, a great post by Firebirdude ( , (in part to make it reproducible, in part because I am hesitant to integrate from multiple sources in multiple countries)

Amazon list:

Head Unit

Install Kit


Rear Camera

Front Camera


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Supraquick (01-10-2019)
Old 01-06-2019, 11:14 PM
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did not even know this was a project! looks great.

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04Green (01-07-2019)
Old 01-13-2019, 01:33 PM
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OK, spoke to soon. I have a slight, constant volume, hiss. It starts as soon as the amp is powered on. It was not there before, at least not that I remember.

My LOC is grounded, both signal and system.

Things that did not make a difference
  1. Muting the amplifier from the head unit.
  2. Power or not power to LOC does not matter.
  3. Disconnecting all the lines to the BOSE amp does not make a difference.
  4. Grounding all the lines (both sides) going into the BOSE amp does not make a difference.
  5. Adjusting the levels on the LOC does not make a difference.
LOC is back by the amp, feeding off speaker outputs from the Head Unit.
I have the METRA kit. There was not an audio pot on the AXXES box. There were several really crappy connectors though.

Deep thinking.
  1. If the sound is the same with our without the inputs connected, or the inputs all grounded, the noise is NOT coming from the input side.
  2. I can think of no reason that the noise would creep in on the speaker side of the amp. If it did, it would be there before the amp powers on.
  3. The only other connection that was disturbed was the Amp On signal. Is there any way that noise could be going down that line and pissing off the amp?
Any thoughts, anyone?

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Old 04-21-2019, 07:58 PM
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Do you happen to know if this particular headunit supports the changing of the logo on bootup? (obviously since this is an RX-8 I would change it to Mazda.) I know some android head units support this feature, I think its under the developer/advanced options if so. Looks like the install went well for the most part! Looking at picking up one and doing a similar install myself.

Steering controls work as well?

Debating on how much display lag there would be with torque paired to an OBDLink MX adapter. Curious about the handsfree navigation with google assistant and phonecalls as well.

Last edited by 1300CC; 04-22-2019 at 03:51 PM.
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