[Guide] RX8 Seats conversion

[LawrenceSelly]

Overview
This guide will show you the basic method of installing RX8 Seats into a mk1.

The same method can be used for installing MK2 seats, and that's an important detail, I had Mk2 seats fitted already, however, the process is exactly the same. You could also use this guide for fitting mk7 Celica seats, S2000 seats, and Mk3 seats.

What you'll need to buy

• A pair of RX8 Seats... duh!
• Some MK1 seat rails, or MK1 seats you are planning on throwing away.
• A pair of RX8 Heated Seat Switches (and connectors with some pig tails)
• A pair of 30A fuse equipped relays (and a 20A fuse)
• Some 2.5mm automotive cable (3m of red, 1m of black)
• Some type of connector system with crimp terminals
• Some 6.3mm spade terminals (female) or use the ones in the connector kit. Or some relay flying sockets
• At least 8 pairs of m6 nuts and bolts, only 10mm long.
• Can of black paint, try to get the stuff that bonds to bare metal. (or get a can of zinc primer too)

What tools you'll need

• A welder of some kind, I used a stick welder and some 6013 rods.
• A grinder, with cutting discs, a metal grinding disc, and a flappy disc.
• A drill, and some metal drills. (6mm drill mainly)
• Measuring / Marking equipment
• Wire strippers
• Crimping tool for the terminals you're using
• Various Screwdrivers
• Allen keys / Spanners / Sockets
• Electrical tape, and heat shrink
• A sharpie / Marker pen

How To - Part 1: Passenger Side
Compare Seats
Let's start with a quick comparison, Mk2 seats vs RX8 seats:




The biggest factor is the distance between the rails, so double check that yours are close, just encase Mazda made different sizes of seats... for some reason.

MK2 Seat


RX8 Seat


You can see that the rail centers are within 10mm, this is excellent! It will fit... but we already knew that, otherwise I wouldn't have made a guide.

Remove Airbag
RX8 Seats came with a small explosive attached to the side of them. I don't know about you, but I'm not very comfortable with live unprotected armaments inches away from my face, so I've decided to remove them. You could argue that other cars have them, and they are fine; but when they are plugged into an SRS system, they have voltage sinks to stop them going off on their own.

Firstly, a warning.

AIRBAGS EXPLODE WHEN ANY VOLTAGE IS APPLIED TO THEM

There are countless stories of this happening to people so take all due care and attention

Also: if you follow this guide you will have a pair of airbags that you'll need to dispose of. Obviously I would recommend you take these to a suitable local disposal site that can deal with them.

Using a flat head screwdriver, or a trim removal tool, pry open the SRS tab


Using a 10mm socket, on an extension, undo the nut inside the hole behind the SRS tab. Remove the nut buy holding it in the end of the socket, or using a magnet.

Then pull the top of the airbag cover, there are two lock tabs holding it in place.




Once it opens as far as the picture above, you can insert a small flat head screwdriver into black lock tab on the top of the yellow connector. Flick the black bit off, and pull the yellow connector out.

Then pull the airbag up, and it will come out of the hole.

Now the airbag is out, we want to pry the metal cover off the top of it, as it's necessary to hold the panel in place properly.



To do this:

1. Undo the 3 10mm nuts
2. Using a prying tool, pull plastic/rubber type material over the top of the metal tabs on the 3 sides.
3. Using a screwdriver / pliers, lever the lock tabs out against the metal body.
4. Lift the metal plate off the top of the airbag
5. Gently remove the airbag out of the rubber case, and place it somewhere safe.
6. bend the metal lock tabs back using a pair of pliers on the one side.
7. Insert the metal plate back in the rubber assembly.
8. Pull the rubber tabs back over all the metal tabs around the other 3 edges.

Okay, now you can put the cover back in the seat, do the 10mm bolt up, and put the SRS tab back in place. Do the same thing on the other seat, and that's the scary part complete.

Make sure you place the airbags far away from where you're going to be doing the next steps. We're getting the grinder and welder out, and a wayward spark might cause some brown trousers and a hearing aid appointment.

Removing Feet from mk1 rails
The mk1 rails have 4 feet, each is held in place with a large rivet, and a small bead of weld.
To remove them you need to drill / grind the rivet off, and cut along the weld seam. Make sure you don't damage the foot in any way.

This is a picture from my archive of the MK1 rails before I did my mk2 conversion. You can see how they are attached.



Make sure you label the location of each 'foot' FR - Front Right, RL - Rear left, etc..
Also, do one seat at a time, leave the other one complete until you attempt it.

They should look something like this after a bit of a clean up




Put those to one side, as next we need to:

Removing Feet from RX8 rails
Now these are great if you were frustrated about not being able to hack off the MK1 feet.

The RX8 seat feet are held on with two large rivets, and they are thick boiz.



the best way to remove them is to take an angle grinder to the sides of the feet, and remove the tops. Then using a cutting disc, come in on the side of the rivets and lop the tops off.

Then switch to a grinding disc and take the rest of the rivet off so it's flush with the metal.
And finally you can hit them with a large hammer, which should knock them off. If they don't, you need to grind the rivets down more.

Whilst you're removing the feet, lop off the large pegs on the bottom too. At the very least lop off the really long one on the passenger side.

Lastly, knock the rivets out the other side and throw it


Seat belt connector
Before charging in to the feet installation, there's one final thing on the seat's that isn't required. The seat belt connector, and it's wiring.

Follow the wiring around the 4 pin connector on the bottom, and unplug it


Unpick the cable ties, and push the wiring out towards the seat belt (or cut it!) and then undo the 17mm bolt holding the seat belt connector on.


Then throw it that straight


Installing the feet onto the rails
This is the luckiest part of the entire installation, the front rivet holes are exactly in the correct location. For now don't get the welder out, just use 2 m6 nuts and bolts (I used some stainless countersink heads to aid assembly as they are nice and low profile)

Bolt the front feet on, make sure you've got the orientation the right way around.





Even luckier the rear outermost large rivet hole (4th hole down) is the perfect location too, so get that one bolted on.



Annoyingly this means to install the bolt for the seat, you're going to need a spanner, as the rail now covers the bolt hole. Lucky you if you have a set of ratchet spanners!

The rear inner is the only one that needs a new hole drilling, as it's not quite in the right place.

The measurement I've taken, is 4th hole down, 5mm towards the outside edge, 10mm down.


You can see the scratched hole mark.

This means the pointy part of the foot will foul the metal bracket holding the plastic seat connectors, so you will need to nip the end off to make it flush.



thus:



You can see I've already flapped off the paint ready to throw a bead of weld onto each foot.

Test Fit

The trick to getting these in the car, is headrest first, over the center, and then rails in and down, tilting it upright. Don't try and put the rails in first or they won't clear the door edge.

OR take your targa tops off...

When they are in, put all the bolts in loosely, trying not to thread them. Give them a bit of grease too to ease penetration.



Forgive my weird bolts, they are what were installed in the car when it came into my possession. I believe it had bucket seats on rails and then the original seats we're 'thrown' back in before it was sold.





You can see here the requirement of a ratchet spanner.



You'll have most likely needed to tweak the seat to get it to sit nicely, this is why the welder hasn't been used yet. But now the seat is bolted down, and settled (make sure to sit on it and wiggle around a bit to 'seat' the seat. )

Unbolt it gently, and trying not to move anything, remove it from the car. Drape a few damp towels, that you're missus doesn't like!, over the seat parts that might get splattered by weld slag.

Weld a few beads on the edges of the feet, in the same place they were on the MK1 feet. No need for massive seams all the way around, but if you feel like it, go crazy. Just be careful of getting any slag on the seats or into the foam, and do it in stitches so you don't evaporate the grease, and warp the rails.

I've not got any shots of me welding these, as I was too excited to get it back in car.
But here is some shots of the mk2 seat welds to show you what's required:







Then, scrape off any flux / splatter and hit them with a lick of paint.

You can then bolt it back in the car if you wish, but I would hold off for now and wait for Part 2 - The drivers side & Electronics! Which will be uploaded next week.

If you aren't interested in heated seats, then I think you're safe to install the seat now.

[LawrenceSelly]

How To - Part 2: Drivers Side

The drivers side installation process is much the same as the passenger side, the only added difference is a some electrickery, and a heavier seat.

The Seat installation
Again, just like the passenger side, you're going to want to remove the feet from the mk1 (or mk2) rails.

So prop your seat up, and remove those 4 feet. Again, labeling them, or arranging them on a table in the correct order.





Once they are all off, you can do the same with the RX8 seat. But this time rather than getting loads of damp towels and covering the RX8 seat to stop any stray burning metal chips flying into the foam. You can undo the 12mm bolt on the rails, and slide them out of their mountings.





This is also a great opportunity to grease up the rails, and the Acme thread. It's probably not been done since it was built, and it will certainly benefit from it.

Then, hack away at the feet on the RX8 rails, which you can now do comfortably from a bench.
Be careful when bashing the rivets out, as you can easily bend the rail channel, which makes it prone to getting stuck on the other part of the rail.





Whilst you're working on the seat, take a look at the front two motors that support do the bottom seat adjustment.



Mine had only two screws in both sides, and both motors were cracking the plastic gear housing.
I added some more screws, I think they were M5 thread. I just grabbed anything long enough that fit.



No idea why they weren't fitted, it could just be my seat, but do check yours.

You can then bolt up the front two feet, onto the front holes of the rails.

And then go try the rails in your car, to locate the back feet correctly. Make sure to tighten everything down, and you might even want to drill through in the car and throw an M6 bolt in situ.



They should be exactly 17" apart center to center, across the entire length of the rail.

Once you've got the bolts in on all 4 feet, tightened down, you can take them off and weld them onto the rails.

I would also lop off any errant brackets on the rails that don't need to be there.

like this one that protrudes out the side for some reason.



Get it in the bin.

Once you've welded them up, give them time to cool down. Then give them a test fit, and a lick of black paint.

Wiring time

The wiring is fairly straight forward.

A warning before we begin, disconnect the negative on your battery. You're going to be threading cables that could be live under the carpets.

Split into two parts, there is the Heated Seats, and the Drivers side movement.

You'll need some various 12v flexible cable, I used some 2.5mm stuff for everything, except from the battery to my large fuse, which was some 100A battery cable.

I mounted everything under the passenger seat on a little piece of wood, to keep it all together.



I've got an amplifier under my passenger seat, which also needed 15A of power, so it was easier for me to run a 60A fused cable from my battery, to under the passenger seat. Which then went through a 50A fuse into the two relays. One relay is protected by a 20A fuse, for the heated seats. The other by a 30A fuse for the seat movement.

This is the battery cable that I ran down to the seat:


Here is my completed circuitry.



There's a lot going on here, so let me walk you through it.

From left to right:

1. Power in from large 60A midi fuse near my battery
2. Power is then sent up to the amplifier (which has it's own 15A fuse)
3. And down through a 50A fuse to the brown wires which lead to the relays
4. The first relay is for the heated seats. It takes power in, and then sends it out when switched to the heated seat buttons
5. The second relay is for the seat movement, when switched it sends power over the center console to the drivers seat.
6. Then we have a ground bolt, which just saves me running 10 grounds to the chassis. Instead I just run a common ground from this bolt.
7. Then below that, is a 5A fuse and relay hardwired to a 12v cig socket connector which goes to my dashcam. No need for that on your build, but it saves it sticking out of cig lighter.

Everything here is switched by +12 feed from the back of the radio. It's an odd way to do it, but I rarely turn off the radio. And If I want to move the seat without starting the car, I can switch to accessory position, and move the seat around.

You could also use any 12v feed you want, or swap the relays over, have a constant 12v feed into the coils, and then use a ground based switch on the dash instead.

Here is a wiring diagram to document how it's done.



The next steps are connecting the seat up, and the heated seat switches.

For the Passenger seat, as we're not using any of the other seat connectors, you can remove large connector blocks and use the tail of the Red and Black wire that connects directly to the heated seat connector.



Make sure to leave about a foot of cable, so the seat can freely move without tugging a wire.

You can use any switches, but I liked the OEM look of the mazda one's so I bought a pair.



Using a dril, and a file, I cut out the mounting holes and mounted them into the back of the rear cupboard.


I rarely put anything in here, and it seems like a nice place to put them that is accessible, but also out of the way.

If you do decide to get these switches, try and get the connectors with some tail wires that you can splice into. I had to use some very small delphi connectors that fit onto the pins. Luckily there isn't much movement that can happen behind there due to the close proximity of the firewall, but if you decide to put your switches somewhere else they run the risk of falling out.





I also had to make a small hole in the bulkhead carpet to clear the back of the switches.

Up here we have:

• Two yellow wires for power IN from the relay (from one brown wire)
• Two black wires for ground (from one blue wire)
• Two wires, one for each seat, running down to underneath each seat.

You can see on the wiring diagram, how the connectors are pinned. if you get the power wires the wrong way around, the LED in the switches will be on all the time.

There is also a second LED which is illuminated by the illumination circuit, I didn't wire this up as it would involve taking the dash apart to find a wire, but there will be one behind the stereo that you could hook into.

The connector on the bottom of the drivers seat is a 4 pin connector from the connector kit I linked at the top.

You could use any connector, but I recommend something that's easy to get at and operate, as once you put the seat in there, it's hard to get to with two hands.

The wiring for the drivers seat is as follows:
Pin 1 - Grey & Yellow w/red stripe - +12v from Seat movement relay
pin 2 - Purple & White w/yellow stripe - Ground
pin 3 - Blue - +12v from heated seat switch.
pin 4 - All other wires to ground (not necessary, but just encase)

Final Installation

And once you've got that wired up, your cables run, your earths connected.

you can slide your cooled down rails onto the seat, installing the 12mm locking bolts (hand tight only, they are like a locking pin. No need for any torque!)

Take the seat and carefully slide it into the car, head first.

before you bolt the seat down, (or the passenger seat if you've done any under the seat wiring) plug the seat in, connect your battery, and do a full motion test. Make sure everything is working.

Then, once that's done, bolt those seats in!



Test out the heated seats



Go for a spin!

The only thing of note, I've had a lot of comments asking what the seat height is like, as it's a sticking point with a lot of owners due to how low the stock seats are.

If you look at the shape of a 'foot'



You can see the 'step' where it sits on top of the chassis rail.
Theoretically you could cut out a around an inch of metal between that step and the bottom of the seat rail. Which would lower the seat by that amount.

You can also then remove the same amount from the rear feet. which may make installing them difficult due to their bolt location, but you could always cut a slot out of the back of them, so you could slot them in to place, with the bolt already 90% done up, then just do up the remaining 10% of bolt.