I bought my 99 brand new in 1998, and spent over a month looking for a car with a manual and ABS. They basically didn't exist at that point, so I settled for one without ABS and have been regretting it ever since. The popular wisdom is that retrofitting ABS to a car that didn't come with it is far too much work to be worth it, but a year or so ago a friend of mine wrecked his ABS-equipped 2003 at Laguna Seca, and I scavenged the ABS parts off it to try retrofitting.

Why ABS? Because I'm tired of wrecking race tires like this:


One good thing about the Miata is that the ABS system is standalone, it's not tied in with the ECU or a stability control system, so it can be moved as a unit. The downside is that it's only 3-channel, front left, front right, and the rears are activated together.

The parts that are different are:
- ABS rings. On the front these just press onto the hubs, and all of the non-ABS hubs I've seen are machined to accept the rings. On the back these go on the axles, I think you can put the rings on non-ABS axles, but I haven't tried it.

- ABS sensors. These mount to the uprights. Note that the connectors for these things are INSIDE THE CAR. I thought the connectors were closer to the wheel, so I cut the wires on the donor at the fender liner, when I'd intended to get a pigtail off the 2003 factory harness with the proper connector for the sensor. Doh. More splicing required.

- The uprights. The non-ABS uprights (at least on my 99) are the same casting, but are not machined to accept the sensors.

- Master cylinder & booster. Lots of info on these parts in this thread: Some interesting brake information (tech!) - MX-5 Miata Forum

- ABS hydraulic unit (this is missing on the non-ABS cars, obviously)

- ABS computer (on 99 this is a separate box, on 2003 it's integrated with the hydraulic bit)

- all of the brake pipes except the one that crosses over in the back. Front and rear MC to the thing that looks like a prop valve (I believe on a 2003 it's just a fitting, with no proportioning in it). Front and rear "prop valve" to hydraulic unit. HU to driver front wheel, Hu to passenger front wheel, HU to passenger rear wheel.

- the wiring harness

- ABS fusible link

- windshield washer bottle (ABS unit goes where bottle is on non-ABS car)

Here are some lousy cell-phone pictures from when I was scavenging parts off the wrecked car. The ABS unit itself:

Master cylinder

Front ABS sensor

ABS unit and axles sitting on the bench

Removing the front ABS rings from the hubs with unknown bearings in them

Removed


What I've finished so far. Photos for most of this are pending:

- Installed the rear axles+uprights+hubs. I pulled these off the donor as a unit and installed them on my car while swapping the diff ratio.

- Installed the front uprights and ABS rings on hubs.

- Spliced wire onto all four sensors and installed them. The factory routes the wires for the rear sensors up through the fender and through the interior, but I decided to run mine along the bottom of the car. The fronts go through the fenders into the engine back.

- Scouted out the wiring harness splicing required.

- Mounted the hydraulic unit in the car

What's left:

- Finish the harness

- Move the windshield washer bottle

- Install MC, booster, and "prop valve"

- Install brake pipes

- Fill, bleed, and test.

 

On the windshield washer front, FM sells a bottle from a Suzuki Cappuchino that fits in the cowl area, but it's $164.

I found this guy on Amazon for $47:
It fits nicely here:



Here's what comes with it:



Now I just need to make a bracket for it.

 

As for the wiring harness, here's the 2003 ABS wiring diagram:


And the wires from the factory harness on the hydraulic unit:



It needs:

- 3 power wires. 20 amp (green) for the solenoids, 10 amp (blue/white) for the electronics, and "fusible link" (40 amp?) (white/red) for the pump.

- 2 ground wires (black and black/blue)

- 4 pairs going to sensors, (blue, green/yellow), (orange/yellow), (red/white), and (brown/red, light green).

- The brake on switch (green)

- 2 wires to the instrument cluster, for the "brake" and "ABS" warning lights (blue/yellow and pink/black, respectively)

- 2 wires to the data link connector (brown and green/white). The latter goes to the OBD2 connector as well.

I powered up the ABS unit on the bench, and hooked up lights to it. The brake light comes on and goes out as expected, the ABS light stays on. Hm, I wonder if it's unhappy about not having any sensors? Grounding one of the datalink lines made it emit a blink code -- 5 short, 1 long, 2 short. I haven't been able to track down what that means.

The 20 amp fuse for the solenoids is present in my 99 engine bay non-ABS fusebox, and has a short wire underneath that's easy to splice to. The 10 amp fuse for the computer is present in my interior fusebox as well. There's a missing terminal in one of the engine bay fusebox connectors that looks like it's the one for the unrated "fusible link" white/red wire, with a spade terminal to a hot-at-all-times wire.

I need to pull the instrument cluster out and see if I've got an ABS light. I also need to buy some more wire and finish wiring it all up.

 

Very nice work! Subscribed.

 

Nice write up. I'm swapping my 94 ABS for this newer version.

 

Is this because your 99 doesn't have the correct holes in the rear fenders? Or does it have a hole with a grommet but you decided to do it this way for ease of install?

 

I just added abs to a non ABS car this winter. It wasn't as hard as some people make it out to be. In theory it is a very simple install, it's just very time consuming due to the volume of simple tasks that must be accomplished. If you want to talk to someone who actually has gone through with adding ABS to a Non-ABS car I will be more than happy to help you.

 

It has holes with grommets, but they come through right next to the gas tank, deep inside the tunnels that go between the trunk and the cabin. I decided running them along the PPF, zip-tied to the other wiring harnesses on there was a much easier install problem.

The biggest challenge to the installation looks like it's going to be getting the front-to-rear brake pipe in. It needs to go past the intake manifold and transmission and down the transmission tunnel, and the line has a bunch of bends on both ends. It remains to be seen how much I'm going to have to take out to get enough clearance to slide it through.

I've thought about cutting it into two pieces and patching with a flare fitting, but I'd rather not do that unless I have to.

--Ian

 

I'll be doing this very, very soon so I'm watching this thread. Two things I am trying to figure out now are where I am going to get the ABS connector from (without spending too much), and whether the adjustable (Wilwood) brake bias valve can go AFTER the ABS unit.

 

I'm working out the wiring diagram.
Could you just combine terminal E & F together to a single dash ligt?

F Blue/Yellow Brake Indicator - Instrument Cluster - 3C
E Pink/Black ABS Indicator - Instrument Cluster - 1D

I don't think my 94 dash has two lights.

Also, the
Z Blue/White +12V Fuse Block - Hot in Run & Start - Behind Left Side of Dash

needs 'hot in start & run', but my 94 has a Blue 'hot in run'. Would that be no problem to not be hot during start? Would the unit reset/would it matter?

 

Sorry I haven't updated in a while. The turbo had to come out and back in again for, uh, "regulatory" reasons, and the autox season has been running pretty non-stop. I've got a few weekends available coming up, though, so hopefully more progress soon.

Regarding connector, are you talking about the wiring-harness-to-hydaulic-unit connector? I got mine by cutting it off the harness of the donor car, I'd think there ought to be a bunch available in junkyards. If you want to look for a new one, it's a Bosch connector, not one of the Sumitomo ones that Mazda normally uses. Presumably this is because it's an off-the-shelf Bosch hydraulic unit.

The 2003 ABS that I'm using is supposed to support electronic brakeforce distribution (EBD). As I understand it, this uses the ABS system instead of a prop valve, so I'm not sure if there's any benefit to using a Wilwood adjustable prop valve as well. The thing that looks like a prop valve in the system is supposedly just a 1:1 union fitting which doesn't do any proportioning.

--Ian

 

The brake indicator is also used to indicate that the parking brake is on and (I think?) as a low-brake-fluid warning light. The ABS light is used to flash diagnostic codes, which it can't do if you have the parking brake circuit holding the light on, thus two lights.

I haven't pulled my instrument cluster off to see if Mazda put an ABS light on the cluster for non-ABS cars, but if it's not there then I'll probably just wire up an LED somewhere on the dash for it.

As for "hot in start and run", the blue/white wire is (I think) for the ABS computer that's integral with the hydraulic unit. I don't know what would happen if it lost power during starting, although presumably it would power down and back up after the car had started, perhaps re-running the diagnostic tests. It shouldn't be too hard to find a hot-in-start-and-run wire somewhere in your car that you can use to drive a new relay to power the ABS unit, though.

--Ian

 

A couple photos of the rear ABS sender that I shot while swapping out a damage wheel stud:





Mounting this is why you need the ABS uprights -- the non-ABS ones (at least on my 99) are just rough castings where the sensor is supposed to bolt on, only the ABS uprights are machined properly.

--Ian

 

The parking brake makes sense, and I don't need that light so I can use that.
My car came with 94 ABS, so the light is there.

Today I figured all my circuits are hot in run AND start, because my ignition panel and starter button are not factory wires. Starter button just triggers the starter and doesn't break any other circuit. Happy man.

 

So I pulled the instrument cluster off, and there's an "ABS" cutout in the faceplate, as well as a bulb behind it, and what looks like all of the circuitry on the board to control it. This suggests that Mazda only made one instrument cluster for both ABS and non-ABS cars, which makes sense.

OTOH, there's no pin in the wiring harness for that light. Anyone know of a source for instrument connector harness pins?

--Ian

 

I finalized the fitting of the NB2 ABS last week and had a test session earlier this week.
When it works, it's brilliant.

Two issues:
- Faulty LF sensor caused the system to go out and me go off.
- 3-times that day I hit the brakes in the braking zone and the pedal felt stiff and the car wanted to run left, sharply. I lifted and reapplied and still made the corner, but it felt and looked spectecular.

See at 2m00s:

 

Hmm, after moving my NB1 Hydraulic unit to the passenger footwell It would be possible to improve it a bit further.
A no_I_have_not_searched_question:
Is the NB2 unit all-in-one without an auxiliary control unit meaning I could loose one box and a lot or wires?

 

Yes it's all in one. Different wiring, not so much less.

 

Did you get ABS error lights?

--Ian

 

Only where I went off, or just before.