Retrofit ABS into NB
 

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:
https://www.miataturbo.net/attachmen...ine=1372231242

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:
https://www.miataturbo.net/attachmen...ine=1372231242
Master cylinder
https://www.miataturbo.net/attachmen...ine=1372231242
Front ABS sensor
https://www.miataturbo.net/attachmen...ine=1372231242
ABS unit and axles sitting on the bench
https://www.miataturbo.net/attachmen...ine=1372231242
Removing the front ABS rings from the hubs with unknown bearings in them
https://www.miataturbo.net/attachmen...ine=1372231242
Removed
https://www.miataturbo.net/attachmen...ine=1372231242

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:

https://www.miataturbo.net/attachmen...ine=1372231588

Here's what comes with it:

https://www.miataturbo.net/attachmen...ine=1372231588

Now I just need to make a bracket for it.

As for the wiring harness, here's the 2003 ABS wiring diagram:
https://www.miataturbo.net/attachmen...ine=1372232259

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

https://www.miataturbo.net/attachmen...ine=1372232259

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:

https://www.miataturbo.net/attachmen...ine=1376331454

https://www.miataturbo.net/attachmen...ine=1376331454

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.

I did most of the rest of the electrical wiring for the ABS unit yesterday. Since I'd cut off the sensors in the wrong place, the two wires I was splicing to were not keyed and the same color. I'm told that, theoretically, reluctors should give a sawtooth waveform, but looking at it on an oscilloscope while spinning the wheel by hand the slope of the rising and falling edges looked pretty much the same so I'm not sure it matters. No shots of the waveform though, sorry.

As I discovered previously, my 99 instrument cluster has an ABS light in it, but there's no wire for it in the factory harness. To deal with that, I got a piece of the harness from another car and stole a pin + pigtail wire out of it. The connector shell pops open and the pins come out with a bit of poking.

https://www.miataturbo.net/attachmen...ine=1377458741

The car it came from was a non-ABS automatic, so I used the "OD off" pin just because that gave me a unique wire color (red/white), even if it wasn't the right one for the ABS light (pink/black). Had to buy all 3 connectors from the salvage yard, and they charged way too much for, now I've got a huge pile of extra pins if anyone wants one. :)

https://www.miataturbo.net/attachmen...ine=1377458741

It also turns out that the 10 amp ABS fuse power for the electronics that I thought was present in the under-dash fusebox is not there, I must have been smoking crack when I looked at it before. Given that, I decided to just pull all the power and ground next to the ABS hydraulic unit and avoid running additional wires around.

The 20 amp ABS fuse power for the solenoids *is* present in the engine bay fusebox. The 99 fusebox is kind of a strange contraption, it's in two pieces, with wiring connectors in both parts. The 20 amp ABS fuse is connected to a wire in the stub harness that goes between the two parts, but again the pin is missing in the factory harness. I just cut that wire in the stub harness and spliced it over to the hydraulic unit.

The ABS pump power is listed in the wiring diagram as a fusible link with no current rating shown. Since it appears to be 10 or 12 gauge wire in the harness, I decided to go with a 50 amp fuse. Currently that's just hacked up.

So I hooked it all up and did a power-on test with the hydraulic unit disconnected to look for magic smoke coming out. No smoke, but both the ABS light and regular brake light were illuminating on the instrument cluster. After poking around a bit, it turns out that those clever German engineers at Bosch designed the ABS connector so that if it's not connected then a springloaded jumper comes down and connects both of those pins to ground to turn the lights on so that you'd know something was wrong. I plugged it back in and the brake light went out.

https://www.miataturbo.net/attachmen...ine=1377458741

So now it's powering up and doing the same "512" blink code that it did when we tested it on the bench. I still can't find a list of what the codes mean for it, but I guess 512 isn't "no ABS wheel sensor", since it's got those now. Hopefully it means "no pressure in the pump" and that will fix itself once I've got the hydraulics connected, rather than "I'm completely fried and not working". :)

--Ian

Codes are all 2-digit. What blinks?

The ABS light. In the bench test, it's clearly 5 short blinks, 1 long blink, 2 short blinks, then it repeats. I just went out and video'd the in-car one, and there it appears that it might be 2 short, 5 short, 1 long. So maybe that's 25? I dunno.

Bench test:



In-car:



--Ian

Argh, apparently I fail at embedded youtube videos properly. WTF.

--Ian

Looks like 12 and 05, although 05 is unknown.

12 = This Relates to Circuit for left front wheel speed sensor or sensor rotor.

So I installed the booster & master cylinder tonight, and ran some of the brake lines. The 2003 line to the passenger front wheel isn't going in without taking the intake manifold out, so I'm going to splice that one too.

Before cutting the factory lines, I decided to test my flaring prowess with the cunifer lines. I hooked up the master, "prop valve", and the front & rear crossover lines to the ABS unit, ran a short cunifer jumper line between two of the ABS ports, hooked up the last one to a caliper, and put some pressure on it to see if it would seal.

Eventually it did, but I had to crank down on the cunifer lines quite a bit tighter than the factory ones. Is that expected, or do my flares just suck? Also, the factory lines go from loose to tight in maybe half a turn, whereas the cunifer ones seem to be 2-3 times that much.

Incidentally, the ABS unit still blinked the same codes with the hydraulics hooked up, but the ABS light isn't on when the diag line is disconnected (it comes on at power up, then goes off, as expected). So maybe that's not a trouble code after all, maybe that's just what it does when it's happy, I dunno. It doesn't seem to cycle the pump in any kind of self test when I power it up, either. I'll find out if it works once I get the hydraulics finished.

--Ian

Post pics of your flares.

About the light: it appears you sometimes need to erase codes. That is: the light may be off in running mode, but it will still display (old?) codes when in diag mode.

Can't get the exact details about that one yet.

There is a range of flare quality that will seal. You're probably doing the 2nd part of the flare too hard.

Here's one of my test flares. It's silghtly asymmetrical at the top (the ones on the car are a bit better, but none are perfectly symmetrical).

https://www.miataturbo.net/attachmen...ine=1377714535
https://www.miataturbo.net/attachmen...ine=1377714535
https://www.miataturbo.net/attachmen...ine=1377714535

--Ian

Looks fine. Don't forget factory lines are harder and have been tightened before. Hence the less turn to seal.

So not to jack the thread, but I have a related DIY ABS install question I would like to pose... I have non-Miata rear outer CVs (V8 conversion related) that are too large to fit the rear Miata ABS ring. I think they are too large to where I could turn the i.d. on a stock ring and make it fit.

If I can make/fit a different toothed ring onto the shaft, could it be made to work? I would think if I changed the tooth pitch such that the pulse per revolution count was the same as stock, then maybe it would still work.

The ring is just a hunk of steel with teeth on it, so any ring with the same number of teeth and relative spacing is going to produce the same waveform at the same RPM so long as the sensor is mounted appropriately.

If you can't turn the i.d. on the stock ring because there's not enough meat, then you probably need a ring with a larger o.d. That means you'll need to space the pickup outwards, and getting the right gap between it and the teeth is fairly important.

--Ian

Same number or teeth and same distance to sensor would hopefully create a similar result.
If the mass difference of the teeth (thinner ring would make it really equal) matters I dunno, but if so it would be a stupidly sensitive system.

While you are at it, test to see if 20% +- teeth (on all four rings) would affect the calibration (if the allowed slip would increase).
I know too little about ABS calibration to know if the allowed slip is speed dependent in the NB units. If it is different changing rings would be the easiest way to change things (assuming rings gets made by someone).
But then there is the mix of sticky rubber and wet races, changing ABS rings between heats would be a hassle.

Yep agree on those points:
- Change the bracket to maintain the proper sensor spacing
- Cut a new one from steel with the same tooth count, same width, and the same ratio of tooth width to tooth gap. ABS computer won't know the difference.

It's worth a shot.

And... it works! We wound up managing to get the front right factory line installed after all, and only cut the rear line. Also didn't actually need the cunifer -- just bent the original line over 180 degrees so that it went to the passenger side instead of the driver's, cut a foot or so off the end, added a few more bends and a flare, and it went to the ABS unit. Having a bunch of spare line was useful for practicing the flares, though.

Need to bleed the system again and add some rubber hose as anti-abrasion in strategic portions of the new lines. More pictures forthcoming.

--Ian

Some shots of the finished parts. Since we managed to fit the front right line in, and bend the rear line around to where it could be trimmed and flared, I avoided needing to splice stuff. As a result it looks mostly factory, which is not a bad thing.

https://www.miataturbo.net/attachmen...ine=1378364178

The rebent rear line is the one that runs along the firewall that has no black coating on it. I assume this is anti-abraision coating of some kind -- I still need to figure out what to add for that. Heat shrink might've been a good choice, but I didn't think of it until after I'd flared it, so I don't think it'd fit.

https://www.miataturbo.net/attachmen...ine=1378364178

The windshield washer bottle installed:

https://www.miataturbo.net/attachmen...ine=1378364178

Master cylinder -- this is all factory piping:

https://www.miataturbo.net/attachmen...ine=1378364178

https://www.miataturbo.net/attachmen...ine=1378364178

What's this? New toys from FM that just showed up? Alas, too late to install while I was bleeding/flushing the entire system. I sense I will need more brake fluid in the near future.

(Yes, I bought the pansy kit with a parking brake. I still drive this car to work every now and then, so I'll have to live with the extra 3 pounds).

https://www.miataturbo.net/attachmen...ine=1378364178

This little guy was easy to install. Meant I had to take the old FM shock tower brace off, though. (Really old, it's has a sticker saying "Dealer Alternative" on it) It's supposed to fit with it, but not unless someone sells an NB shock hat that has studs about an inch longer than factory...

https://www.miataturbo.net/attachmen...ine=1378364178

https://www.miataturbo.net/attachmen...ine=1378364178

--Ian

Those studs can be knocked out from the top by hitting them, hard.

Then insert a longer stud/bolt/whatever and you're away.

My plan (not tried yet...) is to use either spliced hose (if I could find one thin enough) or the outer layer of small power cables. Split it and twist it tight around the line and then use tape or ties to lock it in place.
Cable shielding is usually much easier to split in several feets length than hose.
Plastidip (if you want to remove the line)?

But for now I just use small pieces of hose and cable ties between the lines to give them some stability where they were close to each other.
Just to clarify, I have moved my NB1 ABS pump to the passenger footwell area. Meaning new lines to MC and fronts, and cut/join for the rears. Five lines through one of the AC FW holes.

Did you move it for clearance reasons? Or for weight distribution?

The hose idea is probably what I'm going to go with, I only need a foot or two because most of the lines are stock. I'm not taking this line out -- there's no way it's coming out with removing stuff like the transmission.

thanks,
--Ian

For clearance, exactly the same problem as with Crusher, the ITB filter needs the space.
And when moving it, why not move it to improve weight distribution in a nerdy way. I changed to the 15/16 MC/Servo at the same time.

Not directly ABS, but I started putting on the rear calipers from FM today.

https://www.miataturbo.net/attachmen...ine=1379191674

Goodwin rears coming off:

https://www.miataturbo.net/attachmen...ine=1379191674
https://www.miataturbo.net/attachmen...ine=1379191674
https://www.miataturbo.net/attachmen...ine=1379191674

FM bracket going on:
https://www.miataturbo.net/attachmen...ine=1379191674

New sport rear rotors. It turns out the Goodwin rears are the same dimension as the sport rotors, just lighter. Still, I can't reuse the ones I have because of the uneven wear from the smaller factory pads, and I didn't feel like buying more Wilwood rotors and aircraft bolts for attaching them right now.

https://www.miataturbo.net/attachmen...ine=1379191674

New rotor on (yes, this is the other side)
https://www.miataturbo.net/attachmen...ine=1379191674

Radial mount bolts on the caliper
https://www.miataturbo.net/attachmen...ine=1379191674

Threadlocker is good stuff.
https://www.miataturbo.net/attachmen...ine=1379191674

Hydraulic line:
https://www.miataturbo.net/attachmen...ine=1379191674

The Wilwoods have an NPT thread on the back, so this adapts to AN.
https://www.miataturbo.net/attachmen...ine=1379191674

Installed. Doesn't actually look all that different from the one I was using with the Goodwin brakes. I could probably have left the junction block in the car and just replaced the flex line.

https://www.miataturbo.net/attachmen...ine=1379191674

Lots more pad coverage:
https://www.miataturbo.net/attachmen...ine=1379191674

Now for the parking brake. Hm. This kit is new enough that mine came without instructions. Factory cable on the top, FM on the bottom. This is the end that goes on the parking brake side (I think). Question is, what's the spacer for?

https://www.miataturbo.net/attachmen...ine=1379191674

Caliper end of the cable (sorry, lousy picture). I think there ought to be a pin that goes in the clevis on the end of the cable and attaches it to the parking brake lever, but I don't have one.

https://www.miataturbo.net/attachmen...ine=1379191674

I need yet more brake fluid to finish flushing it (gone through three quarts in the last month), so it's on hold pending that and some input from Keith @ FM regarding the clevis.

--Ian

I poked at it some more. I had the cable ends oriented properly, and I managed to get them attached at the parking brake handle end, using the washers on the inside of the sheet metal mount, and the pac-man spacers on the ouside.

https://www.miataturbo.net/attachmen...ine=1379211966

Accessing the back of this mount is a pain, but there's a small shield you can loosen (it won't come off without removing the PPF) enough to reach in with fingertips.

https://www.miataturbo.net/attachmen...ine=1379211966

FM supplies clamps to hold the parking brake cable out of the way, but the holes are too small to mount them where the factory cables go. Zip ties to the rescue.

https://www.miataturbo.net/attachmen...ine=1379211966

And I definitely need some kind of clevis pin here. Zip ties to the rescue again, although I'm not going to use this for more than going up and down the driveway.

https://www.miataturbo.net/attachmen...ine=1379211966

My overall impressions so far is that I really need to bleed the system better, and the parking brake is very weak, and won't even hold the car on the driveway. Hopefully proper clevis pins and some adjusting will help that. :)

--Ian

I heard from Keith @ FM today, turns out that I had the cables installed wrong (the washers go on the front of the sheet metal, the big pac-man spacer thingeys on the back), and the clevis just uses a 6mm bolt & nut that somehow got left out of my kit.

--Ian

I would definitely like to know more about the parking brake functionality once you get that all done.

I installed some 6mm bolts & nuts from the hardware store in the clevis, once that was in place and the pads were properly bedded (I substituted some BP-20 pads for the E compound that FM supplied) the parking brake started working a lot better. As FM says, it's definitely weaker than stock and not good for handbrake turns, but it will hold the car on my driveway.

Driving home from work today, the ABS light came on. Cycling power would make it go off again, but after another 30-60 seconds of driving it would come back on. Got home and checked the codes, it flashes "5" <long pause> "5" <long pause> "5", etc. That's different than what it flashed before, but I still have no idea what it means.

The fuses are fine, and it doesn't turn on the brake light along with the ABS light (which is what it does if it's lost power in any of the power lines). That suggests it's either an intermittent internal problem with the hydraulic unit, or a bad connection in one of the ABS sensors. Since I crimped those wires together myself, Occam's Razor suggests the latter is most likely. :)

Unfortunately, it appears to be an intermittent loose connection, because I couldn't reproduce it in the garage, up on jackstands, with the 'scope looking at the sensor outputs. So I either need to recrimp everything (ugh), wait til it becomes non-intermittent, or hook up that other diagnostic wire to the OBD2 connector and see if I can find a shop with the Mazda scantool who's willing to try to scan my bastardized ABS system for codes. :)

--Ian

Brake switch.

You mean the signal coming from the brake pedal to say that the brakes are on?

I thought about that one (it's the only other input to the ABS system) but when the intermittent failures happen they don't seem to correlate with whether or not the brakes are active. Sometimes it happens while braking, other times while just driving down the street. It's never happened while stopped, however.

I'm also not sure how the ABS unit would know if it was getting a bad signal from the brake switch vs just a driver who's being spastic on the brake pedal?

--Ian

The ABS knows the wheel speeds. If they start slowing down faster than say, coasting would, and its not seeing a brake pedal signal, guess what.

I dont buy that. Id say a sensor. Not sure on the code tho...

Well, I drove it to work and back today, 30 miles round trip, and no ABS lights. Since I didn't do anything to the sensors or the wires thereof, I'm thinking maybe the problem was corrosion on the contacts in the ABS connector from sitting on the bench for a year or so. Any suggestions on the best way to clean them?

--Ian

Not on cleaning, but a dab of Vaseline on the contacts before putting the cleaned ones together will prevent corrosion close to forever.

Product called "deOxit" , we use it for aviation connectors.
DeoxIT® D-Series

So in the ongoing quest to try to fix the mushy brake pedal feel after transplanting the ABS, a friend and I did a bunch more poking at it today.

The good news, is that I figured out how to engage the ABS pump in a diagnostic procedure while sitting on the jackstands. If you look in the shop manual PDF that's linked in the sticky links section as a "1999-2001 shop manual" (it's actually a 99-00, not 2001), it calls out a few things.

So the first thing is that the diag procedure won't run if there are codes in the ABS computer. To clear them, you ground the TBS wire and turn the car on without hitting the brake pedal. Let it flash the codes at you on the ABS light, then tap the brake pedal 10 times at a rate of more than once a second. When they clear it will turn the brake light on, and you'll hear the relays in the ABS unit click. Turn it off, then turn it back on, and it shouldn't flash the ABS light at all. This is on page 04-01-4 in the shop manual above.

After that, the diag procedure will run. You keep the TBS wire grounded and key it on with your foot on the brake pedal, and it will engage the pump and cycle the solenoids for each of the three channels in turn. It's not subtle, it's really really obvious when it happens. This is on page 04-13-1.

Once I could reliably do this, I cycled the ABS while bleeding each of the three channels to try to get any bubbles out of the hydraulic unit and into the lines where I could bleed them out. Then I flushed a bunch of fluid through each of the calipers in a standard bleed sequence, and repeated all of this twice. While doing this, the ABS unit would set a code every so often and need to be cleared again. The code was 5 blinks -- perhaps that's 05, which is a "brake switch open or short", according to the code list on 04-01-5.

The bad news is it that all this bleeding still didn't really help the pedal feel, it's still mushy.

--Ian

A couple updates. The ABS error code was, in fact, indicating a problem with the brake pedal switch. I re-crimped it and the spontaneous error codes have gone away, yay.

I got frustrated with the brake situation and sought professional help, taking it to a local race shop (well known and well regarded for setting up Spec Miatas and various BMWs). They bled it multiple times and concluded that there was no air in the system, but that the pedal was still sucky. They recommended upgrading to a 1" master cylinder, so I bought a 929 master from rock auto:

http://www.codrus.com/abs/929master.jpg

Installed, the mushiness is largely fixed, although there's still some slack in the top of the pedal travel that probably means I need to adjust the pushrod. The effort is definitely higher, but it's a significant improvement.

So, my takeaway from this is to suggest that if you're going to use Wilwood front & rear, you probably want a 1" master.

--Ian

Not to bring you down after all your hard work... But. oem ABS units are very hard on braking components during track driving. you're getting a rotor up to thermal capacity than playing patty cakes on them. i've seen allot of rotor failures due to OEM ABS systems. The Pros use a bosch ABS system. it regulates line pressure and not no-off-no-off-no-off like you see on a OEM abs unit. just trying to help.

But but but, the ABS is so glorious, other miata people freak out when sitting in the right seat because I'm not going to make it, then I just push the pedal as hard as I can and it stops. Aint nobody got 10k for the bosch abs. What is weird is that there's a lot of pedal pressure required after you can hear the front tires abs working where it still slows down harder and I've done just about everything possible besides changing brake component size to fix that. Parts store pads in the front and hp+ in the rear on 1.8 brakes with 01+ MSM abs. Its very odd.

But yeah it seems kind of tough on components. I can get wheel and hub temps way above 212°F at just auto-x at both ends of the car with it. I dont have a real number but I spay the wheel with the tire sprayer to help get more heat out of the tire and on some courses spraying the wheel center creates instant steam. I used to only get this effect on the most hard braking of course and only in the front brakes before ABS.

First off, the point is not to engage ABS at every corner on the track, it's to provide a safety net to cut down on the number of expensive flatspotted race tires.

Secondly, in my case said flatspotted race tires primarily happen at autox, not on big tracks, because that's where I use Hoosiers (lightweight tires, a lot easier to lock up) and it's where I'm pushing harder to get times (vs "fun", non-competitive track days). Yes, the photo at the start is of RA1s -- I initially flatspotted those tires doing phase 1/2 of the Evo autox school (48 runs over 2 days, which would be close to the entire useful life of a set of A6s if I had run those). Once the flatspot was created, running them at Laguna finished them off.

Thirdly, there's no way that ABS adds substantially more heat to the rotors during a braking event than threshold braking does. It's basic physics -- the heat comes from using friction to turn the kinetic energy of the car into thermal energy in the rotors. You don't magically get more heat by pulsing the brakes on and off. You could potentially deliver more heat cycles (if the ABS system were PWMing the brakes), except that since ABS stopping distances are within a few feet of threshold braking distances the amount of "off" time in any possible PWM cycle is so small that I'd have a hard time believing it's significant.

Finally, even a street ABS system is not binary. It acts by reducing pressure to a lower value, not by cutting it to zero.

Is a race ABS system better than a street one? Absolutely. To start with, it would be 4-channel instead of 3, and would use technology newer than the at-least-15-year-old tech that was in a 2003 Miata. The software is the big difference -- a race ABS system is not going to have ice mode, would be expected to be used with race tire capable of generating much higher braking loads, and probably includes some tuning parameters to set it up for different car configurations.

It would also, as Leafy points out, cost over $10K, vs the few hundred it cost to put this 2003 system in my car.

Please don't crap in my build thread.

--Ian

Ian,
I am sorry for crapping on your thread. that isn't my intent. i was no insisting that ABS introduces more heat. you're absolutely correct on the fact. I was stating that when your rotor is reaching thermal capacity (at the end of a long braking zone when your abs will come on) the rotor is at it's weakest point. At that rotor's thermal capacity introduce a pulse of 100% pressure and alternate that with 0%. that rotor is taking a pounding. Not to mention the pad takes the force too. We at OG have seen many brake failures due to stock ABS systems. Sometimes it's just a cracked rotor, sometimes it's a car that lost its brake pads. Both situations can cause a severe amount of damage or death.

That being said for Auto-X you're not going to find thermal capacity. The runs are so short the rotor doesn't have time to get near the heightened temperatures. Yes it will help you prevent flat spots on those expensive hoosiers. Also at a track in the rain will have similar Experience, and ABS will be a help.

For dry days on track it would behove you to have a Kill switch for the system.

Have you datalogged the braking gees before/after adding ABS?

--Ian

And yes, I have the power line for the ABS electronics attached to the cruise control switch (after melting the CC at a track day I didn't bother to reinstall it, so the switch was going spare).

--Ian