engineered2win

Ok, made some progress (completely by accident).
I unplugged the battery to tack weld a larger resonator into the midpipe. Then went inside and made spaghetti and meatballs for dinner.
I hooked up the battery, determined to recheck the pinout with my cheat sheet(see above). Flipped the IG on and lo and behold, the damn ABS light turned on! And it stays on... So I jumpered TBS to GND, switched IG back on and viola! Got code 12 (one long, two short flashes) for LF wheel sensor. Unplugged the sensor and checked the resistance and it's open. So need to replace my junkyard sensor. I tried to see if I could get the pump to cycle in diag mode (by holding the brake and turning on IG), but guessing it won't work until I fix the sensor fault.

Only guess is the ABS module got pissed off as my wiring slowly progressed and it needed a reset. I started with the +12v from the engine fuse box, then I added the grounds, then I added the sensors, and finally I added the LEDs/sw12v/brake switch from the cabin. I'll have to turn it all on and jiggle everything and make sure there isn't an intermittent connection. I couldn't find the Bosch pins anywhere, so I had to use the ones that came with the connector I bought from ebay. I cut a short pigtail off on each pin and spliced every conductor together. Straightforward enough, but it did add 18 more junctions.

I found this list of NB2 ABS fault codes:
ABS Diagnostic Procedure
There is no list in the NB2 ABS FSM.

In summary, if your pump isn't working, make spaghetti and meatballs and try disconnecting the battery.

Gee Emm

Interesting. I wonder if we tried that, don't remember doing so but there were many fingers in that pie over the period I was troubleshooting. I see from post 3 that there are three 'hot at all times' wires, one of which goes through the brake switch, so your suggestion seems very worthwhile. Cat for you!

codrus

IME, yes, the unit will not cycle in diag mode unless you have erased all of the codes.

--Ian

engineered2win

I can confirm that the diag mode functions once the codes are fixed. In my case it worked after I replaced my LF speed sensor. I bled the brakes with my speed bleeders as usual and then triggered diag mode once with each bleeder closed and once with them open. I did them individually and didn't notice any air in the system and the pedal doesn't feel any different than w/o ABS.

I'd like to give an update about the NB2 ABS operation on track. This was at Mid Ohio last weekend on my TT6 car. I was running Toyo RR's in the damp/dry and Conti ECS in the wet. For reference the RR has less grip than a good 200TW and much less than the Hoosier R7. The ABS is really only useful in the wet or damp with unknown/changing grip levels. In which case it was pretty handy and rather confidence inspiring. However, I had it trigger a few times in the dry and it was unsettling. Once going into China beach (so about 115mph top speed there) and once over the crest into carousel. Every time it triggered caused me to completely blow the brake zone and thus the entire corner. The decel rate drops quite a lot when it engages and I just barely managed to keep it on the track. This was early on in the day and I hadn't pushed the brake marker too far, so I can see myself going off if I had been at 10/10th's. So I ended up turning it off in the dry using the handy switch I wired on the dash.
After talking with my buddy that races a 944 Turbo in TT3 (with the stock ABS), it functions very similar; if it engages then you've blown the corner, but it may save a tire from becoming square. So I may try to run the Friday practice at Gingerman and see if I can turn ABS on in the dry and manage to drive around the limitations or I just need to leave it off. It's definitely light years away from the modern ABS systems where you just push the pedal to the floor and let the ABS sort it all out.

Leafy

iTrader: (1)

This is another anecdote of normal NB2 abs triggering when not needed and causing a lack of braking power. We really need someone in this thread besides me to have used the MSM abs module. I realize is has the same part number from mazda if you re-order it but I never had this issue even on A7s, navalhawkeye can attest that I had the hardest stopping miata he's even been in by really just stomping on the pedal and letting the abs sort it out.

codrus

My NB2 ABS did not do what engineerd2win's did. I would engage it on the track fairly frequently in the dry, with RRs, and it was what you'd expect for max braking. The rear end gets a little unstable at max braking into T2 at Laguna (130 down to 45 or so), but then my Miata doesn't have any aero.

Also, FWIW, I dunno what the "good 200 TWs" are these days, but the RRs on my Miata had more grip than the Rivals or RE-71Rs that I've used. I keep hearing about how fast modern 200 TW tires are, but that just doesn't match up with my experiences.

--Ian

mr2daj

iTrader: (-1)

wrong thread

rascal

I have retrofitted NB2 ABS onto my non ABS NB1 track car. I swapped the whole shebang, booster, master, lines, uprights,etc.

It also works as expected , ie like codrus experience and no issues like engineered2win had.
This is with aero and on A050s, the top of the tree R spec here in Oz.

Skilaufen

I ended up with two knuckles that don’t have the holes for the ABS harness. I have the ability to drill and tap the holes, but I am have the devil’s time trying to find the size and thread count of the two sensor bracket bolts and the single bolt for the upper bracket. Any change someone knows what the sizes of those two different bolts are? I am trying to keep it in line with what Mazda originally used. Thanks in advanced.

thebeerbaron

iTrader: (1)

If it's on the Miata, it's likely one of:

* M6x1.0
* M8x1.25
* M10x1.25

Gee Emm

From memory, they take a 12mm socket. But who cares?! They don't HAVE to be any size, it's just a bolt to hold something on - too small, drill it out, too big use a washer.

Skilaufen

That was very helpful. All three are M8x1.25 and your advice put me in the area i needed to be to match it. I am replacing the knuckle along with everything else in the rear as the car spent 6 winters in the north before it came south with us for its permanent home. The bolts are frozen and corroded. The first bolt head sheared right off when I tried to take it out (minimum force was used when it happened). After a complete replacement of the rear suspension, almost all of the corroded parts will be gone. Thanks again.