Some ABS questions...

[itbrokeagain]

No I think its pretty cool especially if it works. I was just wondering if it is worth all that time and work for something that might be marginal at best. But I hope I am wrong and it is the best thing since sliced bread. Carry on.

 

[itbrokeagain]

What about cutting brakes?

 

[casm]

What about cutting brakes?

Then the whole point is moot since you're pretty much at the mercy of engine braking and whatever ends up stopping you. Hopefully it's something soft, but if you lose the brakes entirely you've likely got bigger problems to worry about.

 

[kastein]

Considered cutting brakes and stuff like that (2stix suggested them, iirc. Too lazy to check page 1) but I decided I'd rather put something in that I can disable entirely with a flip of a toggle switch just by cutting power and leaving the valve body to fend for itself, kinda like how people disable XJ ABS by pulling fuses and relays. This also allows me to do more of an "incremental" install and testing procedure, I can stick the modulator in my DD and bleed it properly and then leave it there without the HCU even connected to it, then engineer, test, and install the HCU as time permits.

Bleeding the ABS supposedly takes a DRB II system at the dealership to cycle the ABS pump and solenoids/valves, but I'm betting after I pull mine open it'll be pretty easy to figure out how to hot-wire it to bleed properly. Since the valve body is a single piece of billet aluminum with the passages milled into it, I should be able to see where they all lead and draw up a schematic after I've pulled the valves out. It's looking like (unless someone is awesome and finds pics of a cut-open valve body and chopped up valves) I will be completely dissecting the modulator I have right now and then using another one to actually build this.

 

[kastein]

Update... got some more junk.

I settled on the UP380046 brake lines from NAPA for the rear. They're 21.36" long and have a 3/8-24 connection at the body end, along with a 3/8-24 and a 7/16-24 on the body end, which has a bolt hole through it like the stock XJ ones. I picked up two 7/16-24 flare plugs for the ports I won't be using.

Also picking up another two WJ ABS modulators at the all-you-can-carry next weekend at a local junkyard. Since each one only has 3 ports (one shared for the rear wheels) my plan is to pull the HCU off the side of each modulator and use one modulator for each axle. I'm thinking I will have to build a custom HCU for each and run one master cylinder output line to the front line input on each modulator (leaving the rear input and output on the modulators unused) but I'm not entirely sure.

I was hoping to find a four-output modulator but I haven't seen one yet. Seems that most SUVs/trucks have a common line to the rear axle still.

 

[GoSlowGetStuck]

Interesting concept. I'm curious to see what you come up with from the electronics/control perspective of things. My guess would be that integration with the WJ modulator will be a bear, but for your sake I hope it's easier than I think.

I've heard these systems referred to as ABLS = active brake limited slip. One of my local wheeling buddies has an Xterra and it uses this instead of an actual limited slip in the rear. On the road and in snow it works pretty amazing, but off road he says he would take a "real" limited slip any day.

kastein, if you run into a dead-end with the WJ modulator, you might want to look into modifying a line-lock to work. Lots of guys run these on drag cars so they can apply brakes, apply the line-lock (just a solenoid in-line with the front brake lines) then release brakes, and the line-lock will hold the front wheels while they burnout with the rears. Of course, without your foot on the brake pedal you won't have any pressure, so you would still need a pump or accumulator as well. So in the end you probably would have an arrangement of a pump, several solenoids and check valves to keep the whole thing from blowing up.

So maybe you are better off figuring out that WJ modulator. Probably more fun anyway.

 

[kastein]

I've considered the line locks / cutting brakes type stuff... seems more difficult to use. I'd love to have a switch for the front and a switch for the rear just like a full selectable locker, but all put together for less than the cost of a single autolocker. Not sure I'm going to be able to hit that goal and I know it won't stand up to the same kind of abuse, though.

We'll see. Now that I have a few more modulators (I've been calling the electronics part of the unit the HCU, and the metal block + valves the modulator, not sure if this is correct terminology) lined up to be available next weekend, I'm much less worried about irreparably damaging my first one by pulling it apart, so I'm going to just gut it and fully map the hydro circuits sometime. At this point I don't intend to make use of the stock HCU at all since it's all custom chips and stuff I can't reverse engineer easily, I may reuse the wheel signal processing/filtering portion of the circuit (I've never built something with reluctance pickups before, it may be easier than redesigning it) but that's about it.

Total spent so far:
$40 - WJ ABS module
$20 - WJ ABS sensors
$15ea - UP380046 brake lines (for the rear, going to run an extra line so the modulator can live in the engine compartment, though it could probably mount on the rear axle or under the rear seat)
$3 - 7/16-24 inverted flare plugs

Expected expenses:
* another two ABS modules (only one more required if someone else follows my steps on this, but I need an extra to pick apart for info) - we'll call these 10 each since I'm going to be getting two huge turbochargers, a WJ booster/MC, two WJ ABS modulators, a stack of coil on plug ignition modules, some spare dana 30 shafts, and a bunch of other junk all for $100
* tone rings - probably get these at the all you can carry
* costs of installing tone rings - find out which of my friends are machinists, bribe with beer as required
* custom electronics... this is definitely going to need some.