Looking good; it's turned into a very clean setup. I like the braided lines, and all of your shiny nuts and bolts make me want to raid a junkyard for fresh replacements.

As many trips to the yard as I've made lately (nearly every day for two weeks), I finally made a "shopping list" for hardware.

One day it's been 6mm nuts and bolts, the next, 8mm, and so on.
Under door panels is a rich source for perfect condition 6mm stuff, rear seat mounting spots are good for 8mm and I always keep an open eye for weird spacers, brackets and doo-dads.
Don't forget rubber body plugs (look in the trunk) and electrical harness mounting clips.
There's lots of weird and wonderful stuff to be found once you train your eye to look for it.

Limit your search to Japanese cars.
Although European cars are also metric, they use a different convention for the thread/head relationship.
On our cars the most common wrench sizes will be 8,10, 12, 14 and 17mm.
On a European car, for the same bolt sizes (and yes, the threads will interchange) the wrench sizes will be 9, 11, 13, 15mm, etc.

Nothing worse than working with a bunch of fasteners (say, on the UIM) and having to stop and find a 13mm socket when all the others are 12mm.
Drives pro mechanics crazy.

This disparity also holds true for American hardware stores.
The 8mm bolts/nuts at Ace Hardware will have a 13mm head instead of the Japanese spec 12mm. One Ace around here has a special selection of "small head" metric fasteners which are Japanese conformant but they have the gall to charge more for them.

Screw that, shop the junkyard instead.

I've read that you can use the complete 929 MC and booster in place of the NA unit, applicable years are between 92-95. I'll be picking one up this weekend and hopefully I like it, otherwise I might have to get one of those 1" MC's to fit the stock NA booster if I want a stiffer pedal. Good work on figuring that all out and telling us all about it.

That's what I originally wanted to do but couldn't find any 929's to pirate.
Lots of 626's- which don't work for us- but not a single 929.

Since I never saw the car, I don't know how easy that swap might be.
If you're lucky enough to find one, make sure you grab it's proportioning valve as well (if it's not mounted like ours), just to give you another option when you install.
Also, pay attention to the location of the vacuum nipple on the booster...if it's not where the stock one is you'll have to figure out how to make it work.
There are a huge variety of formed hoses on different cars that might work out and you should grab one if necessary.
Our hose has the check valve inside it but most cars do not...the standard external check valve will work just fine.

Finally, make sure you are doing this with the correct outcome in mind.
Swapping the MC has no effect on braking distance- that's what the calipers and rotors will do.
All the MC changes is the pedal feel/travel.
This change in "feel" might translate into better braking practice but it would take larger rotors and calipers to significantly affect braking distance.

If you do try the 929 setup, please post pics- I'd love to see it.

It's best to keep the stock proportioning valve unless you really know what you're doing, since the other valve might be set up for vastly different brakes and it could make your brakes go way out of balance, vastly increasing stopping distances.

I don't claim to really know what I'm doing and in general, would agree.
In fact, that's something I considered when I first spied the Q45 MC.

I did a bit of research to assuage my concerns.

First, I disassembled a proportion bypass valve (Mazda's terminology) just to see what it looked like.
Basically, just a spring-loaded restrictor...actually pretty crude.
Then I looked at the FSM, which makes no distinction between the single and four-piston caliper systems when speccing the proportioning valve...I believe Mazda uses the same valve for both.

This lead me to conclude that the basic function of the valve is simply to prevent the rear brakes from locking before the fronts and our stock valve (along with the Toyota unit I also took apart) was not especially precise in how this was done.

In theory, the integrated Infinity valve appears to function identically to the Mazda unit although the Infinity part cannot be taken apart, so I'm only speculating. Duplicating the function would explain why the Infinity outlet ports are reversed from normal practice...the front circuit is the rear port, the rear comes out the front (OK, that just sounds weird...).

Anyway, the point of all this is to say that I think that the braking systems would have to be way different- say rear drum instead of disk- before the proportioning valve would make too much difference.
On a street car I doubt you'd ever notice and if the car is tracked, I'd hope you have a better and more precise valve to work with- if not twin cylinders with a bias bar.

None of this is meant to discount your advice, Black91n/a, and I did state previously that the 1" Subie cylinder with the stock valve was my main recommendation- but if someone wanted to get a bit further into the experiment, a different valve might be interesting ( and more easily adaptable) to try.

As an aside...
Yesterday I had the opportunity to make a "panic stop" under controlled (albeit wet) conditions and the brakes worked perfectly.
Not a scientific test but comforting nonetheless.

Thought this was over, eh?
Nope.

Earlier in the thread I casually wondered about the relationship between booster and master cylinder.
Does a larger MC require- or benefit from- a larger booster unit?

I've done some reading and the answer seems to be "Yes".

The cars that originally came with the 4-piston calipers have a different booster- physically smaller but twin diaphragm.
Of course, finding a suitable booster to try on our cars is not as simple as finding the master cylinder but a phenomenal twist of luck put such a unit right in my hands.

Wandering the junkyard last Saturday- getting ready to leave, actually- I glanced at a car in passing and stopped short.
I could see a Honda sticker under the hood and what grabbed my eye was the booster assembly.
Most- if not all- of the Hondas I've looked at have the master cylinder mounting bolts clocked at an angle instead of horizontally like ours. I've pretty much ignored Hondas as a source for cylinders/booster for this very reason.

This one though was horizontal and because the engine was already gone, I could get a good look at it.
T'was obviously a dual diaphragm booster (they have multiple steps on the sides) and looked to be the same size as my single diaphragm unit (approx. 9.5").
The master cylinder was also MIA and when I looked inside the cabin, someone had already undone all the hardware...back in the engine bay, I simply lifted the booster out.

I walked it over to the (only) RX7 in the yard (whose booster I'd already procured a few weeks ago) and it popped right in.
A perfect fit.
Stud length was identical to the stock Mazda piece (2"), diameter was the same...the only difference was the Honda part was about 1" deeper.
Looked like it'd work.

I bought it.

BEYOND HERE BE DRAGONS...

At home, a side by side comparison showed that the Honda booster had two significant but overcomeable differences.

First, the shaft that the clevis fits on was 8mm instead of 10mm like the Mazda's.
The Honda clevis was too short and too narrow to fit my aluminum brake lever, so that would have to be changed somehow.

Second, unlike any other booster I'd looked at, the Honda did not have an adjustable pushrod for the MC and it was clearly too short for any of my master cylinders.

The clevis was a simple fix.
I took the stock Mazda clevis and threaded a 8mm helicoil into the 10mm threads.
Worked like a champ and the clevis now threaded onto the Honda shaft.

The pushpin was a bit harder and required turning an adaptor to slip over the pushrod and extend it the necessary amount.

All told, both mods took under an hour and the booster was ready to install.

Because of the braided steel lines I'd already put in place, the front brakes were able to remain connected as I removed the master cylinder and old booster.
The rear brake is a hard line and had to be undone.
No biggie, I took this opportunity to install the new speedbleeders on the rear calipers and was soon all done.

Now for the $64,000 question...did it make a difference?

Oh yes, it certainly did.

In fact, of all the changes I've made so far- including the initial swap from the 7/8" to 1 1/16" MC- this was the single most dramatic difference in feel.

I don't know how to describe it really but it feels like I've doubled the rotor and caliper sizes...this thing feels like it has BRAKES!.

Need more seat time with them to get a better idea, but I'm pretty stoked.

If anyone is interested, the Honda booster came off a 1997 Integra GS-R.
It's the only one like it in the yard so I don't know if any other years or models use it.

If you can deal with the (relatively) minor mods needed to adapt it, this would make a perfect match to your upgraded master cylinder.

I too would like to see.

Great find. i wonder what the feel would be like with just the booster upgrade and stock MC?

Here in Houston a Integra GS-R would never even make to to the junk yard. The ricers would be all over it.

I wonder if a standard Integra or Civic booster would work?

Just wondering, why don't you think a 626 booster/MC will work?

My guess is that you would be overboosted but I am no expert, so feel free to try it.
I am not aware of the science behind matching the two units but have to figure that the OEM engineers are and they put smaller boosters with smaller cylinders.
From what I can tell after a bit of online research, the Integra came with a 1" cylinder to match this booster, so I'm in the right ballpark.

Remember...none of what I've done affects the actual braking, this is all done to alter the "feel".
To physically change the brake performance you'd have to go to the wheelwell and change caliper piston size, rotor diameter, pad characteristics and tires.

IIRC, the studs on the booster aren't long enough to clear our firewall.
Either that or the bolt pattern is wrong.

I've looked at so many cars that they blend together but I do remember ruling out the 626 as a donor.

That's not entirely true. I've done quite a lot of looking into alternate brake bias valves and I've found that there's a HUGE variety of biases out there. Everything from weight distribution, wheel base, disk diameter, piston diameter, number of pistons, tire size and especially ABS affect it. Case and point is the Miata, much remained the same from 1990-2005, but it had about 5 different valves as the brakes got bigger and the ABS was added and got more sophisticated. For "normal" driving you probably won't notice, but for panic stops you might end up going backwards into the bushes if you get it wrong and will almost certainly end up with longer stopping distances as the bias will probably be worse.

Moral of the story is that the bias valve needs to be matched to the brakes at the wheels and the car, NOT the master cylinder. Unless you really know what you're doing keep the stock valve.

In theory, I suppose I would have to agree.
In practice however, I can absolutely guarantee that my stopping distances have not gotten worse, nor does the rear end want to lock up.

Unfortunately, I have no way to quantify my "foot dyno" impressions with hard data, so I'll accede to your more theoretical advice.

Just out of curiosity, have you seen the pressure graphs for the five different examples of the Miata or are you just going by part numbers?
A simple change in the config of the part- say, a relocated mounting tab- would result in a new part number even if the actual performance was identical.

A sterling- and closer to home- example would be the S4 and S5 NA BAC valves...two different part numbers but the same part, difference being the connector shape and nipple orientation.

Had I been more prescient, I would have tried to come up with some sort of "before/after" data to semi-validate the at-this-point unprovable statement that I have gone forwards, not backwards, with these mods.
When I started the process however, I had no idea that I'd get as deeply into it as I did- certainly not to the extent of deleting the prop valve.

It's possible that in a few weeks I could arrange a comparison between my car and a T2 (it's in the finishing stages right now) but since we have different tires and brake pads, it would be a very questionable dataset.
At this point, reverting back to the stock setup to make a more valid comparison would be arduous at best and, given that I'm not trying to sell this project to anyone, pointless from my perspective.

I do appreciate your caution Black, and believe me, would not have posted the project if I felt it was reckless or dangerous.

I suspect that most folks will stop at the larger MC swap that retains the stock lines and valve, so your concerns would be allayed.
I on the other hand, am happy with the setup I ended up with and feel perfectly comfortable with the brake performance it provides.

http://www.flyinmiata.com/tech/stock_bpv.php

Info on the different valves is in the link above, notice how different they are (although their way of calculating "bias" is wrong).

My dad's 1992 Miata has brakes off of a 1994 and he swapped from the stock 1992 valve to the 1994-1997 non-ABS vavle and noticed that the front lockup he'd been having on track got much better. I know the FC has too much rear bias on track, so I think the 1994-1997 non-ABS valve might be better, but I'm planning on using an adjustable valve.

Note also that different pad friction coefficients will change the bias, since the brakes will need different amounts of pressure to apply the same amount of torque to the wheels.

Any valve will be imperfect, since it's only a 2 slope curve, but they can be better or worse and it's almost certain that a non-stock valve will be worse.

I got my 929 booster and MC, I'll report back once they're in and I'll get some pictures. It certainly looks like it'll work, but don't hold your breath on the report, it may be a while before I get to it, I've got a lot of other stuff to do too.

Isn't there a hint of "Do as I say, not as I do" here?

If "it's almost certain that a non-stock valve will be worse", how do you justify swapping out valves and ending up with an adjustable one?

As you note, simply swapping the brake pads will affect bias and who among us is still using OEM pads?
Furthermore, like many here, I've also changed wheel diameter and width, both of which will also change brake performance.

As always, when modifying any system, especially one as crucial as the brakes, the onus will fall one each builder to monitor the resulting performance and proceed accordingly.
To make a blanket statement that any change from stock will be worse seems a trifle too broad though.

Good luck with the 929 swap, like to hear about the results.

I'd put myself into the category of "unless you know what you're doing". For me, at the track, the stock valve gives too much rear bias, so I'm planning to use the adjustable one to get the bias back to where it's closer to ideal.

Fair enough.

What does too much rear bias feel like?
Obviously, totally locking the rears and still not stopping would be an extreme example but the valves you've tried are only subtly different, so what's tipping you off that it's still not right?

Locking rear brakes is what tipped me off. This is bad as it's unstable and can lead to a spin, but it also means that you can't brake quite as hard as you could with perfect balance. It's a common issue amongst racers.

I haven't actually used any other valve, I figure I'll just go straight to an in-cockpit adjustable setup so I can make it just right. I looked up the specs for a lot of valves and some are WAY different, I can tell you that much right now.

One thing to add about the 929 MC, be sure to get the banjo fitting that goes on the front port of the MC. It may be very difficult to source the correct parts needed to make the proper connection without it.

What kind of banjo is it, a double, perchance?
Mitsubishi Monteros use a sweet double banjo if you need one.

Jeez, I know way too much about obscure brake hardware now.

A couple comments here -

One item that was not mentioned that affects brake bias is the weight and location (height) of the center of mass of the car. That will affect the weight transfer from the rear to the front and thus the brake bias.

Size and type of tire will also impact this. In fact our actual braking distance is pretty much governed by the tires, rather than the size and type of brake system (but the bias does come into play here). If you can can lock up your tires, then your callipers and rotors are not your limiting factor in stopping.

In racing you are attempting to use every single ounce of traction you have without locking up the tires. This is called Threshold Braking. Once a tire locks up you lose traction on that tire. If the rears lock up first, the back end loses grip and will try and pass the front end going into the turn, which is a Very Bad Thing.

What does it feel like? Like the back end is completely loose. Not fun.

You want to adjust the bias so that the fronts lock up just a hair before the rears. That way the front will lose grip first and the chance of a spin is reduced.

So many things affect what the correct rear bias should be set to. The grip of the tires under braking, the weight of the car, wheelbase, the weather (you need more rear bias in the rain since you don't brake as hard). It's no surprise that Mazda tweaked the bias setting for the Miata as they introduced and developed the models.

-b

Just a single banjo that has a 10mm female flare on the other end, so that you can hook your brake line to it. There's a picture here: http://robrobinette.com/mastercylinder929.htm

The FC swap will be similiar, but will require the use of a tee to get the two front lines to hook up to the single front port on the 929 MC (at least for a non-ABS FC and an ABS 929 MC).

Update:
Brakes have been working fine.
Even had to make a semi"panic" stop the other day when the moron in front of me tailended the car in front of him...my car stopped with no drama or weird handling...road was wet, too.

However...it's been in the back of my mind to try the big 1 1/16" MC again now that I have the larger, double diaphragm booster.
That MC had the best, most positive "pedal feel" but needed a lot of effort with my original booster, something I thought should be a non-issue now.

Black91n/a would be happy as well since I'd have to reinstall the stock Mazda proportioning valve.

Since I had completely redone all my hardlines to fit the last install (oh, optimism!), this "reconversion" wasn't as simple as it should have been and I had to cobble it together figuring that I'd tart it up if I decided to keep it.

For those not keeping up, the "new" system has the 9 1/2" Integra double-diaphragm booster, the stock RX7 proportioning valve, a Subaru 1 1/16" master cylinder and freshly rebuilt calipers with braided steel lines and Hawk HPS pads on all four corners.

Based on my past results I was expecting a short throw, firm pedal that didn't require undue force to operate.

That's not what I got.
Car stops fine but the pedal travel is longer than I remember from the first time I had this MC in and effort is not as linear as I expected.

I'm thinking that I may have miscalculated the booster pushrod to MC piston distance and there is slop in there that shouldn't be.
This Integra booster does not have an adjustable pushrod and I'm having to make spacers that slip over it and extend it's length to mate to the recessed piston on the MC.
I thought I was careful in my calculations but it feels like the pedal travels a ways before braking actually starts, which is exactly what I'd expect if the pushrod is too short.

This pushrod length is a pretty finicky adjustment- 10 or 20 thousandths can make a lot of difference (brakes will drag when the rod is too long) and even though I've done it before, I think I screwed it up this time.
Fortunately I used braided lines for the connections to the master cylinder, so it can be slipped off the booster studs without undoing anything (I am really getting tired of bleeding brakes!).
This means I can slip on a new rod spacer without much trouble and see what happens.
That's the plan for today.

Frankly, after all the time I've put into this project (it;s now been over a month), I look back longingly at the twin MC/bias bar set up I fabbed up for my 240Z.
No booster, no proportioning valve, much simpler plumbing.

Knowing me, no matter the outcome of today's labor, I'll probably explore that option next.

*sigh*

Thanks for being the guinea pig for this stuff. Tons of great info.

You're welcome, although I must admit, "taking one for the team" was not the original plan.

I pulled the MC (again!) and recalculated the pushrod extender length...turns out I was spot on the first time.
Since I was unhappy with the results and it's so easy to swap, I decided to make a new, longer one anyway. I figured that the worst that could happen was the brakes dragging for a little bit.
My driveway has some angle to it and I decided that if she'd "free roll" in neutral I'd risk a longer ride.

The original measurements lead to a pushrod that was .625" with a .400 recess to slip over the Honda rod...so I was extending by .225" to mate with the MC piston.
I made a new piece (with the same recess) that was .685 long and figured I could whittle it down if need be.

Doesn't seem to be necessary.
Even with this "preload" on the piston, the brakes don't drag...I must admit I'm somewhat at a loss for an explanation.
Pedal travel is back to what I expected and the whole "feel" is quite good.

I took her out for a short (20 mile) drive to get some heat into the system and everything stayed kosher- no drag, no loss of pedal, etc. Didn't have occasion to make a really hard stop but normal type braking is the best it's been so far.

So, I guess I'd call it a success.

Now to start calculating for the twin MC setup...

Well, I now have an "explanation".
The brakes DO drag, it just takes a few hard stops to make it happen.
I traveled a very twisty, curvy road today and by the bottom the brake pedal had almost no play left at all. They weren't seized but getting close, I think.
Fortunately, I had come prepared and ten minutes later the correct spacer was in and all was good.

So, for the record...DO NOT SCREW WITH THE PUSHROD LENGTH.
Make sure it's correct and let it be.
You CANNOT "tune" the brake feel by preloading the MC piston.

Live and learn.

Fate conspires against me.

As I wandered the junkyard yesterday I had to make way for one of their giant forklifts bringing in a new victim...er, car, which was dropped almost literally at my feet.
It was a 929, the first one I've seen since I began this brake treasure hunt.
There was no hesitation or questioning, I knew I was going to nab the booster/MC- after all, this was the mythological combo that triggered the whole quest in the first place.

The car was intact, engine in place.

Looking back on it, I wonder what the book time would be to R&R a Mazda 929 booster assembly, cause it ain't easy to do. After clearing away the obvious impediments- wiper motor, cruise control actuator, various hoses and electrical runs- I thought I was ready to weasel the booster out.
HA!

Not gonna happen.
OK then, remove the MC from the booster, something I'd been hoping to avoid so brake fluid wasn't dripping all over the place.
Helped some, but still no go.

Long- agonizing, frustrating, sweaty- story short, I ended up removing the entire intake and driver's side valve cover before the booster was able to be squeezed- by the hair of it's chinny, chin chin, out off the firewall.
Took 3 1/2 hours all told.

So, what did all this effort net me and, more important to the (hazily distant) spirit of this thread, how difficult is this combo to adapt to a stock RX?

The booster is deeper than the single diaphragm unit I started with (lo, these many iterations ago) by about 1".
Shouldn't be a problem for most folks.
The port for the vacuum hose is on the wrong side- think 10 o'clock instead of 2 o'clock- and poorly angled...the vacuum hardline on the firewall will have to be modified to suit.
On the upside, the booster pushrod is a 10mm thread, so the stock clevis for the pedal will screw right on.
Thank Jeebus for small favors.

The master cylinder itself has but two outlet ports instead of our stock three.
Fortunately, the front circuit port (at the very end of the unit) comes stock with a banjo, so it's already machined flat and will accept the two port banjo from the Mitsubishi Montero I noted previously.
The stock proportioning valve bracket from the RX will not fit, you'll be on your own figuring where and how to locate this valve.
The 929 low fluid sensor looks strikingly similar to the stocker- even down to the connector- but if it won't work, I'm sure the RX piece will go right in...the reservoirs appear identical save that the 929 part has a screw retaining tab and my stocker does not. The reservoir caps will interchange.

All in all, starting with a stock car, swapping to the 929 set up would not be terribly difficult as long as you were careful with the proportioning valve placement. You'd have to tweak the hardlines to mate with the valve and the driver side front line would need a bit of bending as well, but nothing too major.

I suppose I'm almost duty bound to install this and report on how it feels but the prospect does not thrill me- I've installed more boosters/MCs in the past month than most folks do in a lifetime.
If it does go in, it's going to be the final install (oh yeah, like you haven't said that before!) before winter, so I'll redo the hardlines (again!) to make it look pretty. I'm going to clean and paint the booster first- it took some abuse trying to get it out- so it looks nice as well. I'll also have to fab up some sort of bracket to mount the prop valve...so anyway, it may be a week or so before I know whether this is truly the "Holy Grail" or just a tin cup.

I'll keep you posted.

Damn dude you really been threw some headaches with this lol.

The guys at the junkyard where I got my booster indicated that the engine had to be pulled, you seem to have pretty much confirmed this.

I should be starting in on my install this weekend, but I won't be able to report back for a while, as I'm still waiting on some parts that I need to finish the job. I'll do a writeup when I'm done.

Well, pulling the engine would have made life a lot simpler but was not an option, so I did what I had to do.
I usually try to be respectful towards my donor cars- and the people who will follow me picking at it- but I admit that halfway through this removal, all the nice-guy stuff ended and I went medieval on it's ass.
Sadly, this car was not up on blocks and I couldn't access the engine mounts, which would have been my first choice...undo the motor and just wedge it over the necessary 1/2", done.
Oh well, what's done is done.

Well my 929 booster and MC are in the car and I've hooked up the front lines (came from a 1992 929 with ABS if anyone wants to know). Because I'm ditching the stock proportioning valve and going with one that's adjustable from the driver's seat, I've got some more plumbing changes to make for the rear lines, and I've got to wait on some fittings for that. Because of that it'll be a while before I can report back on how it feels. I mounted a tee for the front lines on the proportining valve bracket (same tee as on the rear axle). I trimmed the bracket so that it's only held on by the one nut, which I'm hoping will be alright, as the reservoir gets in the way of it reaching the far nut. The 929 reservoir looks bigger than the FC reservoir (seems appropriate, bigger MC needs more fluid) and the connection on my sensor was different, so I swapped in the FC sensor, it fits right in. The clevis definitely needs to be swapped since it's narrower than the FC one.

I took some side by side pictures of it and my stock MC/booster, I'll post them up later.

Well here are the pictures, 1992 929 ABS MC/booster on the right, stock 1991 NA non-ABS FC on the left.

Yup, that's it all right.
Shown in the third pic is the reversed vacuum line nipple, in the greater scheme of things not all that big a deal, but worth noting.

Also semi-visible is the difference in outlet ports, again, pretty easy to overcome (especially if you've been hoarding brake lines/fittings like I have).

Neither the extra depth of the booster ( see pic 2) nor the extra height of the reservoir (pic 3) should pose any problems for a stock car.

Did yours not come with the prop valve and it's bracket?
Neither are particularly useful, just curious.

A quick comment about the clevis...because of our "racing" aluminum pedal assemblies, the RX has by far the widest clevis of any car I've seen in yard.
It's a blessing that the input shaft of the 929 booster is the same thread as the RX and the clevis will simply screw on. This is not the case with some of the other boosters I have and makes for one more step to deal with.

That's all that it came with, minus the banjo fittting which I hadn't figured out that I needed. I bought it from the Mazda dealer as I had a bunch of other stuff to get from them anyway.

If you are able to perform your own picking at the yard, the 929 w/ABS not only has that banjo on the MC but 3 identical banjos on the top of the ABS unit...which I snagged, naturally.
The ABS also has a couple of short, interestingly configured hardlines that are worth nabbing as well.

My 929 combo is all set up and ready to install- made a new bracket to mount the prop valve and installed the Montero double banjo on the front port. Painted the booster, cleaned the MC and reservoir.
Opened the hood of my car, stared at the current brake set up, stared at the 929 unit...and decided not to bother.
I already have the bigger double diaphragm booster and a 1 1/16" MC and it's all plumbed in and working fine.
Can't really see how the 929 could be any better (although I'm sure it's better than the stock combo).

Think I'm just going to call it quits and sell off the 929 set up.
So Black, it's up to you to tell us how you like this one...

I should have all the parts I need to put the car back together by the weekend (doing more than just the brake work), so hopefully by next week I'll be able to report back on how it feels.

The siren call was too much to resist...I decided to try the 929 setup myself.

It wasn't the MC or the booster that intrigued me, it was the proportioning valve that it had.
On the two output ports were large hex extensions that the lines screw into...I'd seen similar looking parts on a few MCs but didn't pay much attention (and didn't know their function).

Did some research and found that they're residual pressure valves, meant to retain a minimum pressure in the lines to increase the pedal firmness. They are commonly seen on cars where the MC is lower than the calipers (think floor mount pedal assembly) and gravity would cause the fluid to drain back to the MC.

I thought it was odd that the 929 would use them since the MC wasn't low and was curious how they worked. Both Wilwood and Tilton sell these valves and I read all the install PDFs to see if they were position sensitive and saw nothing to indicate they were. I investigated this because I wanted to mount the prop valve horizontally below the MC to make a cleaner install.

I also decided not to push my luck with an unknown bias curve, so I swapped the spring from a spare RX valve into the 929 valve- they are physically almost identical (the 929 part has two mounting holes instead of one), hoping to keep the front/rear bias consistent with my previous experiments. Kind of waiting on Black91n/a's results with the aftermarket adjustable bias valve before spending the money on one.

It was pretty simple to plumb the MC/prop valve to achieve the layout I wanted, here's how it looks installed...
http://img.photobucket.com/albums/v78/clocker/929mc.jpg

Note the Mitsubishi Montero twin banjo fitted to the front circuit outlet port (ignore the plug in one hole, it was later removed)...this not only gave me the two ports I needed but also meant that both front calipers would enjoy the benefits (presumed, at this point) of the residual pressure valve.
Also note the layout of the vacuum line nipple.
I had originally planned on modifying the firewall hardline to better fit this layout but I had a hose with integrated check valve that was useable, so I delayed the modification till I decided it would be permanent.

I remade the front brake circuit hardlines to better fit this new arrangement...
http://img.photobucket.com/albums/v7...ker/929mc2.jpg

...which eliminated the braided steel softlines and several connection points.
I've actually come to enjoy the challenge of fabbing nice looking hardlines...it's not as easy as it looks but done correctly, makes a big difference in the engine bay appearance.
I keep meaning to redo the line for the rear circuit but am waiting till I finalize the booster/MC to do so.
I've also considered investing in a pro-quality flaring tool so I can make lines from bulk hardline and quit depending on generic pre-made lines but that will have to wait. Besides, for a part like the front passenger side hardline it's actually simpler to bend and use two pieces with a splice connector than attempt to weasel one piece into position around all of the engine bay components. Try removing the stock line with the engine installed and you'll see what I mean.

I had a dinner engagement last night so I ran out of time to bleed the system, that's on the agenda for this morning.
Should be interesting to see how this works out.

System is bled...finally.
For the first time during this long journey I had to bench bleed the MC, I couldn't get anything to happen on the rear circuit.
Made up a quickie bleed kit from a spare chunk of hardline and a few inches of soft tube, gave it a few quick pumps and was good to go.

Took a short test drive through the neighborhood to confirm that I actually had brakes- always a good thing to check- and am ready for a real run.

The pedal feels quite different...very short throw- by far, the shortest yet- and very firm.
Oddly, for as stiff as the pedal feels, it's quite easy to modulate.
At first I was concerned that I'd installed an "ON/OFF", all or nothing type of system but that doesn't seem to be the case. Some seat time will give me a better idea.

Now I need to get a longer drive in to get some heat in the system and see how she responds.
I guess my main concern is that the brakes will drag- after all, the residual pressure valves are supposed to make the brakes drag a little, just not enough to hurt.
In theory, at least.

We'll see.

Can you give us some more info about what adjustable prop valve you are using? pics? source? Would be lovely, thanks

I'm sure he'll chime in when ready but I'll bet he's using either a Wilwood or Tilton unit.
The Wilwood is the cheapest and most common, it's rebadged and sold by many "speed" companies.
As far as I'm concerned, the downside to the Wilwood (and it's clones) is that it is tapped for a 1/8 NPT and supplied with an adaptor for -3AN tube nuts. This means your stock line won't fit and so far I've been unable to find a 1/8 NPT male to 10mm x 1 female fitting, so a custom line would have to fabbed up.
The Tilton comes with the correct metric port but is almost twice as expensive- best price I've found is $90.

I took a longer drive...or, to be more accurate, I attempted to.
Brakes began dragging severely within 10 miles, so bad that I had to stop and let them free up several times as I limped home.
Giant PITA, believe me.

During the long limp home I decided that the problem had to lie with the residual pressure valves...maybe suitable calipers have some sort of adaptation to accommodate the extra line pressure or something, I don't really know.

This left me in somewhat of a pickle as the new brake lines were perfectly fit to the prop valve with the residual valves in place, losing those valves would mean all new brake lines (again!).
In a fit of desperation I decided to attempt gutting the residual valves and using them as spacers only, thus preserving the current layout.
I chucked one up in the lathe and turned down the end, which appeared to be folded over to retain the innards.
This proved true and a spring and valve assembly popped right out leaving an empty hex piece that wouldn't affect the line pressure at all.

Reassembled and rebled the system.
First test ride...OK.
Second- longer- test ride- OK.

I think it's going to be fine but I'll not be convinced till she's been run longer.

Pedal travel increased about 1/2" (now totals about 1") and the ultra firm feel has disappeared...this combo- the 929 MC/booster + RX7 prop valve- is just about equal to the last few setups I've tried.
Definitely better than stock.

I guess my last option before stopping will be the adjustable valve that Black91n/a is going to try so I, like everyone else, will just have to wait and see what he thinks.

I ended up getting a Wilwood lever type valve from Summit Racing and some 1/8" NPT to M10x1 inverted flare adapters from Flyin' Miata: http://www.flyinmiata.com/index.php?...umber=14-76255

I managed to brake one of those 1/8 to M10 $11 fittings and had to drill it out to extract it from the bias valve, but managed to save the valve (probably my fault, I think I tightened it up too much). So now I'll be using inch size flare nuts with the Wilwood supplied adapters, if I can get some today, being a holiday and all. I've got the lines run to where the valve is going to be, right beside the shifter on the passenger side of the tunnel. I managed to use a single piece of line from the MC to the valve and then another single piece from the valve to the tee at the back (requires transmission and exhaust removal). I did it that way to eliminate the joint where the stock prop valve was and to eliminate the need for another couple joints to splice in lines to and from the stock line to the rear. I also re-made the front left hardline to make it reach the tee I added where the stock prop valve once lived. It's a bit tricky feeding the lines in through and around everything, but it's doable. A note to those who think they might try it, make a template out of a short piece of line for the section going up and around the tunnel, then copy it onto the finished piece, that way there's much less risk of screwing up a large piece of line. Also, make sure to secure the line to the chassis and use gromets where the line goes through the tunnel.

Lots of racers have done what I'm doing, that is taking out the stock valve and adding in an adjustable one, so it's nothing new really. I'll report back as soon as I've gotten a chance to drive it, but there's still quite a bit of work left to do on it, and I don't want to put the transmission back in until I've had a chance to bleed and pressure test the system.

Why the lever instead of the infinitely adjustable screw type?
The convenience factor?

Well, I found a new thing that it's possible to screw up.
A longer test ride this AM locked up the brakes again.
As I sat by the side of the road I tried to think of what could be the cause...I'd eliminated the residual pressure valves, so that couldn't be it and the MC and booster had been removed as a complete unit from the donor car, so I doubted that booster to MC pushrod was misadjusted.
The only adjustable thing left was the pedal to booster pushrod and that had been set to the same length as all the other installs but it was the only logical option left short of deciding that the booster was faulty.
Unfortunately, I had no tools with me- ever the optimist!- so the only thing I could do was pull the vac line from the booster and release the assist.
This immediately freed the brakes.

I managed to make it home, although not having the vacuum assist working meant that I essentially had no brakes.
Let the car cool down and checked the brake pedal free play.
None.
Loosened up the adjusting rod till there was about 1/8" play before I could feel the rod engage with whatever it is it does in there and drove for a while to heat up the brakes.
Stopped, and checked freeplay, which had decreased.
Without adjusting anything I drove some more.
Brakes didn't drag so I increased speed and made a few harder stops (I'm in a giant Costco parking lot which has become my personal test area).
This time when I stopped I adjusted all but a RCH of the freeplay out, figuring that the system had heated up to it's normal temp.
More test runs/stops and all is still good.
Out onto the highway and several stops from higher speed and she's still fine.

So, I may have figured it out.
Now I'm sorry that I sacrificed the residual pressure valves to my misdiagnosis but that's the way it goes when you fumble around in unknown territory.
If I spot another 929 in the junkyard I'll pull the prop valve and maybe try it again.
Maybe.

Anyway, the moral of the story is don't assume anything on your adjustments.
Start loose and fine tune till you're right.

I hope I can remember my own advice...

I figured it'd be easier to tune from the drivers seat. While I won't be able to get as close to perfect on the setting, it'll be easier to change for changing conditions (ie more rear brakes when wet) while being able to change back to the original setting. Besides, how close to perfect could I really get with a knob anyway? It'll always be somewhat imperfect.

I may decide to go with a knob later on, or if I'm feeling really ambitious, I may try to make a lever arrangement with more levels of adjustment, focused more around the range that I need. I don't really need it to be as adjustable as it is now, since I'll really only ever set it to two or three settings, so it'd be nice to have, say 10 settings in that narrow range to get the best of both worlds.

I'm guessing that once you get it dialed in you'll hardly ever touch it again.
Pics of the install?

I'll post up some pictures later, but for now I'll be concentrating on getting the transmission back in and generally getting it back together. It won't help that I'll be busy the next 3 weekends either, so it may take a while.

I would assume so, since I can lock up the rears for sure, even with race tires. The brake booster/master cylinder change is a mod for feel ONLY. It has nothing to do with adding braking force or anything along those lines. The different proportioning valve in my case is because on track the car will lock the rears before the fronts, which is bad.

Yea. That's pretty bad. Do you have it balanced now? What are race tires? Slicks?

I haven't had a chance to get the car back together yet as I've been busy and I managed to sprain my ankle playing rugby. The race tires in question were Hankook Z211, hard compound, 225/50/15.

Back from the dead, seven months later...because I never stopped working on this project (just stopped writing about it).

Two major news items to impart...

-No matter what your brake system is now (assuming basic functionality, natch), the easiest and by far best bang fer the buck mod you could do is adding a master cylinder brace.
I had been aware of the concept for a while (see Black91n/a's excellent writeup here) but it wasn't till I was working on the project car (FD) that I saw how dramatically the firewall and booster can flex if left unbraced.
I immediately made one (albeit simpler than Black's) for my dd FC.

Seriously, this is one mod that will produce an immediate and easily perceptible result...your pedal feel/modulation will improve.

Note: All photos are of the FD but the concept and execution are functionally identical. This is also true for the MC/booster info to follow...)

My braces are just simple truncated triangles cut from 3/16" aluminum plate.
They mount just as Black91's do and the ends were filed/sanded to butt flush against the MC end.
When installed, this flat plate brace does not hit the MC dead in the middle- it's offset by @1/8".
Since these were prototypes I figured I'd deal with that later, I was more interested in the results and hoped this offset wouldn't matter.

In practice, it does not.
I could (and probably will) tart the design up and make it fit perfectly but the simple easy design works just fine.

You should try it.

-I have continued my pursuit of suitable swap candidates for our cars.
My FC currently sports the booster/MC from an Acura Integra (1" bore diameter, twin diaphragm booster) which in my opinion works just as well as the 929 parts
(to be fair, I never tried the 929 setup with the brace, so results aren't directly comparable).

Always in the back of my mind was the 1 1/16" Subie MC and the inconsistent results I'd gotten both times I'd tried it.

While researching the Honda parts I came upon a thread where the Integra guys were upgrading their systems to a different model booster and describing dramatic improvements.

I took this with several grains of salt but it did get me thinking.
Prior to this I'd never given any thought to the possibility that boosters were "tuneable" for feel and pretty much figured that one similarly sized booster was the same as any other.
If this wasn't true, perhaps my large Subie MC needed the matching Subaru booster to work as intended.

Now, there's a reason I had never tried this.
Subaru builds their chassis around the brake booster.
Swear to god, it's ridiculous how tight the confines around the booster are, it took me nearly an hour to weasel it out without scarring it up (the donor car was a 1997 Subaru Legacy 2.5l GT and the engine bay was empty).

With a matching booster and MC finally in hand, I prepped for install into the 3rd gen (which, bear in mind, has a nearly identical brake system to the FC). One nice thing about this Subaru booster is that the input shaft is 10mm, so the Mazda clevis will screw right on- Honda and Toyota use 8mm which requires modifying your stock clevis.
This is it plumbed to fit our custom hardlines...
http://img.photobucket.com/albums/v78/clocker/Red36.jpg

http://img.photobucket.com/albums/v78/clocker/Red35.jpg

And installed into the FD...
The brace is also visible in these shots...
http://img.photobucket.com/albums/v78/clocker/Red39.jpg

http://img.photobucket.com/albums/v78/clocker/Red40.jpg

The setup is superb.
A worthy upgrade from the 929/Integra brakes, IMO (I'm now hunting one for my FC).
Pedal is firm, responsive and surprisingly easy to modulate.
I had been afraid of ON/OFF brakes with this much larger MC but that is not the case.
Paired with the brace, I don't see how you could do much better with stock calipers/rotors.

When I do find a candidtae for my FC, I'll also be trying the 929 proportioning valve with residual pressure valves.
Dunno how that will work but it's the last variation I can think to try.