The Holy Grail (Part Deux)
 

Back with a new junkyard treasure...this one is for all us NA guys (as far as I can tell, ALL NA's, 86-91).

One of my first upgrades was losing the single piston front brake calipers and replacing with the far sexier 4-piston "turbo" units.
I know this is a very popular mod, judging from questions asked on this forum.

Since then I've been relatively happy with the braking but I'm a fairly sedate street driver, so not much was really asked of them.
A month or so ago however a friend drove my car and thought the brakes sucked.
"Your brakes suck", he said and since then I've been hyper aware of how they feel.

"Eh", I thought, "not so bad, really"...but then again, I'm used to them.

When I performed the caliper swap I rebuilt all four calipers, installed all new rotors, pads (Hawk HPS), stainless brake lines and a new master cylinder so if indeed my brakes sucked, it wasn't because of substandard/worn out parts.

I decided that the problem- such as it was- had to lie with the stock NA sized MC...it wasn't large enough for the increased piston size in the new calipers.
This was a problem.

Turbos are rare as hen's teeth in my junkyards...the only one I've seen in the past two years was basically but a shell with little left to pick.
I could just buy a new turbo model MC but it wouldn't fit on my NA booster assembly, so I'd have to come up with a booster also.
This was also a problem.

Having read every thread I could find about brake system upgrades, all that's really available is the mythical 929 MC...which again, only works on the turbo booster.
Well, crap.

I'd now gone from being perfectly content to obsessing about my brakes constantly.

Then I ran across a nugget of info posted by Scathcart.
He claimed to have found not a 1" MC like the 929 unit, but a 1 1/16" MC and best of all, it would bolt right up to the NA booster.
Unfortunately, for reasons unknown, he did/would not divulge the origin of this master cylinder.

At least though, I now knew such a part existed and figured if he could find it, so could I.

And I did (although I have no idea if it's the same one Scathcart was talking about).

A caveat...
The following info does NOT describe a total "plug-n-play" upgrade.
Just like the 929 mod, brake lines will need to be fabbed.
In addition, the brake booster pushrod will need to be shortened and the booster pushrod to MC piston clearance will need resetting.
Neither of these tasks is particularly difficult/expensive/time-consuming...but be forewarned.

Without further ado, allow me to introduce the 1 1/16" Subaru Outback (mid-nineties to 2000 model years, I believe) master cylinder...
http://img.photobucket.com/albums/v78/clocker/MC1.jpg

http://img.photobucket.com/albums/v7...ker/MCsize.jpg

It's already been mounted on a freshly painted (Hammertone black) NA booster and the pushrod has already been shortened by .275". This is slightly more than I calculated it needed but this leaves some wiggle room with the adjustment, so should be OK.
I also made a fresh gasket to go between the booster and MC.

Tomorrow I'll go to NAPA for some brake line(s) and will post what has to be done to get her in all the way and functional.
Then we'll see what the brakes feel like.

Stay tuned.

interesting.

Subscribing and looking forward to the update

Yes, definitely want to see what comes from this.

waitaminute..did you swap out your master cylinder for a mexican one?

Si.

Bueno! :bigok:

subscribed!

South of the border :icon_tup:

I bet this works like a champ. Lookin forward to updates. A bigger m/c bore makes a noticeable difference in applied pressure at the calipers.

so many autoparts now are mexican, ole'

OK, here's today's schedule.

This MC has but two outlets, the stock Mazda unit has three,
I need to find a three way junction to split the front port into two lines- one goes direct to the driver's side front, the other to the proportioning valve (after which it continues to the passenger front).
It looks like the two short Mazda lines from the stock MC can be reconfigured to work, so I'll just need one more line (three way junction to proportioning valve) to complete the circuit.

Since I'm using the stock proportioning valve in the stock location, those two connecting lines will be unaffected by this swap.
If I can locate the junction block properly, the DS front brake line should only need minimal tweaking to attach.
I want this swap to be as non-traumatic as possible, just in case it doesn't work I can simply reinstall the assembly that's in the car now (no parts from that are being used...I have a separate booster, valve and lines to play with).

Outside of the minimal fab required, the only objection- and it's totally aesthetic- I have to the Subie part is the reservoir.
In the Outback, the booster/MC assembly sits at an angle and the reservoir is oppositely tilted so it sits level when installed.
This is not the case in the RX and the reservoir will sit "nose-down" when mounted.
Shouldn't matter performance-wise, but it does look weird, I think.
So I'm going to make a quick pass through the junkyard and see if a better configured reservoir can be found.
One setup that's intrigued me is commonly found on Mitsubishis and features a remote reservoir that connects via tubing to the MC proper...not sure this can be retrofitted but would look cool as hell if possible.

For some reason, 90% of the cars in the yard are missing the reservoir caps so finding a useable part is one thing, finding one with a cap that's not filled with water and crap is another altogether.
The MC I snagged not only had it's cap but was filled with fresh, clean looking fluid and I'm not going to substitute a crummy looking part just to make it sit a little nicer, so we'll just have to see what happens.

Wish me luck.

Ignore if you wish but...When you say "NA brake master cylinder" you mean cars that came with single piston calipers, right? Because the GXLs came with 4 piston fixed calipers like the TII's so I imagine the master cylinders are the same as well.

^^^^^^that's what im wonering to
but i would like to see how this is gonna go?

Just something to keep in mind about the 7's brakes in general, and oversized MC's specifically. Compared to just about any other car i've driven, FC's have a very long brake pedal travel, about double what some other cars are, so if people get into your car from something else, they'll only be used to pushing the brakes down a certain distance with a certain force, and if the brake feels softer (which it will, since its a longer stroke), they may think they suck. I personally like the longer travel since it makes it easier to modulate and a little harder to lock up in a panic stop (altho with the stock braking hardware, i can still lock all 4 wheels with potenza RE01R's). It just takes a little bit of getting used to, but there is plenty of capability there. A larger MC won't increase braking ability at all, it will just change the distance (shorter) and force (greater) required to achieve the same braking.

That being said, good job finding something that improves your car to you, and gives the rest of us another possibility for replacement parts!

It's a nice find, and it doesn't sound like that much trouble to adapt, but...

As Khanartist mentioned, why not just use the booster/MC combo from an NA that had 4-pot brakes? Are there no NAs in the junkyards around you either? Verts and GXLs had them, and I think the S4 GTU did too (I'd check if the specs thread still had pictures :(). It's mainly the S5 GTU guys that got screwed with the single piston calipers. These are the part numbers listed in the S4 & S5 parts fiche:

S4/S5 Turbo Booster: FC06-43-800 / FC06-43-800A
S4/S5 Turbo MC: FCY8-43-40Z
S4/S5 NA Booster: FB05-43-800D
S4/S5 NA MC: FB02-43-400C / FB02-43-400D

There's no distinction made for NAs w/ 4-pot brakes, but it would appear that either they use the same booster & MC as the turbo models. Or the extra "D" part number is a larger bore MC for the NAs. One thing I do know is that my turbo MC had a mounting point for the throttle cable on it, while the MC in my vert does not, but they both had 4-pot brakes. Food for thought I guess. Good luck with your project.

Not sure if this will help, and I'm trying to go by memory, which may have failed me, but I thought there was a 3-way junction block for the brake lines at the rear of my Vert, and I think all 3 ports are female. You might look at yours and if I am correct then perhaps a salvage car would have one, possibly also at Napa.

I thought the 4 piston calipers were for only cars with ABS like my 90 turbo. I'm watching this thread beacuse I was thinking about going to 4 calipers for my 91 NA

No, like I just said, it's just the low-end models that didn't get them.

The OP had me confused there for a while. Yes, the S4 GXL, Sport and TII's (edit: and 'verts and GTU) had the 4-piston calipers, so they should have the 'better' MC and booster, no? In general, if an S4 had factory 5-bolt wheels, it had the 4-piston calipers.

As far as S5's are concerned, even the base ones are 5-bolt, but not all have the 4-piston calipers. Also, I thought the stickies say no GTU model in S5, only GTUs, or am I wrong?

Yes, you are wrong. The base model for S5's IS the GTU. It is far different from the S4 GTU. The S4 GTU became the S5 GTUs.

Unless you are talking about 91 and later 2nd gens, then they were coupes or turbos only.

However, you are correct about which models have which brakes. I am a little suspicious of the 91 and later cars, they may or may not have had the 4 piston brakes.

Subscribed! good luck..

So, apparently my terminology was imprecise enough to generate a slurry of corrections...mea culpa.
My car is a NA that originally came with the single piston calipers.
It has (had) the smallest of the possible MCs.

There, now that's cleared up, I'll carry on.

It's in and bled.
I've driven it briefly.

As it sits in the pics, this was an extremely simple mod to execute.
I'll not detail the four hour sidetrack I took with the Mistsubishi remote reservoir save to entitle it "There Will Be Blood" and underline the note to myself- "New single edge razor blades are very sharp".
'Nuff said about that.

I found several short brake lines and a three-way junction (all on Toyotas) that fit my needs.

It may ultimately be neater to start with virgin lines but I was easily able to rebend these to work and the end result is not hideous.

Without further ado...
http://img.photobucket.com/albums/v78/clocker/MC2.jpg

http://img.photobucket.com/albums/v78/clocker/MC3.jpg

I have yet to adapt the low fluid sensor to my stock wiring but that's no big deal.

I agree with everything you say and the last sentence exactly predicts the results I got.
Pedal travel is significantly reduced- easily 50%- and the initial bite and casual trail braking are seemingly instantaneous but a panic stop takes more effort.
Whether I like this is too early to say, I'll have to drive around for a while and get used to it.
There is no denying that the braking feels much different.

I did notice that there are several Subies with the same MC design (so I know it'll fit) with smaller 15/16 bores and I now wonder what they might feel like.
I've gone from one extreme to the other with this 1 1/16" MC and it's possible that the slightly smaller unit is the sweet spot.

Hard to tell and having just swapped one MC and bled the system, I'm in no particular hurry to do it again.

Don't get me wrong, I'm glad I did this and the results are a qualified success, so I'm going to live with her for a while and see what I think in a few weeks.

Maybe someone else would like to guinea pig the 15/16" MC and tell us what happens.

You are the King of the JYDIY.

Thank you...I think.

A few musings...

-Subarus seem to be the Type O of automotive donors. So far, both my electrical and brake searches have ended with a Subie. Odd, that.

-Mitsubishis and Lexus use the nicest hardware...if you're looking for a rich supply of nuts and bolts, start with them. I rarely leave the yard without a few dozen bits of hardware and when I'm at home trying to mock something up, I can usually find just the piece I need. Look to the interior of the car- under the dash and under interior panels for nice bright and shiny nuts and bolts.

-I freely admit to knowing little about brake system design and this project has me wondering about brake boosters. I originally thought to grab both the booster and MC from a donor car- which would have opened up many more possibilities- but the RX's double walled firewall makes booster mounting stud length a real issue. I couldn't find anything that would work. I must admit here that removing the booster in many cars is a real nightmare, especially with the limited tool selection I carry to the yard, so my efforts were less than vigorous. In comparison, swapping the booster in the RX is a piece of cake...

So now I'm thinking about how boosters and master cylinders are supposed to be matched.
Do larger cylinders require- or benefit from- larger boosters?
Does swapping out the booster- assuming it's physically possible- provide the same noticeable (and predictable) change in feel that the MC does?

Inquiring minds want to know.