V2Rocket

What kind of things should I look into if I want to use a different master cylinder on my 944?

I am not doing a V8 swap, but I need the extra space for my supercharger stuff. Honestly, figuring out how to mount the damn thing is pretty much all that's keeping me from going forward, and I've decided that the master cylinder is in the way.

I have found that the master cylinder of the mid-90's Mazda Millenia is less than half the length of the 944, roughly the same diameter, and has a very similar bolt spacing (which means it could attach to the 944 booster relatively easily).

The only thing I can really think of that would be an issue is the operating pressure of the Mazda cylinder vs. the Porsche one and the total area of the brake pistons. The Mazda has 2-piston calipers in front and single-piston rears, whereas the 944 has large single-pistons all around.

I don't have the money to buy the dual-master setup and would probably buy a junkyard MC and rebuild it.

Anything else you can think of?

gt1scca

LOL, I know that now, Spencer.

What is the bore of the Mazda MC?
Front bore of the 944 master (all years and models) is 23.81mm.
Rear bore is 19.05mm, and 20.64mm for the S, S2 and 968.

Wilwood makes a 1.0" bore master that performs OK in a manual configuration.
Also, what is the stroke of the Mazda master?
If the Mazda bore and stroke are close, it should work just fine.

John_AZ

Sponsor 944online has a steel dual use ATE/Girling. IAN may have an answer for your specific need:

http://www.944online.com/cgi-bin/ASI...41+brakes-9441

V2Rocket

i want to keep the vacuum assist if i can, and the mazda mc would almost bolt up to the 944 booster, maybe just use an adapter plate.

i dont know the exact dimensions of the mazda mc, i can tell you it is a very short unit and so i would assume the stroke is short as well.

this weekend i will probably go to the parts yard and just buy it, if i dont end up using it i have a millenia anyways i could use it for

gt1scca

You may be surprised...

For example, the compact Wilwood and Tilton masters have up to a 1.12" stroke, and the entire MC is only ~3.5" long.

If the Mazda cylinder doesn't work out, the Wilwoods sell for less than $80 new.

alex

Are you sure you are going to be able to keep the stock brake booster? It is really intrusive... You might want to plan on going without. On the hybrids board there are ongoing threads about brake and clutch master cylinders and solutions for going without the stock booster.

V2Rocket

ill take a peek over there, i want a setup that is nearly the same pedal feel and brake response as stock, and from what i hear (from the man himself, tonyg) all-manual is pretty gnarly.

thirdgenbird

anyone know the piston size on stock NA calipers?

alex

I only mean that you might not have a choice about using the stock booster, that's all. I would love to keep the stock pedal feel too- but the LT1 won't fit with it. There are other options, though. DVC is using an electrically boosted MC, he really likes it, but I haven't seen a price anywhere yet... and I have a feeling it is not cheap.

There are also other power boost options, but I don't know enough about it to comment more than that. I have heard that the system (bmw, I think) one guy was running he did not care for, so he is trying to go to a manual dual MC setup.

alex

Also, what are you planning on doing for brakes? I am going to do the ls430 cal/boxster S rotor conversion for the fronts. I will probably do the rx7 cal/951 rotor conversion for the rears once it has been finished.

V2Rocket

alex, im not messing with brakes for now, im not doing a swap yet lol, right now im still focusing on the SC!

gt1scca, what did you find the 944 stroke to be

gt1scca

Full stroke for the 944 (1987 N/A measured) is 36mm, or ~1.4".
I couldn't find a specification listed, so I physically measured stroke on a "parts car" master cylinder.

V2Rocket

is there a single piston or two of different diameters?
from what point were you measuring the "bottom" of the stroke?

V2Rocket

bought the mazda master today, got it apart and measured, stroke appears to be about 1-3/16, or 1.19"

bore is rougly an inch. the nice thing is that this MC is exactly half the length of the stock (i believe ATE) 944 master.

close enough?

gt1scca

I think so. 1.4" is bottoming the piston in the bore (944 MC), which is not normal stroke. Normal piston stroke falls short of that to prevent damage, etc.