I'm interested in finding a chart similar to the following one for the miata http://www.flyinmiata.com/tech/stock_bpv.php listing how the proportioning valve in the FD modifies the line pressure.

I'm also wondering if there was a different proportioning valve for the 99+ cars. I know they changed the size of the vacuum assist unit (I believe giving less assistance than previous models). Did the master cylinder size stay the same throughout all years of the FD?

As you can see looking at the link for the miata, mazda started off really conservative with the rear brakes, and throughout the years made the car more and more fun (bean counters at mazda would probably say more dangerous lol). I'm wondering if mazda did that with the FD as well. Like the FD, the miata had a "sport" brake package available which increased the rotor size by pushing the calipers further out... just like 99 brakes . Cheap and effective. Mazda also did some other interesting stuff for 99 like decreasing brake vacuum assist, decreasing power steering pressure, etc. I'd love to make a definitive list of all the "tweaks" cause we've kinda been living in the stone age with the 93 parts... that was just the first stab at the FD and it got progressively better over the years

-Heath

Miata Proportioning Valve Chart:

 

Never seen that info for the FD. You'd probably have to manually put something like that together with a brake pressure gauge or something.

This also seems to be something for a brake engineer, that sort of stuff gets over my pay grade .

Dale

 

I have a feeling the ausies may have some info as they have access to both 99 and 93+ cars. I dont know if the proportioning valve is listed separately from the ABS unit on the parts diagram (I know the ABS units changed) but if it is, and there is a part number change, it may suggest they changed the proportioning valve. Same with the master cylinder size... though, I'm pretty sure that one would be even easier as it should be stamped on the top of the MC, like ours and the 929 unit. I know for a fact the vacuum assist unit is smaller/provides less assistance.

-Heath

 

Here you go:

Brake Pressure Gauge

Now get to work!

...I will be expecting colorful graphs / charts



edit: ^ FYI the gauge goes in place of the bleeder valve

 

ill make dan buy it for me as a business expense LOL (R/D right??)

 

Believe our FSM has a plot of what we got originally. Later manuals form Japan should show nay differences. Not eth 2002/06 ABS is a straight line, this would be due to EBD electronic distribution in the newer ABS units. The S8's had EBD so if they used straight line proportioning, it would be dangerous without the control circuits

 

Interesting post,

Some time ago, had been doing some research and found one blog where 94-96 model proportioning valve has been changed to miata NB model.
http://www.kameson.com/RX-7/P-VAL.htm
You'd find some visual comparrison of proportioning valves.

It would be interesting to get more information about brake biasing differences made between the years of production.

 

I know 01-02 FD's got EBD (which I would love BTW) but you are saying that there is no prop valve on the side of those ABS units as a result? I gotta do some more digging then.

 

Same here would love to have ABS unit with EBD. I did a lot of researching on swaping 02 Miata ABS unit with EBD as it would have been a lot cheaper. Basically came out with nothing, just found out that the same unit was used in Subaru Legacy.

01-02 FD3S abs unit actually did have proportioning valve on the side, but prop valve itself just might be straight through.

 

i'm also of the understanding that the later FD's got a restrictor in the PS pressure hose, and thus had less assist.

i didn't check, but i bet the part has superseded and if you try to order a 93 spec part you'd get the later one.

i'm not sure when they switched, the 99MY seems like a good choice though

 

Yeah there are exciting parts that we don't have access to unfortunately . Along the years they tweaked the FD little by little, and as far as I can tell all the upgrades (which I'm trying to assemble a list of) basically made the car "crisper" and an even better driver centered car.