I'm in the process of preping my 99 UK turbo for 2011 Subaru Cup and part of the process is improving the brakes, basically I can use anything fitted as OE to a WRX classic, at present my car as 2 pot fronts and single pots rears which will be swapped for 4 pots fronts and 2 pot rears as per WRX RA, I can also remove the ABS as per WRX RA, my questions are regarding the UK turbo and WRX RA master cylinders.
Firstly the OE UK specced car as ABS and therefore only 2 outputs on the M/C, I'd expected the RA M/C to have 3 outputs 2 for the front 1 for the rears, but it turns out that the RA non ABS M/C as 4 outputs.

When I've removed the ABS on my previous car (Nissan 200SX) I sourced a Z32 (300XZ TT) non ABS M/C which had the requisite 3 outputs 2 for the fronts one for the rears, this was T'd to split the single line between the 2 rears hubs, in the single line to the rear before the T piece I fitted a bias valve to allow the brake balance to be adjusted, this system worked very well considering it used mainly Nissan OE parts.

The problem I have with the Impreza is the fourth brake output on the RA M/C , how do I incorporate a bias valve? do I blank off one of the rear outputs and use a single pipe T'd after thre bias valve to feed the rear brakes ? or would it be better to retain the stock UK spec M/C and split the feeds with another T piece?

Or am I missing a simple solution? what have others done to include a bias valve in a ABS delated system?

 

You could "T" the two outputs into one for the bias valve and then T them after...

HTH

dunx

P.S. Just in-case the fourth port isn't shared with the third on the piston itself...

 

yeah I'd thought of that but it just seemed a bit point less, mat as well just block the 4th outlet, I think I'm just going to use the OE 2 output M/C and T front and rears,
I found this which looks a good solution, https://www.europaspares.com/BRAKE_P...OCKS_4518.html
but in the end I don't think it as any real benifits over T'ing the pipes and includeing a bias valve.