[Mk2] [Turbo] Difference Prop Valve ABS vs Non-ABS

[Glenn_k]

Can anybody tell me the difference between the proportioning valve of an ABS vs a non-ABS mr2?
I know that a non-abs valve splits the front brakes, whereas an ABS valve splits both brakes in the ABS unit.

I need to know, because i've removed my abs pump, but kept the ABS prop valve as I don't think its much different. Now i've split the lines with t-pieces, after the prop valve.

Thanks!

[Danbob]

I can't say for certain for the mr2 specifically, but usually a non abs prop valve will cut line pressure to the rear brakes at a predetermined pressure which prevents the rear wheels locking up under braking.
An ABS system with an EBD (electronic brake distribution) function will do this electronically using the abs unit and therefore the "proportioning valve" in abs cars is usually just a distribution block with no pressure cut.
The abs system can manage the brake distribution more efficiently than the single stage proportioning valve, as it follows the optimum pressure curve for the rear wheels instead of flat-lining at the predetermined pressure.

If the MR2's abs system did function as an ebd system, then removing the pump without swapping to a non abs valve could lead to your rear wheels locking up under normal braking.

Saying that, this all applies to normal cars, the mr2 is a little different being mid engined, with more weight over the rear tyres they can transmit more brake torque without locking up, maybe Toyota just relied on getting the brake balance right in this case and didn't bother with a prop valve on the non abs cars.
My non abs car often locks up the rears if I brake too hard on a track.

[Glenn_k]

Thanks for your reply!

Can anyone else say if this is the case for MR2's as well? I've also read that a proportioning valve usually crosses the brake lines, so that you can't spin your car easily on heavy braking.

On my ABS prop valve, there are 2 entrances and 2 exits, which makes me think that it only adjusts brake pressure to generate a 60-40 split (front-rear).

[Glenn_k]

This is a picture of the current setup of my master cylinder/prop valve.
F stands for front, R stands for rear. Brake lines are split after the prop valve; the front split is visible in the picture.

Can anyone tell me if this is the right way to plumb them?