ABS to Non-ABS conversion

This is a continuation from this thread.

When removing the ABS from the GVR4, what is the preferred Non-ABS proportioning valve to use?

After reading this thread and the table of different valve split points here, its still unclear which valve to use. If all wheels "braked" the same amount, what would be the proportioning split? I understand from the table that the smaller number means reduced bias on the front brakes.

I can still get the lines, but the Non-ABS valve is NLA from Mitsu according to the local parts guy. What, in your opinion, is a good alternative? Anyone have a part number?

Ken

 

Just plug the unused ports.

 

[467]

I got a 4200 from a 90-91 FWD in a junk yard. I really haven't tested it yet to see if it is optimum for me. The the table of different valve split points show the valves generally available from the various non-abs models.

It really depends on your set-up, springs, pad choices, tire grip all play a part.

Ward


quote:Originally posted by KenW:
This is a continuation from this thread.

When removing the ABS from the GVR4, what is the preferred Non-ABS proportioning valve to use?

After reading this thread and the table of different valve split points here, its still unclear which valve to use. If all wheels "braked" the same amount, what would be the proportioning split? I understand from the table that the smaller number means reduced bias on the front brakes.

I can still get the lines, but the Non-ABS valve is NLA from Mitsu according to the local parts guy. What, in your opinion, is a good alternative? Anyone have a part number?


Ken

 

[atc250r]

What about an adjustable proportioning valve like Wilwood makes? It is only $40 from Summit Racing.

John

 

[GVR-4]

quote:Originally posted by atc250r:
What about an adjustable proportioning valve like Wilwood makes? It is only $40 from Summit Racing.

John I was thinking the same thing.

 

quote:Originally posted by 467:
[QB] I got a 4200 from a 90-91 FWD in a junk yard. I really haven't tested it yet to see if it is optimum for me. The the table of different valve split points show the valves generally available from the various non-abs models.

It really depends on your set-up, springs, pad choices, tire grip all play a part.

Ward

So the ideal is for front and back to take about an equal share of the braking effort?

 

does all this save any weight ?

 

[467]

No, the fronts do most of the work beacuse the front is heavier, and downward forces on the front tires increase when braking due to CG, thats why you have proportioning valves. I believe the ideal is to get front lock up just before rear lock up for max braking force without causing rear instability.

Ward

Quote:
So the ideal is for front and back to take about an equal share of the braking effort?

 

Yes, removing ABS saves weight. Not much, though. What it does is remove underhood complexity, improve brake pedal feel, and arguably make them easier to modulate at the limits.

I went with the 92 AWD valve because it has a lower split point than stock and I had one sitting in my driveway. I want as much braking performance from the rear as possible. Due to our longer wheelbase, when stopping, we won't transfer as much weight as a TEL (all other factors being equal) so our rear brakes can do more work.

Mark

 

[blacksheep]

Mark - Isnt the 92 AWD valve designed for ABS? Did you block off the ABS ports ? Thanks!

 

Nope. I had one from a non ABS car. I guess I should have said that it was a 92 TEL AWD.

Mark

 

quote:Originally posted by GVR-4:
quote:Originally posted by atc250r:
What about an adjustable proportioning valve like Wilwood makes? It is only $40 from Summit Racing.

John I was thinking the same thing. Read the last half of the original post and you will see why this not so easy.

 

[bazeng]

just adding a note:

i've done this removal and also removed the ABS WIRING LOOM..

it probably weights around 2 - 3 kg's i'd say
(loom goes from the abs module in the engine bay all the way to the boot (computer in boot, next to arial)

its quite easy to do.. just alot of pulling and requires carpet removal / front and rear seat removal also.. also dash removal.. and front 1/4 panel removal also.. oh yeah.. and the plastic cover over the front LHS wheel needs to be taken off also

easy if the car is stripped i should say..

just thought i'd add this for anybody who wants to remove everything to do with ABS..

oh yeah.. u are required to either cut a wire in the middle (under the rear seat) which connects to the rear ABS sensors i believe.. thats the easy way to do it, you could possibly unplug it from underneath but i coulnd't be bothered at the time since i wont ever be using the abs loom again and also the 4bolt will go in soon..

 

[cheekychimp]

atc250r and GVR-4,
The problem according to the linked thread is that our brakes are not proportioned front rear. i.e. not one chamber for the front and another for the rear. In our cars one chamber controls the front left and right rear whilst the other controls the front right and left rear.

If that's true a proportioning valve could give some interesting results ... /ubbthreads/images/graemlins/grin.gif

John, you're pretty knowledgeable ... could the brake lines be re-routed to give a straight front back bias?

Paul

 

[belize1334]

I was digging around a bit and it seems that MANY of the adjustable prop valves that I see are single channeled, i.e. they accept only one line and transmit only one line. That being the case, it seems to me that you could choose a traditional Mitsubishi prop valve with too much rear bias (like one of the FWD TEL units) and then install two adjustable valves downline on the rears (one on each rear line). Then you could tune each rear wheel (though you'd probably end up having them basically the same) until you got the balance you want. For that matter you could put one on all 4 lines and then tune every wheel till you got the PERFECT balance, assuming sufficient precision in the valves. We'd still be stuck needing to source non-abs prop valves from other Mitsu cars but they're a dime a dozen at the junk yard.

 

[Dialcaliper]

Here's an old thread for reference - it'd be nice to see the info in it get saved

Prop Valve Info

From what I can tell, the stock type valve or the GGSX are the most rear biased of all the valves until brake pressure hits about 1100psi, which is pretty high, especially if you have upgraded calipers and rotors.

From what I can find, 1200psi seems to be at the fairly upper limit of brake system pressures on everything except an all out race car. If your system is going higher, you need a brake upgrade. 3000psi is the typical max operating pressure of flex-stainless brake lines.

A lower split point will make the car more even more front biased. However, the GVR4/GGSX valve has a sharper 0.4 reduction rate on the rear compared to a DSM valve (0.3), so under very hard braking (over 1100psi), the bias will end up less rear biased than the DSM, but only after that point.

The Wilwood and Tilton prop valves are 0.3 reduction with an adjustable split point.

Our brake system is set up with two independent diagonal circuits (LF/RR,RF/LR) so that if you rupture a brake line, you will still have the ability to brake. This is "a good thing". The stock prop valve is really just two separate valves in one assembly.

The proper way to use an adjustable valve is to change the setup to front only with a splitter block from the master, rear only from the other port on the master, and regulate the rear with an adjustable prop valve. Put the splitter for the rear after the prop valve. Whatever you do, keep the two master cylinder channels separate - your life depends on it.

Also, whatever you do, do not put two prop valves in series! Especially with the different reduction ratios, the system will go to hell very quickly, and you will have *excessive* front bias (You'll end up with almost 0.6 reduction ratio in the rear, and a very strange 3-segmented rear pressure curve, along with the potential for valve interaction - the valves are controlled by springs, and you can end up with unpredictable oscillation in line pressure at certain points, sort of like water hammer in your plumbing). If you want to control multiple wheels separately (asking for trouble), use a distribution block with no valve in it.

Also, be aware that the adjustable prop valves can only raise the split point to 1000psi or so. After that, it will start reducing, which means that on your front brakes, you will never get full master cylinder pressure under hard braking. This should only be done in situations like rally or dirt/circle track, where you know full well the effect you're trying to achieve and how to tune it. Front prop valves have no place on a street or tarmac race car.

If you really want to get that serious and start redoing your brake system, get a dual master/bias bar setup - the adjustability is far more useful than a prop valve for racing situations.

 

[kartorium]

I didn't really see this thread until now. So sorry if this could have helped others out earlier.

I did exactly what dialcaliper described above about 1-2 years ago using the wilwood valve. To this day it works fine and I've yet to have any issues.

Tuning a valve like this to work *ok isn't that difficult, however getting things exactly right has proven to be more difficult because its hard and dangerous to create lock-up situations in order to adjust things. I tuned in slippery conditions so that I could get decent lockup without excessive speed and danger.

This is what my setup looks like.



In the picture you see I have one line into a T fitting that then branches out to the front brakes (which are wilwoods also), then the other line from the MC goes to the proportioning valve and then a custom line was made to end up in the same location as the stock valve. At that location the stock lines were rebent and put into a T fitting. The pressure at both rear tires is therefore the same, and the pressure at the front two is not changed.

Please excuse the sh*tty bends in the stock lines. At the time I wanted to retain as much of the stock stuff as I could. Some day I'll just remake them all and get proper line straps to clean things up.