How would this work on a 2001+ ABS car ?

 

It's been a while since I've had my hands on a stock 2001+ 3-channel ABS system, but I believe it still has a single brake line running from the master cylinder to the ABS pump, and then onwards to the rear brakes. You would just remove the factory prop valve and install the Wilwood piece with our adapters as normal.

The Wilwood valve works just like the factory prop valve - it just allows you to alter the knee point by adjusting the ****. The adjustment being made and the logic behind it isn't always intuitive for most folks, so I'll be doing a short tech article later this week on the logic behind an adjustable prop valve and how to set it up in your car.

 

If there is no proportioning valve to replace the Wilwood prop valve will do nothing.

 

A proportioning valve works by limiting the pressure applied to the rear brakes above a certain knee point.
Let's take your example of no current proportioning valve. We can think of this as simply a union where a proportioning valve would be meaning the rear brakes are seeing full pressure. By installing a proportioning valve in place of that union in the rear line, you can limit this pressure applied to the rear brakes. This means that even if you aren't replacing a proportioning valve, adding an adjustable proportioning valve will still work to the same effect.

 

The 01-05 ABS controls the pressure to the rear to the level of max tire slip according to the ABS calibration.
Using a mechanical prop valve to limit the max pressure available to the ABS/EBD sounds daft to me.

Replacing a static mechanical prop valve with an adjustable one is a good thing, then you can increase the pressure for the knee. I have one myself.

If you disable the ABS/EBD on the 01-05 you might be able to dial in better rear brakes, but as long as it's active any mod you make will not allow any more slip on the rear tires than the ABS calibration does (and Rcomps and slicks have more grip to give at higher slips than street tires for which the calibration is done).

The brakes on the 03 I had was pretty awesome in balance on simple Rcomps (RA-1 etc). It always snaked a bit due to EBD modulation but never too much (I struggle to get the same feeling on the 99 with the adjustable valve).

 

Steal fittings are nguyen.

 

The ABS system is calibrated for a stock setup. Stock brake size and pad compound, stock tires, and stock suspension. The point of adding the proportioning valve to an ABS equipped system would be to set the front/rear bias as close as possible for this new setup (best to dial it in with ABS disabled) so that the ABS system doesn't have to do as much work. The result will be better brake bias/distribution of braking force in a racing application. We ran a setup similar to this on the 949 Racing 25 Hours of Thunderhill.

 

ABS only is one thing (and I agree with the setup procedure, balance is just as important with ABS, if not more), ABS/EBD is something else since the front/rear balance is continuously adjusted using the ABS sensors and pump.
Unless you disable that function there is no way to get more brake in the rear than the system allow. To get less brake in the rear is not needed IMHO since the ABS/EBD is doing a good job.

Changing the number of teeth on the ABS sensor rings could be one way to fool the ABS, but that's something different.

 

Sound like a recipe to get the ABS into limp/disable mode.

 

You are saying the system works by speed differential, not pressure monitoring? I don't know what the system is looking at but am a little interested.

If the ABS/EBD is performing modulation with speed/slip feedback and you have altered the mechanical proportioning, how will this effect the performance of the brake distribution improperly? Altering the pressure distribution is not altering the ring feedback which you I believe you are saying is the feedback variable for the system. Even with ABS/EBD, a proportioning valve should have no ill effects and should allow an installer to now better match brake components. It shouldn't be necessary with stock brakes. For racing, the bar type valve installed in the car is a nice idea for different drivers.

Changing the number of teeth on the rings for the wheel speed sensors would put the system in perpetual slip thereby activating ABS prematurely or possibly put you in a predefined slip region continuosly.

 

Perfect timing. Order placed.

 

It will have no ill effects but you will not be able to move the balance rearward as you can when you replace a static prop valve with an adjustable one (which is the point I have been trying to make).
Since the system is looking at slip even too large pistons in the rear calipers should (experience would be valuable of course) be handled without mods, not in a good way of course since the EBD will need to act earlier. This situation could be modified with an adjustable prop valve to reduce the max pressure. But if this will make the EBD more sluggish, I don't know.
I see it as adding a mechanical prop valve in series with an computerized one working of the ABS sensors.The theory/practice is to change the number of teeth on all 4 wheels, to fool the ABS that you are running at a higher/lower speed (allowed slip can be different at different speeds, even outside the ice-mode). It works to fool ancient ABS systems on other cars, especially if the slip is measured in absolute speed and the speed in only taken from the ABS sensors, not from the trans.
I have not investigated the Miata ABS enough to say that it would have any effect, but altering the pulse trains coming from the sensors could be another thing to try (no need to machine several sets of rings and change them between tests).

 

Gents, can we break the ABS discussion into another thread? Thanks.

 

My point is that based on the feedback circuit outlined, your product will work with ABS (as would any prop valve). If you alter rear base/mechanical pressure with a prop valve and ABS/EBD uses wheel speed sensors, you are only evaluating slip % based on brake controller pre-programmed values. Mechanical pressure variation will help ABS/EBD on a system with brakes installed with a non-stock proportion. You can mechanically program (via the prop valve) the brake system to work within the electronically defined slip parameters. EBD doesn't fundamentally change any of this unless it is using pressure feedback as a component of the feedback circuit, which i doubt.

So, uh... I'm helping you sell some product Andrew because it should work ABS/EBD or not.