'04 ABS Can't Use Prop Valve - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-28-2013, 03:25 PM   #21
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As good as Crusher's brakes were, Emilio built it with OEM calipers to save points in NASA classing. It occurs to me I can improve the pad wear issues with a nice BBK too. Research and design the brakes as a system to achieve proper balance like Emilio described earlier and then flip the ABS switch.
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Old 10-28-2013, 03:42 PM   #22
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Emilio,

Was the booster in your setup from the NB1 ABS or non-ABS? It looks like I will be happier with the MSM booster at 6.4:1. The other question is how much effect the 1" MC has and if there is a ton of difference between the 1" 929 MC and the dual Willwood in terms of bias and pedal feel.

It looks like Crusher had strong front brakes and strategically handicapped the rear brakes with smaller calipers and less grabby pads. According to the information listed above, all miatas had 32mm rear pistons until the 35mm sports showed up.

After all of this hardware is sourced, how much are you actually asking the prop valve to cut? It seems like we are searching for ultimate mechanical grip before any hydraulic or electronic wizardry is employed.

I don't have any NA8 or NB1 rear calipers but I have at least 2 or three sets of NA6 rear calipers that show the same 32mm bore. Would they bolt to sport brackets over sport rotors? I've done lots of Miata rear brakes but never looked at them that closely.

Still curious if the 2 piece rear rotors were a typo in Emilio's earlier post...

I love my brakes now - ROCK hard pedal, fade proof, easy to modulate and predictable. The pad wear I mentioned in the original post is a concern but I don't see anything I have learned in this thread making that better so replicating Crusher's non-EBD balance seems to be the new focus.
Non ABS NB1 boster.
Our SuperMiata 2 pc front rotor assemblies (discontinued)
Goodwin V4 DBA 2pc rear rotors
NB rear uprights are all the same. Bolt Sport or base brackets. NA8 rear calipers bolt right up to Sport brackets to fit over Sport rotors, (that's what we did on Crusher.

1" master is 1" master. I don't think it matters which one it is. We use the Wilwood simply because it's easy to work with. M/C does not affect bias. It just makes for a firmer pedal. There is sort of bell curve for brake feel/modulation. Too much leverage and you have a mushy pedal that's too sensitive and difficult to modulate. To the other extreme of way too much leverage where the pedal is like a rock but the effort is so high that finessing 10-20lbs of modulation is also very difficult. It's also difficult to sense when brakes are fading with super high pedal effort systems. I find that a peak effort somewhere in the 20-45lbs~ish range at threshold works for me. The trick is getting reasonably low effort threshold braking while still retaining good control at low line pressures. For my driving style at least, how the brake behave at very low line pressures is critical to finding that last bit of lap time.
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Old 10-28-2013, 05:16 PM   #23
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Originally Posted by emilio700 View Post
Non ABS NB1 boster.
Our SuperMiata 2 pc front rotor assemblies (discontinued)
Goodwin V4 DBA 2pc rear rotors
These Rotors (including both sides of course)? How significant were the directional fronts to the overall effectiveness of the system and would the OEM single piece rears be 'good enough' - especially when paired with straight vane fronts?

It sounds like I'm some rear calipers, prop valve and pads away from having a 'Crusher Jr.' brake system. I can't imagine wanting a firmer pedal than I get with my 15/16 MC but all of the above including a 929 1" MC are pretty budget friendly if I keep OEM rotors.
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Old 10-28-2013, 07:49 PM   #24
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Originally Posted by mr_hyde View Post
These Rotors (including both sides of course)? How significant were the directional fronts to the overall effectiveness of the system and would the OEM single piece rears be 'good enough' - especially when paired with straight vane fronts?

It sounds like I'm some rear calipers, prop valve and pads away from having a 'Crusher Jr.' brake system. I can't imagine wanting a firmer pedal than I get with my 15/16 MC but all of the above including a 929 1" MC are pretty budget friendly if I keep OEM rotors.
No change in power. The 2pc were lighter is all. The fronts were/are custom made directional friction rings.
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Old 10-28-2013, 08:03 PM   #25
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So, summarizing and addressing the title of this thread: The prop valve installs in the rear line before the ABS block but is pretty close to open since we are reducing the static bias to the rear with smaller calipers and pads with less bite. The ABS will take over if it detects slip but it should be doing less EBD work because this combination of pads, rotors and calipers has a better natural balance. True statements?
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Old 12-14-2013, 12:51 AM   #26
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We set up our cars to have perfect brake balance w/o abs the race with the ABS on all the time, wet or dry.
<snip>
Crusher uses an NB2 ABS brain from an '01 IIRC.

Emilio,
On your installation, how did you switch the ABS off? Which power source (wire) do you have your switch in?

I ask because it looks like the system will fault if the car is moving with any wires open. Or do you not have a ABS fault light?
I would like the ability to turn the system on & off on the fly.
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Old 12-14-2013, 10:50 AM   #27
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Emilio,
On your installation, how did you switch the ABS off? Which power source (wire) do you have your switch in?

I ask because it looks like the system will fault if the car is moving with any wires open. Or do you not have a ABS fault light?
I would like the ability to turn the system on & off on the fly.
crusher is a race car. There is no oem ecu or dash. power for the ABS was switched through the smart wire.
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Old 12-14-2013, 11:30 AM   #28
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That's what I thought, so you just basically removed all power at the same time. Man, I like that Smartwire!

I will try switching the small power (Z, on the hmu) just like turning the key off. I just don't want to find out the system remains active, because it detects it is still moving.

Last edited by GraemeD; 12-14-2013 at 11:41 AM.
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Old 12-17-2013, 01:31 PM   #29
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The most critical aspect of brake balance for low lap times in a medium to low hp Miata is the balance at low lines pressures. This is the area used for trail braking, delicately rotating the car into a turn at optimum slip angle with all 4 tires. If the straight line threshold braking bias is by 25%, you can drive around it and still get max cornering speed. If you can't trail brake because low line pressure is off 25%, you're going to spend a lot of time sideways and being slow mid turn.

Adjustable proportioning valves only change the knee point to begin choking rear line pressure. At low line pressures when trail braking, the prop valve isn't even being engaged. This is important: Prop valves only affect high line pressure, straight line threshold braking.

If the brake balance at low brake line pressure is off, no amount of bias adjuster, ABS, On/Off switch will fix it. You simple screw up every corner entry, every lap. Getting the pad .mu, rotor diameter, piston area, master cylinder diameter, brake booster all right is key.
This is the best explanation I have read about properly setting up brake bias with a prop valve. All to often people focus only on threshold braking. Props.
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Old 12-17-2013, 02:08 PM   #30
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Originally Posted by GraemeD View Post
I will try switching the small power (Z, on the hmu) just like turning the key off. I just don't want to find out the system remains active, because it detects it is still moving.
I just put the small wire on a toggle and it works fine. *

*Edit - I didn't bother with the ABS light in the dash but I'm sure it would be 'on' when the ABS is switched 'off' in my setup.

Last edited by mr_hyde; 12-18-2013 at 03:39 PM.
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Old 12-18-2013, 03:07 PM   #31
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When I swapped a 2003 ABS system into my car, I put the 10A ABS electronics power line on a switch (the now-unused cruise control switch). It works as expected -- flip it off and the ABS and brake idiot lights come on, and the car will now happily lock up the tires. Flip it back on and, after a few second boot/test time, you're back to ABSing.

The ABS & brake lights come on whenever any of the 3 power lines to the ABS unit is not carrying power, and there are some relays in there to make sure that happens in a fail-safe fashion.

--Ian
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Old 12-19-2013, 12:39 AM   #32
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Thanks, That is good news, I have a DPST switch that I will use and also open the "brake" warning light portion of the circuit. My reasoning is that the low fluid switch will still activate the light with a loss of fluid. But if the ABS is keeping the light on, you would never know you are loosing fluid. So turn off the "brake" portion of the ABS warning and you still get the low fluid warning.
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