ABS makes it raw.. keep it off!

 

^^ Flatspot many Hoosiers in your V8 Miata while racing for contingency?

 

I'm guessing no.

 

I'm also guessing no...I'd like ABS on my 92 because of the same reasons listed above. I run my 13s and slicks on the track when it's cooler...and in sub 60 degree temps they work great (as does the car) ...problem is...they are easy to lock up at 100mph...

So I'd like it for that, for the fact I still autocross it and for the fact I street drive the car still.


I talked with Jason about the 01 ABS option once and it seemed like a good idea...but I'd probably need his help lol

 

I have the ABS components lined up from a 01+ Miata so I think I'll be installing it in the track car as soon as I get another car of mine taken care of.

 

Anyone finish this swap yet?
I have finally gathered all the parts.
Spindles, Knuckles, Hubs, Axles, wheel speed sensors, Pump, Computer, Brake Booster, Master Cylinder and lines.
All that coupled with a big lightweight brake kit from 949 should make my car WHOA as well as it GOES.
I hope to have it finished in time for the Toledo Pro Solo. Just doesn't look like there is time for Blythville.

 

I have a complete ABS system from an MSM donor car in my '90 track car. I used everything from the pedal set (MSM pedals add +5whp and look cool ) to the hubs. The hard lines fit perfectly with the slight exception of the rear line crossing the fuel lines at the passenger's feet. I mediated this with some rubber and zip ties to keep them from wearing on each other.

The ABS block needed to have some mounting points fabricated. I discuss it in and around post #53 here:
http://www.mazda-speed.com/forum2/in...,24668.45.html

My project was made easier by the fact that I was using the whole drivetrain and had the ABS hubs and sensors already. A pair of wires goes to each corner (yes, even though the rear is a single channel). The unit needs a heavy power source (30A), a medium one (20A) and a small one (~5 to 10A, probably much less current is drawn there). I have the little one on a toggle switch on the dash right next to my EBC toggle. I figure when the 'Zoom' switch goes up, the 'Woah' switch should go up too.

It rained the first day at Laguna and I used the ABS - it worked as expected. My plan was to leave it off for dry conditions but I have found that the proportioning bias doesn't work correctly if it is off and braking from much over 100mph is a little hairy even in the dry. My current lack of aero in a ~250whp ~2100 pound car isn't helping. Flat-spotting insurance sounds like a great investment too even though I'm on $600 worth of NT-01s and not twice that of Ho Ho's...

 

Can you comment on lap times with the system on/off in various conditions? Are you running OEM brake pads and rotors? You said you have NT01s - what size are they?

I will write a few things which probably most of you know, but maybe didn't think of them all at the same time:
Static friction is higher than kinetic friction (in general) which means that a tire skidding (kinetic friction) has less grip than a tire on the limit of skidding; so if we can have the tires on the verge of slipping ALL THE TIME while braking (for that matter also while accelerating) it would reduce braking distance etc. all the good stuff.

With tires being ~hyperelastic materials things are not as straight forward as Coulomb friction, and they generate maximum grip when they're stretched slightly (when they're cornering this is the slip angle, when braking/accelerating it's called a slip ratio: read more here: http://en.wikipedia.org/wiki/Slip_ratio ).

So slip ratio around 20% is optimal (is this true about all tires - definitely not, just like optimal slip angle is not a constant for all tires). For the sake of argument, let's say 20% is ideal for all tires.

So how does the ABS work: it measures wheel rpm, it measure vehicle speed and it figures out what the slip is when the brakes are applied. You just keep you foot down and it "cycles" the pressure in the caliper lines so that the wheels stay around optimal slip (there's a lot more going on, but that's the essential part). Just from the essentials I can see a few things which may make factory ABS on a non-factory tire/wheel/rotor/brake pad combo non-ideal:
-maximum grip slip ratio may change
-if tire diameter changes wheel slip is not calculated correctly from wheel rpm
-changing ultimate tire friction coefficient has an effect on ABS system
-changing brake rotor inertial properties has an effect on ABS system
-change brake pad friction coefficient has an effect on ABS system

Now, I've corded a few R6s and know the feeling in my stomach every time I see/hear a tire lock up, but I feel that I'm paying for R6s in order to get the ultimate grip from them in every direction, so not being able to use them optimally with factory ABS would BRAKE my heart

ABS comes with a "map" just as any other ECU, so if you're "map" is not tuned for your braking system it will not function at its best.

Am I a good enough driver to make a non-ABS car go around a track faster than the factory ABS... no idea

Nik - very good at Need For Speed III Hot Pursuit

 

I have only had the car on track 4 days since I put it together. The brakes are OEM sports with XP10/8s. The Nittos are 225 15s. I'm not a good enough driver to comment on lap times but I am sure that at my skill level, I'm faster on ABS.

 

So I'm about 75% of the way through with the ABS Addition. Here is what I have done so far.
1) Changed front Hubs, Upper control arms and ran the ABS sensors
2) Changed rear knuckles, axles and ran the ABS sensors
3) Mounted the ABS Pump
4) Ran all the ABS Hard Brake Lines
5) Converted my non ABS Maser Cylinder to an ABS Master Cylinder

So what I have left to do
1) Sort out the power sources for the ABS System
2) Sort our the ground sources for the ABS system
3) Route the signal to the ABS lamp on the dash
4) Mount the ABS Computer and RaceLogic Traction control unit

5) WIN

The best I can tell this setup will pay for it's self in one season of AX due to reduced tire wear.

I'm curious to find out if any of the other guys that started down this road have made any progress.

 

The ABS in my XP autocross car is working very well. A full year of $1600 Avons staying round. It's great!

-- Glenn

 

Tuba,
What year system did you source to put yours together. I don't have any experience with the earlier ones, but the NBB has all the brains and controllers in the ABS block so I didn't have a separate ABS computer to deal with. My ECU can't do traction control without adding more robust wheel speed sensors so I won't go down that road.

After the first few events, I stopped trying to drive the car with the ABS off. The rear bias just gets too hairy without a portioning valve. The valve is on my list to do as early as this season, but I need to get several other things sorted before I screw up brakes that are working fine otherwise. I want to do a shakedown day by the end of March to see how much I've screwed the car up this winter.

As for the ABS in general, I do really like it. Not only does it keep me from flat spotting tires, but as a lower-end driver, I can practice threshold braking and know where I'm at based on the the pedal vibrating rather than a wheel locking up. Regularly engaging the ABS (i.e. using them on purpose instead of threshold braking) will thrash a set of pads in just a few sessions on a heavy road course. I know I'm improving as a driver when the lap times go down consistently AND the pad life increases over time.

Beyond the driving impressions, my pedal is rock hard - better than any of my other miatas and is very easy to modulate. I'm very happy with the upgrade.

 

I went with a 1997 unit. I was able to source a totaled car and get all the parts from it and already had a 1997 ABS Computer and harness that were pre-wired for the Traction Control. As for the traction control, what I am using is the unit from Race Logic. I'm glad to hear you guys have had success. I'm hopping it all works when I fire it up.

 

Some guys have reported issues bleeding the ABS system and there has been some discussion (probably m.net?) about a process that involves putting the car in the air and spinning different wheels to engage the ABS while you are bleeding. The dealer also has an interface specifically for the purpose of cycling the ABS block while bleeding to remove air. The chances of their lawyers letting them touch the brake system you installed from a wrecked car are somewhere between slim and none.

All that said, I bled mine traditionally and have a rock hard pedal. It was so hard in fact, that I was sure something was wrong when I finished bleeding. A very slow and cautious test drive - fine. A spirited test drive - fine. A cautious session at the track - great. A flatout session at the track - ...

 

Once I have it all set up and installed I am going to do an initial "bleed" with a power bleeder. Then a "traditional bleed" and then manually cycle the ABS pump while bleeding them. The procedure to manually cycle the pump is in the FSM.

And I'm sure a dealer would have a hay day if I brought my car in for service.

 

Yeah, drive it down there, avoiding the attention of every LEO in town, and tell the sales guy you want to trade it on a minivan... When he looks up book value and offers you $600 for trade, you'll have some hard decisions to make...

 

Rotflmfbo

 

I purchased shocks for my 91 with out realizing I had abs.
The mechanic who installed them used zip ties to add the abs to the shocks.
They are oem shocks front of car.
Is there any way I can mount the abs unit ?
Thanks,
John

 

zip ties work fine for the rest of us

 

Are any of you guys running an adjustable prop valve? I have a 97 on race rate Fat Cats, I run a 205 street tire at autocross. I had been racing for years in other cars not equipped with ABS and I never had a locking issue but I found with the Miata it locked the fronts extremely easily causing very irritating flat spots. I managed to find a specialty vintage shop in PA that will shave used tires for $25, had to do that with a couple tires before I added the prop valve. My point is since I added the prop valve I have no issues braking hard and not locking the front tires. I run aggressive HP+ pads. Honestly I found the optimal balance with the valve fully opened, if I were to do it again I would just pull the stock prop valve and replace it with a union.