foko

if anyone has experience with removing ABS from their FD, i have a couple questions:

1. does simply removing the ABS fuse simulate no ABS accurately? does the ABS hydraulic unit do any proportioning or other magic? will it simply be a passive conduit if unplugged?

2. if replumbing without the ABS, did u retain the factory proportioning valve? i would likely add a cockpit mounted bias valve but this is different than the stock proportioning valve. it is an interesting device in that it retains a linear relationship up to a certain pressure, but then decreases rear brake pressure a fixed percentage above a define mastercylinder pressure. the pressures are in the manual, but it's hard to extrapolate what 4000 kPaf is exactly (is it 50% brake application, 75% etc)?

the reason i ask these questions is that i'd like to remove the ABS from my track only car. the ABS unit failed at the track last weekend and i'm weighing the options (replace, remove, etc)

thanks
fabian

bradrx7

Fabian,
I don't have ABS and use twin manual M/Cs.

1) You need to remove the pump. Yu can also remover the computer in teh left rear of the hatch area.
2) Replumb. Just follow the lines and reroute. One item to get for the MC side is the brass brake line connector from the top of a second gen's rear axle.

A proportioning valve is ot the answer. The M/C is made to do the work for you.

BTW, Todd Serota mentioned he drove your car recently. I've known tood for years, he's a great guy.

good luck,
Brad

bond007

Fabian,

It depends on which fuse you are going to remove -- just a warning here from prior experience.

I had a friend with a base model, and at some point, he believed his ABS to have failed. It was a bear to drive on the track, even his instructor commented it was undriveable.

What happened, was since he didn't have a rear wiper fuse (remember, base model), at some point, he blew a fuse, and scavenged the rear wiper fuse...

Well...the rear wiper fuse also supplies power to the ABS computer, and that was why his car was so horrendous to drive. Replace the rear wiper fuse, and viola! ... the car brakes properly again.

So, you'll want to make sure the the ABS fuse also removes power from all the necessary components.

Regards,
--Ashraf Farrag
93 RX-7 (lives for track)
94 MX-5 (commuter/autocrosser)

the_glass_man

iTrader: (2)

Could you do the same with two Wilwood M/C's?

DamonB

The ABS pump itself does not do anything except when under anti-lock conditions. It does no proportioning or anything else. If you want to simulate without it just pull the relay inside the black box on top of the pump.

BigIslandSevens

iTrader: (4)

http://members.aol.com/rotoryhead/rx7/absremoval2

http://members.aol.com/rotoryhead/rx7/absremoval3

http://members.aol.com/rotoryhead/rx7/absremoval4

http://members.aol.com/rotoryhead/rx7/absremoval1

That's what i did with mine. Removed the ABS pump, all other hard lines. T'd the fronts together to the factory front output from the MC.

The rear line I ran into my wilwood bias controller. I used the front output from the Mc for the rear. From the controller "out" I went straight to the factory rear hard line. I used the fixed detented controller for now as i didn't want people messing with it if the hood is up.

I followed this roughly. Without the line lock in my set-up.. Damn drag racers
http://www.nopistons.com/forums/inde...ic=20181&st=0&


I have another question about a different solution... Could one use a master cylinder off a NON ABS FC and use the factory proportioning valve unit? Sort of the "poor mans" removal set-up... Not sure on MC output differences or anything . just brainstorming

the_glass_man

iTrader: (2)

Could you post the pictures in another format, they are all coming up ASCII. I would like to guess they probably work on IE, but I don't have IE for a reason.

Thanks.

DamonB

I'm not sure but here's a great deal of info on what a proportioning valve really does.

http://www.stoptech.com/whitepapers/...ing_valves.htm

Gene

iTrader: (1)

Great link Damon

DamonB

That link answered one of my questions in that racecars which run dual masters don't run proportioning valves (for that matter nobody with dual cylinders should have a proportioning valve installed). That didn't make sense to me because ideally as the rear end gets lighter and lighter under braking you would want less and less of a percentage of brake power back there (which is what a proportioning valve does).

Racecars don't use proportioning valves because they assume you will always stop as hard as you can and so the static proportioning between front and rear stays constant at all times. You just adjust the balance to keep the rear from locking up at full braking but the downside is that under anything less than maximum braking you are under utilizing the rear brakes and thus over working the front brakes. Not important on a racecar though that spends all its time braking as hard as it can.

macdaddy

The reason you don't use a proportioning valve when you're running 2 master cylinders is that the proportioning is done using the balance bar between the two cylinders (what the StopTech article refers to as an "adjustable reaction linkage"). This determines the amount of brake fluid your single brake pedal moves in each circuit (front and rear). Since brake fluid is essentially non-compressible, this is directly proportional to the pressure applied to each circuit. This is the ideal set up. Some race cars allow you to change the position of the balance bar from the cockpit while running. This is obviously an advantage when road conditions change during the race, using up fuel changes the static balance of the car, etc. Many simple race cars, however, run this type of setup with the balance bar not adjustable from the cockpit during the race.

Whether adjusting front-rear brake balance with a balance bar or a proportioning valve, you adjust the balance so that your fronts lock up just a hair before the rears - so as to keep the car from swapping ends. When you brake at less than threshold, you are "underutilizing" both front and rear brakes, but in the same proportion as when you are braking at threshold.

DamonB

No. The balance bar adjusts the front and rear brake pressure relative to eachother and that ratio stays linear (slope of the graph is constant) regardless of pedal effort. A proportioning valve works completely differently. A proportioning valve has the ability to vary the ratio of front to rear brake pressure depending on how much pedal effort you put on the pedal. The knee in the curve is the point where the proportioning valve changes the ratio between front and rear braking force. That's a very fundamental difference between the proportioning valve and the balance bar. The proportioning valve is in effect two fixed balance bar settings that select themselves automatically based on brake line pressure.

I understand how balance bars work and what they do but they do not function in the same manner a proportioning valve does.

A balance bar can produce this:

No matter how you adjust the bar the result will always be linear.


A proportioning valve can do this, which is impossible to achieve with a balance bar:

macdaddy

Agreed.

TailHappy

For what it's worth, I inadvertantly temporarily disabled my ABS one time by forgetting to put the ABS rings on my half-shafts when I replaced them. Did an autocross that way and it was so bad I immediately went home and switched the parts back out. The car was RIDICULOUS to try to brake solidly with. I would swear it was locking up prematurely, but maybe it was just because I was so used to this car having ABS (pedal feel seemed horrible with ABS disabled), maybe the ABS needs to be bypassed completely, or maybe it needs proportioning valves, as you guys mentioned.

the_glass_man

iTrader: (2)

Thank you BigIslandSevens! Click thumbs for fullsize.

speedx7

sweet link man

BigIslandSevens

iTrader: (4)

Thanks Glass man Hope these help some if the need them.

suganuma

Have any of you that have dedicated track FDs removed the stock ABS system?

I mean, I can understand the attraction getting rid of all of that clutter and a little weight, but does the car perform better without it?

TIA,

Ikestaa

I removed mine, along with switching over to a wilwood pedal setup, and tilton masters. I've still got a fair amount of work to do on the car, so it will be a while before I can get any impressions. I've driven cars without ABS at the track before, and had no problem threshold braking with them. Rain will be a little tricky, but just another learning curve. It may be slightly quicker with ABS, but I'd rather remove the clutter, and drive with one less electronic aid.

BigIslandSevens

iTrader: (4)

Do you have any part #'s of the pedals and masters? that is a nice set-up so far. What type of raceing/driving do you plan on doing mostly? What brake set-up? Thanks
Dave

Ikestaa

The car will be street driven, but will hopefully see a number of open track events. The brakes themselves will stay stock until I can get the car on the road. Eventually I'll go with a kit up front (most likely Stoptech's) and probably the 99 RZ setup in the rear. The actual part # for the pedals is 340-4828. If I had to do it all over again, I think I'd try to go with a floor mount setup from Tilton. I did a mock-up and test fit out of wood for the floor mounts and it looked like it wouldn't fit right, but I think you could get it to work with some work (mounting the pedals a little higher and closer to the firewall). The masters are all Tilton's 75 series cylinders. They're nice and compact to allow for easy mounting. The only thing that had to be cut under the dash was the HVAC tube that goes over towards the door. I may be able to route some flexible tubing in its place though.

macdaddy

Suganuma:
Most road race sanctioning bodies require removal or disablement of ABS for competition for most classes. It's not about improving performance - it's about relying on driving skill instead of electronics - it also keeps racing more affordable and helps level the competition. For a dedicated track car that will NOT see wheel-to-wheel competition, I'd definately keep the ABS (it's legal for Solo I and II, and is a performance advantage).

Ikestaa:
You know that the caliper cylinder/piston size of the StopTech kits for the FD are sized to go with the stock master cylinder and rear brakes, right? With dual MC's and a balance bar (+/- RZ rear brakes), you might get better performance with different-sized cylinders than what they sell for the stock FD. They will do custom jobs - but if you don't have the engineering expertise to figure out the optimal design yourself, you probably want to talk to the guys at StopTech early on and see what they recommend.