suzukisteve

iTrader: (4)

I know a popular mod on these cars is to delete ABS, because it generally, for lack of a better term, sucks. In 1995 they upgraded the ABS module, in fact an easy way to tell the difference between a 94 and 95 car is to look at the ABS pump. I have been told that the 95 is better, but it is still three channels.

What I am getting at is, I have a 95 and my ABS sucks. I generally think ABS is a good thing and the driver that convinces himself he can out brake ABS in a modern car is a fool, so I do not want to delete my ABS yet. I want to sort out my ABS as much as possible before giving up on it. I had an incident today, where my front left tire locked up going down a right turn in a canyon. I scared the hell out of a motorcyclist on the other side of the road. I feel really bad about it, and yes had I been driving slower this would have not happened, but also the ABS did not do its job correctly. I did a couple more stomp test, and found that one of the tires would lock up with the ABS, while the other wouldn't (I think it was always the left side, but it may have been the right once or twice).

Here are the mods that I have done to the braking system:
Chase Bay SS lines
Chips motorsports 929 mastercylinder
New front left wheel speed sensor
Rebuilt brake calipers, both front and rear

Give me suggestions to make this thing work better, before I rip it out.

Project88Turbo

iTrader: (22)

So, let me preface this with the assumption of only basic knowledge of how ABS systems work.

In a heavy braking situation, the ABS unit compares wheel speeds and if a wheel is stopped or slowing significantly faster than the others, it should cycle the ABS pump and activate the solenoid for the channel that is "locking" up.

So, if you hear the ABS pump activate during this time, but a wheel just locks and doesn't release or you don't feel the pedal pulsate, it's likely a solenoid or internal passage may be blocked in the ABS hydraulic unit.

In the most basic sense, the ABS unit is supposed to relieve pressure to the channel/ wheel that is locking up which should allow it to start turning again. More than likely, a combination of age and lack of brake fluid changes has gummed up something. There are some brave souls that have rebuilt these units, and there are some that have installed newer ones from the last of the Rx-7s. So there are some options out there to fix it.

And as far as a good driver out braking "modern" ABS, I'm not sure the FD qualifies as modern. Something like the RX-8 4 channel, with EBD, BA, and ESC is pretty impressive though and big leap forward from our cars.

Vince

suzukisteve

iTrader: (4)

I have flushed the brakes a couple times. Maybe it is time to pull the ABS unit and clean it out??

Project88Turbo

iTrader: (22)

The biggest problem with cleaning it is there are passages that are normally closed unless it's activating the solenoids. So, you'd have to disassemble the unit. And the hard part of that is there aren't "rebuild kits" for all the seals and o-rings it would need.

There is a thread with some part numbers in this sub forum if you search ABS rebuild.

Vince

billyboy

If the ABS is working, the pedal will pulse, usually the inside front going light will instigate it. A mate's car had a very mixed up old and new wiring harness mated together and it would lock up a front, because of incompatibilities. He was quite surprised when after a fire the whole car was rewired with a 2000 system and pump and he felt the pulse for the first time,

If there's a diagnostic box like in a rhd, that would be my first point of exploration, way before ripping into a pump.

tomsn16

iTrader: (283)

'95 ABS pump here if needed
https://www.rx7club.com/market/1163304

j9fd3s

iTrader: (3)

there are also a couple of relays on the ABS pump, one of which fails all the time NA23-43-7A3
the other is HG82-43-7A2

usually they stick on, so the pump just runs all the time, but its not 1999 anymore

Spalato

iTrader: (33)

Here is some inspiration for you:

Wiring modification to implement updated ABS unit | Pale white Rx-7 build (pale-white.blogspot.com)

DaveW

As an aside, in my 31 years of driving my '93 FD, I don't recall ever feeling the pedal pulse or having locked up a brake. I guess I've never braked hard enough to trigger it, which is surprising since when it was fairly new I often demonstrated to passengers how good the brakes are by braking really hard. I certainly have felt the ABS pulse in other cars, but usually on slippery surfaces in the winter.

billyboy

This typically happened on the equivalent of ~ 100mph jink right, followed by a sharpish right a few hundred feet later. Noticeable from my vantage spot, by a small puff of smoke...may have been assisted by him running the kerb too!

DaleClark

iTrader: (55)

Hey Stephen!

FD's ABS isn't super modern but it DOES work. I've had it save my bacon a few times.

That said, get the car up to 40 or so on a flat, clear road and NAIL the brake pedal. You should feel the ABS pulses in the pedal and hear the "chirp chirp chirp" of tires locking and unlocking. The braking should be dead straight.

If one wheel locks totally up, something is wrong. Not sure if there's a troubleshooting guide on that. Probably not a wheel sensor since the ABS light will come on if a sensor isn't phoning home.

Dale

suzukisteve

iTrader: (4)

So I've heard some of yall say that you never have had ABS go off on your car. The other day while driving my 2017 Civic to work I had to make an emergency stop and I barely felt my ABS engage, it also was a very rapid pulsation. My Rx-7, by contrast has large slow pulsations in its ABS and yes, one of the wheels will lock up sometimes. I may need to look into those relays that J9FD3S was talking about. I dont have the confidence to swap to a 99 spec unit, plus if my memory serves me correctly, that unit is a 4 channel unit, which would require pluming an extra brake line.

j9fd3s

iTrader: (3)

that is correct, to get the 4th channel you need a separate brake line to each wheel. you would need to add an extra rear. in theory its not too bad

billyboy

The system in the last version VI cars (ECU on pump), still only runs 3 lines.

Strangely enough, in simpler cars of the past, you used to look at what wheel wasn't locking.

F1blueRx7

iTrader: (5)

There's something wrong, it could be the ABS pump itself, but usually if one side is locking up harder than the other I'd be looking at the brake calipers a little harder as well to ensure none of the pistons are sticking. I had to replace three pistons when I rebuilt my calipers due to pitting in the sealing surface.

I removed my ABS pump because it was leaking, I kept all the parts just in case I wanted to reinstall it or replace it but I have zero problems without it, maybe I just don't push the car hard enough to tell.

When I had my 89 Turbo FC there was a mazdatrix ABS delete kit that looped the lines where the pump was. Those ABS pumps were much worse than the FD Pumps, also died leaking. I locked the brakes on that car and the car turned sideways on I-95 at 70 MPH. It did this without an ABS pump, I believe this was due to a caliper issue, I wasn't able to reproduce (and wasn't willing to try) before the car was destroyed by a drunk driver.