Should i throw out the a.b.s or use it on the new race car?

[Ted]

I'd keep ABS, you know that feeling when its gone slightly pear shaped, or you need to carry full braking across the face of the corner? Knowing you can do that and steer, while panicking, is quite reassuring when you get out the other end still facing the correct general direction. Only downside is that when you do hit the wet grass, it won't pull up so well.

Speaking of EBD, EBA is quite interesting too. Sometimes it thinks that you really wanted to brake hard but you are just too soft with the pedal, so then goes to max braking with ABS pulsing away.

[Caffeine]

BTW, AFAIK the NB ABS are all three channel - that is one each for the front wheels, and one for the rear. This means that either rear wheel can signal the ABS unit about an imminent lockup, but the unit will pulse both rears.

The 10AE was 3 channel, NB8B and later are 4 channel.

[greenMachine]

BTW, AFAIK the NB ABS are all three channel - that is one each for the front wheels, and one for the rear. This means that either rear wheel can signal the ABS unit about an imminent lockup, but the unit will pulse both rears.

The 10AE was 3 channel, NB8B and later are 4 channel.

Caff, you want to put a small wager on that - like, oh lets see, ... your house?

[de Bounce]

I thought you needed power to the ABS unit to open the lines to the brakes. There's a reason you need the ignition on to bleed an NB8B. So I don't think you can do easy back to back tests like that.

I am almost absolutely sure that the brakes on an ABS car work with no power - the mind boggles at an abs car not stopping because power failed, they are designed to be fail-safe. Happy to be corrected though (well, not really happy, I don't think I want to know that an electric problem will affect my brakes!).

The brakes in my NB8B work fine with the fuse pulled.
I have always pulled the fuse on my ABS equipped cars when competing on dirt.
As for bias towards either front or rear - unknown.

As for bleeding your brakes with the ignition on, I doubt if that does anything.

[deviant]

Some manufacturers advise having ignition on to bleed the brakes, I think it is something to do with the ABS pumps working and not letting air get trapped which is vitally important!

How good is the ABS in an MX5? The WRX I used to track had ABS and brake force distribution which was set up very well for fast driving...the tyres would start howling before the ABS kicked in and it would even let you get just a little bit out of shape under braking which was ideal.
The MASSIVE downside (and its the same for a lot of modern cars) is that after all the safety systems have been activated the car 'cross checks' its systems for 5-10 seconds, at the next corner the brake pedal would be absolutely rock hard. I could still brake okay but it took a herculean effort, at the next corner they would be back to normal.

I have also found that some cars the ABS is way to keen to kick in. The tyre is giving its maximum grip at the point it is howling so it is no good if the ABS kicks in before that point.

[greenMachine]

... The tyre is giving its maximum grip at the point it is howling so it is no good if the ABS kicks in before that point.

this is getting to the real nub of the question.

I would hope that Mr Mazda, when he was setting up the ABS, recognised that this was a sporty car, and that the ABS would need to cope with sporty driving. Hopefully, this means that instead of cutting in at 85% (to pick a number out of the air), we get a much higher percentage braking force before the ABS is tripped.

It was principally the resolution of this question that lay behind my suggestion above for a proper back-to-back test of an ABS equipped car using the ABS, and then without the assistance of the ABS.

Does anybody know of anyone who has hacked ABS software? It would be really interesting to get a handle on the algorithms used, and their suitability (or not) for track use. Hmmm, perhaps I will take a wander over and have a look on the big board ...

[lightyear]

I was told you can put resistors in line to allow the abs to kick in later. But still haven't found the relavent info.

[greenMachine]

I was told you can put resistors in line to allow the abs to kick in later. But still haven't found the relavent info.

I doubt it. As I understand it, the sensors on the wheel generate a form of pulsed signal (I'll let the geeks expand/correct ), and the ecu (not the engine ecu) interprets that. I suspect there is an element of the wheel speed and wheel speed delta, as well as comparison with what other wheels are doing. You would need to generate some pretty sophisticated signals (not simply delta amps or ohms like a temperature sensor) to fox it. They run diagostic tests too, which would need to be fooled by any additional inputs/modifications. If it gets confused it simply shuts down.

I am not saying it can't be done, but it is not like plugging in a piggyback ecu.

[Fatty]

yeah i thought you could use a resistor to reduce the output of the ABS sensors, thus making them kick in later. but upon reflection i think i may have been thinking of the g sensors that are used as part of the traction control system on later model cars. apparently the g sensors on some cars output a 0-5v signal that varies up or down from a "normal" position of 2.5v, depending on if you're turning left or right. so yeah those can be easilly fiddled with.

if the abs sensors do indeed use a pulsed output then yeah, it would be a lot more tricky to find a work around. i know you can get a "digital pulse adjuster" from jaycar. it may work...but at $80 a pop, for all 4 wheels it'd soon add up. in which case, an adjustable prop valve would probably be the way to go.

[greenMachine]

If you want to have the latest 'must have' before it becomes a 'must have', try http://www.bosch-motorsport.com/cont...rochure_en.pdf . The mind boggles at how you could play with this, and on-the-go adjustment too!!

Remember when we just got in cars and drove them?

No sign of any hacks yet

[greenMachine]

... in which case, an adjustable prop valve would probably be the way to go.

Fatty, the two are not alternatives, but complementary. See my earlier post referring the use of both. The idea is to dial out as much 'premature' ABS intervention as possible. You would still want to do this, even with a re-mapped ABS. More aggressive mapping of the iABS intervention is a separate issue, not affected by a prop valve.