Hi I was wondering if anyone knew how difficult it would be to keep ABS with a bigger brake kit or get it set up correctly. I have heard of peole fitting bigger brakes then having an accident because the wheels locked up. So can ABS be kept or reset for the new setup? how? Electronic jiggery pokery or a mechanical solution?

Safety is my consideration when looking to go down a bigger brake route.

try this...

 

http://www.300zx.co.uk/forums/showthread.php?t=119634&highlight=abs

 

should give you all the info.

 

al.

Explanation by Jeff of Zedworld about ABS - how & why it works etc :

 

 

ABS and Big Brake Kits

 

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The tech answer to the question of how your zed abs system will react to larger calipers / discs is explained a little lower down , it is a bit of a read but well worth it if you want know the definitive answer to the question.

 

The real world solution

From the tech answer below it is clear that the abs system can be effected and not in a good way, however and this is crucial to remember when fitting a brake upgrade kit "just because it works on car xxx, it must work on your zed " approach, is way wrong. What you need to ensure is the brake upgrade kits is either designed with the characteristics of the original braking system taken into account to minimise the differences, or the donor car brake system has the same or very similar characteristics and in that way the ABS system WILL work as originally designed.

 

To this end upgrades such as the Nissan Skyline GTR 33/34 Brembo calipers and discs will work with the 300zx set up as the Pressure-Torque And Pressure-Volume Relationships ( explained below ) is compatible, however the Nissan 350z is not, after market kits designed as vehicle multifit are also rarely compatible.

 

One final word of warning, disconnecting or disabling ABS safety systems WILL effect your insurance and could in the event of a fatal accident leave you carrying the can!

 

Jeff TT

 

 

Definitions

ABS – Anti-lock Braking System – An electromechanical control system designed to monitor and influence wheel dynamics, and ultimately vehicle dynamics during braking manoeuvres. In order of priority, these systems are intended to enhance vehicle 1) stability, or the prevention of over steer 2) steer ability, or the prevention of under steer and 3) stopping distance. Typical systems consist of 3-4 wheel speed sensors, an ECU containing the algorithm processing the wheel speed information, a series of solenoid-driven valves, and a pump-motor subsystem which can be actuated to interrupt and release brake fluid pressure from the wheel-end brake components (calipers and such).

 

ABS Control In Super-Slow-Motion

In order to best explain how the ABS "depends" on the base braking system, let's have a look at a typical ABS event at the micro level – from the processing algorithm's perspective.

Say you are driving down the motorway at 75 MPH ( tut , tut ) when all of a sudden a lorry in front of you spills its load of water across all three lanes of traffic. Now, this alone would not be so bad, except the water is still sealed in large drums anyone of which would certainly make a mess of your zed, time to take evasive action.

Being the trained high-speed individual that you are, you immediately lift off the accelerator , dip the clutch (if your zed is a manual), and at the same time hit the brake pedal...but in the heat of the moment you hit it a little too hard!!

 

Previously the ABS ecu was hanging back watching the world go by, seeing a constant stream of 75 MPH signals from its four wheel speed sensors. Let’s call this "observation mode." Upon your application of the brake, however, the ABS snaps to attention, its antenna up, ready for action.

You have just hit the brake pedal after all, and who know what’s coming next.

After 50 milliseconds (it’s actually much faster than that – 7 to 10 milliseconds is typical – but it easier to work out) the ABS takes another snapshot of the wheel speed information in an attempt to figure out what's going on. This time the wheel speed sensors are all reporting a speed of 74 MPH. Doing a quick calculation, the ABS determines that in order to have slowed 1 MPH in a 50ms period the wheels must be decelerating at a rate of 0.91g’s. Because you are driving a sports car, the engineer who calibrated the system ‘taught’ the ABS that your car is capable of decelerating at this rate, so the ABS continues to hang back and watch the event from the spectator’s booth. No problem so far.

 

The next 50ms, however, are a little more interesting. This time around, the wheels are reporting 72.5 MPH. Now, it may not seem like a big jump, but to slow 1.5 MPH in a 50ms window equates to a deceleration of 1.36g’s. Not alarming, but the ABS ‘knows’ that based on this deceleration level, the wheels are probably beginning to slip a little more than they should – after all, your car is probably not decelerating at quite 1.36g’s..and any error between the two indicates slip.

 

ABS is now in "ready mode." It’s probably too soon to jump in, as the wheels might spin back up on their own in the next 50ms loop, but things are definitely looking bad!

 

As the first drum of water bounce left and right, missing your car by inches, you stay on the brake pedal but push even harder. This time around, the left front wheel speed sensor is registering 68 MPH – a 4.5 MPH drop in the last 50ms, or a deceleration level of 4.1g’s. Doing the math faster than you can (after all, you are busy dodging barrels of spring water), the ABS quickly comes to the conclusion that, unlike the left front wheel at this moment, the car cannot possibly be decelerating at 4.1g’s. Best case is that the car was decelerating at 1.0g (or thereabouts) over the last 50ms, so the ‘real’ vehicle speed is still somewhere around 71.5 MPH, even though the left front wheel speed is reading 68 MPH – a 3.5 MPH error.

 

So, based on a wheel deceleration of 4.1g’s, a slip level of 5% (3.5 MPH¸ 71.5 MPH), and a couple other factors not listed here, the ABS jumps in and enters "isolation mode." (Note that the wheels are nowhere even near "wheel lock" – the 100% slip point.) The first thing the ABS does is shut off the hydraulic line from the master cylinder to the left front caliper, isolating the driver from applying more pressure – after all, it was the driver that got us into this mess in the first place.

 

Next, the ABS starts work in "decrease mode," releasing the excess pressure from the left front caliper in order to allow the left front wheel to re-accelerate back up to the vehicle’s actual speed – 71.5 MPH in this case. Since the ABS knows how quickly the wheel is decelerating (4.1g), how fast the car is actually going (71.5 MPH), and the pressure-torque characteristics of the left front caliper/pad/disc assembly (we’ll come back to this one in just a second), it can precisely calculate how long to open its release valve to vent that extra pressure, leaving just enough pressure in the caliper to maintain 1.0g of deceleration (or thereabouts).

 

Let’s say that calculated time turned out to be 10 milliseconds. Bang! Valve opens, pressure is released, and 10ms later it closes, leaving just the right amount of pressure in the caliper so that the wheel spins back up to exactly 71.5 MPH, but continues to decelerate at 1.0g. Everything is going as planned.

 

Time to close the loop and enter "increase mode." Once the ABS sees that the left front wheel has returned to near the ‘real’ vehicle speed, it slowly reapplies pressure from the master cylinder to make sure that maximum sustainable brake force is being utilised. To this end, the ABS calculates precisely how long to pulse open the isolation valve, slowly building pressure at the left front caliper until once again the left front wheel begins to slip. It performs this calculation based on – you guessed it – how quickly the wheel is re-accelerating, how fast the car is actually going, and the pressure-torque characteristics of the caliper/pad/disc assembly.

In our hypothetical little world, the ABS calculated that four pulses of 5ms each were necessary to build the wheel pressure back up to the point that the wheel began to slip again, returning to "isolation mode."

The cycle is repeated on all four wheels simultaneously until either the driver gets out of the brake pedal, or until the car has come to a stop. Hopefully, this did not include punting a drum of water or two along the way as the ABS kept all four wheels slips in the 5%-10% range, allowing you to turn and swerve to your heart’s content as the drums bounced out of your path. Happy car, happy driver.

 

 

The Potential Impacts Of "Big Brakes"

Let’s now take the exact same scenario, but add a twist: you are returning home from having that long-sought-after big brake kit installed. You know, the one that required new 18" wheels to clear the 8-piston calipers and 16" brake discs. Driving around the car park you couldn’t believe the improvement in pedal feel and initial bite they displayed. These things must really throw a boat anchor behind the car at high speeds, right?

Well, let's see.

Resisting the temptation to run in the fast lane at triple-digit speeds, you once again find yourself behind the lorry at 75 MPH. drums fly and you again stamp on the brakes, but with the increased confidence of your new hardware to slow you down in time. Plus, you now know how the ABS works, so you hit the pedal hard confident that you will have both deceleration and steer ability. It couldn’t get any better.

Like scenario 1, after the initial 50, 100, and 150 milliseconds the ABS takes snapshots of the wheel speed information and registers 0.91g’s, 1.36g’s, and 4.1g’s on the left front wheel. Again the ABS quickly comes to the conclusion that, unlike the left front wheel at this moment, the car cannot possibly be decelerating at 4.1g’s. Best case is that the car was decelerating at 1.0g (or thereabouts) over the last 50ms, so the ‘real’ vehicle speed is still somewhere around 71.5 MPH, even though the left front wheel speed is reading 68 MPH – a 3.5 MPH error. So far, so good – just like last time.

Here’s where things start to get interesting, though. ABS enters "isolation mode" and shuts off the hydraulic line from the master cylinder to the left front caliper, isolating the driver from applying more pressure. Next, the ABS starts work in "decrease mode," and once again calculates that 10ms are required to the excess pressure from the left front caliper in order to allow the left front wheel to re-accelerate back up to the vehicle’s actual speed – 71.5 MPH in this case. Unfortunately, this calculation was based on the standard vehicle’s pressure-torque characteristics of the left front caliper/pad/disc assembly. Let’s talk about this briefly while the drums roll in closer.

Pressure-Torque And Pressure-Volume Relationships

When a braking system is designed and installed, the components are chosen to provide a certain deceleration level for a certain amount of force applied by the driver to the brake pedal. While the overall relationship is critical, there are many ways to achieve the same end…but fundamentally the parts are chosen to work together as a system.

One of the most important relationships for the ABS engineer is the pressure-torque (P-T) relationship of the caliper/pad/disc assembly. In so many words, for a given brake fluid pressure, X, the caliper/pad/disc assembly will build up a certain amount of torque, Y. For the sake of argument, let's assume that adding 100 PSI of brake pressure to the stock caliper in our example vehicle generates 100 ft-lb. of torque.

Another important relationship is the pressure-volume (P-V) characteristic of the system. This relationship defines the swelling or expansion of the brake system for a given increase in pressure. Let’s also say that our stock vehicle brake system ‘swells’ 1cc for every 100 PSI.

 

Unfortunately, there are several big-brake systems available today which pay no regard to the original P-T or P-V relationships of the original vehicle…and in fact many make it a point to affect drastic changes in these relationships in order to give the consumer that feeling of ‘increased bite.’ While the upside is certainly a firmer pedal and higher partial-braking deceleration for the same pedal force, the trade-off can be ABS confusion.

 

Back To The Water Drums

So, back to our example – the ABS has just calculated that a 10ms pressure reduction pulse was necessary to vent that extra pressure, leaving just enough pressure in the caliper to maintain 1.0g of deceleration (or thereabouts)…but the new system with its decreased P-V characteristics (increased stiffness!) releases twice as much pressure as the stock system in the same 10ms window (the equivalent of a 20ms pulse with the stock system)! Of course, the increased P-T characteristics (bigger discs! bigger pistons!) don’t help either, as now three to four times as much torque has been removed from the wheel as with the stock system, leaving only enough torque to decelerate the wheel at, say, 0.3g. In ABS land this is known as a ‘decel hole’ and feels just like you momentarily took your foot off the brake pedal.

 

Now, given that huge pressure decrease, the ABS quickly enters "increase mode," trying to correct and build the pressure back up near the vehicle’s maximum sustainable brake force. This takes time and time equals lost stopping distance.

 

The ABS calculates precisely how long to pulse open the isolation valve and determines that four pulses of 5ms each are necessary, just like before. Because of the new P-T and P-V characteristics however, after only two pulses the wheel is again being forced into slip, leaving the ABS scratching its head and wondering what’s going on. Not expecting wheel slip so soon, the ABS quickly releases pressure in an attempt to recover, but the damage has already been done.

 

The cycle is repeated on all four wheels simultaneously until either the driver gets out of the brake pedal, or until the car has come to a stop…but this time the ABS is always one step behind. In some cases the ABS is robust to modest changes in the base brake system, but in extreme cases there can be a significant negative impact to the vehicle’s steer ability (increased front wheel slip due to poor control) and a measurable increase in stopping distance (multiple ‘make up’ decrease pulses).

So, your chances of stopping in time or swerving to avoid one of the bouncing drums have been decreased. In this game, inches count and you sure need every one.

 

So Big Brakes Are A Bad Idea?

Well yes and no in fact, if designed and chosen properly, these upgrades can make the most of these control technologies while providing all of the cooling and thermal robustness advantages these kits have to offer.

In many cases fabricated adapter brackets to mount them to a variety of different cars, to market the kit as a ‘one-size-fits-all’ without first determining if the system will be compatible with the remaining foundation braking system.

 

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Last edited by JeffTT; 30th November 2008 at 19:04. Reason: spelling

 

 

Controlled tests conducted and results posted by NickZ32

http://www.300zx.co.uk/forums/showthread.php?t=119968

 

With that read above, my own discussion thread on the brake upgrades with a very good contribution from Legrath (knowledgable man!) :bow:

http://www.300zx.co.uk/forums/showthread.php?t=120045

 

 

 

 

HTH

tell me you didn't just type all that?!?! lol.

 

al.

try this...

 

http://www.300zx.co.uk/forums/showthread.php?t=119634&highlight=abs

 

should give you all the info.

 

al.

 

I wouldn't want to get involved a quick drawn showdown down with you mr slickfingers :rofl::rofl:

tell me you didn't just type all that?!?! lol.

 

al.

 

every single word....

 

nope, thank god....:rofl:

So the safest option is go for a skyline upgrade or do nothing improve disks and pads. right?

Save the hassle and just ditch the ABS.

Save the hassle and just ditch the ABS.

 

I understand the reasons behind saying that but i don't think you'd fair well if you ever smashed into anyone or (hope it never happens) kill someone - the insurance company will void the claim and if the courts are involved they are not going to look favorably on someone that removed a safety device.

 

Don't mean to put a downer on it but its different to engine mods and the likes.

 

If its for track use, your cool remove it but for the road it was designed for a reason

So the safest option is go for a skyline upgrade or do nothing improve disks and pads. right?

 

Assumption here is that this is a road car and for road use - I personally would refresh the Zed's braking system and upgrade the pads or disks. If I had the cash to go for a major upgrade, I would make absolute certain that it was an upgrade which either works on the same ABS system as the Zed or was specifically designed to work on it (Brembo, Stillen, K-sport etc)

 

Save the hassle and just ditch the ABS.

 

Under no circumstance would I consider removing the ABS system on a road car. ABS is there for a reason.

 

As Stenorth has mentioned, I would hate to be in an accident facing the liabilities if I had removed it.

Assumption here is that this is a road car and for road use - I personally would refresh the Zed's braking system and upgrade the pads or disks. If I had the cash to go for a major upgrade, I would make absolute certain that it was an upgrade which either works on the same ABS system as the Zed or was specifically designed to work on it (Brembo, Stillen, K-sport etc)

 

 

 

Under no circumstance would I consider removing the ABS system on a road car. ABS is there for a reason.

 

As Stenorth has mentioned, I would hate to be in an accident facing the liabilities if I had removed it.

 

The reason i hit the wall was because of the abs. If i didnt have it i would of skidded and stopped....

The reason i hit the wall was because of the abs. If i didnt have it i would of skidded and stopped....

 

Was it faulty?

Well when upgrading your brake calipers if you fit ones with incompatible volumes you risk having the ABS activating at entirely the wrong moment maybe every time you hit the brake pedal.

 

Just something to take into consideration I think........

I have not got ABS on the black Z and to be honest I just dont miss it ever.

 

Maybe it's the biker state of mind in me having presence of mind to lift the pedal when the wheels lock momentarily tho ;)

Was it faulty?

 

No, it just kept locking unlocking etc and it didnt manage to stop in time, if i didnt have abs i would of been able to stop alot quicker and then i wouldnt of hit the wall..

Well when upgrading your brake calipers if you fit ones with incompatible volumes you risk having the ABS activating at entirely the wrong moment maybe every time you hit the brake pedal.

 

Just something to take into consideration I think.......

 

Exactly

 

I have not got ABS on the black Z and to be honest I just dont miss it ever.

 

Maybe it's the biker state of mind in me having presence of mind to lift the pedal when the wheels lock momentarily tho ;)

 

ye, we never had abs years ago, made you a better driver

Edited January 8, 200916 yr by wow300

I have Ksports on and the ABS is all buggred up. This is the 1st car i have had with abs and it is crap

The reason i hit the wall was because of the abs. If i didnt have it i would of skidded and stopped....

 

 

:rofl: that's the funniest thing I've read all week. If you didn't have it, you may have skidded and lost control causing a larger accident.

I have not got ABS on the black Z and to be honest I just dont miss it ever.

 

Maybe it's the biker state of mind in me having presence of mind to lift the pedal when the wheels lock momentarily tho ;)

 

It not anything to do with "the better driver", which is a load of *****ck tbh because no one is always on the ball, my point is by removing a safety device you've opened yourself up to a world of pain if the insurance or mr plod find out.

 

From what i've been reading, you can have greatly improved braking (from calculations with better materials etc and still stay inside the abs working parameters.

Well when upgrading your brake calipers if you fit ones with incompatible volumes you risk having the ABS activating at entirely the wrong moment maybe every time you hit the brake pedal.

 

Just something to take into consideration I think........

 

well that's where doing abit of research and working the sodding thing out my be useful. If your lazy ring up one of the break specalists like stoptech or brembo etc they willing and give you the information you need

Exactly

 

 

 

ye, we never had abs years ago, made you a better driver

 

It probably made you a more careful driver, granted, but its there for that day when you wake up 6am and your off to work and its icey and you're not awake.

 

fair enough on a track, abs is a pain in the arse, i know it is but on the road where there's oil, ice, loose surfaces abs is a good idea.

stenorth, you should never drive these cars without giving them your full attention.

 

to rely on driver aids is a mistake imo, driving without them does make you more part of the driving experience.

 

if you can't hack the thought of being without abs, be my guest and continue to use it. but have a read of car mads post...........

So how do u know if you've got ABS fitted without doing the obvious and skidding ?

Go onto some loose surface like loose gravel and hit the brakes..... that'll show whether you've got ABS or not !

I think all z32 came with abs, but ye as above.

 

It is a primitive abs system.

I think all z32 came with abs

 

Apparently not - I know some n/a's didn't have it, not sure about TTs tho...