Disabled the driving aids. Here are my impressions.

[chrisl]

Originally Posted by diss7

The point is still being missed, that the car brakes harder without ABS. Because this car can trigger abs on g-forces.

Go test it yourself if you don't believe me.

Then throw in better brakes and tyres.

Car will still trigger abs at the same g. It doesn't know the car is able to brake much harder now, so it'll engage the abs at the same point regardless.

I take it you have some documentation showing this? Or perhaps test results with an actual G-meter?

[diss7]

Originally Posted by chrisl

I take it you have some documentation showing this? Or perhaps test results with an actual G-meter?

I have noticed it, specifically on the track.

With abs on, I brake at a certain point. With abs off I can move that point closer to the corner.

If you don't believe me, do your own testing.

[strat61caster]

Originally Posted by diss7

I have noticed it, specifically on the track.

With abs on, I brake at a certain point. With abs off I can move that point closer to the corner.

If you don't believe me, do your own testing.

Don't you get better braking with a small amount of lock up? The ABS would kick in before the optimal braking point "threshold braking" regardless of tires or wheels.

"The optimal amount of braking force is developed at the point when the wheel just begins to slip."
[ame="http://en.wikipedia.org/wiki/Threshold_braking"]Threshold braking - Wikipedia, the free encyclopedia[/ame]

For your point to be valid you would have observed no increase in braking performance with the upgraded tires and ABS on compared to OEM tires and ABS on. I'm with chrisl, I'll believe it when I see it, I don't have the resources to test it. Armchair racing ftw.

(Side Note: The brake pads/bbk won't change your stopping distance unless you're taking brake fade into account, OEM brakes are more than adequate to lock up the wheels even with stickier rubber)

[chrisl]

Originally Posted by diss7

I have noticed it, specifically on the track.

With abs on, I brake at a certain point. With abs off I can move that point closer to the corner.

If you don't believe me, do your own testing.

Oh, I believe that threshold braking allows you to brake later in perfect conditions than ABS does, at least with many ABS systems (though with a lot of ABS systems, you can still threshold brake without disabling ABS, you just have to hold it at the threshold just before ABS enables). However, as strat61caster said, what you'd really need to compare isn't ABS on vs ABS off, it's ABS on with stock tires compared to ABS on with sticky tires. If what you're saying is true, there should be no difference. I'd be willing to bet that in reality, you do still have improved braking performance on sticky rubber with ABS engaged than you do with stock rubber.

[Kazuya]

This forum thread tags just gets better with every hot topic.

[diss7]

Originally Posted by chrisl

Oh, I believe that threshold braking allows you to brake later in perfect conditions than ABS does, at least with many ABS systems (though with a lot of ABS systems, you can still threshold brake without disabling ABS, you just have to hold it at the threshold just before ABS enables). However, as strat61caster said, what you'd really need to compare isn't ABS on vs ABS off, it's ABS on with stock tires compared to ABS on with sticky tires. If what you're saying is true, there should be no difference. I'd be willing to bet that in reality, you do still have improved braking performance on sticky rubber with ABS engaged than you do with stock rubber.

And with ABS off its better again. Because with the sticker rubber (and we're talking semi slicks by the way) the ABS kicks in before the tyres slip, because it registers a higher g-force than it thinks the car is capable of (on stock tyres, which is obviously what it'll be programmed for.)

[enwave]

Originally Posted by diss7

And with ABS off its better again. Because with the sticker rubber (and we're talking semi slicks by the way) the ABS kicks in before the tyres slip, because it registers a higher g-force than it thinks the car is capable of (on stock tyres, which is obviously what it'll be programmed for.)

Is this true? I was always under the impression that it took a fraction of a second change in tire rotation speed slowing down to trigger ABS. Like they almost have to lock a tiny bit before the ABS releases and pulses. Like, significantly faster than an expensive BBK and race pads could even yield.

I had no idea they were g-force triggered. This makes a big difference in the effectiveness of the system when compared to no ABS at all. I'd like to see some documentation on that.

EDIT: quick googling seems to yield that most ABS systems are magnetic wheel speed sensors and not g-force sensors. It appears that a gyroscope is occasionally used for when the car is rotating, but not for accel/decel in ABS. TCS does use accel/decel, so I'm sure the data could be shared between the two systems. I'm interested in finding out what this car has.

Sent from my iPhone using Tapatalk

[stugray]

I wasnt even aware that the car has a G-force meter.
When I log G-force using torque & the OBD-II port, the G-force meter is read from my phone....

[dodj]

Originally Posted by diss7

And with ABS off its better again. Because with the sticker rubber (and we're talking semi slicks by the way) the ABS kicks in before the tyres slip, because it registers a higher g-force than it thinks the car is capable of (on stock tyres, which is obviously what it'll be programmed for.)

I thought abs used pulses from the wheel hub not an accelerometer. If it uses an accelerometer that would be true, but less so if it uses pulses. It would not work in wet or icy conditions if it didn't use pulses either.
But for abs to be really effective for MAX tire braking performance, you would have to include a lot of variables (fuel load, tire compound, track surface, driver weight, etc) so the stock valving/pgming is likely pretty far from optimal.

[strat61caster]

Originally Posted by diss7

And with ABS off its better again. Because with the sticker rubber (and we're talking semi slicks by the way) the ABS kicks in before the tyres slip, because it registers a higher g-force than it thinks the car is capable of (on stock tyres, which is obviously what it'll be programmed for.)

So you saw an increase in performance with sticky tires and leaving ABS on?

That contradicts your point entirely about the ABS being "G-force triggered".

Originally Posted by enwave

EDIT: quick googling seems to yield that most ABS systems are magnetic wheel speed sensors and not g-force sensors. It appears that a gyroscope is occasionally used for when the car is rotating, but not for accel/decel in ABS. TCS does use accel/decel, so I'm sure the data could be shared between the two systems. I'm interested in finding out what this car has.

Trust your research, not random forum posts. I'd say 99.99% of new cars sold today have a handful of accelerometers scattered throughout the car that seem to be primarily for airbag deployment, wheel speed sensors are more reliable for ABS and allow for different compound tires to be fitted without a loss in performance of the system.

Throw some low rolling resistance overinflated rock hard tires on and an accelerometer based ABS would allow you to lock up the wheels all day long, no company would sell that system, it'd be a catastrophe the second a hyper miler went off the road.

[BRZ21]

abs is read from reading wheel speed sensors and comparing them to each other. thats why even on a sheet of ice abs will kick on because the one milli-second it releases the brakes on one wheel and reads that w/o braking the car would be doing x mph but when the brakes are applied (at the driver's current pressure) it is doing y mph.

with that philosophy, if you put stickier tires on and leave abs on the car should stop faster than stock tires with abs on. the car doesn't care how much grip the tire has in general, only at the moment its trying to stop.

with all of that said, abs systems are generally on the aggressive side, meaning they'll generally engage the moment they feel slippage and then will release the brakes (pulsing) slightly BEFORE they will slip again, so yes, technically if you are able to threshold brake within the small window you can stop a car faster than abs can.

all of that completely excludes tc and asc

edit: that is also only in straight line braking. cornering will effect this as the inside wheels and outside wheel speeds will vary.

[diss7]

Of course it uses G-force data, thats how it determines what is going on for the EBD and stability as well.

My posts are not contradictory. With stock low grip tyres, you can lock them up, ABS then kicks in. Removing the ABS might acheive a fraction more braking performance, but marginal.

Increase the tyre compound, and the ABS is noww triggered by g-force, not tyre slip. The car is registering a g-force beyound what the stock system believes is safe, so it pre-emptively engages ABS, as it believe lockup is inevitable (as it probably would be on stock tyres)

If you think I'm full of shit, thats fine. Easier to dismiss something you dont want to believe.
The whole concept was put in my head by Toyota Racing NZ. I was having a moan to one of the tech guys that I wasn't really noticing any increased braking performance with my bbk and semi slicks, not as much as I expected anyway. He said that they noticed the same thing while testing the TR86 race car (which has full slicks) so had to reprogramme the parameters, or remove the aids entirely.

There are other tuners/software developers that know about this also. They have been asked if they would provide information on how to reset/adjust these and their response was one of hesitation.

Like I said, put some semi slicks on, go to the track and find out for yourself. I know what I experienced.

I would upload track data, but I've only been recording using the inbuilt iphone GPS, which is only 1hz. Its far from accurate, as can be seen by the wavy lines it records me doing on the track. I want get a 20hz gps receiver, and a bluetooth OBD plug. Both the app and the car can record GPS, and then I can compare.

FYI I'm getting this gear to analyse my data to improve my lap times, not to prove something I already know to be true.

You can see here why theres no point looking at my current data, by how inaccurate 1hz is. Plus I didnt log/record anything from the car.

https://www.facebook.com/photo.php?f...9&l=5d0598dcb7

Edit - to clarify (as previous posts by others above are still filled with misunderstandings) the ABS works on tyre slip OR g. It can engage typically with it detects slip, or if a preset g value is exceeded. Its not one or the other.

AGAIN, put some very high grip tyres on, and go test for yourself if you don't believe it.

[stugray]

So if the car decides it needs to engage ABS based on G-force (excessive deceleration) being above a certain limit, What does it do?

If no wheels are slipping and they all show the same rotation, what could the ABS possibly do to remedy the non-situation?

I am really curious, because engaging ABS based on G-force doesnt make any sense.
I would like to see that in writing.

So if you are going up a steep hill, ABS will be less likely to engage, and if going down a steep hill , the ABS is MORE likely to engage?

[Ralph Spoilsport]

Thanks for your observations. Sorry you getting such a shit shower for it, it's totally unwarranted in my view.