Disabled the driving aids. Here are my impressions.

[strat61caster]

Originally Posted by diss7

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)

I have literally never heard of this from a reliable source. Not in any of my vehicle stability or dynamics courses, none of the technical papers I've read.

It's great that a race team told you this, but I'd love to see ANY reliable evidence of this being true. That is, an accelerometer used as a hard cap to ABS. Link to those tuners and software developers you mentioned?

Here's a manual that seems to focus on Toyota systems.
http://www.autoshop101.com/forms/brake09.pdf

Of note is probably page 10/23 (p. 118) which calls out a 'deceleration sensor' used for AWD systems and determining road conditions, likely snow or gravel vs. smooth surface. The rest of the document focuses on wheel speed sensors being the primary input for ABS, you can see it in the wiring diagrams.


Unless you start coming up with evidence you're just spouting crap on the internet. As an aside, I really wish SAE articles didn't cost like $24 a pop, should have downloaded a fuckton when I was in school.

Edit: realized you never credited an engineer. I know all too well that racers usually find the fastest way around the track but they don't always get the science behind it right.

[diss7]

Originally Posted by strat61caster

Unless you start coming up with evidence you're just spouting crap on the internet.

This may come as a surprse to you, guy; but I'm not here to prove anything to you. Just because I can't provide the information YOU need to believe something, does not make it untrue.

I started this thread to provide my feedback/impressions of what removing the aids achieve.

If you need more data to satisfy your own doubts, I've stated numerous times how you can do it.

If you can't, thats fine. But it doesn't then become my responsibility to provide this for you.

[WolfsFang]

There is no way the abs uses a g force sensor. How will it know if you are on ice or snow.

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[diss7]

Originally Posted by 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?

It pulses the brakes in the same way that it would if slip was detected.

[diss7]

Originally Posted by WolfsFang

There is no way the abs uses a g force sensor. How will it know if you are on ice or snow.

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READ the previous information I have posted.

If works to G or slip.

If you're on ice or snow, its going to be slip that triggers it.

If you are on a dry road, with stickier tyres, you will reach the g limit before lockup, this is when its the g that is activiating the ABS.

[WolfsFang]

Originally Posted by diss7

READ the previous information I have posted.

If works to G or slip.

If you're on ice or snow, its going to be slip that triggers it.

If you are on a dry road, with stickier tyres, you will reach the g limit before lockup, this is when its the g that is activiating the ABS.

I have slicks on my car it with stock brakes I have locked them up twice before abs locked in. It doesn't make sense for it to use a good force sensor at all

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[Rio]

This thread is like the Energizer Bunny. Going, going, going...

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[enwave]

Originally Posted by Ralph Spoilsport

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

I think the recent posts in this thread have all been pretty civil and full of general curiosity. We're no longer talking about just @diss7 and instead learning about how ABS is working on our cars. I know I'm definitely not trying to change his mind, just trying to learn.

Far from definitive, but http://www.toyota.com/esq/glossary.html mentions g-sensors are on cars with VSC, but are tied to VSC and sort of implies they aren't part of the ABS system. But we may never know without talking to someone at Toyota/Subaru directly, or seeing some manuals/techdocs.

Really interesting stuff here. That definition of VSC and @diss7 experience makes me lean toward g-sensors affecting ABS, which makes me feel even more understanding of disabling it.

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[sanmarcosfrs]

No aids here! Daily driven for 16 years. While disabling everything isn't the best idea, it's not exactly a death sentence either

[diss7]

Originally Posted by WolfsFang

I have slicks on my car it with stock brakes I have locked them up twice before abs locked in. It doesn't make sense for it to use a good force sensor at all

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Sorry, I don't believe this.

Are you talking about bald road tyres, or motorsport slicks.

Were they even warmed up?

It's contrary to what I have experienced if this is legitimate.

[WolfsFang]

Originally Posted by diss7

Sorry, I don't believe this.

Are you talking about bald road tyres, or motorsport slicks.

Were they even warmed up?

It's contrary to what I have experienced if this is legitimate.

I have Yokohama a048 and they were warm. I was driving around my town late when a saw a big branch on the floor that I braked hard for. Heard my tires lock up, I tried to lock then up again with hard braking but it could not do it again. Instead the car just braked hard but no abs came on.

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[strat61caster]

Originally Posted by diss7

If you can't, thats fine. But it doesn't then become my responsibility to provide this for you.

That's a fair statement, we're all here willingly after all.

My issue is your describing a system in a way that goes against everything I know to be true and people are believing you without asking for evidence besides your butt sensor.

I'm curious though how you think this works, the wheel speed sensors make sense:
-wheel speed drops very quickly
-wheel is locked up
-release brake pressure
-wheel unlocks, speed increases
-reapply pressure
-repeat

What happens when a the accelerometer trips?
-max acceleration detected
-release brake pressure
-accleration drops
-reapply brake pressure when acceleration drops below braking level?

In my experience I would not trust an accelerometer to regulate my brake system, they're finicky even when set up properly and to get the kind of fidelity, consistency, and longevity out of a unit you'd have to spend a considerable amount of money, a far cry from the LED system outlined in the manual I posted.

Every technical paper I've found focuses on wheel speed sensors, this goes back to the 60's, any mention of accelerometers is meant for acquiring road conditions (ice vs. tarmac as mentioned previously) and nothing more.

http://papers.sae.org/2000-05-0236/
http://papers.sae.org/2002-01-2229/
http://papers.sae.org/2008-01-2985/

Thanks for the discussion, I never bothered to look up wheel speed sensors until today, you learn something new! Again, I'd love to see some evidence of an ABS system utilizing accelerometers for anything other than determining road conditions.

[Deep Six]

I have 4 track days running Khumo V710's (30 UTQG) HP+ fronts HPS rears. I use the 5 sec Track Off (because I can never remember the pedal dance sequence or I'm late as usual for a session). Two heavy braking points 130-70 and 105-45 and I have not felt the slightest bit of ABS modulation. In my AMG the ABS was so pronounced the vibration could be seen in go pro videos. This car however had DTC 70 all around and was braking from 155 into the first turn.

[diss7]

Originally Posted by WolfsFang

I have Yokohama a048 and they were warm. I was driving around my town late when a saw a big branch on the floor that I braked hard for. Heard my tires lock up, I tried to lock then up again with hard braking but it could not do it again. Instead the car just braked hard but no abs came on.

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Few things.
Thats a semi slick not a full slick.
Just driving around town, it will almost certainly not be at optimium temperature. I also note that you appear to live in quite a cold state.
Your ride height suggestes less than ideal alignment, with respect to grip under braking.
If you're driving around the street on those tyres, you almost certainly have them at too high a tyre pressure, which will drastically affect their performance.
Finally, a quick stap on the brakes as you describe could indeed lock a cold, poorly aligned semi slick.
Go do some big braking off the front straight of your local race track, with 30psi warm (so probably 24psi cold depending on local conditions and your driving style) with a known alignment (you may already have this) and see if the results are the same. Try it with the fuse installed, and with it pulled.

Originally Posted by strat61caster

That's a fair statement, we're all here willingly after all.

My issue is your describing a system in a way that goes against everything I know to be true and people are believing you without asking for evidence besides your butt sensor.

I'm curious though how you think this works, the wheel speed sensors make sense:
-wheel speed drops very quickly
-wheel is locked up
-release brake pressure
-wheel unlocks, speed increases
-reapply pressure
-repeat

What happens when a the accelerometer trips?
-max acceleration detected
-release brake pressure
-accleration drops
-reapply brake pressure when acceleration drops below braking level?

In my experience I would not trust an accelerometer to regulate my brake system, they're finicky even when set up properly and to get the kind of fidelity, consistency, and longevity out of a unit you'd have to spend a considerable amount of money, a far cry from the LED system outlined in the manual I posted.

Every technical paper I've found focuses on wheel speed sensors, this goes back to the 60's, any mention of accelerometers is meant for acquiring road conditions (ice vs. tarmac as mentioned previously) and nothing more.

http://papers.sae.org/2000-05-0236/
http://papers.sae.org/2002-01-2229/
http://papers.sae.org/2008-01-2985/

Thanks for the discussion, I never bothered to look up wheel speed sensors until today, you learn something new! Again, I'd love to see some evidence of an ABS system utilizing accelerometers for anything other than determining road conditions.

I can't enter into more technical detail regarding this discussion than I already have. I don't doubt the sources you are providing or your knowledge at all. All I am doing is providing the feedback on what I believe is happening and way.

I'd really like it if someone decided to try to replicate my findings, independantly from myself.