Who knows their ABS system?
06-01-2006, 12:03 PM
#1
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Who knows their ABS system? Stock 10 bolt abs ring on the carrier (3 ch.) is 106 or 108 teeth I forgot the exact #. My new ring is 128 teeth. The abs light is not on, so the system is seeing a tone, but for every revolution of the axle, the abs system will see approx 20% more tones from the rear axle than it should thinking the car is moving faster than it actually is. Like I said the ABS light is off, and the low trac light doesn't come on, so all is happy on the dash. But I would like to get the ABS performance back to where it was because I plan on road racing quite a bit.
Question is, how can I modify the electrical signal to report ~20% less signals per axle revolution? Is this even possible? Electrical guys?
Input or suggestions appreicated.
Question is, how can I modify the electrical signal to report ~20% less signals per axle revolution? Is this even possible? Electrical guys?
Input or suggestions appreicated.
06-01-2006, 09:58 PM
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How would it know to how to synchronize? Does it look at the VSS (vehicle speed sensor) and calculate the difference to compensate?
What I'm thinking is that it sees the rear axle moving at a different rate than the front wheels, not enough to set a code or turn the INOP light on, but enough to degrade the performance of the system when its needed under heavy braking. We were out road racing a few weeks ago in the rain, and the ABS didn't seem right. And I didn't feel too confident with diving into turn 1 with the way it was working.
I guess a better question might be, how does the brains of the ABS operate? Synchronize?
What I'm thinking is that it sees the rear axle moving at a different rate than the front wheels, not enough to set a code or turn the INOP light on, but enough to degrade the performance of the system when its needed under heavy braking. We were out road racing a few weeks ago in the rain, and the ABS didn't seem right. And I didn't feel too confident with diving into turn 1 with the way it was working.
I guess a better question might be, how does the brains of the ABS operate? Synchronize?
06-02-2006, 08:24 AM
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I am not, by any means, an expert on this subject. I have just recently experienced quite a bit of trial & error. I do believe that the system makes it's own calculations to compensate and synchronize. I think it is a very smart and sensitive system. I don't think it will operate at all if it's not at full capacity.
06-05-2006, 02:45 PM
#5
A dakota digital box can probably do what you're looking for. They make a box that's often used for modifying tach signals and vss signals.
That's a good question about the adaptive mechanism for 3-channel. With a 4-channel it would be reading wheel speed. With a 3-channel it's reading driveshaft revolutions. Seems like the abs computer would have to be able to compensate for different gear ratios... If so, then it seems it could handle the faster output rate of your abs ring too.
That's a good question about the adaptive mechanism for 3-channel. With a 4-channel it would be reading wheel speed. With a 3-channel it's reading driveshaft revolutions. Seems like the abs computer would have to be able to compensate for different gear ratios... If so, then it seems it could handle the faster output rate of your abs ring too.
06-06-2006, 06:40 AM
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Originally Posted by John_D.
With a 3-channel it's reading driveshaft revolutions. Seems like the abs computer would have to be able to compensate for different gear ratios...
The tone ring is on the differential carrier, so gear ratio shouldn't matter. I see what you are saying, but that would only hold true if the sensor/ring were on the driveshaft or pinion. Having it on the carrier will measure actual wheel speed.
I will look into the Dakota box, but if its going to cost $$$ than I might just take it easy on braking and live with it. Thanks for the suggestions.
06-06-2006, 07:03 AM
#7
A digital converter like mentioned above may work for you...there are also other ways by using a modified VSS converter. You can also make slight adjustments with tire diameter selections.
If you're going to be road racing, ABS is not going to be you're best option. 3ch is even worse. You'll be limiting yourself to tires you can use as well as relying on the computer to tell you when your braking is not proportioned correctly...ABS works well for general driving and straight line stopping distances but certainly not during RR conditions. I hope you don't have TCS as well...
Instead of using ABS as a crutch, allowing the computer tell you when it thinks you need it activated, remove it, take quite a bit of weight out of the front end, increase heat transfer in your engine and bay due to air flow.
Our ABS delete kits all include proportioning valves and allows you to completely removes ABS and associated brackets cleaning up the engine bay quite nicely. You can view our kits in our braking section of the website.
Good luck with your car.
Steve
If you're going to be road racing, ABS is not going to be you're best option. 3ch is even worse. You'll be limiting yourself to tires you can use as well as relying on the computer to tell you when your braking is not proportioned correctly...ABS works well for general driving and straight line stopping distances but certainly not during RR conditions. I hope you don't have TCS as well...
Instead of using ABS as a crutch, allowing the computer tell you when it thinks you need it activated, remove it, take quite a bit of weight out of the front end, increase heat transfer in your engine and bay due to air flow.
Our ABS delete kits all include proportioning valves and allows you to completely removes ABS and associated brackets cleaning up the engine bay quite nicely. You can view our kits in our braking section of the website.
Good luck with your car.
Steve
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06-06-2006, 08:27 AM
#9
Originally Posted by roy
Leave the ABS in there, It does more good than harm on road courses.
I completely disagree; please refer to my comments as to why I make this statement. 3 channels is a very poor design. Pulsing pressure on both rear brakes simultaneously on a turn provides poor results. The four channel setup is better, but still lacks response.
Retaining ABS, a driver is crippled by tire diameters selections one can change. This prevents the driver from attaining better traction over/under-steer results from tire selection. Change the diameter of your tires, change the braking performance i.e. different rotors, different pads completely change the OEM design intent of the cars ABS performance. This is why I state ABS is really is a hindrance rather then a help.
If your car is stock, you drive it daily and use it for general use, not performance racing i.e. drag or road racing, certainly, ABS can provide positive results during hazardous road conditions.
Straight-line stopping, ABS can provide shorter “more controlled” braking on an OEM setup (If the driver uses ABS correctly). I’ll mention this now so that no one asks what do you mean “correctly”? The reason I state “correctly” is to the fact that the average driver when in a panic stop during brake pulse sensation (when ABS is active) , many unaware drivers believe there is something wrong with their brakes so they release the pedal thus negating braking enhancements. There still are many folks who still manually pulse their brake pedal.
06-06-2006, 09:31 AM
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I understand what you guys are saying and I plan on taking all that into consideration. I've been thinking about it, and if the abs is going crazy under braking (in dry condidtions) I am probably being to agressive on the brakes and should correct my driving style. I guess what started my concerns with the abs was when we were running in the rain last month. There were a few times where it got hairy and it wasn't a comforting feeling having the rear axle start to lock and hop. This is probably a combination of a 3ch braking system, the geometry of our torque arm suspensions, and the fact that I am on stock shocks/spings/ride height and the car takes a nose dive under braking which probably adds to unloading the rear.
I run R compound tires on the street in the front unless the skinnies are on but that is once in ahwile. I think I would be fine without abs because in the dry it seems the grip of the front tires overpower the brakes and would take alot for them to lock up anyways.
I will have a look at your delete kit, but I don't plan on touching anything anytime soon. Do you have something that plugs into the stock sensors to get rid of the light on the dash? I suppose black electrical tape on the inside of the panel would suffice though.
I run R compound tires on the street in the front unless the skinnies are on but that is once in ahwile. I think I would be fine without abs because in the dry it seems the grip of the front tires overpower the brakes and would take alot for them to lock up anyways.
I will have a look at your delete kit, but I don't plan on touching anything anytime soon. Do you have something that plugs into the stock sensors to get rid of the light on the dash? I suppose black electrical tape on the inside of the panel would suffice though.
06-06-2006, 09:44 AM
#11
Black electrical tape or just remove the bulbs the next time you're in the dash.
What you've described (rear wheels locking up first), can be dangerous if not corrected. Think of when you were kid (not knowing your age)…in snow, playing around with the emergency brake puts the car into spins very easily. During cornering, the rear end if it locks as you stated can put your car in a spin easy.
You want to use the most clamping force possibly without locking your wheels while in correct proportion. This will provide very good braking characteristics. A proportioning valve can help you tremendously. The valve can fine tune your bias to correctly adjust for a variety of parameters. What the valve does is gives you the ability to adjust pressures to equate for traction variances with different tire combos, different rotor/pad/caliper combos.
What you've described (rear wheels locking up first), can be dangerous if not corrected. Think of when you were kid (not knowing your age)…in snow, playing around with the emergency brake puts the car into spins very easily. During cornering, the rear end if it locks as you stated can put your car in a spin easy.
You want to use the most clamping force possibly without locking your wheels while in correct proportion. This will provide very good braking characteristics. A proportioning valve can help you tremendously. The valve can fine tune your bias to correctly adjust for a variety of parameters. What the valve does is gives you the ability to adjust pressures to equate for traction variances with different tire combos, different rotor/pad/caliper combos.
06-06-2006, 10:14 AM
#12
the ABS operates off the the change (delta) in wheel speed. because of this, that slight tooth count change is not critical.
its like this... the wheel is traveling 30mph... suddenly its going 5mph. the computer knows this 25mph change over x number of milliseconds is too great... so it lets off that brake... so the wheel can only slow down so fast....
this is why it can limit your braking on a road course.. it doesnt realize you have super sticky tires, so when it does kick in, you're not using the full potential you could get.... now IDEALLY, you would tune the ABS for the slicks or R compound tires or whatever... then it would work great. this is what F1 and other cars were doing before the sanctioning bodies outlawed ABS.
now me personally, id leave the ABS on there anyway.. because i realize that while the ABS only lets me use 90% of the potential... my skillset isnt strong enough to exceed that anyway... id rather overbrake a tad and have ABS help so i can steer into the turn, then lock them up and slide out to meet MrSandtrap and his friend Tirewall.
its like this... the wheel is traveling 30mph... suddenly its going 5mph. the computer knows this 25mph change over x number of milliseconds is too great... so it lets off that brake... so the wheel can only slow down so fast....
this is why it can limit your braking on a road course.. it doesnt realize you have super sticky tires, so when it does kick in, you're not using the full potential you could get.... now IDEALLY, you would tune the ABS for the slicks or R compound tires or whatever... then it would work great. this is what F1 and other cars were doing before the sanctioning bodies outlawed ABS.
now me personally, id leave the ABS on there anyway.. because i realize that while the ABS only lets me use 90% of the potential... my skillset isnt strong enough to exceed that anyway... id rather overbrake a tad and have ABS help so i can steer into the turn, then lock them up and slide out to meet MrSandtrap and his friend Tirewall.
06-06-2006, 11:52 AM
#13
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Originally Posted by SJM Manufacturing Inc
Black electrical tape or just remove the bulbs the next time you're in the dash.
What you've described (rear wheels locking up first), can be dangerous if not corrected. Think of when you were kid (not knowing your age)…in snow, playing around with the emergency brake puts the car into spins very easily. During cornering, the rear end if it locks as you stated can put your car in a spin easy.
You want to use the most clamping force possibly without locking your wheels while in correct proportion. This will provide very good braking characteristics. A proportioning valve can help you tremendously. The valve can fine tune your bias to correctly adjust for a variety of parameters. What the valve does is gives you the ability to adjust pressures to equate for traction variances with different tire combos, different rotor/pad/caliper combos.
What you've described (rear wheels locking up first), can be dangerous if not corrected. Think of when you were kid (not knowing your age)…in snow, playing around with the emergency brake puts the car into spins very easily. During cornering, the rear end if it locks as you stated can put your car in a spin easy.
You want to use the most clamping force possibly without locking your wheels while in correct proportion. This will provide very good braking characteristics. A proportioning valve can help you tremendously. The valve can fine tune your bias to correctly adjust for a variety of parameters. What the valve does is gives you the ability to adjust pressures to equate for traction variances with different tire combos, different rotor/pad/caliper combos.
Originally Posted by MrDude_1
the ABS operates off the the change (delta) in wheel speed. because of this, that slight tooth count change is not critical.
its like this... the wheel is traveling 30mph... suddenly its going 5mph. the computer knows this 25mph change over x number of milliseconds is too great... so it lets off that brake... so the wheel can only slow down so fast....
this is why it can limit your braking on a road course.. it doesnt realize you have super sticky tires, so when it does kick in, you're not using the full potential you could get.... now IDEALLY, you would tune the ABS for the slicks or R compound tires or whatever... then it would work great. this is what F1 and other cars were doing before the sanctioning bodies outlawed ABS.
now me personally, id leave the ABS on there anyway.. because i realize that while the ABS only lets me use 90% of the potential... my skillset isnt strong enough to exceed that anyway... id rather overbrake a tad and have ABS help so i can steer into the turn, then lock them up and slide out to meet MrSandtrap and his friend Tirewall.
its like this... the wheel is traveling 30mph... suddenly its going 5mph. the computer knows this 25mph change over x number of milliseconds is too great... so it lets off that brake... so the wheel can only slow down so fast....
this is why it can limit your braking on a road course.. it doesnt realize you have super sticky tires, so when it does kick in, you're not using the full potential you could get.... now IDEALLY, you would tune the ABS for the slicks or R compound tires or whatever... then it would work great. this is what F1 and other cars were doing before the sanctioning bodies outlawed ABS.
now me personally, id leave the ABS on there anyway.. because i realize that while the ABS only lets me use 90% of the potential... my skillset isnt strong enough to exceed that anyway... id rather overbrake a tad and have ABS help so i can steer into the turn, then lock them up and slide out to meet MrSandtrap and his friend Tirewall.
Nice explanation!
Are you a GM tech? Most resources on the net don't get into the inner workings that deep. I have the 3 GM service manuals for my model year, but I cannot seem to find the one that covers brakes. I wonder if there is more explanation in there.As far as braking into a corner goes, I think for the most part I'll be fine in the dry just adjusting the way I brake. It was a couple of those times in the wet that it started to dance around a bit and I did what I was instructed to do if i couldn't stop, go straight off. (there was plenty of runoff). I did get stuck in the wet grass though. Car was fine, pride was damaged a little.
06-06-2006, 12:33 PM
#14
I'm not a GM tech, but I am a Mechanical Engineer.
There's much more involved with how ABS functions...since you referenced the reluctor wheel as a tone wheel, you probably have researched it somewhat...though correct, I don't believe I've seen anyone else in here refer to it this way.
Without boring you...typical sensors used to measure speed in systems are variable reluctance sensors or latter magnetoresistive sensors typicaly seen in modern ABS systems...try a google search on it if you want to learn more about them. There's probably a good bit of info out there if you want to learn more of the specifics.
The GM manuals and GM techs would not typically get into this type of theory of detail...there is no need for this from them.
There's much more involved with how ABS functions...since you referenced the reluctor wheel as a tone wheel, you probably have researched it somewhat...though correct, I don't believe I've seen anyone else in here refer to it this way.
Without boring you...typical sensors used to measure speed in systems are variable reluctance sensors or latter magnetoresistive sensors typicaly seen in modern ABS systems...try a google search on it if you want to learn more about them. There's probably a good bit of info out there if you want to learn more of the specifics.
The GM manuals and GM techs would not typically get into this type of theory of detail...there is no need for this from them.
06-06-2006, 02:09 PM
#15
Thanks for the clarification on the location of the reluctor, I had never really paid attention to where it's located exactly...
If you plan to be braking into the corners a bit, having ABS can help because it can modulate the brakes on the inside front wheel, letting you achiever higher braking force with the more heavily loaded outside front wheel.
But even so, I'm running a SJM abs delete kit plus a Billingsley manual brake conversion on my racer. (which is still in progress in the garage at the moment...)
If you plan to be braking into the corners a bit, having ABS can help because it can modulate the brakes on the inside front wheel, letting you achiever higher braking force with the more heavily loaded outside front wheel.
But even so, I'm running a SJM abs delete kit plus a Billingsley manual brake conversion on my racer. (which is still in progress in the garage at the moment...)
