Traction Control Function

[bbjones121]

I don't think this was ever part of the Subaru ECU, or probably only on some auto tranny models. Does anyone know if there is any way to create a traction control function in the ECU or in a standalone ECU? I know I wouldn't probably use it too often, but it might be nice to have as a safety net if I ever let any one else drive the car or when I am first learning to control a 1800lb car with this much power.

[Evan78]

I just took a look at the Cars101.com page for the 2011 WRX/STi (http://www.cars101.com/subaru/impreza/wrxsti2011.html) and it lists VDC as available on the WRX and the STi. On the STi, it also says you can have VDC on with traction control either on or off. I haven't kept up with features for the last several years, so I don't know how far back this goes, but perhaps you could implement all the sensors necessary to keep the system functional.

WRX:

Continuous' all wheel drive, mechanically controlled 50/50 front/back power split
VDC (vehicle dyanmics control) electronic stability control with off button.
TCS (traction control system) all speed traction control senses slipping wheels and applies brake to the wheels (s) to help maintain vehicle motion
STi:

VDC (vehicle dyanmics control) electronic stability control with normal, with Traction and off modes (use VDC button)

I'm sure there's some aftermarket traction control system out there if a factory system can't be used. It would be a nice option, I imagine it's been discussed by people building other FFR cars.

[Xelerator]

Might be a good idea for wet track conditions:

http://www.racelogic.co.uk/index.php/en/other-products/traction-control

[BrandonDrums]

Might be a good idea for wet track conditions:

http://www.racelogic.co.uk/index.php/en/other-products/traction-control

Oh that's cool stuff, LOTS of onsite documentation to go through but it looks really promising...

[Evan78]

I'm pretty sure I've seen a demo of it on youtube. Their software looks pretty cool, lots of options.

[bbjones121]

that would be perfect

[crobin4]

Kinda makes one want to lobby for ABS to be retained,uh.

[Niburu]

I was planning on using my footwork as the ABS and Traction Control, to me this is right up there with wanting an automatic transmission option. But that's just me griping, these things would make good additional options or at least leave room for some 818 aftermarket support. They don't need to be on the priority list of things that need to be on the car. I've been driving a non-ABS open diff 1990 Miata for almost a decade now (at certain points as the daily driver) and have never felt the need for any nannies. Granted the Miata is a low power car so you get yourself into less trouble, this I think is what most people are going to have to be careful with - the GO pedal.

[bbjones121]

I was planning on using my footwork as the ABS and Traction Control, to me this is right up there with wanting an automatic transmission option. But that's just me griping, these things would make good additional options or at least leave room for some 818 aftermarket support. They don't need to be on the priority list of things that need to be on the car. I've been driving a non-ABS open diff 1990 Miata for almost a decade now (at certain points as the daily driver) and have never felt the need for any nannies. Granted the Miata is a low power car so you get yourself into less trouble, this I think is what most people are going to have to be careful with - the GO pedal.

You obviously did not read the first couple of posts.

[crobin4]

I was planning on using my footwork as the ABS and Traction Control, to me this is right up there with wanting an automatic transmission option. But that's just me griping, these things would make good additional options or at least leave room for some 818 aftermarket support. They don't need to be on the priority list of things that need to be on the car. I've been driving a non-ABS open diff 1990 Miata for almost a decade now (at certain points as the daily driver) and have never felt the need for any nannies. Granted the Miata is a low power car so you get yourself into less trouble, this I think is what most people are going to have to be careful with - the GO pedal.

Oh, I agree all right. I don't think I'll need either. But, I would hate to see some shove 400HP in it on Street Tires, and go wrap it around a tree. Ever see someone take a Z06 to the AutoX and turn off the nannies, because they think they can handle it?

[Evan78]

I was planning on using my footwork as the ABS and Traction Control, to me this is right up there with wanting an automatic transmission option. But that's just me griping, these things would make good additional options or at least leave room for some 818 aftermarket support. They don't need to be on the priority list of things that need to be on the car. I've been driving a non-ABS open diff 1990 Miata for almost a decade now (at certain points as the daily driver) and have never felt the need for any nannies. Granted the Miata is a low power car so you get yourself into less trouble, this I think is what most people are going to have to be careful with - the GO pedal.I agree that ABS and traction control are not ESSENTIAL items in the 818, but they certainly have their uses. I also drive a Miata w/o ABS and have been fine, but in a panic stop situation, there's no question that I would prefer to have ABS. Even more so if conditions are less than ideal or if one of my loved ones is driving the car. There's a reason why many race series choose to ban some of these systems, they allow for superior performance to what any human can do on their own. It's great to find and exceed the limits of the car in a safe environment where the consequences are minimal, but one mistake on the street can be a life or death situation. The mistake does not have to be your own, there are a bunch of other drivers on the road that you have no control over and no how great your footwork is, the "nannies" can mean the difference between driving away and being hauled away.

[Nativo]

Guys;
Just install a Hydra EMS and it will allow us to develop a traction control system. This EMS has 15 outputs that can be programed with up to 4 different paramaters.

[crobin4]

Guys;
Just install a Hydra EMS and it will allow us to develop a traction control system. This EMS has 15 outputs that can be programed with up to 4 different paramaters.

Like the concept, one problem two words: emissions testing. I've thought about standalone and may eventually go that rout.
Keep um coming.

[Niburu]

Ever see someone take a Z06 to the AutoX and turn off the nannies, because they think they can handle it?
I've seen someone do this in a GTR at an autocross and lose it, on a wide sweeper, which I wouldn't have believed had I not seen it. Next run the nannies were obviously back on.
I'm not saying we shouldn't have ABS or TC or DSC or whatever, but I'd sure like it to be optional if it makes the kit cost more, and definitely still have the ability to turn them off.
I understand there is a time and place for all that stuff, this is why my current daily that I haul the kids around is an E46 BMW 325i with all the nannies left on (it is a 5spd manual though - I can't give that up).
I just don't see the 818 being that kind of car.

[thebeerbaron]

The usefulness of ABS and traction control depend entirely on the quality of the implementation. Bad ABS is worse than no ABS in more cases than you would believe. Traction control is the same. My best guess is that ABS will transfer over just fine from the donor (is it any good there?), but that rolling your own traction control would be devilishly difficult. Lots of track time in lots of conditions, etc etc. It could be done, probably, but I don't think it'll be as easy as dynotuning your engine (which is a different thread).

As far as using this to nanny family members or other drivers of your 818 - whatever happened to old fashioned trust? I know who I can and cannot trust to drive my car and I'm more than happy to say "you're not ready". That said, I know the Cobb Accessport (common Subaru ECU tuner), can have maps for "valet mode". Reduced power and responsiveness across the band. Maybe that's what you really want?

[Evan78]

I'm not saying we shouldn't have ABS or TC or DSC or whatever, but I'd sure like it to be optional if it makes the kit cost more, and definitely still have the ability to turn them off.I'm pretty sure it's a given that these would be optional items. They're so obviously not needed, especially at this price point. I don't think you have anything to fear.

[Oppenheimer]

Why would it cost more? ABS is part of the donor, all the components are already there. You'd need to do a wire-diet to delete the function. I'm thinking it would be just as easy to simply add a disable switch on the dash. That way you don't have as much to fear letting someone else take it for a spin.

[PhyrraM]

One of the reasons I love my '02 WRX is that it didn't have any of that stuff. It has ABS, nothing more. The AWD is completely passive, using simple differentials and viscous couplings for the center and rear. It has a certain amount of understeer built in to keep it safe without the nannies, but lift throttle and technique can cure that. Or a $100 rear sway bar upgrade. Predicatable, passive and reliable (because there is nothing to break).

It's no less fun than any of those cars with the nannies, or at least the cars that I have drove. Some cars with electronic aids can be so fast that one unexpected twitch can scare the crap out of you. Sure, the car may catch itself, but not before it's time for new underwear. Some nannies are downright intrusive, instanly killing the fun.

I think it's kind of ironic that in racing, where being the fastest IS the stated goal, electronic aids are (for the most part) banned. While on the street, where fun should be the primary goal, they are used to make cars amazingly fast. The cars are so fast that they can be a bore to drive at anything close to a sane speed.


(Yes, I know about track days and safety aspects.)


On a related note, having these electronic aids allows manufactures to build basically over-steering, 'fun' handling setups (to please magazine reviewers) and keep them drivable by everyday people with the nannies. What is going to happen in 10-15 years when we turn these cars over to our children and young adults and the electronics stop working? We all know that if it's not related to the engine, brakes, or stereo many folks don't, or cannot afford to, fix things properly.

[bbjones121]

When I let someone else drive the car you can be sure that I will be enabling the trac control and hope there is ABS. That would be stupid and irresponsible, to say the least, if you turned the keys over to a vehicle this powerful without some failsafes that could protect their lives.

[Evan78]

As far as using this to nanny family members or other drivers of your 818 - whatever happened to old fashioned trust? I know who I can and cannot trust to drive my car and I'm more than happy to say "you're not ready".My friends and family are not developing their driver skills any more than the normal non-enthusiast population is. If they're not ready today, they'll probably never be ready. Obviously, more people will be "ready" for a car that has more electronic aids/protections than one without. They would also provide some safety net for them to get someone accustomed to the car before turning them loose with no protection. Just like training wheels on a bike.

[bbjones121]

Haha...what happened to trust? I wouldn't even trust myself in this car for a little while.

[PhyrraM]

The more I think about it, the more I think that even ABS will be a chore. I'm *guessing* that the 818 will not use the Subaru front knuckle (because it's in the back). I think it will use the roadster/65 coupe front knuckle with a 5x100 hub and a caliper adapter to use Subaru rotors and brakes.

Sorry, thinking out loud. Carry on......

[PhyrraM]

Haha...what happened to trust? I wouldn't even trust myself in this car for a little while.

QFT! Gonna be a learning curve for sure.

[D2W]

When I let someone else drive the car you can be sure that I will be enabling the trac control and hope there is ABS. That would be stupid and irresponsible, to say the least, if you turned the keys over to a vehicle this powerful without some failsafes that could protect their lives.

I think its stupid and irresponsible to allow anyone to drive your car that they may not have the skill to handle. That's like letting my 14 year old ride my R1 with a throttle stop. ABS and traction control aren't going to stop them from wrapping it around a tree.

[bbjones121]

I think its stupid and irresponsible to allow anyone to drive your car that they may not have the skill to handle. That's like letting my 14 year old ride my R1 with a throttle stop. ABS and traction control aren't going to stop them from wrapping it around a tree.

Umm...you do realize that would probably eliminate everyone you know from driving your car? And even more confounding...you do realize you just made a comparison to an underage kid on a motorcycle?

[Evan78]

This thread is getting off topic. The original question was about options on implementing traction control.

[bbjones121]

This thread is getting off topic. The original question was about options on implementing traction control.

Agreed

[Evan78]

So far, 3 options have come up:


OEM - can it be used?
Race Logic - con: probably more expensive than OEM components, pro: lots of tuning options
Hydra EMS - cons: not obd2 compliant, cost, pros: plenty

I'm not too familiar with the Subaru system, anyone care to shed some light on implementing it on the 818?

According to the info I found, it uses the brakes to control slip, so I'm assuming the ABS system would have to be maintained. I wonder if going from 4wd to 2wd would make a difference. I'm guessing not, the system just cares about wheel slip, so not driving the front wheels would probably just mean they're only going to slip under braking instead of braking and accelerating.

[armstrom]

I can vouch for the Hydra EMS. For several years I was the exclusive dealer for the hydra on the Toyota MR2 platform. I designed the plug and play harness adapter and sold complete PNP kits. Great EMS with lots of extra features. It will convert the car to speed/density fuel metering (eliminating the MAF) but WILL require tuning. Simple changes to your intake or exhaust will alter the VE curve of the engine requiring changes to the fuel and timing maps. MAF based metering (like the stock ECU uses) can tolerate small changes in VE without needing to be adjusted.
-Matt

[armstrom]

most of your basic traction control systems simply reduce engine power when slip is detected. This is usually a progressive system similar to a rev limiter. Every system does it slightly differently but it usually involves retarding timing and/or skipping ignition events entirely. A proper vehicle dynamic control system may be MUCH more complicated and can leverage differential braking to help correct steering inputs and stop wheel spin as well as control of differentials to direct power to different wheels. Systems like this are probably beyond the scope of the 818 project.

[crobin4]

To reiterate: There is no active OEM traction control on Subarus specified as preferred donors '02-'07
We have Race Logic and Hydra at this point.
The OEM ABS would possibly be used for sensors for the above systems.

[mn_vette]

Which models of subarus had traction control. I would have thought that it was pretty useless with AWD and they wouldn't have bothered to put it in. ABS is always good, if you aren't pushing the car past its limits then it won't kick in, and if you are then you might want to be able to steer while braking. You can stop sooner if you just lock up the wheels, but you have no control and tend to flatten one side of the tires. If the 818 uses the same hubs as the donor it should not be a problem to use the stock ABS/ESC controller.

[Evan78]

Which models of subarus had traction control.Good question. As I quoted in post #2, it seems to be on 2011 WRX/STi, but I'm not sure what year it got added.


You can stop sooner if you just lock up the wheels, but you have no control and tend to flatten one side of the tires.This is not true. You can usually stop quicker in certain conditions where locking up the brakes allows you to penetrate a top layer of material to get down to something firm (snow, sand, etc). On pavement, ABS should stop shorter than locking up the wheels.

[Evan78]

To reiterate: There is no active OEM traction control on Subarus specified as preferred donors '02-'07
We have Race Logic and Hydra at this point.
The OEM ABS would possibly be used for sensors for the above systems.The fact that it's not available on the preferred donor years does not rule it out. Race Logic and Hydra are not likely to be on your donor car either.

[forced4]

Why not use front Subaru hubs/spindles for both front and rear? That way OEM ABS could be retained....or am I missing something?

[Evan78]

Why not use front Subaru hubs/spindles for both front and rear? That way OEM ABS could be retained....or am I missing something?As far as I know, FFR has not confirmed what hubs/spindles they intend to use. While it very well may be related, the conversation is about implementing Traction Control, not ABS.

[bbjones121]

Good question. As I quoted in post #2, it seems to be on 2011 WRX/STi, but I'm not sure what year it got added.

This is not true. You can usually stop quicker in certain conditions where locking up the brakes allows you to penetrate a top layer of material to get down to something firm (snow, sand, etc). On pavement, ABS should stop shorter than locking up the wheels.

I have a hard time believing that since rubber gets tackier when warmed up. Why do they spin out before a run down the dragstrip?

[Evan78]

Different tires are designed for different operating temperatures. People don't do that with a normal street tire unless they don't know any better.

If you want to learn more about tire behavior, do some reading on slip angle. To put it in general terms, tires achieve maximum traction with a very small amount of slip.

To think about it another way, locking up a wheel forces a small portion of the tire to do all the work of stopping. If it is allowed to roll, you distribute the work to the entire tire.

[crobin4]

The fact that it's not available on the preferred donor years does not rule it out. Race Logic and Hydra are not likely to be on your donor car either.

Point taken

[crobin4]

Different tires are designed for different operating temperatures. People don't do that with a normal street tire unless they don't know any better.

If you want to learn more about tire behavior, do some reading on slip angle. To put it in general terms, tires achieve maximum traction with a very small amount of slip.

He is strong with the force.

[PhyrraM]

A stopped tire skidding on the pavement has a small layer of molten rubber under it that has a significantly reduced coefficient of friction.

One of the the reasons some surfaces work better with a skidding tire is the small 'ramp' of material that forms in front of the wheel sometimes helps out alot more than one would think.

[Evan78]

he is strong with the force.lol

[bbjones121]

Different tires are designed for different operating temperatures. People don't do that with a normal street tire unless they don't know any better.

If you want to learn more about tire behavior, do some reading on slip angle. To put it in general terms, tires achieve maximum traction with a very small amount of slip.

To think about it another way, locking up a wheel forces a small portion of the tire to do all the work of stopping. If it is allowed to roll, you distribute the work to the entire tire.

I agree that makes sense in theory. I am a mechanical and electrical(not applicable here) engineer. But find me a real world study that proves this. It is pretty mixed.

[Evan78]

I agree that makes sense in theory. I am a mechanical and electrical(not applicable here) engineer. But find me a real world study that proves this. It is pretty mixed.Which part?

[audsyn]

I agree that makes sense in theory. I am a mechanical and electrical(not applicable here) engineer. But find me a real world study that proves this. It is pretty mixed.

Here you go. It's not mixed at all. ABS resulted in significant improvements in stopping distance on all types of pavement, wet and dry. (But not on loose gravel, as has already been discussed.)

http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/VRTC/ca/capubs/NHTSAabsT4FinalRpt.pdf

[bbjones121]

Which part?

Stopping distances with abs or locking the tires are almost identical in real world tests.

[bbjones121]

Here you go. It's not mixed at all. ABS resulted in significant improvements in stopping distance on all types of pavement, wet and dry. (But not on loose gravel, as has already been discussed.)

http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/VRTC/ca/capubs/NHTSAabsT4FinalRpt.pdf

I was trying to find that. thank you.
Around the same time, popular science did the same test on an accord and explorer. Almost identical stopping distance locked or not.

[mn_vette]

Stopping distances with abs or locking the tires are almost identical in real world tests.


No its not. On normal pavement from 60 to 0mph if you lock the tires the tires will heat up and the stickiness of the tires will help slow down the vehicle quite a bit. This tends to destroy your tires. ABS tries to keep the brake pressure just under where the brakes will lock up, but it is still limited by the traction of the tires.

When you start throwing in gravel then its better to just lock up the brakes, but I'm guessing most of us won't be driving our 818 hard on gravel.

[bbjones121]

So what the DOT is saying makes sense. Older ABS systems stopped longer than locking tires, but newer systems are better at recognizing/maintaining the threshold and can stop quicker.

[mn_vette]

If you read through the report you will notice that the type of stopping surface makes a HUGE difference as to which is the best method of stopping. The technology has gotten better, but locking the tires is still going to be better at stopping on dry pavement, but it is destructive to the tires and you can not control the vehicle. Think of a semi jack knifing, its going to slide where ever it goes, but with ABS on your car you can still go around a corner while breaking(given there is some kind of traction) or swerve out of the way of a little kid in the road.

But back to the traction control question. If you were to add it as a saftey precaution for normal driving I think it would be a great idea. i'm not sure the cost of the aftermarket systems would be worth while though.

It might be cheaper but more work to find an OEM system that you could add from somewhere, but you would have to find one that works with the same kind of sensors and applies the brakes for you. I don't think there would be any compatable with the WRX ECU to reduce torque from the engine. But anything is possible.

[bbjones121]

Got it. Sorry to digress off topic. Now we know about the safety benefits of getting ABS to work on the 818.

[PhyrraM]

So what the DOT is saying makes sense. Older ABS systems stopped longer than locking tires, but newer systems are better at recognizing/maintaining the threshold and can stop quicker.

Older systems used just speed sensor input and sometimes tied the rear brakes to one actuator. The system could basically stand alone. In fact, if you go through part numbers, the ECU was the same across many models for some manufactures.

Newer systems are better because they are also programmed with vehicle specific info, such as mass and and tire friction, to help with calculations and even predict impending lockup. Such features and info will be useless, or even a detriment, when used on the 818.

Of course, newer systems also have better computers and faster relays/soliniod/etc.

[Niburu]

I really don't think it's going to be very difficult to stop an 1800 pound car.

[mn_vette]

I really don't think it's going to be very difficult to stop an 1800 pound car.

I don't either, but if we put the brakes and tires of a 3500# car on it I bet it will be very easy to put enough pressure on the brakes to lock them up quickly. The large momentum difference in the cars will make the brakes seem much more powerful.

ABS will definatly be on my list of add ons for this build. The stock subaru system should work just fine for this even though the car is much lighter. The ABS computer should just see it as a lower friction surface.

[bbjones121]

I really don't think it's going to be very difficult to stop an 1800 pound car.

Best point yet! Moving along now.

[Evan78]

locking the tires is still going to be better at stopping on dry pavement, but it is destructive to the tires and you can not control the vehicle.
So what the DOT is saying makes sense. Older ABS systems stopped longer than locking tires, but newer systems are better at recognizing/maintaining the threshold and can stop quicker.Where in the report do you see that?

I don't see them testing locked tires on any dry surface. They test lockup ("Full Pedal" in the report) in the following tests: wet jennite (straight line), grass, loose gravel, abs pads 0-3, and split-mu. In virtually all of those instances, ABS outperformed locking up.

Here's a quote from Section 3.7 "Surface Friction Measurements" (pg 13) (emphasis mine)

The nominal peak coefficient of friction and slide skid numbers of each test surface were determined using standardized American Society for Testing and Materials (ASTM) procedures and equipment. The peak coefficient of friction, determined by using ASTM procedure E1337 with an E1136 tire, usually occurs just prior to wheel lock up when longitudinal frictional forces between the tires and the road surface are the greatest [8,9]. As with the peak values, the skid numbers (100 times the sliding coefficient of friction, determined by ASTM procedure E274 with an E501 tire) presented in Table 3 represent approximate values, as they vary slightly on a daily basis [10,11]. Factors such as surface temperature, weather conditions, pavement aging, and wear all contribute to surface friction variability.

[bbjones121]

Where in the report do you see that?

I don't see them testing locked tires on any dry surface. They test lockup ("Full Pedal" in the report) in the following tests: wet jennite (straight line), grass, loose gravel, abs pads 0-3, and split-mu. In virtually all of those instances, ABS outperformed locking up.

Here's a quote from Section 3.7 "Surface Friction Measurements" (pg 13) (emphasis mine)

Read page 6 and 41. It is in the technology, not the physics, so why do you keep on about that?

[Evan78]

Read page 6. It is in the technology, not the physics, so why do you keep on about that?I am "keeping on" about it because I am trying to learn something. My interpretation is contrary to what you and mn_vette are stating, so I'm trying to understand what data or statements are leading you guys to the conclusion that locked up wheels will stop in a shorter distance than an ABS equipped vehicle. Except for the loose gravel example, I just don't see any evidence of that and I'm asking what you see that I don't.

Here is page 6:

The earlier studies also found that stopping distances on hard, paved test surfaces either stayed the same or were reduced for four-wheel ABS-equipped vehicles. Stopping distance increases of over 25 percent occurred in several cases on loose gravel. In some cases rear-wheel ABS slightly reduced stopping distances and, in other cases, increased it.

The current ABS performance evaluation differs from those previously performed by VRTC in several significant ways. First, the vehicles tested have newer antilock brake systems than those tested in the earlier studies. Second, the vehicles were tested on more surfaces than in the past. Third, the vehicles were tested on a number of surfaces having sudden coefficient of friction transitions (past VRTC testing has found that some antilock brake systems have problems dealing with such transitions). Fourth, the vehicles were tested in additional maneuvers. Again, past VRTC testing found that some systems exhibited braking deficiencies while performing certain maneuvers (e.g., braking while in a hard curve).
Page 41:

The results of this study indicate that for most stopping maneuvers, made on most test surfaces, ABS-assisted panic stops were shorter than those made with best effort or full pedal applications with the ABS disabled (see Table 6). Furthermore, the vehicular stability during these stops was almost always found to be superior with ABS. Although it was not specifically quantified in this study, the absence of excessive yaw while braking enhanced the ease at which the driver could maintain lane position, especially when compared to stops made with panic brake applications and the ABS disabled on split-mu and low coefficient surfaces.

[bbjones121]

I am "keeping on" about it because I am trying to learn something. My interpretation is contrary to what you and mn_vette are stating, so I'm trying to understand what data or statements are leading you guys to the conclusion that locked up wheels will stop in a shorter distance than an ABS equipped vehicle. Except for the loose gravel example, I just don't see any evidence of that and I'm asking what you see that I don't.

Here is page 6:

I don't think you understand what page I am on. I made a comment because i couldnt find the documents i was looking for. All i found was older stuff. Advanced ABS systems should be able to stop quicker. In real life testing on older ABS systems, the breaking distance was similar if not worse than a lockup. The physics are there, but the technology was not. Now it is.

By the way, a normal car could gain from spinning to warm up the tires before a drag run, the main arguement that nobody tried to correct me on was the fact that once warmed up, they only maintain a greater traction if they don't spin again.

[Evan78]

I don't think you understand what page I am on. I made a comment because i couldnt find the documents i was looking for. All i found was older stuff. Advanced ABS systems should be able to stop quicker. In real life testing on older ABS systems, the breaking distance was similar if not worse than a lockup. The physics are there, but the technology was not. Now it is.I assume you mean figurative "page" since you gave actual page numbers of the report. The report references older systems having deficiencies in specific circumstances, but even then I didn't see any assertion that the older systems took longer to stop than locking up on dry pavement in a straight line. Also, when they say older, they must mean pretty old by today's standards. The report is from 1999 and they used mid-90's vehicles as their "modern" test vehicles.


By the way, a normal car could gain from spinning to warm up the tires before a drag run, the main arguement that nobody tried to correct me on was the fact that once warmed up, they only maintain a greater traction if they don't spin again.You're right that even normal street tires have an optimal temperature above ambient temp. I can count my trips to the strip on one hand, so I won't pretend to know much drag racing specifically. It's pretty easy to overheat most street tires, though I couldn't give any temperature range that might be considered ideal.

[bbjones121]

Not page number, I meant stance/opinion. This was an old report and from the sounds of it, a more recent report would probably show abs stopping quicker than a lockup on dry pavement.

[Evan78]

Since even the 1999 report doesn't show lockup outperforming ABS (since they didn't test the lockup situation except on wet surfaces and off-road situations), I guess you'd have to go back to some pretty old ABS systems. The cars tested in 99 were model years 1993-1997.

[Evan78]

Now lets find some traction control information...

PhyrraM seems to be the master of oem subaru information around here, I'm surprised he hasn't give us the year by year changes to ABS, traction control and stability systems.

[Evan78]

According to Cars101, VDC (vehicle dynamics control) became standard on WRX and STi in 2008.

[LoadedGuy]

Slightly off topic but while I was thinking about how the 818 would corner like it's on rails

I saw this and thought "that's not what I had in mind"

http://i104.photobucket.com/albums/m180/two2tone/pb-110225-suv-jwphotoblog900.jpg

[bbjones121]

Since even the 1999 report doesn't show lockup outperforming ABS (since they didn't test the lockup situation except on wet surfaces and off-road situations), I guess you'd have to go back to some pretty old ABS systems. The cars tested in 99 were model years 1993-1997.

This info is available out there if you look. Start with some independent sources, motor trend, popular mechanics, popular science. I am done with this. Search google, it is pretty mixed and i am guessing that perception is from somewhere. Don't you think if gov agency said this today there would be a lot of dumb people pulling their ABS fuses.

[thebeerbaron]

Just throwing this out there, but Going Faster (http://www.amazon.com/Going-Faster-Mastering-Race-Driving/dp/0837602262/ref=sr_1_1?ie=UTF8&qid=1301621437&sr=8-1) covers the topic of braking very, very well. If you read and understand the relevant sections, you'll understand how maximum braking is achieved. Sometimes the internet is not the best place to learn fundamentals.

Back to traction control -

Looking at the Factory Five Roadster, there are fifteen years worth of kits and development out there. It's a heavier chassis, sure, but some of these cars are putting down far more power than an 818 is likely to have. I don't know if any of them are using traction control, but that'd be a good place to start looking to find some people with real on-the-car experience. I'm assuming it would be aftermarket stuff, rather than from the donor vehicle.

I think it would probably be possible to produce a generic 818 traction control template using one of these aftermarket systems. Like how Cobb specifies the exact mods you need to run one of their off-the-shelf tunes, I bet it would be possible to say 818 with X engine and Y mods and Z suspension, use template XYZ. But since the only traction dyno I know of is a skidpad, I'm thinking this is going to be an expensive endeavor. But after these kits start rolling out, it'll be interesting to see if the market fills in this niche.

[Evan78]

I don't get it. You recently said this:


This was an old report and from the sounds of it, a more recent report would probably show abs stopping quicker than a lockup on dry pavement.

but you keep alluding to there being plenty of information out there that shows ABS as worse or about the same, but don't actually provide any information:

This info is available out there if you look. Start with some independent sources, motor trend, popular mechanics, popular science. I am done with this. Search google, it is pretty mixed and i am guessing that perception is from somewhere. Don't you think if gov agency said this today there would be a lot of dumb people pulling their ABS fuses.
I'm glad you're done with it. I've seen plenty of tests, and in every one where there's lockup, the result is so much longer that they throw it out and try again until they can threshold brake without locking up. Part of the reason I was trying to clear it up is the very reason you mention - I think it is inaccurate to say that you'll stop quicker by forgoing ABS and just locking up the brakes and telling people that it is true could give someone the idea its a good idea to pull their ABS fuse.

You don't need to convince me or anyone else, so drop it if you prefer. I was merely asking you to backup your assertion since the report you referred to seem to contradict your position.

If I'm wrong, I'm fine with that, I don't really care. I'd rather learn that I am mistaken and end up with a sliver of new knowledge. I just don't find anything that supports you. Maybe you're just better at the google than me.

I was trying to contribute to this thread and stay on topic, but I didn't want to let what I think is incorrect information related to a safety issue go by without saying anything.

[PhyrraM]

The only reason that Subaru added traction control at all is because of the pending law requiring stability control. They use the same hardware, so "why not?". Prior to that, they did use electronic clutch packs to distribute torque, but nothing that engaged the engine or brakes to call "traction control".

The '02 WRX had a overly aggressive ABS program when released. When bumps of a cetain intensity (such as train-tracks) were hit under braking, the ABS would occasionally get confused by the bit of slip it introduced and would completely release the brakes for a moment. It's very disconcerting, to say the least, and possibly dangerous. It was fixed with a firmware upgrade before the '03s came out.

It's little unknowns like that lurking in software that makes me VERY cautious of adapting any OEM system.

[Evan78]

Just throwing this out there, but Going Faster (http://www.amazon.com/Going-Faster-Mastering-Race-Driving/dp/0837602262/ref=sr_1_1?ie=UTF8&qid=1301621437&sr=8-1) covers the topic of braking very, very well. If you read and understand the relevant sections, you'll understand how maximum braking is achieved. Sometimes the internet is not the best place to learn fundamentals.Thanks, I haven't read that one before. The reviews are very good, I just ordered it.

[bbjones121]

This took 5-10 minutes to find these on google, a couple more minutes for posting. I have to post this for the reason you gave, to help people better understand "Correct" information about a safety system on a car.

Recent Dec 2010 Insurance Institute for Highway Safety www.iihs.org/research/qanda/antilock.html
"Adequate braking is easy to achieve on dry roads with or without antilock brakes. Even if wheels lock, the coefficient of friction between tires and road surface still is relatively high, so a vehicle stops relatively quickly. It is even possible on some surfaces to stop sooner without antilocks than with them, although such instances are rare."
They go on to talk about packed snow or gravel shortening the stopping distance more than antilocks would

from NHTSA.gov website
http://www.nhtsa.gov/cars/problems/Equipment/absbrakes/page1.html
"Do cars with ABS stop more quickly than cars without?
Perhaps, but thats not the main purpose of ABS. It is a system designed to help you maintain control of the vehicle during emergency braking situations, not necessarily make the car stop more quickly. ABS may shorten stopping distances on wet or slippery roads and most systems may shorten stopping distances on dry roads."

Federal Highway Administration
http://www.fmcsa.dot.gov/documents/abs-book.pdf
"ABS does not necessarily shorten your stopping distance,
BUT it does help you keep the vehicle under control during
hard braking."

Harris Technical Services - Traffic Accident Reconstructionists
http://www.harristechnical.com/articles/abs.pdf
"Antilocks don't make much difference in stopping distances on dry roads but they can help a driver maintain control
when the wheels would otherwise lock during emergency stops."


You made a comment about what date you think there might have started to be a shorter stopping distances with ABS on dry pavement than without ABS, after reading into this more, it might not even be to this day. But judging from this article in Popular Science in June of 1998, which shows an Accord stoping quicker with ABS than fully locked on dry and an Explorer stopping quicker without ABS, I would imagine newer ABS systems anytime after 1998 to be better able to stay in the optimal friction area longer, thus even making SUVs such as the Explorer stop better with ABS.
http://books.google.com/books?id=fhabaMVQ9wkC&lpg=PA75&ots=X2kJYs-_Cz&dq=abcs%20of%20abs%20accord%20explorer&pg=PA75#v=onepage&q&f=false


lastly, here is a good chart to illustrate the physics of it:
http://www.drivingfast.net/images/car-control/braking/braking-efficiency.png
1310

As you can tell, if an ABS system is good enough to maintain your tire slip at around 20%, you are best off. I am guessing that this common verbage about ABS not necessarily having a shorter stopping distance on "dry" pavement has something to do with the ABS capabilities or technology limitations back in the day.

As PhyrraM pointed out, "Older systems used just speed sensor input and sometimes tied the rear brakes to one actuator. The system could basically stand alone. In fact, if you go through part numbers, the ECU was the same across many models for some manufactures.

Newer systems are better because they are also programmed with vehicle specific info, such as mass and and tire friction, to help with calculations and even predict impending lockup. Such features and info will be useless, or even a detriment, when used on the 818.

Of course, newer systems also have better computers and faster relays/soliniod/etc."

Can we move on now and you can PM me if you any other questions about google searching?

[thebeerbaron]

Thanks, I haven't read that one before. The reviews are very good, I just ordered it.

It's not just braking, it's turning, line, and a bit of race-craft. All the classroom sessions at the 3-day Skippy school are drawn from it. It's a good balance of technical and understandable, but it'll take a few readings to get through some bits. I recommend it as off-season reading for anyone who wants to learn, and even for people who think they know it all already. I've had a lot of "a ha!" moments reading it.

[Evan78]

Geez, I can't believe you're posting all these generalized statements that essentially say ABS may or may not improve stopping distance in dry conditions. It seems that we're not having the same argument. The statement I objected to (by mn_vette) is that locking up will stop faster than an ABS stop. That is all. Meanwhile, you're attempting to post evidence that ABS vs Non-ABS is about a toss up.

I'm sure that there are instances where thresholding braking can stop better than an ABS system, but threshold braking is most certainly not locking up. I can pull up a bunch of quotes that say X car stops better when ABS is enabled and the original report we were discussing has a whole bunch of test data that shows exactly that.

What I haven't found is test data of how long it takes to stop by locking up vs either threshold braking and/or an ABS stop. I guess the best we've got right now is the drivingfast graphic, which shows locking up is only 70% as effective as threshold braking, which is what ABS attempts to achieve. I'd consider a 30% difference to be quite significant and am willing to bet that modern ABS systems are able to improve upon locking up.

I have no idea why the argument can be misunderstood. ABS is not a miracle worker, it merely modulates the brakes in an attempt to keep the tires at their maximum traction level, which is known to be some point before lockup. Naturally it's possible for a human to do this, but we humans are far from perfect and are unable to perform at 100% consistently.

Thanks for taking the time to post some specifics about your thinking. With all those generalized statements, I can see why some people may think ABS in the dry is a toss up.

[Evan78]

It's not just braking, it's turning, line, and a bit of race-craft. All the classroom sessions at the 3-day Skippy school are drawn from it. It's a good balance of technical and understandable, but it'll take a few readings to get through some bits. I recommend it as off-season reading for anyone who wants to learn, and even for people who think they know it all already. I've had a lot of "a ha!" moments reading it.What?! I was really looking forward to a couple hundred pages on braking technique ;-)

[bbjones121]

Geez, I can't believe you're posting all these generalized statements that essentially say ABS may or may not improve stopping distance in dry conditions. It seems that we're not having the same argument. The statement I objected to (by mn_vette) is that locking up will stop faster than an ABS stop. That is all. Meanwhile, you're attempting to post evidence that ABS vs Non-ABS is about a toss up.

I'm sure that there are instances where thresholding braking can stop better than an ABS system, but threshold braking is most certainly not locking up. I can pull up a bunch of quotes that say X car stops better when ABS is enabled and the original report we were discussing has a whole bunch of test data that shows exactly that.

What I haven't found is test data of how long it takes to stop by locking up vs either threshold braking and/or an ABS stop. I guess the best we've got right now is the drivingfast graphic, which shows locking up is only 70% as effective as threshold braking, which is what ABS attempts to achieve. I'd consider a 30% difference to be quite significant and am willing to bet that modern ABS systems are able to improve upon locking up.

I have no idea why the argument can be misunderstood. ABS is not a miracle worker, it merely modulates the brakes in an attempt to keep the tires at their maximum traction level, which is known to be some point before lockup. Naturally it's possible for a human to do this, but we humans are far from perfect and are unable to perform at 100% consistently.

Thanks for taking the time to post some specifics about your thinking. With all those generalized statements, I can see why some people may think ABS in the dry is a toss up.

No problem. We actually are just in a disagreement about the interpretation of the generalizations. That is why I offered proof on my interpretation. In 1998 a Honda Accord stopped several feet sooner with ABS working compared to a full "lockup" skid. A Ford Explorer stopped sooner in a full "lockup" skid than with ABS. These were done on dry pavement for clarification. I saw some other test also around this same time period when I first started researching this. So as far as I know, I have provided you proof on my interpretation of the generalizations, while you have not. If you want to pursue it further, go ahead or we can just agree to disagree on what the national institutions' generalizations mean.