Porsche Stability Management

[funster]

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

[Sammy]

Originally Posted by funster

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

I vaguely remember that Formula 1 use to allow ABS and banned it...

I agree that ABS is not faster in all situations.

[racer_d]

Originally Posted by funster

... which is why they don't put abs on race cars.

Yes and no. The use of ABS on a race car is dictated by the sanctioning body, not the race car maker. Many series don't allow it for 1) "man vs machine" arguments as to who is doing the actual driving - driver or car; 2) Cost ; 3) Potential for using the ABS to do other things (like a traction control or Stability management program which would give the car an unfair advantage)

Porsche (with the help of Bosh) has developed some very advanced and capable ABS brake systems. Their systems actually allow a certian percentage of "lock" that is dialed out of a street cars ABS system.

ABS doesn't always improve or hurt a cars stopping distance (there are way to many variables to discuss here, like the one above about driving on snow and clear pavement at the same time) but it DOES make a car safer, since it allows one to maintain STEERING capabilities to aviod accidents.

[MNBoxster]

Originally Posted by racer_d

Yes and no. The use of ABS on a race car is dictated by the sanctioning body, not the race car maker. Many series don't allow it for 1) "man vs machine" arguments as to who is doing the actual driving - driver or car; 2) Cost ; 3) Potential for using the ABS to do other things (like a traction control or Stability management program which would give the car an unfair advantage)

Porsche (with the help of Bosh) has developed some very advanced and capable ABS brake systems. Their systems actually allow a certian percentage of "lock" that is dialed out of a street cars ABS system.

ABS doesn't always improve or hurt a cars stopping distance (there are way to many variables to discuss here, like the one above about driving on snow and clear pavement at the same time) but it DOES make a car safer, since it allows one to maintain STEERING capabilities to aviod accidents.

Hi,

You're quite right about the sanctioning bodies, but of course, these change their rules and tech requirements often from the cumulative pressure of sponsors and competitors.

ABS will almost always hinder a car's stopping abilities, it's inherent in how it works though I concede there are many variables to consider.

No arguement about ABS's ability to preserve the steerability of the car, but that arguement requires that the Driver actually use this capability to steer away from the trouble and as I stated, as a rule, Drivers are not taught to do this or how. Consequently, there is no statistical data showing significant accident reduction due to the advent and adoption of ABS...

Happy Motoring!... Jim'99

What car stops fastest on a sheet of ice?

With ABS or without ABS??

Hypothetically, all this being equal.

I gotta believe with ABS...been there ...done that!

[MNBoxster]

Originally Posted by Sammy

...In theory ABS is slower than non-ABS (I completely agree with this); however, a human being cannot break faster than ABS with any level of consistency regardless of skill. You can put Andretti, Montoya, Bondurant, etc, in the same car and let them stop in a straight line 100 times and if they are lucky they just might be able to outstop the ABS a few times. Put them in a turn and the liklihood decreases because the weight shift is much more complicated. As you have mentioned ABS pulses faster than any human being could consciously "lift" off the pedal due to the reaction time. There is no such thing as a zero second reaction time that when a driver recognizes the wheels locking up that he/she can instantaneous lift and reapply the brakes. On the other hand a skilled driver cannot consistently stay at the edge of locking the wheels... He/she can do it better than we can, but not faster than ABS...

Hi,

Sorry, not buying it. I have demonstarted this and seen it done by professionals. ABS is not even designed to decrease the stopping distance, it's sole purpose is to prevent wheel lock, it does not increase the brakes efficiency. In fact, because the calipers are not clamped continuously (where mechanical energy is transferred to heat energy and expelled from the system), it reduces the brakes efficiency and results in longer stopping distances. And this says nothing of where the threshold is set by the control unit. It can be argued that if you activate the ABS at all, you're already doing it wrong. It is possible to understand and feel when the car will lockup and thereby avoid it...

Happy Motoring!... Jim'99

[MNBoxster]

Originally Posted by bmussatti

What car stops fastest on a sheet of ice?

With ABS or without ABS??

Hypothetically, all this being equal.

I gotta believe with ABS...been there ...done that!

Hi,

as racer-d stated many variables to consider. But, generally, here I agree with you that ABS, if not stopping in a shorter distance altogether, will not be as far behind a non-ABS system than on dry pavement. But, realize that here too, it's main advantage will be one of maintaining control...

Happy Motoring!... Jim'99

Originally Posted by funster

Sammy, you are mistaken, the abs senses a skid and begins its pulsing and won't stop pulsing until it senses that all skidding has stopped. Once this happens your stopping power depends on when the wheel with the least traction stops sliding. Try this test if you ever have a car in the snow(and you are confident that you can do it safely). Drive with one side of the car on a plowed surface with good traction and the other side of the car on a slippery part and apply the brakes to activate the abs. You'll see it takes significantly longer to stop than if the wheels on dry pavement could utilize all their traction. (some abs systems are better at this test than others) The same principles are true on a race track when cornering. if you hit a small bump on a wheel on the inside of your turning circle and set off the abs you can decrease the ablity of your car to brake and fairly skilled drivers can do this better than the abs which is why they don't put abs on race cars.

Hey Funster, in your example (one side on snow one side on pavement) at least the car will track reasonably straight...right? At least this has been my experience. And an advantage of a car with ABS.

[funster]

No Question, wirh the abs the car will track straight and will tend to pull without abs to the side with traction. Abs is great on slippery surfaces to preserve the directional control of the automobile, of that there is no question and as a safety feature, it's tops. Porsche brakes are fantastic and it's seldom that the abs activates as I try to stay just below that point. Abs has come a long way from its early days and I'm sure that it's only a matter of time before it will surpass the abilities of even the finest of drivers.

My daily driver is an SUV (Explorer XLT Sport 4x4) and the ABS is kicking on every day! ABS is great on wet leaves too. Those buggers are slick.

[racer_d]

Originally Posted by MNBoxster

Hi,

You're quite right about the sanctioning bodies, but of course, these change their rules and tech requirements often from the cumulative pressure of sponsors and competitors.

ABS will almost always hinder a car's stopping abilities, it's inherent in how it works though I concede there are many variables to consider.

No arguement about ABS's ability to preserve the steerability of the car, but that arguement requires that the Driver actually use this capability to steer away from the trouble and as I stated, as a rule, Drivers are not taught to do this or how. Consequently, there is no statistical data showing significant accident reduction due to the advent and adoption of ABS...

Happy Motoring!... Jim'99

Seems we agree! It would make sense that some people avoided accidents because of the ABS providing them the ability to avoid an accident, thus not providing any imperical data that ABS did not reduce the number of accidents.

I would say that now that ABS has been around for nearly 20 years in passenger cars, even if people learned "by accident" of its advantages it is something that SHOULD be on a passenger car. Race car? maybe not.

I love to threshold brake as much as the next would be racer when i am at the track.

Then again, the discipline to apply only threshold braking without locking them up, when another car is suddenly stopped in front of you, or in your lane etc, is very hard to master. Frist thought is "stop" car ASAP.. mash brakes to accomplish.. get "deer in the headlights" syndrome and hit the vehicle/object you were trying to avoid.

Years of Drivers Ed/Autocross events and experience in general has taught me that sometimes "stopping" isn't the best option. Steering is... sliding is... accelerating is.. As mentioned, way to many variables to come up with 1 rule for all instances.

I will enjoy the ABS my new car has for DE/AX events. I will enjoy it on the street. But thank goodness my car doesn't have PSM so I can still enjoy sliding her around

[MNBoxster]

Originally Posted by racer_d

Seems we agree! It would make sense that some people avoided accidents because of the ABS providing them the ability to avoid an accident, thus not providing any imperical data that ABS did not reduce the number of accidents. I will enjoy the ABS my new car has for DE/AX events. I will enjoy it on the street. But thank goodness my car doesn't have PSM so I can still enjoy sliding her around

Hi,

Since we each have some considerable Track experience, I'm not surprised that we agree.

One small point though, your hypothetical about the accident which didn't happen and therefore not added to the Ins. Stats may be valid. But, the ins. statistic of rear end collisions/mi. driven remains unchanged since the advent of ABS. So while I am also sure that some accidents have been avoided due to ABS and not reported, not enough to positively impact the statistics. The rate remains the same...

Happy Motoring!... Jim'99

[Sammy]

As always, I appreciate the respectful discussion of a contested claim.

For what it's worth, my claim is not from my own making but simply regurgitating a statement that was made from one of those three names that I threw out there. I happened to have the opportunity to ride/drive a S2000 around a handling course with one of those experienced racers and the question was directly asked "can you brake faster than ABS?" The response was the statement I made... This was supported by another person who has written vehicle dynamics books and trained countless people on the theory of maximum handling.

Every formula 1 race I've ever seen (road course) has had numerous instances where a driver slid a wheel and ended up too far in a corner resulting in losing a place and many times wrecking the car. If anything they become conservative in braking because they can't afford to lock a wheel. This is where the driver skill comes in and separates the men from the boys...

[shaman1204]

Quote:


"ABS will almost always hinder a car's stopping abilities, it's inherent in how it works though I concede there are many variables to consider.

No arguement about ABS's ability to preserve the steerability of the car, but that arguement requires that the Driver actually use this capability to steer away from the trouble and as I stated, as a rule, Drivers are not taught to do this or how. Consequently, there is no statistical data showing significant accident reduction due to the advent and adoption of ABS...

Happy Motoring!... Jim'99"


While attending the FBI Academy I had to take the 40 hour Tactical Emergency Vehicular Operator's Course (TEVOC) in Quantico, VA. We had one practical where you maintain the vehicle in a straight line driving approx. 55mph heading directy towards a barrier. On each side of the barrier were two lanes with lights above them, once you crossed a line and tripped a light you had to slam on the brakes and activate the ABS and steer the car into whichever lane was illuminated. It felt like you were going to crash into the barrier every time, but the excercise shows you just how the ABS was designed to allow the car to be steered in a safe direction. ABS has nothing to do with improved stopping distances, at least that's what we were told. The TEVOC course was awesome, we had a Mustang, Camaro and a bunch of Caprices. Taking the course really shows you how much you can push a car and what they are really capable of.

[z12358]

Let me state first that I've only had two DE track days in my life and I consider myself to be an average driver. To me this ABS and PSM discussion is not about whether a man can outperform the machine but more about frequency of measurements and adjustments (FMA). In both ABS and PSM, it is clear that the machine can measure and adjust more frequently than the driver. We now only need to decide when the benefits of FMA outweigh its costs (i.e. the time it takes to perform them).

I believe that over the long term and on average, FMA will improve the performance of ANY driver. Let me explain. A very good driver may be very good at nailing (sensing, anticipating, predicting, etc.) the threshold (lock or slide) 99 times out of a 100 without the benefits of FMA, but that 1 time out of a 100 when he misses it, the car ends up smashed into the concrete. With FMA, that same driver may slightly underperform during those 99 times but will signifficantly outperform that 1 time when he would have crashed otherwise. Having a car to drive and a life to live, to me, is a signifficant outperformance over the long run.

I also believe that by tweaking the FMA (optimizing time spent vs information gathered and adjustments made) it can be fine-tuned so that each driver can outperform with it even in those 99 times out of 100, making it a hands down winner. The FMA (PSM, ABS) in our cars have been tuned for an audience of millions, thus not optimally matched to each of us individually.

To those suggesting that FMA migt hinder learning, consider this: Decreasing the chance of ruin (car, limbs, life, etc) increases the average length of time a student will spend studying, and the level of enjoyment while doing it. So I do believe that a student with FMA will end up learning more than a student without one. Something like the tortoise winning over the hare.

It rained on my first track day, then the sun came out, making the track a mosaic of wet and dry patches in the afternoon. Both times that the PSM switched on, I was thankful that it did. My instructor didn't know I had PSM and he commanded me on "saving my a**" like a pro, each time me telling him that it was the PSM and not me. That same day, TWO GT3's from the black and red run groups slid out into a wall. I wonder if they had PSM, ABS, or none.

Z.

[MNBoxster]

Originally Posted by z12358

Let me state first that I've only had two DE track days in my life and I consider myself to be an average driver... Z.

Hi,

Your logic is kinda skewed. You may not think the discussion is about Man outperforming the Machine, but it is, or at least has been. It's not about a cost/benefit analysis of FMA/speed, it's about making the car perform at it's best and a skilled driver will do so better without the hindrance of these electronic aids than with them.

A 1 chance in 100 arguement of the type you have stated again, has little to do with the discussion. No one said these devices weren't safer, everyone here has supported their use for the average guy. Besides, again, you're proposing an analysis, not a judgement. There is at least a 1:100 chance of losing control and wrecking the car everytime you attend a Track or DE event (if not everytime you drive the car), is that justification enough not to do it? To some perhaps, but not for others.

As for other cars losing control, you're assuming that they didn't have these aids which may or may not have been true. Even with these aids, you can stretch the performance envelope sufficiently that the car breaks away and the Laws of Physics take over. Perhaps these cars were so equipped (they at least certainly had ABS) and their Drivers were deluded that these very aids would prevent them from pushing too far. That's just as good a supposition as the one you're making. And bolsters the arguement made by myself and others that these aids can become a crutch and impede learning.

So far as fine-tuning the aid's computers, there are several problems. First, you'd need the codes and the manufacturer is unlikely to release them for liability purposes, if for nothing else. Second, these aids do nothing but respond in a pre-programmed fashion to some innocuous signals received from various sensors. They do not have any idea of the intention of the driver, or what's in the Driver's Mind, what he sees, feels and relates to his/her experience base.

It's about Control. And these aids take control away from the Driver, and usually at a time when their concentration is required elsewhere. This control acquisition also takes place well short of the edge, where some combination of engineers and techno geeks decided an appropriate all-around Safety Margin should be.

In my lengthy and considerable Track experience, I'm fortunate enough to say that I've only kissed a wall twice (though in adverse conditions), but I've had more than my share of personal experience with Runoff areas and other competitors (their fault and mine) . But, in each event, costs were not so great (certainly acceptable given the risk I chose to take, and necessary to be competitive), no bent, or broken, people resulted (always the best thing), but learning took place. Some risk is inherent in all Motorsports whether it be Class Racing, DE or Auto-X.

For the General Public, operating on Public Roads, these aids are probably a good thing as I've stated before. But, for a skilled Driver, on or off the Track, these aids can be a hindrance. We're fast getting to the point where the only Driver input will be pointing the car - steering, what with all the Egas throttles, CVTs, Accident Avoidance Braking Systems, Smart Cruise Control, Back-up Warning Systems, Self-Parking, and the like. At what point will the lack of Driver input and Control still be considered driving and not simply a Ride-Along? ...

Happy Motoring!... Jim'99

[ohhh my]

There's some good discussion here. Just wanted to bump it for others to read.