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+--- Thread: stock performance at the track (/showthread.php?tid=2014)
- APXD 30 - 11-23-2009
George3 wrote:
Quote:
Bob- agreed. If you have a car with ABS you must learn to use it. And, you can still steer your car while in an ABS stop, not so in a lock-up without ABS. One of the schools I attended taught students high speed steering-while-braking exercises under full ABS and going in between cones! Amazing. The only disadvantage that I see is Antilock brakes add system complexity, cost and weight to the race car… which is irrelevant for DE.
Not having driven a non-ABS car on the track ever or on the track is many, many, years this is my biggest challenge. I want to do it but an concerned by the tire expense at the same time as, inevitably, there will be flat spotted Hoosiers in my future.
I only had slicks at TB and once stalled under braking at T6 due to a brief stab, nearly running out of track. I would actually prefer the car had ABS. As for stability control, I do not see its place in upper run groups.
- stentech1 - 11-27-2009
I have 3 cars without abs. If the brake system is well set up(proper master cylinder sizing pad composition this also includes in car bias adjustment) abs is not something I prefer (unless its snowing). Many street/track cars are set up with brake pads that have such aggressive initial bite that a lock up is too easy to do. With pads that have less aggressive bite it will require more effort from the driver. Many of the cars we are accustomed to driving also have brake boosters that decrease the effort that needs to be made by the drivers leg. On the Panoz I run Performance Friction compound 97 pads they require allot of leg effort. To me this is better than a boosted brake system where minor variations in pedal effort can be the difference of over braking for a corner or worse locking the brakes and flat spotting tires. I have never flat spotted a tire or had a lock up condition that could not be corrected by backing off the brakes for a split second and than reapplying. I feel a major part of this is the brake systems in these cars are well selected parts that are correct for the application. I have had abs intervene way too early and hurt braking distance more than help it. There is a level of connectivity to the brakes that a 100% hydraulic non boosted brake system has that is very hard to find in any street car braking system. Another thing I don't like about ABS is the inability during a spin for the abs to become inactive. It is constantly looking for wheel speed sensor output and we have had cars that have hit walls because the ABS would not allow full lock up. The abs system is looking to keep the car moving even if the direction of travel is into a tire wall after the car spins around. But who knows how many more spins would happen with out ABS. I have talked to de participants that said when they began to spin they tried to lock up the brakes and they would have slid safely down the track but the abs wanted to keep the wheels rolling and the rolled them right into the wall damaging the car.
- Terry - 11-30-2009
This is interesting. I have had several ABS-equipped cars and at least one without. In my experience, once a spin is initiated ABS does not prevent the desired lockup. OTOH, if the driver feels the beginning of a spin and tries to lock'em up prematurely (i.e., when the car could still be saved), so that the car is still moving in a straight line, more or less, ABS will prevent the lockup. By the same token, if the car is headed straight for the wall, ABS will prevent lockup, but this is generally considered to be a good thing since you can still brake and steer simultaneously.
- stentech1 - 11-30-2009
Abs can not prevent a spin once the car has exceeded a certain amount of slip angle. The car movement is lateral in a spin as supposed to the direction of tire rotation. Once a tire is going in a direction perpendicular to tire rotational axis it is not possible for any driving aids to help. About the only thing that may help would be lateral thrusters like a space ship. Apparently Porsche has heard about your Gt3 experience at Pocono and all the other tracks you have spun at and is considering implementing this as its future stability control system
. Of course it will require a new fancy acronym. Its going to be called POSISAPS. which stands for Porsche Oh Shit I'M Spinning Again Prevention System. I look forward to driving one. It is also rumored they have recruited several RTR people to aid in its development. The information about the cars that hit the wall were based on the statements of the drivers and the continuous desire for abs to reestablish wheel rotation. This keeps the car form just locking up and going harmlessly down track. Instead the abs carried the car across the track into the wall. If the abs is sensing wheel rotation it will prevent lock up. If a driver turns in early and runs off at track out than locks up the wheels they will spin and the car will travel in the direction of travel. If this is going down track they will simply slide down track but due to the abs not allowing lock up unless the cars is completely sideways where no wheel rotation is present the abs will keep the car going in the direction of travel even if it is towards a wall. If the distance is less than the required distance to bring the car to a stop impact will occur as it has on several occasions. This is according to the people involved in the incidents. I do without question that ABS has certainly prevented more incidents and impacts than it has created but unfortunately the systems can only function according to the parameters set forth by the abs control system in the vehicle.SM
- JoeP - 11-30-2009
Great system, Steve. It might be helpful to augment POSISAPS by a bunch of airbags on the OUTSIDE of the car, like a Mars lander or something.
- JoeP - 12-01-2009
Hey, if someone is unsure about the transition to next run group, this eBay listing might provide a bit of a cushion:
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=150392101866
- bobt993 - 12-01-2009
Hey Steve, when I took you out for a ride, I was early apexing every corner. No PSM and we actually stayed on the track.
Not the easiest technique to learn, but when you get a handle on it, it's damn fast. One issue on the 993/996 platform that is a concern is "glide mode". This happens when the g-loading exceeds a figure Porsche consider not possible on these cars in stock trim. Basically you have no brakes and desperate pedal pumps eventually return the brakes. - Terry - 12-01-2009
I think Steve is missing my point although he got in a nice jab. Yes, I am living proof that there are times when "both feet in" is a really good idea because it can keep your car on the track or at least way slowed down by the time it goes agricultural. And you want to spin then to use up as much kinetic energy as possible. My point was just that ABS will not defeat the spin or prevent lockup - and that is a good thing. Steve's late night sand mound testing procedures should examine the phenomenon more closely.
- emayer - 12-01-2009
JoeP wrote:
Quote:Great system, Steve. It might be helpful to augment POSISAPS by a bunch of airbags on the OUTSIDE of the car, like a Mars lander or something.
Those crazy Germans (and Joe) think of everything!
http://www.youtube.com/watch?v=lKZspCU8q3Y
Sorry for the diversion, but I have it from a knowledgeable source some of the technologies under consideration for the next S-class (2011-12). They've prototyped things like a "god's eye" on board display utilizing merged images from multiple camera feeds with automatic crash avoidance- basically an amped up version of Pre-Safe with steering control also. Ultimately the goal is to have on board telemetry both for crash avoidance and to facilitate denser packing of cars on the Autobahn under computer guidance with the theory being that it will improve traffic flow and reduce the need for roadway expansion. Talk about nannies!
- betegh9 - 12-01-2009
HMMMMMMMMM!.................... Veri interesssssting.