mark kibort

sorry greg... I have to disagree with you again

porsche GT3 cup cars had ABS. racing abs by the way and the new GT3 R has it too.

thats why i refered to it.

guess you dont know as much as you think, again!

YOU SAID:
"Continued debate of that point is absurd.

Porsche Cup Cars do not have ABS...although you keep referring to them having it.

Continued debate of that point is absurd."


if you can be wrong about this "little" detail, what else might you be wrong about????

http://www.supercars.net/cars/2413.html


http://www.supercars.net/cars/4646.html

"Braking performances of the 2002 Cup-Carrera not only surpass the performance of all predecessors thanks to the optimised ventilation of the front wheel-housing. For the first time in Cup-car history, the front axle features six-piston fixed callipers, and brake discs measuring 350 mm in diameter (2001: 330 mm). At 330 mm, the diameter of the rear brake discs remains unchanged. The standard ABS, modified for motorsport purposes, also stays the same.
Read more at http://www.supercars.net/cars/2413.html#KCJtkczobpQk7gXQ.99"

dr bob

[ ]

GregBBRD

Sorry you are so confused and this discussion has reached the limit of your ability to logic.......but do you need to be such a butt about it? ("guess you dont know as much as you think, again!")

I was speaking of the current generation of Cup Cars, not the older 996 cars. I'm talking about true competitive Cup Cars...not the "hand me downs" in the hands of the club racers.

I've personally retrofitted ABS to several of the 997 Cup Cars.....and know, personally, the huge improvements to be had.

I never "blow smoke" out of my ***. Pretty secure in what I know. If I don't know, I'm completely comfortable saying I don't know.....unlike you. I don't know what you do for a living....but I've spent my entire life (the past 45 years) doing exclusively Porsches...for both the street and track.

So, I'm guessing I do know a little bit more than you do.....and as uncommon as it is, for you to listen....you might learn something, if you did.

You show me videos from literally years ago....."racing" Anderson in the rain....on your home track! I have no idea what he was doing in his car....he might have decided to back way off and just get to the finish. But like the guy that just got run over by Stewart....you were clearly doing everything you could, to keep up.....thinking you could be a hero, keeping up with the better driver.

How much have you improved since then...aside from adding more power? You talk about being a "hero" in 2002.....that was 12 years ago!

Here's the reality: You are a club level driver that reached a plateau long ago. Is this because you reached the limit of your ability? Is this because you reached the limit of your car? Who knows? Who could ever help?

You refuse to stop and listen....you seem to be happy just arguing...from a completely absurd point of view...

YOU ARE NOT BETTER THAN A COMPUTER CONTROLLING ALL 4 WHEELS FROM LOCKING UP WHILE HOLDING THOSE TIRES AT MAXIMUM BRAKING POTENTIAL!!!!!

mark kibort

Greg, we have been jabbing each other for years. yes, mark was in a pro race just crusing around. tell you the truth, I was too. i didnt want to stack the car, and obviously the bmw ahead of both of us, did, but it was just an example of racing in the rain, with my buddy mark, having a good time and doing a lot better than a lot of "wanna be pros" out there.
Oh, i was fighting for my life?? really.. do you notice the calmness of my hands and the rarity of the back end stepping out, and when it, just a little, did how fast it came back?? thats an hour race with out even a major wiggle . while the other pros were crashing into one another or smacking into walls!
Yeah, so I cant drive.... your right....

you keep on jabbing me about my driving, so ill continue to fight back.
you make statements without really thinking about them.

now, why would i talk aobut cars I race with , when none of the new cup cars are in our group. you went to great lengths to correct a sailient point, about cup cars not having ABS. didnt it enter that thick head of yours that I was refereing to older GT3 cup cars.... uhhh, like the ones i race with. but you would rather misread or assume, to get a jab in. to make your point, or to make a put down.

yes, ive gotten way better as a racer over the last 5 years or so. its not lap times when racers get good, its judgement. this is something you just dont get. lack of mistakes, keeping the equipement healthy, making good racing decisions. thats the advanced racing evolution. NOT, lap time. everyone plateues there. Not everyone advances to be great race car drivers.. Even within the top pros. lots of money and televised races, dont make a race car driver. Lots of top racing experience, makes a top racing driver.

let me just say, ill go toe to toe with anyone, anywhere, period.

Next, ABS.......... yes, the computer thinks much faster, but what it is doing at a slow scan rate, ends up being less effective than a skilled foot.

you still didnt answer my question. how does really pressing hard after abs engages (and ive done this by the way) engage the rear abs to work?? do you not remember that the rear tires are tied to the gear box when in gear, or should we do this test in neutral or with a car that has an automatic transmission.

hey, dont let this bantering show you any disrespect. I do respect you and listen to everything you say. im thinking hard about it now, but i do have a feeling that when it comes to abs on the 928, that its not worth anything more than an early warning system to lock up.

Since im on the track, on a monthly basis... as much as most all pros are, I can do any test that might give me a different result than i have seen in my racing experiences.

mark kibort

as a side note of you accusing me of being "such a butt about it"

wow, you can sure dish it out , but you cant take it.

Greg, FOR EXAMPLE:
you said that I " Kept on referring to cup cars having ABS" that this was absurd,and discussing it was absurd, when i clearly showed you that there were cup cars, that i race against that HAVE ABS.

Then you dig into my abilities without any reference points to measure against.

I think that is being quite a butt, by anyone's measure.

Lets step away from the coffee machine for a second before reposting, ok??

mark kibort

Bob, make a point! I dont even think there is one now. ive tested our ABS on the 928 and i can stop faster....
It is 3 channel and i dont think there is a way that the ABS can dig into the rear tires on a high speed decel with the car in gear......
but again. what is the water you want to force down my throat?

I have a fade issue at the last part of a 4 second braking sequence. ive measured the temp at fade to be near the limit of the pads im using temp wise. I dont think the bias change will help all that much, because i dont think there is a way to take 25 of the stopping force and put it to the rear, to get rid of that last 1 second of braking seeing the fade.

in a high speed downshift, i have 200-150hp of decel power. I dont know how much incremental force i can apply to really take lessen the stopping distance, because im going to use all of the potential of the front tires. and they are big front tires by the way, and very sticky.

Ill try some abs test at the track, on video to show the difference between using it and not using it. laguna is a great place to test this, because there is a good amount of run off room . Ill approach and hit the brakes the exact same place at 130mph and see if ABS vs a skilled foot works better. its an easy test.

dr bob

[ ]

GregBBRD

I frankly have never watched a single one of your videos.....so I have no idea of what techniques you use to drive.

The guys that I've raced with, instructed, and had on teams all seem to be doing clutch in downshifts while engaging the brakes into ABS.....so they can be ready to accelerate out of the corner, when they get to the point where they can put power down. The rear tires are uncoupled from the engine, when this happens, in the cars I have worked on.

From the question you are asking, I can only assume that you do all your braking with the clutch out, stuck in the same gear that you entered into the corner in, without doing a downshift? When do you do your downshifts? After the apex?

Against my better judgment, I decided to post a little bit about my experiences and what I thought worked well. I'm sorry nothing I have to say offers you any hope of curing your brake fade problems. I thought that engaging and using all of the brakes, instead of just the fronts, might transfer some of the heat to a different axle, but alas, that just isn't possible.

The really tough part, for me, is going to be to go to the Corvette Forum and convince all those guys that they need to throw their ABS systems in the trash, since they too have a bunch of weight in the front, with a very light rear.

I'm almost certain that I will need your help convincing them of this, over there on the Corvette Forum, but I'm done wasting my time on this thread.

mark kibort

Greg, what we have here is a failure to communicate.... maybe later over a beer we can discuss.
no, i shift and use the clutch very quickly, as i approach the turn, and you know this.

the corvette guys might only want to toss their ABS out if they can stop better without it.

by this comment, you obviously dont understand the point i was trying to make. ABS can work, and it works well on the cup cars i run with, as well as modern ABS systems. i just dont think it works well on the 928 for racing..... AND, you still didnt answer my question. how does ABS work on the 3 channel system with the rears. as you know, there is a certain slip percentage that give maximum grip. ABS has a much greater differential to work with before it engages, so its far beyond this optimum area. how fast it reacts and cyles is also important. How does the rear abs work, if you are in gear and on a high powered decel with the engine connected to the rear tires? I can only imagine the instantaneous forces on the driveline by the speed fluctuations that could shear most drivelines in short order, especially since the force is at the limit of grip of the rear tire, multiplied through the gear box and reflected to the short shaft and torque tube.

Thanks for trying to help. i just dont see how the ABS sytem and the Bias bar, that doesnt change pressure, even with more front pressure, to the rears, could help. I dont also see , by downshifting, and keeping the decel RPM high, that any more rear braking can lessen slow down distances and rate.......... that much. again, as we slow down, in gear, down shift and in gear again, there is 150 to 200hp available to slow the car down by the rear. ... I can calculate the actual rear tire force or rear wheel torque based on the gear you are in. but, i would be willing to bet , there is not much to be gained during a threshold braking with so much weight transfer to the front during a 1.5 to 2 g slow down.

If you take the 200ftlbs available at the engine at 6000rpm, and use 2nd or 3rd gear multiplication. that works out to near 1000ft-lbs of decel force at some points. i wonder if the rear end , can even except 500lbs of force, or 500ft-lbs of torque, while only having 300lbs on each wheel. there is a chance that any brake bias to the rear will just fight against this force and go up in heat in the rear rotors..

anyway, i have an issue in the last 1 second of the braking segment, out of 4 total seconds, from 130mph to about 45mph. thats a LOT of heat. dont know if the rear brakes at full capacity , totally optimized, would loose a full second of this exercise.

anyway, dont take it too personally.... just a buch of boys here discussing the stuff they love.

GregBBRD

Mark:

On the teams I was involved with, we never had any drivers which performed gear braking downshifts. This technique has not been encouraged or taught for many, many years.

The thought, obviously, is that gear braking is very hard on the entire vehicle (axles, transmission syncros, transmission gears, clutch, connecting rods, bearings, etc.), whereas using the rear brakes is much more efficient, since they have very close proximity to the needed resistance, the brakes were designed for this job, and the cost of replacing pads is much lower than the wear and tear caused by gear braking.

As a matter if fact, we would study driver's films very closely and watch for any sign of gear braking. We would want the drivers to be in the proper gear to exit the corners, and encourage then to physically dowshift the transmission through each lower gear as they slowed, but would never allow them to release the clutch. Instructional sessions with any driver seen doing any gear braking, would take place, along with the logical reasons we wanted to change their driving habbits. (There's a long story associated with this, that I will not bore you with.)

Obviously, the sequential transmissions and lack of ABS in the current Cup Cars virtually mandates gear braking, however the entire drivetrains had to be designed for this to occur. Super light pistons, titanium rods, triple disc clutches, larger transmission gears, and an entire trail of superceeded axles were needed to counter this requirement. Even with all if these pieces, broken connecting rod bolts were very commonplace and Porsche Motirsports America had to ask Porsche Motirsports in Germany for permission to change the titanium rod bolts to a stronger steel rod bolts.

Looking back at this thread, it is fairly obvious that you revel in trying to find little details that I may overlook to attack my credibility. Try and understand for me to include every detail would take many hours and consume an incredibly amount of bandwidth, plus bore everyone to death.

Try to keep in mind my prior statements....

All I've done, for 45 years is prepare street and road racing Porsches. 60-80 hours a week. Thousands and thousands of hours if thought and meticulous craftmanship. My abilities and knowledge is renowned, in this community. You'd be stunned at the people who seek my opinions and thoughts. Yes, I grew tired of professional and club racing and intentionally removed my physical self from this venue a few years ago. Yes, I continued to build engines and transmissions and kept mentally current about what was happening, in this "world". I'm currently considering a very high level effort that wants me to return to this world.

The reason I participate, at this level of discussion, is to pass my knowledge on to others who are using my beloved 928s. The amount of absurd crap I absorb from "want to be engineers" and people that have tiny pictures of what is going on is insane.

I recently went through a entire thread of utter nonsense from one of these idiots who insisted that his "928 Performance Chip" was the ultimate performance tool, to never be improved on and that any of my efforts were a complete waste of effort. An entire thread of absolutely stupidity and personal attacks.

All of this being said, your personal knowledge and abilities are way beyond me, so I completely understand why you would disagree and argue with my thoughts.....

I do find it interesting to think how you are possibly going to improve your car and your driving ability, from this point forward. It would seem, from your posts about lap times and accomplishments that you have been "stuck" at the same plateau, for many years. (You seem to talk about lap times and things you accomplished 10-12 years ago.)

You talk about having no weight on your rear tires, yet resist (reject) any of my thoughts to increase the front spring rate/front end geometry to keep the front end from "diving" so badly, which is what causes the weight transfer to the front tires.

You resist the fact (reject) that use of the rear brakes will reduce your brake fade.

You resist the fact (reject) that having all 4 corners braking at the limit of adhesion is the fastest way to slow a car.

You resist (reject) the thought that a computer can think and react faster than your own body.

Yes, the current ABS system, in your car, isn't optimum....it's 30 years old. But you fail to see that for a minimal investment, you could have a current ABS system (out of a wreck) which would improve the current ABS, literally by light years.

Sorry that I can't help you, but I do wish you all of the success that you are capable of achieving!

mark kibort

Greg, what can i say... its like beating my head against the wall.
just earlier, i posed a basic question about transmissions to you, because i have a ton of respect for you , and you answered the quesiton ... a very basic one, incorrectly. (the one about bliping the throttle having no bearing on matching the speeds of the driveline). yet, you said, with utter confidence, that he was "dead wrong". turned out , that he was right to a certain extent, and my smooth shifting technique, and maybe others, unknowingly, is the reason you can get a blip to actuallly save synchros. partially engaging the clutch coming out of gear, and throuth neutral , the blip, that drags the driveline up to engine speed before full depression gets it all synchronized and then into gear. ) anyway, you were dead wrong about the basic forces of the INT plate and its operation. (remember, the tiny little H adjusters that have "all that force " on the.) you can be wrong. you are not an engineer. you are a mastrer mechaic. you are stuck in your own rut of doing things over many years...... kids these days are doing things in their sleep on bikes, that we thought were death defying. your racers you studied 30 years ago , driving the "pants " off a corvette, would be beat by miatas at a track near you by todays drivers. everyone is going faster.
Im not stuck in a rut. im at the limit of the 928 i drive, and by all metrixs this is true.
you see you dont understand my background in eng and athletics. i used the same techniques to improve and better my performances then, as i do now. video tape review, physics, point to point optical speed measuring tools, etc etc etc......
you say , engine braking is not used? hard on the transmission??? engine? reallly?? how is 200hp 200ftlbs out of the engine in reverse force, any harder than 500hp 500ftlbs on the acceleration side?? that analysis makes no sense . really?.... show me one video tape of a pro that doesnt downshift to get the RPMs in the max HP range and keep them there, even during braking sequences. No one coasts up to a turn. they all do it.... engine braking is a fact of racing, and whether sequential, or not, racers...... good racers do it and great racers do it well, and keep the forces minimized on the drivetrain by matching up the forces. if you dont do it correctly, when you come off the brakes in a turn after a trail brake, you are in the wrong gear and have to make a shift mid turn that could upset the car. so, whether you want to or not, you are using engine braking to slow and stabilize the car into and around turns.

i read what you wrote above and just shake my head. who comes down from a high speed straight and jsut pushes in the clutch , leaves it in and goes through the gears???? ahhhhhh no one.... show me one video of this technique by anyone....... anywhere.!!!!!!

again, a world of respect for you, but if you start to dig into my abilities as a driver, ill have to fight back with the same force of your abilities as a mechanic. You are not God. you dont know everything. in fact, you are a jack of a lot of trades, but not master of all. (some for sure) some of your information is 40 years old! by what you say above and your inability to discuss this topic at a high level an use some common sense, makes me think you (we) should keep the discussion in areas you are expert in....engine building!

oh yeah, just so you know greg, whenever you lift off the gas in your race car, its engine braking.... you cant avoid it... so what you say, sounds like you might not understand the basics.... reallly.... think about it very carefully.. actually watch the videos of mine or other pros and show me one that doesnt use engine braking. in fact those that would effectively "coast" up to and around turns, only to let the clutch out at the exit, would be a danger to those around them.

you say im at a plateu. really?? ive show you why the improvements that i make every year are not only about lap time. by the way, im running times that the top pro teams in grand am, world challenge , and others have run, with cars 15 -25 years newer. (and with a LOT of tuning and engineering behind them. my car was slapped together, with some care and thought yes, by no means as prepared as the pro teams, and always on used tires. remember, 1:36.1. 3 seconds faster than Angelelli and the road and track test of porsche GT3 test at laguna in 2008 on new DOTs, as fast as the winner of the world challenge GT in 1999, and faster that most of the field in 2005 to 2008 in grand AM. Again , in a car that was far below the technology bar. I did it driving around a lot of deficits , and studying the techniques of those that were truely fast! it made me a better driver. when i finally get a chance to run a truely prepared car, that experience will do me very well.
There is a reason i can run this old 928 to this level and hold it together, never worrying if it is going to break. 15 years, against all the odds you made agaisnt it..... and by the times ive run, 4 seconds faster than Mark A. ran at the same power level (actually 30hp less), its not because im running it slow.
(and with a lot less bolt ons too... no motons, big brakes, etc etc)
you're the expert..... how is that possible???

GregBBRD

F^ck!

I never said that people simply throw in the clutch and coast. I said that they don't do gear braking....which, in the racing world I come from, is defined to be downshifting through the gears to slow the car.

With ABS, here's how braking is done:

The car is left in gear, the brakes are applied [approximately 60%, them progressing to 80% as the car takes a "set" (ABS is engaged, at this point)]. The reduced speed required to get through the corner is approached, the brake pressure is gradually reduced (trail braking). During this trail braking phase, the clutch is depressed, the correct gear is selected, the throttle is blipped, the clutch is released, and the car is ready to accelerate when the time comes to do that.

Notice that the car is allowed to take a "set" and that basic "set" is not disturbed, but simply "altered" by increase and decreases in braking forces. The rear tires are asked to do a very consistent thing....with no jerking or rapid changes in adhesion.

I'll let you describe how gear braking (downshifting through gears to slow the car) acts on the entire vehicle and especially the rear tires.

Please enlighten us!

Yup, I'm the idiot and have no idea what I'm talking about!

Let's pretend that for over 25 years, any class of real racing that I participated in, the other people didn't get their asses handed to them!

Continue what you currently are doing!
It's working great!
Your improvements over the past 12 years are simply stunning!
It's completely amazing how much faster you are today, than back then!
You are amazing!
I am an idiot!
Now that you've so eloquently made that obvious,
I'm done here!
Have a great time!

mark kibort

I dont know how i can missinterpret this:

you said! :
"We would want the drivers to be in the proper gear to exit the corners, and encourage then to physically dowshift the transmission through each lower gear as they slowed, but would never allow them to release the clutch. "

If you dont release the clutch, you are not connected to the wheels, and that Coasting my friend!

mark kibort

yep, you describe, to a T what i do as i approach a turn, right to the gear shift in or near the non brake area of the turn entry, just after the trail brake segment. no disagreement here.

actually, the lap times vs 10 years later, are better. remember, you said 3 seconds is an eternity. going from a 1:40 to a 1:38.9 is a huge diff, with no changes to the car. then, the instant power went from 137.5 down to over another 2 years to a 1:36.1. By any measure, this is substantial improvement. getting close to my best theoretical lap. but what do i know... ive only been racing in the modern era for 15 years now, and logged well over 150 races. and these are not time trial races, these are battles where the top 4 guys change the lead over the race. something many, even top pros, dont get to experience.

anyway, the only think i disagree with you at, is the 80% final set before anything is disturbed down the straight before the trail brake sequence. ABS doesnt engage at 80% (plus, you are now guessing using these made up % values)
by definition, ABS is engaged at 101%. other wise, you wouldnt need ABS. you see this is a circular conversation because you know so much, you cant understand the basics here. a backhanded compliment, but still true. 80% of anything, is slow in racing. you need to be able to use 100% and use it without upsetting the car in doing so. this is something im good at and have helped others do the same thing on the track. l very simple concepts and techniques, that i wont bore you with.

so, in summary.. everyone uses "in Gear braking" its just a fact and result of going through the gears, releasing the clutch with each shift and using brakes at the same time. ( i hope you didnt think i was suggesting that you dont use the brakes) you use both... thats why i made the comment , that on the rear, with over 100 to 200 hp to play with it is a natural ABS for the rear tires. If there is max slip % for gear braking achieved, then any additional rear bias will just go up in heat.

Look at the data.. there has been tests on cars and motocycles for front, vs rear vs both , rear brakes dont had that much braking force, and the engine braking in some cases can equal the forces capable of perfect slip % on the rear tires, and thats what we all shoot for as racers to slow at the fastest rate.

you are not acting like an idiot..... you are acting ingnorant..... ingorance can be taught, stupidity is forever...

GregBBRD

Uhhhh....thought I was done.

Although I'm sure your ego won't allow you to admit it.....

Tire technology (even the "hand me downs" that you are using) has improved more that three seconds a lap, in the past 12 years.....probably anyone that has ever turned on a single motorsports event, knows that!

You have actually gone "backwards"! That's priceless!

And as far as modern ABS systems go....excuse me, but you don't know your *** from a hole in the ground....otherwise we would not be having this discussion.

80% of a driver's potential braking pressure will activate any current ABS system....probably more like 60%, from a big guy like you. They have to "leave" in a "percentage margin" to make sure that the little guys that drive (who can't push as hard) can still activate the ABS. I'm not sure if you are intentionally "nit-picking" at tiny details (like the actual percentage) to avoid looking at the "big" picture and admitting you are wrong....or if you really don't understand my points....which are pretty damn clear!

One other final point....if you insisted on doing downshifts and releasing the clutch when going into a corner ("Ricky Racer" driving style), you would have been sent home from any team I've ever been involved with! Gone! See you later! Come back when you know how to drive! The money you paid to drive would have been refunded, after the cost of the practice (you would have never gotten beyond practice) transmission repair, the cost of a clutch, and the cost of the axles were deducted. You'd owe more money, if you blew up an engine.

You might want to think about that, before you sign up with Kevin to drive....he's without mercy billing drivers for any damage they do.....and his contracts are bullet proof, for him. I'm not sure how much an Aston Martin engine, transmission, and drivetrain pieces are worth, but they sure don't sound cheap, to me.

And yeah, I'm definitely the ignorant one, in this discussion. Don't know what I'm talking about. Have no experience to back up what I'm saying. Completely without data and facts.