Shelbyguy, did you get a chance to discuss the ABS systems with the people you mentioned earlier? I've been racking my brain thinking about how the ABS unit's software might be setup.
Big Brakes - Who's done 'em.
- Thread starter 2003snake
- Start date
abs units arent reprogrammable by mere mortals. too much product liability for ford/bosch.
the 00r uses the same abs ecu and hcu as the normal cobra.
there are some excellent abs threads on cornver-carvers. (just resist the temptation to post. thats free advice.)
the 00r uses the same abs ecu and hcu as the normal cobra.
there are some excellent abs threads on cornver-carvers. (just resist the temptation to post. thats free advice.)
Shelbyguy, you say you pull the ABS fuse on track. Are you not concerned about locking up and flat spotting a tire? Tell you the truth, I have been toying with pulling the fuse, but I'm so paranoid it'll cost me more in rubber in the long run, that I leave it in and adjust my braking zones accordingly. I'm well aware of the problems ABS presents on track when a car spins, but I haven't typically been fast enough to be pushing the envelope hard enough to put myself into that situation.....though I fully understand it is only a matter of time as I get quicker.
are you getting the abs engaging when you're on track? if so, try stickier tires. i can count on one hand the number of times my abs kicked in on the track.
ABS doesn't know if you have boots or not, nor if you have more or less piston area. All ABS is looking for it lack of rotation. Granted some of the newer EBD systems do monitor pressures, they'll still be balanced against the rotational aspect as well. A stopped wheel is a stopped wheel regardless of how it became so.
Boots ARE grossly over rated. They provide peace of mind to those who are in the salt belt perhaps and those who never bother to look at pad wear.
I run in more dust and dirt than you'll ever see on the street and run the same calipers six years running. Common sense and cleaning is is all that's needed between pad changes. The Honda comment is based probably on the Dynalite caliper which has min value on the street. That caliper uses pads that are just to thin in a caliper that's too light for the application IMHO. Thus the taper wear of the pad is greater and if the pad run very low they become a binding part of the caliper and can pull burrs on the caliper body.
This is dust: http://p068.ezboard.com/bhillclimbracing
And I have no issue with non booted calipers.
Boots ARE grossly over rated. They provide peace of mind to those who are in the salt belt perhaps and those who never bother to look at pad wear.
I run in more dust and dirt than you'll ever see on the street and run the same calipers six years running. Common sense and cleaning is is all that's needed between pad changes. The Honda comment is based probably on the Dynalite caliper which has min value on the street. That caliper uses pads that are just to thin in a caliper that's too light for the application IMHO. Thus the taper wear of the pad is greater and if the pad run very low they become a binding part of the caliper and can pull burrs on the caliper body.
This is dust: http://p068.ezboard.com/bhillclimbracing
And I have no issue with non booted calipers.
ShelbyGuy said:
Yeah, the only thing I talk about over there is the ALMS stuff and that's only because I actually see it. I'm no engineer...at least not yet...so I try to keep from getting flamed.
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Todd TCE said:
The pads had quite a lot of pad left when they came off. Some taper wear, but not bad. My point about the dust boots is purely from a street car standpoint. How often do you change your pads on the hill climb car? I'm sure its far more often than my Cobra as I'm rolling over 4 years and 30,000 miles with one pad change. I'm sure that interval will be even greater with more pad area and rotor. I don't get in there that much to clean it up, as the car isn't going to see the track all that much for quite some time. Same thing with my Honda. Maybe its a Dynalite thing, but it happened to me, so I'm a bit biased for street car use. I'm switching to different Wilwood calipers anyway and I'll probably move the Dynalites to the rear.
As for the ABS. No, the ABS does not moniter pressure as far as I know, but it is programmed a certain way for an expected pressure upon braking. In a four channel system, it compares the speed of the four wheels to each other and calculates if one is locked/locking up if its outside the range of accepted deceleration rates. If it is, the unit cycles, releasing the caliper (as the unit has now taken control of hydraulic pressure from your foot) until the tire is rotating at an accepted speed. Then, the unit reapplies pressure back to the caliper where the tire locked up. If the braking system has changed so that pressures differ widely from the original system that the ABS unit was programmed for, the unit will output the wrong amount when reapplying pressure to that caliper. All the sudden the wheel is locked up again when it was expected not to and the unit has to cycle again. Imagine everytime the unit goes to reapply pressure again, the wheel locks up. That would cause some pretty long stopping distances. Even a significant change in pad material could cause this on stock calipers, because the coefficient of friction is so much greater. I'm 99% positive that the programming for the stock ABS device is far more complicated than I attempted to explain.
pressures are not going to vary unless you change the master cylinder, and the master cylinder has enough piston swept area to feed just about any caliper you're going to find.
the pressure applied to the caliper pistons depends on the diameter of the master cylinder piston and the leverage applied by the brake pedal (eg., how far down from the pivot point the master cylinder pushrod is) going to a caliper with bigger and more pistons does not increase brake pressure. quite the opposite.
i was more concerned with deceleration g-forces being greater than what the algorithm in the abs ecu would expect. my math says that a 14" rotor isnt going to apply much more brake torque than a 13" rotor, but a 14" rotor and slicks combined with threshold braking might tickle something.
the pressure applied to the caliper pistons depends on the diameter of the master cylinder piston and the leverage applied by the brake pedal (eg., how far down from the pivot point the master cylinder pushrod is) going to a caliper with bigger and more pistons does not increase brake pressure. quite the opposite.
i was more concerned with deceleration g-forces being greater than what the algorithm in the abs ecu would expect. my math says that a 14" rotor isnt going to apply much more brake torque than a 13" rotor, but a 14" rotor and slicks combined with threshold braking might tickle something.
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Alcon 4 piston 14" fronts, with 13" Alcon rear rotors. Huge difference in stopping power - went from 13" "cobra" brakes (PBRs).
http://store.roushperformance.com/detail.aspx?ID=330
:coolman:
http://store.roushperformance.com/detail.aspx?ID=330
:coolman:
ShelbyGuy said:
I should have explained myself differently I guess. When the ABS unit takes control, it expects a certain torque created by the rotor at certain pressures. If that torque is changed by a new setup, the ABS unit will not be able to function correctly.
Unfortunately, I believe I understand this in my head, but I'm having an extremely difficult time conveying it across the internet. School starts this weekend, so I guess I'll dig my book out and do some basic calculations to see how widely stuff can vary.
My whole point with my argument, is that if you don't take the ABS unit into account knowing what it is capable of (not just applying and releasing pressure, but actually modulating) that your braking system will be less effective on the street...and on the track knowing that it won't work properly with it enabled if designed that way.
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This thread is great. I just read this whole thread as I too am wanting to ditch my stock brakes.
except the abs doesnt actually modulate anything. you make it sound as if its constantly varying pressure. all it does is release pressure to the wheel with the stopped exciter ring, then build pressure again so your pedal doesnt go to the floor.
locking the brakes is a function of the tires, more than anything else. brakes dont stop the car, tires do.
take your car out and lock up the brakes so you feel what it does. and doesnt do.
locking the brakes is a function of the tires, more than anything else. brakes dont stop the car, tires do.
take your car out and lock up the brakes so you feel what it does. and doesnt do.
ShelbyGuy said:
Agreed. My lock threshold went up tremendously after I put on the Kumho MXs. Granted I do not have some 100000 pistion brake setup, just the Cobra R Brembos. That is all 99.9% of us will ever need anyway.
Also, the ABS in this car does not modulate, it just lets go and then applies a constant pressure, usually until you have come to a complete stop. Normally when the ABS trips on the street for me, it is due to a dip in the road, road dot or reflector etc. I let off the brakes and reapply so the car will actually stop.
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LargeOrangeFont said:
It does modulate. I'm just going to need a bit more time to explain, because I spent the whole day on planes getting out to Road America for the next race. I'll try to get something up later tonight.
ShelbyGuy said:
In my terminology, that would be modulating. If it senses a tire begin to slip at an unacceptable rate, it closes the valve to keep the driver from applying more pressure. It bleeds it off (not all at once) until it sees the wheel begin to accelerate again. Once it does that, it reapplies pressure (again, not all at once) until the wheel comes to an accepted slip rate. If it goes too far, it repeats the cycle. I call that modulating, because it doesn't just turn it on and off, but ramps pressure up and down.
Like I said in the response above, I'm going to try and get something up that better explains what I'm getting at.
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moridin2004 said:
Reading your above post I understand what you are saying. :beer: That said, I have driven some cars that "modulate" much better.
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you'll be at the generac 500 this weekend?
ShelbyGuy said:
Yeah...I'm actually in my hotel right now. Today was a setup day. Got the "garage" area and pits mostly together for practice on Friday afternoon.
Are you going to the race?
Did you go in 2004?
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if i make it up, i'll probably go up saturday. much easier to get back in town (chicago) saturday night than sunday night.
here are my pics from 2004
http://nitro.vapornet.net/2004/ALMSRA500/
here are my pics from 2004
http://nitro.vapornet.net/2004/ALMSRA500/
ShelbyGuy said:
I worked the race in 04. Did you have your car at the track? I was roaming around (taking a break :-D ) to see the track and ran across someone with an 03/04 Cobra. I was on the quad at the time. Was that you that I talked to?
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