Traction control issue?

[CSG Mike]

Originally Posted by Porsche

That is correct in a NORMAL setup, a setup employing either a properly functioning front/rear brake proportioning valve, or an EBD computerized system. (Electronic Brakeforce Distribution).

Doing the pedal dance creates an ABNORMAL setup; the EBD is now disabled. The EBD was there for a good reason. It was to create the stable balance you describe as true of "any front engine car."

But, we've just turned it OFF. Your description may no longer be applicable.

That changes things. There could be unintended consequences if the rear brakes are now getting the same hydraulic pressure as the front brakes. Due to weight transfer under heavy braking, the fronts can tolerate a great deal more braking pressure before locking up than can the lightly loaded rears.

(I know you know this, Orbital, I'm elaborating a bit for the benefit of some of our readers who may be less familiar with these issues.)

On another note, it's interesting to see that a number of autocross competitors who have tried the pedal dance have found it to be counterproductive, creating worse problems than the one they were trying to solve. A number of those competitors avoid the pedal dance.

I suspect their experience may be due to the very sharp corners they encounter where they hike their inside hind leg (wheel) well up into the air, thus locking it up under braking, which then gets the ABS system riled up. It doesn't like that. Mike, on the other hand, is driving through much larger radius corners on road courses where I suspect he has both rear wheels rolling on the ground.

I'm just speculating about all this stuff.

I actually generally drive over every berm and bump; this is where good suspension comes in.

However, if I don't do the pedal dance, VSC/TC will kick in virtually every time there's even a HINT of wheel lift. Additionally, I can't trail brake without the pedal dance.

Autocrossers generally brake deep, rotate, and power out, due to the nature of their setups (they favor quick small direction changes and fast response, over static cornering grip; this is MASSIVELY beneficial in slaloms, but at the cost of heavily pushing in sweepers). This makes it so they don't run into the trail braking problem that I have.

I can't count the number of pictures of my car (and most cars I drive) on two wheels.

These pictures are at different corners.

CSG David:



Me:

[Porsche]

Originally Posted by CSG Mike

I actually generally drive over every berm and bump; this is where good suspension comes in.

...

I can't count the number of pictures of my car (and most cars I drive) on two wheels.

Heh. (Nice photos.)

You're on the power, though, right? You're not braking heavily at that point. Don't some of the autox guys suffer from increased "ice mode" incidents with the pedal dance? They're still braking when they raise up and lock one wheel, which the ABS dislikes intensely it appears. "Do that, will you? I'm taking away your brakes, then!"

[CSG Mike]

Originally Posted by Porsche

Heh. (Nice photos.)

You're on the power, though, right? You're not braking heavily at that point. Don't some of the autox guys suffer from increased "ice mode" incidents with the pedal dance? They're still braking when they raise up and lock one wheel, which the ABS dislikes intensely it appears. "Do that, will you? I'm taking away your brakes, then!"

There are a few rare instances where I'll lift a rear wheel while braking, but I've yet to experience "ice mode".

As always, YMMV, but my on-track experience is duplicated by quite a few guys in SoCal.

[Porsche]

Originally Posted by CSG Mike

There are a few rare instances where I'll lift a rear wheel while braking, but I've yet to experience "ice mode".

As always, YMMV, but my on-track experience is duplicated by quite a few guys in SoCal.

Oh, I believe you, Mike.

Always have.

Your experience is what encourages me.

[Suberman]

I thought the traction control off setting cannot be actuated if the traction control has been active at any time during an ignition cycle. Not the pedal dance (which I shall try) but the press and hold traction control off. I've had to switch off and restart the engine to be able to switch off the traction control if it has been active.

[FRSBRZGT86FAN]

Originally Posted by AdrianG

To turn EVERYTHING off you need to do the pedal dance. This will permanently disable traction control as well as ABS & EBD. You're on your own until the car is restarted, and the traction buttons do nothing. The pedal dance must be done with the car fully warmed up and stationary within a minute of starting..

Everything you said in your post was very correct and helpful except for the mention of the brake pedal dance disabling ABS, ABS can never be disabled and won't be disabled by the dance. The only way its disabled would be to pull the fuse on it, and in reality it won't give you an extreme advantage not having it.

[OrbitalEllipses]

Originally Posted by Porsche

That is correct in a NORMAL setup, a setup employing either a properly functioning front/rear brake proportioning valve, or an EBD computerized system. (Electronic Brakeforce Distribution).

Doing the pedal dance creates an ABNORMAL setup; the EBD is now disabled. The EBD was there for a good reason. It was to create the stable balance you describe as true of "any front engine car."

But, we've just turned it OFF. Your description may no longer be applicable.

That changes things. There could be unintended consequences if the rear brakes are now getting the same hydraulic pressure as the front brakes. Due to weight transfer under heavy braking, the fronts can tolerate a great deal more braking pressure before locking up than can the lightly loaded rears.

Are we sure there's no integral/internal prop valve? The front brakes will have more torque just due to the rotor size and piston area, but you have a point...I'm just not sure how applicable it is. EBFD is just another safety oriented driver aid; it brakes better and with more precision than an unskilled driver could ever hope to.

Mike, if you're lifting rears a lot... have you considered different (sprung stiffer with firmer rebound) shock tuning and removing the rear anti-roll bar?

[Suberman]

EBD is just a refinement of ABS. Brake proportioning valves limit brake line pressure to the rear wheels mechanically. ABS can do the same job electronically.

EBD is more active in cornering or other left to right asymmetrical road grip situations.

Lifting two wheels on the same side of the car isn't maximizing available grip. Lifting one wheel (should be the inside front for rwd and the inside rear for fwd) is an artifact of roll stiffness compromises. Ideally, the roll rates are adjustable front to rear an all four wheels will contribute cornering grip. If fixed roll rates are required then maximum grip will inevitably lift the inside none driven wheel. The more power you have the sooner that inside wheel will lift if you seek maximum cornering grip under power. Under braking all four wheels should be firmly on the ground.

[CSG Mike]

Originally Posted by OrbitalEllipses

Are we sure there's no integral/internal prop valve? The front brakes will have more torque just due to the rotor size and piston area, but you have a point...I'm just not sure how applicable it is. EBFD is just another safety oriented driver aid; it brakes better and with more precision than an unskilled driver could ever hope to.

Mike, if you're lifting rears a lot... have you considered different (sprung stiffer with firmer rebound) shock tuning and removing the rear anti-roll bar?

Not sure what you're getting at... the FRS/BRZ has really short droop, but we lift rears from catching air

[Porsche]

Originally Posted by OrbitalEllipses

Are we sure there's no integral/internal prop valve?

No we're not. At least I'm not sure. My reading tells me that the EBD has replaced the mechanical proportioning valve on modern cars. I don't know if that's true. I'm thinking, as perhaps you are, that surely they must have some mechanical backup to prevent rear wheel lockup in the event of EBD/ECU malfunction. But, I don't know.

That's why I'm asking people with more experience driving these cars with EBD disabled. I'm reluctant to employ empirical testing on public roads. I don't like the lack of runoff areas, among other things.

I certainly don't wish to learn about this at the expense of a fellow motorist.

The front brakes will have more torque just due to the rotor size and piston area, but you have a point...I'm just not sure how applicable it is.

LOL!

It gets "applicable" right quick when the rears try to pass the fronts heading into a corner.

Try it sometime. Then come talk to me. I'll buy you a beer if you survive the experience.

EBFD is just another safety oriented driver aid; it brakes better and with more precision than an unskilled driver could ever hope to.

"…could ever hope to" implies that it's possible, if improbably. It is not possible.

Perhaps we have a different idea of the function of the EBD system. My understanding is that this system provides a level of control heretofore UNAVAILABLE to a driver. Basically, the EBD/ECU controls the braking force at EACH individual wheel, independently of the other three wheels. I never saw a road car with even two, never mind four brake pedals, the EBD equivalent. People whine about heel-toe being difficult. Imagine giving them FOUR brake pedals. It would be a Candid Camera moment, don't you think?!

Even in modern race cars, I doubt the driver is manipulating the front/rear brake bias LEVER in real time in the midst of heavy braking, down into a corner. She sets it and then accepts the level of front/rear bias for the upcoming corner. There's no skill involved other than the normal threshold braking skills required; the front/rear bias is set, at least until she adjusts the lever again. In any case, none of this is applicable to any road car I've ever driven. The front/rear brake balance is what it is, as set by the manufacturer in my cars. It's not something I can alter through skill in real time on the road. As Mike alluded to, I can alter the balance a bit with different pad compounds, etc. But, again that's a fixed state, once selected, and cannot be altered on the road by any especially skillful use of the brake pedal by anyone or me.

Again, I've read that modern cars do not have brake proportioning valves, which leaves me wondering what happens when we turn off the EBD? Does it bite, now? I don't know. Like you, my first thought is that they cannot be that stupid as to create a monster in the absence of a functioning EBD system.

Well…

Mike assures us that this is not a problem. He's driving the car at the limit, or close enough that his experience reassures me that it would be safe on the public roads. Call me cautious, though.

I should add, too, that where I'm really going is here: I want to turn off the ABS, too. Don't like it. It's dangerous, in my opinion. (But, we're straying way too far from the OP's questions.)

Where will that leave me? In a coffin, maybe?

I wouldn't like that.

I've asked people to disable everything, pull the ABS fuse, and hit the track. Then tell us about it. So far, I have not read of anyone doing this.

Care to be the first? It could be perfectly safe on some tracks at certain corners, I'd think. Just don't do it where you could hit anything if things go awry. Safety first.



If it doesn't work out, return to the pits and plug that ABS fuse right back in.


I long for yesteryear when cars were simpler and the man at the wheel was in control, not a computer.

Ah well, nice chatting with you. :happy0180:

[Porsche]

Originally Posted by CSG Mike

Not sure what you're getting at... the FRS/BRZ has really short droop, but we lift rears from catching air

Oh, you do not!





Do you?

[Porsche]

Originally Posted by CSG Mike

...

Say, Mike... about your ABS fuse.


Any chance you might yank that out for a lap or two, along with doing the pedal dance?

[CSG Mike]

Originally Posted by Porsche

Say, Mike... about your ABS fuse.


Any chance you might yank that out for a lap or two, along with doing the pedal dance?

The boss won't be very happy if I flatspot our tires... we don't exactly operate on a large budget... we're only on our 3rd set of tires. We try to conserve our resources and use them as efficiently as possible.

Now when our tires are bald.... (might have to wait a bit).

[Kodename47]

Check out Fensport's car here in the UK. Its a turbo track car (GT86R) and he runs the Toyota Sprint Series. He removed the ABS fuse and did nothing but slow him down. The brakes just liked to lock up and made the car unstable.
http://www.gt86ownersclub.co.uk/foru...able+ABS#49563