Traction control issue?
 

In all honesty, I just treat the traction control on my FR-S 6MT like a toggle switch. Most of the time if I want it off I would just hold down the left button ~5 sec so all the traction/VSC lights come on. But seems like there are various degrees of disabling using combinations of the TRAC button and the right VSC button, but seems like it should/would affect the Auto more than the MT.

I have noticed something recently that got me curious, my left traction control button is intermittent when I simply press it momentarily while driving. Sometimes the TRAC OFF light would come on but other times nothing happens. Not sure when it is allowed and when it isn't allowed to come on. The long 5 sec press still works every time to turn all nannies off. Any idea?

Traction control issue?
 

Its a toyota system as i used to have it on my TC and now same with the BRZ, pressing the left "Trac off" button for half a second will disable the traction cantrol action momenterly and only works under 30km/h i beleive, this allows you to escape from a pile of snow or ice if ever stuck (it will let both wheels turn freely without controling their engine power nor braking on them, Lsd is still active though)and will the go back on by itself. Now a half second press of the right vsc sport button tunes down the computer assistance in the vehicle and lets you have a bit of fun but will attemt to save your live if control is lost (more experienced drivers will see a contrary effect :p and would prefer to turn off all the gismos completly). Last but not least the "lets have some fun mode" and i really do not suggest anyone to use it unless you had enough experience with this toy because she can be extreemly tail happy and that could be dangerous or fatal, press and hold "trac off" button to turn off all electronic assistance except for ABS of course!

Thanks I'll take it out today and try the 1/2 sec press below and above 30km/h (don't make me do the conversion to mph right now :)) and then see if it goes away automatically.

Haha you americans always have to be different :p dont quote me on the speed im not sure but it acts that way at a certain speed you can figure the rest out

The half second trac off button will also let you get wheel spin from a dead stop. Useful if you're just doing launches. I've forgotten to turn off trac when launching and it just accelerates like a snail.

Here's how the traction works on the Canadian version (I don't know if other markets are different):

- VSC Sport mode can be enabled with the right button at any speed. It will stop reducing power so much but will still apply rear brake if you slide more than a little bit.
- A short press of the left button will disable traction control until speeds exceed ~40km/h (or until the rear wheels reach 40km/h). This can be combined with VSC.
- A long press will disable traction/VSC and remove power restriction and the car will no longer apply rear brakes when you slide. The system will however turn itself back on if it detects a zero-grip scenario on the rear wheels (for example, one comes off the ground). On top of this, you still have the other computer aids (ABS, EBD). This can only be done when the speed is under 50km/h (though the manual says you have to be stationary).

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.

- Start the car (mine's MT so I move it to neutral at this point)
- disengage the e-brake if it is on
- pull the e-brake 3 times, locking it on on the third pull
- tap the brake 3 times, holding it on the third
- release and pull the e-brake 3 more times while holding the brake pedal, locking on the third pull again
- release and tap the brake pedal 2-3 more times

If it worked, the traction control lights will come on and the traction buttons won't turn it off again. The only way to re-activate the assists are to restart the car.

This *can* be done on the US version of the car while moving, if you're not activating the system via driving. E.g. if you're driving on the highway, you can still do the long press.

If a rear wheel lifts or the system detects single wheel spin, the "electronic diff" is still active, and will engage. This will be indicated by the slip light flashing in the tach, and the VSC/TC lights turning off. They will turn back on and the slip light disappear when the car stops detecting single wheel spin.

This CAN happen while hard driving, and will force the car to understeer, which is why we recommend anyone tracking do the pedal dance. At this time, I can replicate this issue at will.

The ABS is disabled?

Maybe, but I'd be surprised if this were true.

Perhaps someone could test this on the road/track. It would be easier on the tires to test this in the wet to avoid "squaring off" your tires if in fact the ABS is disabled.

ABS is not disabled. EBD is.

That's my understanding, yes.

Mike, can you share your experience with the EBD being disabled. It is my understanding that these cars no longer employ a brake proportioning valve to manage the front -> rear brake balance under varying conditions. The EBD now manages that; but, if it's disabled, then wouldn't both front and rear wheels get identical brake force? That's not good...

I'm only speculating here, but I'm concerned about doing the pedal dance for the street and then finding myself zooming into a downhill corner out in the country and having my rears lock up and try to pass the fronts into the corner.

I don't like that kind of excitement. ;)

Can you share your experience, please, and help me understand this better?

Thanks.

The system, from my experience (no actual measurements) has a front bias. Unless you purposely put a much more aggressive compound in the rear, you won't have any rear locking up issues.

In fact, you won't have any rear locking up issues since ABS is still active :D

What it does do, is let you properly trail brake.

Any front engine car is going to have significantly more front brake than rear brake. Only mid and rear engine vehicles will deviate from that.

Thanks, Mike.

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:

http://vanhap.com/imgs/2011/July/07-...s/VP2_0464.JPG

Me:

http://vanhap.com/imgs/2011/January/...s/VP2_6428.JPG

http://i3.photobucket.com/albums/y75...0607103356.jpg

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!" :D

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. :)

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.

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.

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?

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.

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

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.

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. :D

"…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?! :lol:

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? :D

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:

Oh, you do not!





Do you? :confused0068:





:)

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).

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

ABS has its limits. One unfortunate side effect which can catch out even ordinary road drivers, though they will not be aware of the reason for the crazy behaviour of their vehicle, is the inability to lock the wheels in a yaw event means you really have to keep steering the vehicle through the entire emergency event. ABS means the car will continue to travel in the general direction the front wheels are pointing. On the track at very high speeds this can be very dangerous and may be a reason ABS is not found on competition cars.

ABS is tricky to duly implement on motorcycles also, for different reasons.

EBD has no such drawbacks unless ABS also operates. As I understand it, EBD uses wheel speed sensors and the ABS line pressure bleed valving to equalize wheel slip among the four wheels regardless of brake line pressure or wheel loading. This maximizes total braking force. In theory it could be programmed to permit four wheel lockup with the singular advantage that the lockup would be truly simultaneous.

I doubt very much that EBD would remain active if the ABS were to be disabled on a street car as it would be difficult to write the software. Also, if the ABS malfunctions on a road car the brake line pressure relief valves MUST remain closed so EBD could not operate. A competition car could just return to the pits if a partial failure of the ABS/EBD were to occur.

For this reason I doubt road cars rely only on electronics to limit line pressure to the rear brakes. The mechanical proportioning valves are anvil reliable, rarely failing in the entire service life of the vehicle. Indeed, if they do fail it is usually the load variable mechanism that fails, the rear line pressure still gets limited but defaults to the lowest, light load setting. The consequences to an ordinary driver of ABS/EBD failure with no backup mechanical brake proportioning valve could be very serious indeed.

I'm puzzled by the post suggesting rear droop could be reduced by fitting stiffer springs and deleting the roll bar when the opposite would be the case. Roll bar springing is ineffective for simultaneous wheel movements on the same axle.

Thanks for this.

Their experience is what I anticipated.

When ABS systems were first implemented on road cars by Audi and Mercedes, I think(?), they had switches for the driver to turn ABS OFF. I remember that the racing Corvettes had ABS OFF switches many years ago. An interesting Car & Driver(?) article had a journalist riding along with a Corvette factory driver at a race track, the driver spun and smacked into the Armco barrier. He said "Oops, I forgot I had ABS turned ON." The ABS took him right into the barrier.

With further advancements in technology I suspect that all of these systems are integrated into a design that no longer permits one to turn OFF the ABS safely; other required systems are dependent on the ABS functioning.

Bosch Motorsport offers a racing ABS system, albeit at $8000+. But, even their far more sophisticated system is apparently not without some problems. Porsche 911 drivers still experience "ice mode" under some conditions even with the expensive Bosch system.

I guess I'll just have to abandon any thought of turning ABS OFF.

I haven't tried this "pedal dance" you speak of, but it reminds me of something.

"For Infinite Traction, press and hold X, then press Triangle, Square, Square, Circle, Select, R1, L1, release X, Press and hold R2 then press Down, Up, Left, then release R2. Remove your left shoe and sock and (with your right hand covering your navel) press X with your big toe and Triangle with your pinky toe. If done correctly, you should hear a beep."