Random question on the ABS fuse

[renfield90]

Originally Posted by dwx

It's definitely a combination of system and technique. For instance Bill Cook and his previous drivers never experienced it but at Dixie Mike King drove his car and had it happen all the time. Do you guys left foot brake? That seems to make the problem worse but may just be an effect, I had a tendency to stab the brakes more when I LFB.

I have read somewhere the ABS logic may take into account how fast you are braking, it might treat a quick stab as panic braking and trigger the ABS.

You can search for "pedal dance" and try it. Using that mode to disable EBD helped the track guys with trail braking, but in general just made ice mode kick in more often in autocross.

Are you using the stock pads?

Yes, stock pads. Do upgraded pads cause a bigger problem?

I've tried the pedal dance with little relief but I'm leaning more and more to using it - I need more experimenting (I've had the car less than 2 months). The less the system second guesses my actions the better.

[renfield90]

Originally Posted by Sam Strano

Physics dictates that you can't stop and turn at the same time, not without lessening the pedal pressure as the cornering force ramps up, which is really trailbraking. Braking hard while trying to turn is not trailbraking and no car will be happy about that because you are asking too much from the tires.

This car has limited droop, and I suspect that some folks are managing to be so hard on the brakes when turning that the inside rear locks, and that will ALWAYS give you ice mode because there isn't any other reason normally that would happen.

A Mustang is something I'm familiar with, and guess what.... plenty of folks complain about the same thing on those. Corvettes too. I have issue with none of them.

The Mustang has a lot of inside droop, and a solid axle... and a lot of weight on the nose that makes it less likely to tolerate being stuffed in a corner on the brakes hard enough to cause you issue with the rear. But still folks have it happen because they just flat overdrive the tires.

The car doesn't freak out if you drive it sporty. Mine doesn't. Andrew's doesn't. This is a driving thing I'm sorry to say.

When it happened Sunday I was braking in a straight line. I was on the brakes hard for half a second, trying to threshold and not kick in ABS, and then suddenly it freaked out. There wasn't any change in my inputs to the car.

I don't think anyone who has ridden with me or watched my driving would say I push the tires too hard with my trail braking. I realize my driving may need to change to keep whatever random ECU parameters cause this to stay within a normal range but it's hard to get more basic than a straight line braking maneuver. Do I need to worry about going over the side of a canyon?

[Scooby South]

I don't left foot... and I have never experienced the "Ice Mode" in my car... But Mike found it right away... it has something to do with the EBD on the car. If you brake and try to use the throttle at the same time, its seems to enhance 'ice mode' more prominently... The Brake logic that is implemented in this car along with the Traction control system doesn't like to have both the gas and brake pushed at the same time... and As Sam said, its very driver dependent. My normal co-driver hasn't experienced it either..and we have about 150 plus runs on the car..

Bill

[renfield90]

I have a theory: what happened to me a week ago may have combined the panic brake feature along with ice mode.

When you trip the panic brake, the car decides the brake pressure for you - modulating doesn't have any effect. Then the other nannies (EBD, likely VSC, ABS) work at a layer underneath that - in other words, they aren't aware of whether the human is controlling the brake or the computer is controlling the brake, they simply respond to the conditions their sensors report. (As an embedded software engineer, this is more or less how I would implement the system. They're probably using an ABS controller from an older model without a panic brake feature and trying to integrate all the systems seamlessly for this one model is too much time/money.)

So if you're in panic brake mode and the ABS then trips ice mode, how do you handle this? Well, you are (apparently) in very real danger of hitting something and (apparently) there's not enough grip to stop the car. My thinking is that the system locks the brake pedal - if you're on ice trying to not hit something and you lock your wheels, you start running out of options very fast.

What happened to me was a LOCKED brake pedal and zero deceleration beyond engine braking. I can go out to my car, empty the reserve vacuum from the booster until the pedal is firm, but it will still have some give. Last week I tried to power through it and the pedal literally wouldn't budge. I'm not lacking for leg strength either.

I can live with "normal" ice mode. I can't live with this. The pedal dance disables panic brake so I'll be doing that from now on and we'll see if it happens again.

[GTM_Challenge]

Originally Posted by renfield90

I have a theory: what happened to me a week ago may have combined the panic brake feature along with ice mode.

When you trip the panic brake, the car decides the brake pressure for you - modulating doesn't have any effect. Then the other nannies (EBD, likely VSC, ABS) work at a layer underneath that - in other words, they aren't aware of whether the human is controlling the brake or the computer is controlling the brake, they simply respond to the conditions their sensors report. (As an embedded software engineer, this is more or less how I would implement the system. They're probably using an ABS controller from an older model without a panic brake feature and trying to integrate all the systems seamlessly for this one model is too much time/money.)

So if you're in panic brake mode and the ABS then trips ice mode, how do you handle this? Well, you are (apparently) in very real danger of hitting something and (apparently) there's not enough grip to stop the car. My thinking is that the system locks the brake pedal - if you're on ice trying to not hit something and you lock your wheels, you start running out of options very fast.

What happened to me was a LOCKED brake pedal and zero deceleration beyond engine braking. I can go out to my car, empty the reserve vacuum from the booster until the pedal is firm, but it will still have some give. Last week I tried to power through it and the pedal literally wouldn't budge. I'm not lacking for leg strength either.

I can live with "normal" ice mode. I can't live with this. The pedal dance disables panic brake so I'll be doing that from now on and we'll see if it happens again.

Any results on this? We've been getting the locked brake pedal even with the pedal dance. Going to try just pulling the ABS fuse this weekend to put the car into "No ABS Miata" mode - something I'm a little more comfortable with.

[acollite]

I have only done 2 track days this year but I have pulled the green fuse both times and have not had any problems .

[Nickse30]

Originally Posted by acollite

I have only done 2 track days this year but I have pulled the green fuse both times and have not had any problems .

By the "green Fuse" you mean the fuse for the abs? So you did this with out any problems? Did the abs light come on? Did the car try to retreat to limp mode?

Im asking this cause im having issues with an ABS sensor and the abs light is on which in-turn activates limp mode. Do u think if i just pull the fuse the ecu will forget abt the broken sensor and if i clear the fault codes my car will get out of limp mode??

I need a solution cause my local toyota and Subaru dealer both need over a month to get the new sensor.? and im stuck in limp mode now

[acollite]

I ran the whole track day like that although a bunch of lights came on in the cluster but the car drove normal with no limp mode

[moomoopanda]

I've had my green fuse out for a month now.. I don't believe I have experienced any limp mode. My ABS is off and my traction control and VSC is disabled.

(And for some reason my e-brake light is always on.)

[solort]

Pulling the ABS fuse or adding a "blown" fuse is not legal for stock or the new street class. I minimize ice mode by changing my line into a corner requiring hard braking by entering wider and braking more in a straight line to limit rear wheel lift, which can increase the chance of ice mode. I have also read someone had less ice mode with more aggressive front pads vs rear pads to get more braking on the front wheels. Trail braking and ABS are not a good combo...

[scionsouth]

Originally Posted by solort

I have also read someone had less ice mode with more aggressive front pads vs rear pads to get more braking on the front wheels.

^^This^^

Had a tC that would lift a rear wheel trail braking which would put it in to "ice mode". I was able to dial out most of it by putting aggressive pads up front and leaving the stock pads on the rear.

[solort]

Originally Posted by scionsouth

^^This^^

Had a tC that would lift a rear wheel trail braking which would put it in to "ice mode". I was able to dial out most of it by putting aggressive pads up front and leaving the stock pads on the rear.

And your car was able to brake better even with the heavier front brake bias? What brand pads do you use up front> I was looking to get Carbotech AX6 pads

[OGSCION]

Originally Posted by solort

And your car was able to brake better even with the heavier front brake bias? What brand pads do you use up front> I was looking to get Carbotech AX6 pads

Yep, the braking capabilities were significantly improved. I was running dot r-comp tires at the time so the fronts had plenty of grip. The ability to trail brake became a lot more consistent and I could also get on the brakes harder and later.

I used the Hawk HP+ on the front. For autox I bet just about any pad that works well at low to medium temps and has good initial bite would be fine.

[350matt]

Originally Posted by moomoopanda

I've had my green fuse out for a month now.. I don't believe I have experienced any limp mode. My ABS is off and my traction control and VSC is disabled.

(And for some reason my e-brake light is always on.)

Which fuse is the one to pull the 40A or the 25A one?

and the e-brake light on the time means the active 'diff' is on where the brakes are applied to the spinning wheel to try and give some LSD action