Rock Hard Brake pedal in the middle of an autocross run...

[wparsons]

From what I understand, the pedal dance leaves basic ABS enabled, but disables all other functions entirely (TC, VSC, EBFD, applying brakes to a rear tire in the air, etc). That means no ice mode anymore.

The ABS/VSC system can definitely apply brakes without you touching the pedal, try to spin the car with VSC on and you'll feel it applying brakes to a rear wheel to stop the spin.

[renfield90]

Originally Posted by wparsons

From what I understand, the pedal dance leaves basic ABS enabled, but disables all other functions entirely (TC, VSC, EBFD, applying brakes to a rear tire in the air, etc). That means no ice mode anymore.

Close but not quite. Ice mode is a basic feature of ABS; as long as ABS is active, ice mode is possible.

[wparsons]

Do you know anyone that has had ice mode happen after doing the pedal dance?

[renfield90]

I have.

[rx3]

This appears to be the only option to get rid of ice mode:
http://www.bosch-motorsport.de/en/de...s_1_230947.php
(I talked to people who are running on Mitsubishi, Mini, BMW, Peugeot and they have all experienced too).

[CSG Mike]

Originally Posted by wparsons

Do you know anyone that has had ice mode happen after doing the pedal dance?

I can replicate it at will. A minor driving habit change/correction is all it takes to never run into it. As long as you *squeeze* on the brakes instead of slamming on them, you should never run into ice mode. Squeezing is the proper technique, and you can squeeze very quickly and hard. It's the "panic stop" type slamming that causes ice mode.

[rx3]

Originally Posted by CSG_Mike

A minor driving habit change/correction is all it takes to never run into it. As long as you *squeeze* on the brakes instead of slamming on them, you should never run into ice mode.

This maybe true on the track. But ice mode occurs on bumpy roads or roads with uneven traction and ice mode is more likely to occur if you brake in a turn. Even if you brake smoothly.

After all Bosch wouldn't have developed a specific ABS for motorsport purposes, if the standard ABS would suffice.

[CSG Mike]

Originally Posted by rx3

This maybe true on the track. But ice mode occurs on bumpy roads or roads with uneven traction and ice mode is more likely to occur if you brake in a turn. Even if you brake smoothly.

After all Bosch wouldn't have developed a specific ABS for motorsport purposes, if the standard ABS would suffice.

Correct, but based on our datalogging, we've concluded that the ice mode over bumpy surfaces is actually a result of the bumps causing the driver to inadvertantly "stab" at the brake pedal.

You can see spikes in the brake pedal pressure when you go over bumps, while attempting to modulate the brakes...

[rx3]

The ABS does also appear to initiate ice-mode if one wheel is in the air or has no traction and is stopped immediately. This may not occur on the track (which is lacking bumps created by tanks or uneven traction due to cow dung).

[acro]

Here is my silly question whats the purpose of ice mode. I can see no reason for it so far.

[renfield90]

Originally Posted by acro

Here is my silly question whats the purpose of ice mode. I can see no reason for it so far.

Ever tried it on, you know, ice?

I have. I had a rental car in Canada once, saw a patch of ice at the entry to my hotel, slammed on the brakes while going over it at fairly low speed. For obvious reasons it's inadvisable to try this on a car you actually care about.

The purpose of ice mode is to make sure you don't lock your front tires on ice - if they're still rotating, you have a minor amount of control over the car while still on ice. If they're locked, you're effectively a passenger.

Anyway, I activated ice mode and the theory behind it more or less works. The reason it happens to you with high performance tires, high performance brake pads, and race track grade asphalt is the computer can't tell the difference between that and ice - it just sees your wheel slowing down way too fast.

You can activate ice mode on any car with ABS. It's a DOT requirement. It is more or less likely to happen depending on car setup and driving style. If you are having problems with this, change your driving style and/or line. The fastest way through any given corner is the one where you don't engage ice mode. It's a bit of a tautology but chew on it for a bit and you'll find some wisdom.

A motorsports grade ABS system doesn't include an ice mode calculation, and also lets you tweak the parameters to tune your longitudinal slip angle under braking (among many other things). These aren't DOT approved systems and you'll be required to sign a waiver stating that you won't install it on a road going car.

[acro]

Thanks for the explanation, I wonder if cars sold to countries that will never see ice have this as part of the coding?

[renfield90]

They all use the same ABS ECU with the same programming. It doesn't have to be ice that triggers it (could be oil on the road).

[Element Tuning]

Originally Posted by renfield90

Unplugging the steering angle sensor (underneath the steering column plastics) will disable all stability functions.

Unfortunately disables ABS also as I've had a bad steering angle sensor and discovered that.

For me "ICE" mode was never a function of stabbing the brake pedal and ca using ABS. The logic is probably much more complex but it's completely off (How about using air temp as part of that algorithm dumb asses). For me it has been low pedal pressure, little pitch, abs, and low deceleration that has caused "ICE" mode. These occur with high friction race pads, stiff race suspension, high rear downforce, and a car with way to much mechanical front bias.

I don't drive like this but a modern ABS system should allow you to mash the pedal and ABS itself until the car comes to a complete stop. This is what the average person does in a panic stop when they are about to crash into someone. Turning ABS off or reducing deceleration to dangerous levels makes zero safety sense to me.

Now in the motorsports you just want you ABS to signal you to reduce pedal pressure. Bottom line is that I don't brake in a straight line and I push the pedal until ABS cycles and I back off because it's the fastest way around the track. Tracking for just fun and sure you can drive around all of this. Build a pedal box, dual master, non ABS system and you'll be able have optimal brake balance and feel. Before we completely redesigned the brake balance when the ABS turns off I could barely feel the tires lock because there's hardly any deceration.

I need to be able to use more pedal pressure and throw so I'm going to step down on pad friction and install a driver adjustable proportioning valve on the front brakes to reduce the bias there.