simsgw

A few weeks ago, I was discussing privately the on-track need to carry ABS braking very deep into corners with the latest Porsche models. I own a 997.2 of course, but I assumed it would be similar with the dot one. My correspondent demurred and described a problem with the 997.1 ABS that has been seen in autocross events. I haven't permission to quote him, but roughly he spoke of a "black ice" effect and described it as the car getting into an ABS mode that felt like very low or zero traction and then having no way to recover except removing brake pressure and reapplying it. He was not advocating 'pumping' the brakes, just that a single release and reapplication seemed like the only way to get out of this slide according to owners who had described the effect to him.

Has anyone else heard of this effect? Would there be interest in my spending an hour or two writing an explanation? I thought about it since he mentioned it and I see how it happens, but I couldn't find it in a forum search, so maybe it never was an issue of great enough concern to be worth my time.

Opinions?

Gary

p-cardriver

I would think that in either car one would prefer to stay out of the ABS in braking, but hold to the threshhold just before it engages.

I have a 997.1 and have tracked it and certainly been into the ABS to save my bad technique, but never experienced what you describe.

simsgw

Nope.

Good.

jason74

My Toyota 4runner does exactly this in low traction conditions. Annoying and dangerous at times. Never experienced it in 997.1 yet, but haven't been out in slick conditions either.

mdrums

This is mostly a PCCB issue especially on Hoosier or slicks. Also with these street cars it is not faster to go deep into ABS into a corner...the car will absolutely be unbalanced. I use to think this way too until I hired a few pro coaches. Also it is best to pick you brake points and not hit ABS real deep it is ok to just tickle the ABS at times but in no circumstance should one be into ABS into the corner....Trail brake into the corner if the corner is a trail braking type of corner.

Have fun!

simsgw

Won't teach racing on-line, but some day when you've seriously gotten into training I'll tell you off line why your coaches are [overlookin some aspects of vehicle dynamic control they have given insufficient attention], Mike.

Wait. Just noticed your sig line. Will send you a private note.

Gary

utkinpol

black ice mode is a commonly known thing. not sure if it hapens more often with one sort of r-comps compared to oter r-comps, like hoosiers, or something else triggers it, like wrong tire diameters, etc.

it is sort of when on some conditions when you get front axle lifted and rear is planted solid and you slam on brakes hard system thinks that front wheels are slipping, like on ice and it does nasty thing - it feels like pedal becomes very hard, like you are braking but only 20% or so of actual bre pressure goes into calipers. effect is rare but was observed on bumpy tracks. just an another reason to brake less and be smooth with application, always preload front axle first then go full press on a pedal, not just kick it. and, well, it makes sense to leave a bit of room before wall on bumpy tracks. people say thatusually if you get this mode - let pedal and try to press again, 2ndor 3rd attemot should unblock it. or you can pay about of $10K amount to replace stock ABS ECU with a proper racing one. or remove it completely.

i ran my 997.1 at AX for 3 years now, had it only once but did not even notice, it registered ony after as odd behviour 'i did step on brakes but car did not react'. never had it on a track yet.

Nugget

There's a giant thread on the subject over on the GT3 forum:

well, ABS Ice Mode finally got me...

ADias

Gary: That has been discussed in the 997 GT3 forum.

mglobe

And in the racing forum. It's not unique to the 997. I've had it in my Spec 996, and others have reported it in other marques.

simsgw

Okay, we've established that some people are annoyed about it, but I don't post on the GT3 forum and no one at Porsche is paying me a consulting fee. Do any of you here give a damn why it happens? Everything I read sounds like a routine problem with brake systems that I'd be happy to explain, but it isn't worth it if no one in this forum cares. The GT3 guys can find their own expert.

Gary

Nugget

Why should I re-post the comments I already added to the other threads on the subject? I linked to the thread in the GT3 forum and you can read them there.

Do you have comments to add to the discussion that haven't already been adequately covered by the other threads? If so, I'd be curious to read them. My assumption is that if people care they'll want to read the existing threads.

simsgw

Hmmm. Perhaps my question wasn't clear. I'm not interested in the least. I know brake systems.

Gary

Nugget

I guess I just don't understand why you seem to think that here is different than there. If you've got anything to add to the discussion, that's great.

simsgw

Sorry. I'm a little distracted and undiplomatic this morning. Cindy fell and I don't think she hurt herself more than bruises but I'm only killing time while she sleeps it off to be honest. I'll be happy to explain the effect you all described in that GTE thread Tony pointed out, but I'm already familiar with it and too distracted to enjoy a discussion. I'll kill some time explaining how it happens and why, if anyone cares. If not, then not.

Gary