ponderingtom

I participated in a time trial event this weekend and ran into some issues that I'm hoping somebody on here can maybe help me figure out. The specifics: I have a 2017 Z06 with Z07 package. Manual transmission. I had it in Track - Race mode.

On most of the course, everything was great. Stepping on the brake pedal was like hitting a wall. It was awesome. Except... there was one particular part of the course where there was a slalom. It was a wide open stretch with a 2-3 shift midway. I was hitting the braking zone at around 100-110 mph. Almost without fail, when I would hit the brakes, the pedal was really hard and braking performance was maybe 50% at best. I could stand on the pedal, and still nothing. When I applied the brakes, the car was pointed straight ahead and had been for at least 50 or so feet.

I can only assume that ABS is kicking in, but I would think that with Track - Race mode, that would be turned off.

Any idea why this was happening or what I can do to correct it in the future?

village idiot

It's some sort of stupid ice ABS mode. It happened to me when I braked and hit the curbing at Spring Mountain and COTA. I guess the wheel locks up super quick when unloaded and hitting a bump so the car thinks you're on ice. It super limits brake pressure and causes a clusterfuck. It's fairly terrifying, especially because I'm probably more fearless than I should be hitting curbing if that side is unloaded.

Fine, if you think it's good on the street but why the hell is it enabled in RACE mode? How damn obvious does it have to be that maybe one side of the car will be heavily loaded and the other side may have very little weight on it in competition?

ponderingtom

If this is something in the ABS that I can't shut off, then it is going to greatly reduce my level of confidence on the track which makes this car slower. How disappointing. Doesn't sound like a true Race mode.

Bill Dearborn

ABS is never turned off no matter what mode you are in. I agree you more than likely hit some sort of Ice Mode. When that happens you get a very hard/firm pedal but reduced stopping power. Reduced to the point you swear you have no brakes. The so called solution to the problem is supposed to be remove your foot from the brake pedal and then reapply the brakes. Hard to do when late braking from mid triple digit speeds and the car isn't stopping after you have seen god, waited the appropriate three count and hit the brakes. Tends to raise the pucker factor a hell of a lot especially with all of your neurons screaming that you should push harder on the brake pedal Vs take your foot off the brake pedal.

Bill

ponderingtom

Nice. In this case, there was no danger in lifting and reapplying. We were on a huge airfield with nothing but pavement and grass. At some place like Road Atlanta though, this would really suck.

Not that I'm willing to do this, yet, but is there any way to turn this "feature" off with a tuner or something like that?

village idiot

It's not so much that I mind ABS or want it off in race mode. ABS is awesome. If you've ever driven a car on the track without ABS, you learn real quick how awesome ABS is after you flat spot a new set of tires.

ABS is awesome. This "ice" feature shouldn't be active in PTM mode, especially not race or sport modes. IMO, it's negligence and if someone crashes because the ABS is programmed to think it hit an ice patch in driving mode that serves no purpose but competitive road/autox racing, GM should be held completely responsible.

This isn't a Kia Stinger with "sport mode" that makes the gas pedal more sensitive and delays shift points. It's a Corvette in race mode. There's no effing ice. I hit a bump/curbing/whatever.

fleming23

There has been no way to disable this in any way at this point, short of replacing the entire ABS system with BOSCH M4, which I am also not sure anyone has done on a C7, yet.

I have a number of posts about ICE mode with my Z06 on road course and autocross. It sucks and truly kills your confidence in the car. I've hit a number of cones, damaging my splitter and side skirts, as well as had a 4 wheel off at NOLA due to it. Fortunately, no major damage (yet) but it certainly could happen easily enough.

There are some who believe this is less ABS and more vacuum related as it seems to happen during quick transitions from full throttle to brake. It seems if you wait just a moment before jumping on the brake the issue is less likely to happen. That too could just be giving the car yaw sensor a chance to settle so it doesn't think you are about to spin out the car too, not sure...

k24556

Another thing to look at, and this has happened to a few of us. My case was a loose #7 plug wire. Not enough to cause a #7 misfire all the time, but I was throwing a p0300 (random misfire) when this code is set for enough time, then the car goes into limp mode and any brake application activates TC. I smoked my RR caliper at the track first time out and didn't know it. Another track friend gets a P0300 and hasn't found the source yet. This caused a Service ELSD for him and I think tosses his in limp mode. When TCS comes on and you apply brakes it feels like a hard pedal, but you are really trying to overcome the brake pulsing by the ABS module, which is pumping the rear brakes during a TCS activation event.

My case, I could see the system drop out of Race mode and even when braking in a straight line, I was getting activation of the TCS. For me, since the #7 plug wire and plug were changed, My track time is much more enjoyable with no nanny interference

TumblingPanda

Happened to me as well. How was your throttle to brake transition? Abrupt? Smoother throttle to brake transition helped me. You can still go hard on the brakes, but don't 'impact load' the brakes if that makes sense. Try following the 25-75 rule, 25% brakes for a moment to help the load the front tires and then drop the anchor. This has helped me a lot, even with aggressive track pads.

ponderingtom

Great advice. I'll try that. I was pretty much going from full gas to full brake. But I was doing that on other sections of the course and I wasn't having the problem. This is also a very rough airstrip (I think the last time they touched the pavement was when the Russians owned it before Alaska was Alaska. ) so I'm wondering if the pavement in that section could have been causing it as well.

I'll have the car in the lower 48 for the coming winter to run at VIR and CMP, at a minimum, so I look forward to doing some experimenting with it and see if I can learn to drive around the issue.I just wish I didn't have to.

village idiot

Everything I've ever seen or been taught is hard brake pressure up front and trail off slowly.

Bill Dearborn

I don't think it is a designed in ICE mode per se but an action where the ABS senses something unusual. Having used ABS many times on real ice I know it releases brake pressure only on the wheels that are going to lock up not on all of them at the same time and the brake pedal vibrates like hell and actually sinks a little. It doesn't get hard like the so called "ICE MODE" does.

Bill

village idiot

Whatever the hell it is doing is downright stupid and dangerous for competition use. It's obviously making an adjustment to a single corner either. It thinks the whole car is on a slick surface.

ponderingtom

This whole thing scares me. I'm actually in a conversation with several people about actually competing wheel-2-wheel at this event we do up here on Labor Day weekend. There's a vintage 280Z with a chevy 350 swap, a mean as hell C6 Z06, a Porsche 911 4S with a LS twin turbo swap and a Mustang with a Maximum Motorsports suspension. If I end up rear-ending any of them due to stupid ABS, it's gonna really suck.

village idiot

I have no idea how spontaneously imposing a "limp mode" for brakes is a good idea, safe or even made it through GM.

Oh, you hit the inside curbing? ******* SURPRISE, YOU HAVE NO BRAKES FOR THE NEXT 5 SECONDS. Or maybe you will. Who knows!

TumblingPanda

In the grand scheme of things yes. Looking microscopically, I've been taught by instructors and pros that 0-25-100-hold-70-50-30-15-0 is almost always better than 0-100-hold-70-50-30-15-0. The reason is that, in most cases, the brakes will overwhelm the tires. The front tires grip better when they are loaded vs. when they are not loaded (of course, up to the snapping limit). So you are better off going to 100% brakes when the tires are loaded. And the way to load the tires is to introduce small amount of braking (just lifting isn't sufficient?) and wait for a quick moment while the weight transfers to the front before you go 100% on the brakes. This becomes a must do when you have good BBK and narrow front tires. On my previous car (not a corvette), I had 380 mm rotors on the front with 6 piston Brembo GT calipers and track pads but only 245 section front tires. Just stabbing the brake pedal on the track always triggered the ABS. Following the 25-75 rule significantly increased the tire (NT01s, RE-71R, MPSS, BGF SC-2) performance under braking and more importantly my confidence in braking late.

That was my $0.02

Bill Dearborn

ICE Mode is different than triggering the ABS. Normally when the ABS is triggered the brakes work and work well. If you hammer the brake pedal to lock up the wheels (like in a panic stop) the car will vibrate like hell as 4 wheels vary from incipient lock up to somewhat released and back to toward lock up. ICE Mode is something different. The brake pedal feels extremely firm, there is no ABS action varying the brake pressure in the calipers and the brakes barely slow the car.

Bill

village idiot

Okay- it's not "ice mode." I don't care if it's "rose water and gerbil training mode." It happens in race mode and it's not any less dangerous.

spinkick

village idiot

Here is what happens. I couldn't figure out why the same brake point would make me **** my pants and other times it was too early. Then I figured it out after going to Spring Mountain and having it explained to me

No Ice mode (or whatever the hell it is) - Start @1:00

Ice mode coming to save the day