ice mode: When the ABS computer detects tire rotation differential speeds that leads it to conclude that the car is on a low traction surface. The ABS system then reduces the braking pressure, leading to a hard pedal, and not much braking ability.

There is a thread here somewhere by arghx that explains FD ABS operation in detail.

Just curious how many of you have run into ABS 'ice mode' when on track or doing autocross.

I've had this happen to me 3 times now, one was scary (braking in the finish) and the other was annoying, as it cost me what I think was going to be a quick time in a competition run.

Just this Saturday it happened while braking on a bumpy surface. It has also happened on a smooth surface when the brakes were applied suddenly. One of these times was in the finish at an autox with a not very long run out for the finish - that was a bit nerve wracking.

This can be brought on by aggressive brake pads, aggressive braking, and/or braking on bumpy or rough surfaces. Not surprisingly all of these things can happen at an autocross.

If you have run into this problem and solved it, please share your solution.

This is not a problem unique to FD's.

Google for ice mode and you will find a lot of different makes of cars where this is an issue.

This thread at Mazdas 247 has a pretty good discussion on it, though not FD or even RX-7 specific.

 

I have had it happen on bumpy surfaces I originally thought the pads on my new Fd were glazed because of the rust on the rotors when I got it

 

Maybe that is one reason that real race cars do not use ABS.

 

That isn't quite true, there are race series that allow ABS.

A race worthy ABS system starts at a few thousand dollars, however is quite a bit more sophisticated than the FD 3 channel setup, and is a little out of most autoxers budgets.

That said, I am removing the ABS - I have raced without it before by pulling the fuse. Removing the fuse is a less than optimal solution, as there is then too much rear brake bias.

Just wondered how others have dealt with it on our cars. The most common method is probably removing the ABS, but there may be some more creative solutions at hand.

 

Couldn't you balance that out a bit with a less aggressive pad in the rear? I can't say I've noticed that scenario, but I already run a less aggressive pad in the rear than the front which gave me better balance on the track. It could be that I was feeling what you posted, but just never dug too much into why.

 

I would think in this case, a proportioning valve could be used to even things out.

We don't race our Lemons car with ABS, but there are times I wish we had it. Flat spotted Star Specs are expensive.

 

"as there is then too much rear brake bias"

That is strange because when my ABS failed do to a bad +12V connector pin, it was my fronts that would easily lock up?

 

^There are too many variables to mention that would determine whether your front or rears would lock up first if your abs is non functional on a stock system.

My vote is always to keep ABS. The FD's ABS functions great IMO and I've car whored quite a few new cars on track to compare systems. Not having ABS is even worse for AutoX. If you lock up at all, your run is shot. On track you have a little more flexibility, but if it's a time trail, your lap is shot as well... not to mention those expensive tires may be flatspotted. There is a reason ABS is ban in F1, it's because it's a performance advantage.

Never experienced ice mode in an FD with ABS. I think Fritz has once, or something similar, but his opinion is the same as mine. He has also ran full manual brakes in the FD in the past.

 

I may reconsider removing the ABS, but keep in mind the original dilemma - encountering ice mode, some times at rather crucial moments. When this happens there are effectively no brakes.

It doesn't seem very likely that changing rear pads will help, as the problem seems to be more related to rough surfaces and sudden application of the brakes.

Maybe others haven't run into to it, or maybe only once, but I have had multiple occurrences.

So, other than removing the ABS, are there other suggestions?

I have considered that I may need to be a little smoother on brake application, but that may not help if the braking is done on a bumpy surface.

Doing nothing isn't really an acceptable alternative as far as I am concerned.

Any ideas?

 

This Lotus thread is interesting, as this appears to be a big issue with aggressively driven Elise and Exige: Very scary brake problem today... ("ice mode" victim) - LotusTalk - The Lotus Cars Community

The issue apparently cannot be generalized with the following:

* brake pads
* braking style
* surface conditions.

It appears to be more related to ABS just becoming confused.

 

Found this post describing another ABS issue I have encountered: https://www.rx7club.com/suspension-w...6/#post6245170

The fix was 2 ABS relays.

This was recommended to me in this thread as well, but I somehow missed it.
https://www.rx7club.com/suspension-w...nuosly-971892/

Don't know if these relays could be causing the ice mode issues, but replacing them can't hurt.

 

Most FD owners who have had ABS failure do lock up the fronts.

 

I have experienced both. Braking from 85 mph on a relatively good surface the rears would lockup first.

Last week from about 50 mph on a relatively poor surface the fronts locked up first.

 

I had what I believe to be "ice mode" ABS engagement just once so far in my FD.

I was auto-xing stock class on worn V710 in the rain with standing water. I had to brake hard in a straight line after the finish from a high speed.

One run the car refused to slow at my requested rate no matter how hard I pushed the brake pedal. I over ran the pavement straight onto gravel and the car immediately began to slow at a FASTER rate still in a straight line.

No damage or close call safety wise but I was left scratching my head on what had occurred. I had not heard of "ice mode" at this time. It felt much like when I have accidentally had my foot touch the gas a bit when trying to brake on my overpowered/underbraked FC.

 

I think the key to stopping when ice mode is inappropriately triggered is brake as hard as you can. ABS has reduced braking pressure to 25%, so you need to apply a lot of pressure.

 

ABS was removed a couple months ago.
A bit of a learning curve, basically learning to brake properly again.

Let some smoke out of e tires the first few runs, but much improvement since then.

 

Please keep us updated on how you like the ABS delete in Auto-x type situations as you learn the braking nuances.

 

After the first few outings, I have learned to brake properly again.

Way to easy to use too much brake with ABS.

Not having ABS kind of forces you back to good habits.

My autox mentor off and on over the years is a Solo Nationals champ in a stock FD from back in the day when the FD ruled in SuperStock. (or whatever class it was)

He's driven my car many times.

The last outing I finally beat him when we were co-driving the FD at an autox.

Kind of surprised both of us I think

The lesson being that I was braking better than he was.
He came really close though, and better braking on his part would have put him ahead of me.

 

How much weight did you lose after removing the ABS from your car?

 

I did weigh all of that - as I recall is was right at 15 lbs.

Add back a couple of lbs or so for the lines, fittings and proportioning valve, about a 13 lb net loss.

 

glad you are kicking but brother. How many turns you set the valve

 

Thanks Alex!

Currently set at 6 turns from full increase.
There are 9.5 turns total on this valve.

Probably will dial that back a bit dependent on course.

 

Sorry, this was incorrect.

That should say '6 turns from full decrease'

Full decrease is with the **** turned out completely.

My FD has Wilwood 6 piston front calipers, and a 929 Master Cylinder, so these settings are likely different than what would be used on a stock setup.

 

that's bad *** bro post up pics next time you go

 

This is from National Tour a couple years ago - car looks the same as it did then.