Ice Mode - Anyone fix it yet?

[Chili Red]

Originally Posted by Jack

Patrick is referring to the Lotus Scan tool that allows the Lotus technician to activate the abs system while the car is on the lift and flush any air/debris out of the system. A normal brake flush/bleed will not take care of the abs...some suggest doing a flush and then going out on a drive and activating the abs and then doing the bleed all over again...not the best/most thorough way, IMHO. Sometimes there are advantages to having a qualified dealer tech do the service work.

The first time the fluid was flushed the Scan tool was used to activate ABS, this time it was not.

[Charles Rozier]

Just checking... are your tire sizes close enough to factory spec diameters? I experienced a loss of braking and and hard pedal feel on track that sounds a lot like yours, and it turned out that the ratio of my front/rear tire diameters was not close enough to the factory A048 ratio and so the ABS was thinking the rears were locking up earlier and intervened too early. Going back to tires within a few percent of factory A048 f/r diameter ratio fixed it.

If you are on 048's or AD07's this definitely isn't your problem though.

[zygotesoup]

so if im understanding the lotus engineers, there is no loss of breaking with this "ice mode" issue?


if you were to pull the abs fuse to aleviate this, are there any issues you have to worry about aside from not having abs?

[fzust]

Guys,

*corrected*

There are 2 potential problems:
The vacuum is a dead issue. I've pounded through this with the XP car since the inception. It is not related to ABS. This is related to lack of vacuum in the brake booster after a period of acceleration. With no vaccum in the brake booster, you will have essentially zero power brakes until the vacuum recovers. Replacing the check valve that is just off the motor will help. However, we solved it with a supplemental vacuum canister and an additional check valve. This supplements the vacuum available to the master cylinder. We do not have "ICE mode" anymore. The lotus OEM valve is a super-cheap plastic piece of crap and should be the first thing replaced. BTW, currently our tires are BIGGER diameter in the front vs. rear. This solution cured the braking problem when we had properly sized tires and it has not come back with the current configuration.

HOWEVER, the other problem is as Jack stated it:

"The symptoms being described are a result of the Electronic Brake Distribution (EBD) system operating. This system is also referred to as Dynamic Rear Proportioning (DRP) and is, as the name implies an electronic system which, through the ABS control valve block restricts the line pressure to the rear brakes automatically to a pre-programmed algorithm. You can consider it as an electronically controlled proportioning valve which measures parameters like the rate of deceleration and rate of pedal application and uses this data to anticipate a rear wheel lock-up and then reduces the braking effort at the rear wheels as necessary. If the ABS system is left to do this, it can only react to a wheel as it starts to lock and therefore the car can already start to spin before the ABS can start to work. In extreme circumstances, if the driver brakes very suddenly the EBD system can lock off the pressure to the rear wheels completely; what pressure was at the rear brakes as the EBD system engaged remains there and the rear brakes are still working as a result, but further increases in pedal effort will not increase the braking at the rear of the car because the pressure to the rear brakes cannot increase. When this happens the brake pedal goes hard, as it is now pushing against the front callipers and a closed valve only, instead of against the front and rear callipers. The rear callipers are single piston and therefore quite flexible, so they are a major factor in making the brake pedal feel 'soft'. When the valve closes, the brake pedal pressure no longer flexes the rear callipers, hence the increase in pedal hardness. The front brakes are still working just as well as before the valve closed and will give more braking if the pedal effort is increased, while with the rear brakes working as hard as they can the braking is NOT affected. The problem is the driver feels like braking is reduced (even though it is not) because of the change in pedal feel. If the driver continues to push hard on the pedal, the car will continue to slow as fast as it possibly can in the circumstances. If he increases the pedal effort the front braking effort will increase and the rear effort will remain where it was. If he was to back off the pedal for a fraction of a second, the valve will reopen and the rear brakes will operate as normal again, with the pedal feel going back to normal.

In the case of releasing and re-engaging the pedal the car should not be able to slow any faster than it was with the system engaged unless either 1: the driver triggered the system in the first place by stamping on the pedal too fast or 2: the system triggered because a rear wheel was unloaded when the brakes were applied and would have locked up but is now fully loaded once again and able to sustain a greater braking torque. If the rate of deceleration does improve when the pedal is reapplied then it is telling the driver that he is over braking either in terms of the ultimate ability of the brakes (cause 1 above) or the track condition (cause 2 above) and needs to adjust his driving style to suit. If the system were not fitted or disabled and he continued to drive that way he would be in danger of spinning when applying the brakes.

The suggestion that the system is running out of vacuum is just plain wrong. The system carries an internal reservoir of vacuum sufficient for three full brake applications. As with every servo system ever fitted to a car there is a one way valve which prevents the vacuum being lost when the car is on boost. The only way this reserve can be depleted is if the driver is maintaining boost while applying full brakes, i.e.: left foot braking very badly. In this instance I would argue that depleting the vacuum is probably a good thing as it should provide him with a warning that he is doing something awful to the car and it may reduce the speed of impact when he finally hits something as the brakes fade to nothing!! In normal use the throttle is closed when the brakes are applied, there is therefore no boost and the vacuum is automatically replenished as it is used."
__________________

[zygotesoup]

Originally Posted by fzust

Guys,

This is a dead issue. I've pounded through this with the XP car since the inception. It is not related to ABS. This is related to lack of vacuum in the brake booster after a period of acceleration. With no vaccum in the brake booster, you will have essentially zero power brakes until the vacuum recovers. Replacing the check valve that is just off the motor will help. However, we solved it with a supplemental vacuum canister and an additional check valve. This supplements the vacuum available to the master cylinder. We do not have "ICE mode" anymore. The lotus OEM valve is a super-cheap plastic piece of crap and should be the first thing replaced. BTW, currently our tires are BIGGER diameter in the front vs. rear. This solution cured the braking problem when we had properly sized tires and it has not come back with the current configuration.

where can you get the replacement part and how difficult is it to install?

[Arno]

Originally Posted by Chili Red

Yes please post pictures if you have them.. I may just try this if its not to expensive. I can for sure tell if it works or not in one hot lap. I may also try pulling the ABS fuse to see if that helps any.

Then before you invest any time and/or monney I'd first disconnect one of the front wheel sesnors. Just disconnect the plug and tie the cable away a little.

This will disable the ABS, but keep everything else operating normally.

Still have the problem? Possible vacuum issue
Problem gone? ABS is causing your problems.

Simple..

Bye, Arno.

[fzust]

Originally Posted by Arno

Then before you invest any time and/or monney I'd first disconnect one of the front wheel sesnors. Just disconnect the plug and tie the cable away a little.

This will disable the ABS, but keep everything else operating normally.

Still have the problem? Possible vacuum issue
Problem gone? ABS is causing your problems.

Simple..

Bye, Arno.

Arno,

You're correct this is a good approach and we ran the car like this for a while. The ICE mode issue went away in exchange for early lockup of the fronts due to brake bias. However, when reconnected the "ice-mode" reappears. Our supposition is that the lack of brake boost impacts the system less when the ABS isn't trying to pump the brakes repeatedly. Once we fit the vacuum canister, the problem went away permanently regardless of ABS or not.

'soup,

The check valve is a connection between the vacuum hose that runs off of the intake manifold/throttle body. Follow the hose to a fitting that connects to another hose. The check valve is two barbs, one on either side of quarter-sized circle.

[Bleu Omdurman]

I know this issue is "relatively common" but I have not had it on the track at all. Is it possible that cars that are not having this issue have working check valves?

On driving style, it may be important to note that I pride myself on smoothness. Given the Lotus engineer bit above, perhaps this is why I have not had the issue?

I go pretty deep in the corner before I am on the brakes. To the point that I trail brake on those turns that deserve it. I'd hate to be surprised by this issue if replacing the check valve to a more robust version can prevent it.

My car works perfectly in its current condition. Thanks for your thoughts.

[dmh]

Originally Posted by Arno

Then before you invest any time and/or monney I'd first disconnect one of the front wheel sesnors. Just disconnect the plug and tie the cable away a little.

This will disable the ABS, but keep everything else operating normally.

Still have the problem? Possible vacuum issue
Problem gone? ABS is causing your problems.

Simple..

Bye, Arno.

So who is talking of vacuum and who is talking of EDB?
Who experiences the issue on the street and who on the track?
Something seems a bit off here...

[codingparadox]

I've been having this issue at autocrosses a lot, definitely after long acceleration zones. I most noticed it after about an 8ish second full-throttle zone and my codriver and I both got "ice mode" several times at the braking zone right after this acceleration zone. Sounds like I should try replacing the one-way valve.

fzust: Any chance you have the part number?

[Chili Red]

OK, I think Im more confused now than when I started this thread.. Looks like I'm just going to try the Vacuum booster first as I would prefer to keep ABS. If that does not work Ill give the disconnect ABS a try and see if that fixes the problem.

I can repeat this problem at will, so Ill know if its fixed or not immediately.

[jim-clayton]

Here's some pictures. Install location is front driver's side wheel well. The tank came with a check valve. I installed the valve between the new tank and brake booster. I installed nutserts for bracket mounting.

tank here
Summit SUM-G1464 - Summit® Vacuum Reservoirs - summitracing.com

hose here

Summit SUM-230606 - Summit® Stainless Steel Hose - summitracing.com

[jim-clayton]

last pic

[Mr. Oz]

I quit using steel braided hose years ago and now use this.......

Russell Performance

It's lighter, easier to work with and will not damage things it comes in contact with like the steel braided line does. I have seen the steel braided hose actually wear right through aluminum tubing and wiring. My two cents.

Back on topic.

[luxige]

Originally Posted by Mr. Oz

I quit using steel braided hose years ago and now use this.......

Russell Performance

It's lighter, easier to work with and will not damage things it comes in contact with like the steel braided line does. I have seen the steel braided hose actually wear right through aluminum tubing and wiring. My two cents.

Back on topic.

Interesting stuff. Nylon is a bit stretchy though; I wonder if anyone makes a hose clad in Spectra or carbon fiber? Anyone...anyone...

Thanks for the info, Fred, Jim and Oz!

[fzust]

I stand corrected. Although Brake booster vacuum is an issue, Jack's explantation is also the case. With the vacuum booster problem you have ZERO braking force. With the EBD problem there is some, but not enough. I blew my last run on each course at nationals because of this issue. Anyone know someone at Kelsey-Hayes that can re-program the ABS computer? Charlie?

[fzust]

More test results: I ran an event in Tucson this weekend. On the very first run, the ABS dynamic proportioning valve tried to kill me no less than 3 times that run! Remember, my front and rear tire diameters are the same vs. the approximate 1" stagger on stock. However, I can see this being an issue with ANY Elise to some degree or another. Removing the ABS fuse, the braking was far, far better. This piece of code in the ABS for my car is downright dangerous. For now, I will be running without ABS.

[Conan]

Regarding driving style and this issue...

I'm not the greatest driver in the world, but several instuctors and other drivers have noted that I am very good at braking. I have driven several different cars at the limits of their tires and the Elise is the ONLY one that has this issue when I quickly transfer to the brakes from the gas. So I'm not buying the "driver error" reason. If that were the case, all cars would behave poorly for me under braking.

[codingparadox]

Conan: Agreed, I've never had this problem in another car but I get it autocrossing (SS, not prepared) all the time.

[JonL]

I'm convinced for those of us that have experienced it, that the only safe way to run on the track or autocross is to unplug the ABS (sensor or fuse). Just remember to plug it back in when you're driving around town, or your traction control will get a bit overzealous.

Anyone know if the S240 is having the same issue or is it just pre-2007 cars?