mm

First of all, I did not state that you or your assumptions were wrong. I stated that I believed they were flawed, by which I meant to imply that I was not absolutely sure you were wrong, but that I had legitimate concerns about a number of your statements based on my own technical, but not expert, background.

Secondly, I unfortunately only know enough about these subjects myself to be "dangerous." I am not really qualified to speak confidently as an authority in these areas, much less educate someone else, so rather than spread misinformation, I choose to refrain from debating the relative merits or flaws of your arguments as I see them.

Third, yes I realize that marketing does have a huge impact on our modern world, and that it is to some extent advisable to be suspicious of it and the misinformation it can contain. I too like to know how things work. However, I also came to the conclusion long ago that I cannot personally be an expert in all areas and on all things, so at some point, I have to trust what the experts tell me. I feel that so long as I approach things with a health dose of skepticism and do not hesitate to question that which does not seem correct or advisable, this is an acceptable compromise. However, I must also realize and accept that sometimes, I and even the experts will be wrong.

As for ABS, again, I am not an expert, but I believe the data you refer to indicate that ABS has not reduced automobile accident, injury, or fatality rates. This is not necessarily the same thing as saying ABS does not work. I also understand that ABS may not be as effective under certain circumstances for stopping on loose surfaces such as gravel and snow, but that it does at least generally allow steering control to be maintained. I have a car with ABS, I have played with it and personally tested it under a variety of circumstances, and I reasonably confident that in balance, it's far better to have it than not. You can choose to attempt to deactivate ABS on your cars if you wish, or to seek models which are not so equipped. But I feel I would be remiss if I did not inform you that I feel you would be rather foolish to do so.

Finally, do not be insulted. It's not that I feel you are not qualified to understand how EDL works or how your assumptions about it may be flawed, it's that the scope of the necessary discussion and background really goes beyond the scope of this forum and my ability to convey my concerns to you with reasonable ease and efficiently.

Given all that, you have a number of choices. You can dismiss me and my unspecified concerns regarding your assumptions. You can try to learn more yourself by consulting other experts and try to educate yourself in the truth behind the matter. Or you can place a higher level of trust in Audi, their experts, and their ability to develop workable, desirable safety systems for their cars.

In the interest of good will, I will reluctantly attempt to relay in another post where I feel your assumptions regarding EDL may be flawed when I find time, however, please understand that while I do have a technical engineering background, automotive engineering and performance is only an interest of mine, not an area where I have specialized expertise or extensive knowledge.

Peace!

Josh Pinkert

Russ,

First, your speculation is pretty badly flawed. What makes you think the wheel would slow to 3 MPH? The physical scenario you describe doesn't exist in the world that I live in. When a any car coasts onto an ice/pavement split...do the wheels on ice slow to 3 MPH? All four wheels keep moving in both scenarios. That force that keeps the wheels moving is called polar inertia (if I remember my physics correctly). So the wheel slows a little over time...but so does the rest of the car. Its a toss up. Hmm...you know how EDL allows *some* difference in wheel speeds. How much?

I dunno...anyone want to compute the wheel speed differences with the steering wheel at full lock? My point here is that it's great to speculate about the workings of EDL. But rather than think up outlandish scenarios that portray EDL as an evil force, we'd serve ourselves (as gen IV quattro owners) better by taking what we *know* and using it to determine the parameters within which EDL operates.

With those parameters, we'd be better able to explain spin events. From everything I've read on A4.org and the quattro list previously, though...it appears to me that we only know what's in our owners manuals and the Audi sales literature (which IMO is not technical enough to analyze EDL).

I'm not against you here, Russ...I just think you're rushing to judgement. I, for one, wish my A4 had an ABS cut-off switch like my '88 90q had. While I'm at it, I wish I didn't have any airbags and EDL had a switch.

- Josh
- '98 A4qms 2.8
- '72 911T

ErikR

I'm sure they have progressed. We were talking about a 10 yr. old design, that they fixed anyways. The silicone chemistry is pretty cool, with even some electrochemical varaints actually on the market.

I'm sure that gleason hypes it just as everyone else does. I personally find it to be a great design. I have the old lockers in a 4000q and a multi-plate design in a truck, and I like the Torsen better by a long shot. Very smooth and progressive. As I said, though I'll take an x-trac active diff., 6sp sequential anytime.

mm

I believe your contention that a wheel on ice will necessarily slip and/or slow down exclusive of braking or throttle inputs is flawed. Ice has low traction, but not no traction. Generally speaking, given the rotational inertia of a wheel and it's rotational momentum, ice will not necessarily cause a wheel to slip and/or loose traction unless it is braked, accelerated, turned, or otherwise moved relative to its initial mode of travel. Even if a tire does for some reason slide on ice, it will still tend to maintain its speed of rotation due to its momentum, exclusive of a significant source of drag. Also I believe EDL does not seek to lock a wheel (nor does ABS) and so I do not believe EDL should ever induce a spinning wheel to completely lock or slide.

A wheel can loose traction or experience reduced traction, and still continue to turn. Traction has to do with the amount of friction between the wheel and the bearing surface, and relates to how much force can be maintained between the two without slippage. For an unloaded wheel that is not accelerating, braking, or turning, so long as the traction (friction) between the contact patch of the wheel and the bearing surface is greater than the rotational drag on the wheel, the wheel will continue to turn unimpeded. This would generally be the case on ice. It's only when you attempt to brake, accelerate, or turn that you'll experience problems.

Peace!

Russ Burns

I never said EDL was an evil force, EDL like mot thinks probably works great 98% of the time.
I am one of those people who finds themselfs in the 2% range more often than most.
"IF" EDL engages when DE-accelerating, I need to change my driving habits.
On ICE if you de-accelerate, the engine braking can cause the drive wheels to skid.
Believe me, I have put my self in the ditch more than one because of this.
Now if I am using engine braking to slow the car down in a controled manner on ice, and EDL kicks in, I can see where you could get an EDL induced skid on wet ice.
To correct this, you cannot use engine braking alone. You either need to use the brakes, or a combination of both.

Jim said he was very confused why he went into the spin I am assuming he is a fairly good driver. I know when I spin, or slide off the road I know just what caused it.
Now remember we are talking about driving on wet ice. I drive on wet ice conditions at least 5 time a year. I have had a car spin due to an AUTO trans downshift, and reardif locking, and my own stupidity. My one car I have to slip the trans in neutral in order to stop it safely.

Hopfully Jims experience will save me a trip to the ditch.

Russ

Silver S4 2

Given good road-tire traction, under clutch-engaged coasting conditions the engine will reach a closed throttle speed appropriate for the gear and road speed. Under lousy traction conditions, this may not be possible. In other words, the drag of the engine and drive train effectively brakes the drive wheels to the corresponding engine/drive train speed, instead of the other way around. This would exert a definite braking effect on the wheel(s) involved, and could create confusion with an EDL system that measures road speed and wheel rotation. I have experienced this on cars with no ABS or EDL under really slippery conditions, particularly downhill.

Jim De Arras

I just asked your source for your facts, you state them as if you had knowledge of the design

Mitch S

Ok, let's say you are driving on ice for whatever reason and you hit the brakes. Let's just say that there is enough traction for your tires to get some grip so your ABS starts to pulse. Fine. What if...this is a total what if, not saying it's true...you hit the brakes and your tires can't even get ANY traction. So, ABS might take your current speed into account and start to pulse...but then your wheels aren't getting enough traction to trigger the ABS after the wheels start to slow down. Your speedometer says 0 but you might actually be sliding at 5 or 10 mph. You could let off the brakes and get the tires rolling again and hit the brakes hoping for ABS...but then it starts all over again.

What do you think? Is that a totally whacked out idea ?

Mitch

Russ Burns

Part of this is from the weight shift , but it is the compression braking that causes this.

Russ

Russ Burns

This as wet ice, I couldn't even walk back up the road. I had to walk down the ditch to find a more level spot.
Russ