PSA: For MY2001-2002 S4, if you want to disable ESP w/o disabling ABS, pull fuse #42

[SmokinS4]

It's the 2nd 25amp fuse labeled ESP. (There are two 25amp fuses and one 5amp fuse)

I have confirmed that ABS still works, but I am waiting for a track day to determine if it addressed my trailbraking issue.

[infinkc]

cant you just push the esp button and do the same thing? also any codes?

[SmokinS4]

cant you just push the esp button and do the same thing? also any codes?

ESP is not really disabled when you push that button. As a result, ESP tried to "help" me into a turn at Limerock, while trailbraking into turn one (Big Bend).

EDL is also still engaged with the fuse#42 mod, but I'm still looking to crack that nut too.

I have talked to my local Audi sr tech, AoA, and techs at Bosch so far. I have a few more calls to make, but my goals is to completely disable all electronic aids except for ABS.

The challenge in killing all components is that most attempts to thwart ESP/EDL will result in faulting the entire ABS/ESP/EDL system, which means you'll have no ABS and as a result of having no ABS, your brake bias will default to 50/50. A 50/50 split on brake bias will end up with the rear end locking up way too easy.

[AudiA4_20T]

how do you know bosch techs?

[SmokinS4]

how do you know bosch techs?

I don't know the Bosch techs, but surprisingly their customer support for OE applications was rather friendly and confirmed most of the research that I had done so far. He also gave me a few leads to follow up on. Basically, I think he was impressed I knew what I was talking about and appreciated the technical discussion. He even traced the fuse to see what else that affected. (Fuse 41 will fault the whole ABS/ESP system).

He didn't tell me anything new, but he did confirm my understandings (as stated in the previous post).

A few other things that he confirmed:

• EDL is disabled at 80kmh (AWD)
• EDL is disabled at 40kmh (FWD only)
• ABS controls brake biasing and defaults to 50/50 bias when faulted or unplugged
• EDL will shut down when the computer perceives (computer algorithm) that the brakes are too hot
• ABS/EDL and ESP are deeply tied together through the engine management and the instrument cluster, which may make it difficult to disable EDL w/o disabling ABS

I also spoke to Hans Dahlback this week and it appears that fuse #16 on the European cars seems to disable ESP, while that doesn't do anything for the US 2001-2002 S4.

To summarize for AZ:

• If you want to kill ESP only full fuse 42 (EDL is still enabled)
• If you want to kill EDL and don't mind losing ABS, pull fuse 41 (drag racing only, but be careful when braking, since ABS is dead and bias will be 50/50 and skidding is way too easy)

[The_Jerbel]

Good info! Quite valuable to everyone with ESP!

[Mwall]

What is EDL? And ESP is electronic stability........??

[The_Jerbel]

electronic differential lock.

electronic stability protection/program.

[AudiSportB5S4]

this went way over my head, oh wait i have a 2000 and dont have the ESP button, you bastards

[Reich]

Good info but i still don't understand how a 25a fuse ,lots of current, control only the esp. Does esp works with same module as the abs? I can understand that 25amp for abs module or 25 amp for center diff, but esp must be combined with abs since it also work with brakes module. Help me on this one.

[SmokinS4]

Good info but i still don't understand how a 25a fuse ,lots of current, control only the esp. Does esp works with same module as the abs? I can understand that 25amp for abs module or 25 amp for center diff, but esp must be combined with abs since it also work with brakes module. Help me on this one.

there are three "ESP" fuses. The #42 controls the ESP hydraulic pump. The rest work in conjunction with ABS. The reason ESP is disabled w/o killing ABS is that #42 only controls the hydraulic pump. Technically, it's part of the pump as ABS has separate fuses and uses a different part of the same pump.

Please don't confuse EDL with anything related to the differential. EDL uses the brakes to control the car. Think of EDL as a rudimentary version of ESP (and the MY2000 have EDL too, but it's not tied into ESP)


Does that help?

[The_Jerbel]

Please don't confuse EDL with anything related to the differential. EDL uses the brakes to control the car. Think of EDL as a rudimentary version of ESP (and the MY2000 have EDL too, but it's not tied into ESP)

No offense, but WTF are you talking about????

EDL stands for Electronic Differential Lock, and uses the ABS system to isolate which wheels are getting the power through the drivetrain via the torsen diff.

[Kruat]

Is EDL on both manual and tip cars?

[SmokinS4]

Is EDL on both manual and tip cars?

EDL is part of the ABS system. It is a feature found on all S4s: tip, stick, (euro)1999,(US) 2000, (US)2001, and (US)2002 models (including euro RS4)

[SmokinS4]

No offense, but WTF are you talking about????

EDL stands for Electronic Differential Lock, and uses the ABS system to isolate which wheels are getting the power through the drivetrain via the torsen diff.

ESP includes the functions of EBD (electronic brake distribution or 'bias', ABS, and EDL.

Your understanding of the EDL is incorrect. The "Differential" in EDL is a misnomer. Here's a definition from the current Bentley manual. Our torsen is mechanical (no electronics involved). As I said before EDL is a function of ABS.

The Electronic Differential Lock (EDL) is a traction control aid for driving away from a standstill. An electronically-controlled brake application at the wheel that is spinning provides a torque reaction point for the differential. This enables the wheel with better traction to make use of the engine power. EDL is effective in both forward and reverse.

EDL is part of the basic configuration of vehicles with All Wheel Drive (AWD). Although EDL only regulates the front wheels on vehicles with Front Wheel Drive (FWD), EDL regulates all four wheels on vehicles with All Wheel Drive (AWD). This makes it possible to eliminate the driver operated mechanical differential lock.

Onset of EDL regulation is permitted up to a speed of 40 km/h. The upper switch-off barrier for already active EDL is 40 km/h for vehicles with Front Wheel Drive (FWD), but 80 km/h for vehicles with All Wheel Drive (AWD).
The hydraulic unit is equipped with suction dampers. They improve pressure build-up in the appropriate brake cylinders during EDL regulation. The functional range of the pressure relief valve in the hydraulic unit is 170 ± 25 bar.

To reduce the risk of brake overheating, EDL regulation is not permitted above a specific brake temperature. The temperature limit is defined in the ABS control module (w/EDL) -J104-. The control module determines the actual brake temperature via an algorithm. If the algorithm determines that the brakes have reached a temperature below the temperature limit, the EDL system becomes effective again. Function of the vehicle brake system and ABS are not affected by intervention in this system.

When ignition is switched off, the temperature calculated for the hot brakes is stored until ignition is switched on again. When ignition is switched on, the instrument cluster transmits a time signal so that the ABS control module (w/EDL) -J104- can calculate the standing time. This standing time is required by the temperature algorithm for calculation of the new brake temperature. If the indicated standing time exceeds one hour, the brake temperature is automatically set to the lowest temperature in the temperature algorithm.
EDL shut-off for temperature reasons is indicated in the measuring value block for a period of 20 ignition cycles.

[The_Jerbel]

Your understanding of the EDL is incorrect. The "Differential" in EDL is a misnomer. Here's a definition from the current Bentley manual. Our torsen is mechanical (no electronics involved). As I said before EDL is a function of ABS.

Make no mistake, I'm well aware of what the torsen differential is and how it works. EDL is not a misnomer, it's just a round-about system for controlling the differential. The EDL system uses the brakes to manipulate how torque is distributed through the torsen diff. When a wheel loses traction, the torsen naturally will favor the wheels with greater traction. If one wheel completely loses all traction, the torsen diff will send all the torque through that wheel, and the car will go nowhere. By applying resistance to the spinning wheel using the brakes, torque is distributed back to the wheels with greater traction once again.

[I]The Electronic Differential Lock (EDL) is a traction control aid for driving away from a standstill. An electronically-controlled brake application at the wheel that is spinning provides a torque reaction point for the differential. This enables the wheel with better traction to make use of the engine power. EDL is effective in both forward and reverse.

That is EXACTLY what I described in my post above, only in more detail.

[The_Jerbel]

Is EDL on both manual and tip cars?

Yes.

[SmokinS4]

Make no mistake, I'm well aware of what the torsen differential is and how it works. EDL is not a misnomer, it's just a round-about system for controlling the differential. The EDL system uses the brakes to manipulate how torque is distributed through the torsen diff. When a wheel loses traction, the torsen naturally will favor the wheels with greater traction. If one wheel completely loses all traction, the torsen diff will send all the torque through that wheel, and the car will go nowhere. By applying resistance to the spinning wheel using the brakes, torque is distributed back to the wheels with greater traction once again.


That is EXACTLY what I described in my post above, only in more detail.

No, that isn't what you said. There is no "Differential" involved in the EDL. It's a braking system to control torque to the wheel, diff, axle, whatever you want to call it. It'd be just as helpful to say that it's a Electronic Wheel Locking, or Electronic Axle Locking. It's attempting to gain control over the wheel that is spinning ahead of the others. Think of it an anti-launch control. Without it, the open diff in the front would just spin the crap out of one tire. In most applications, as the rear-end squats on a launch, the rear tires (with torsen diff) should be able to plant the power but as the front diff spins, EDL will be applied.

If you know so much about EDL, tell me how to disable it on a 2001 S4 w/o disabling ABS?

[The_Jerbel]

No, that isn't what you said. There is no "Differential" involved in the EDL. It's a braking system to control THE DIFFERENTIAL. It'd be just as helpful to say that it's a Electronic Wheel Locking, or Electronic Axle Locking. It's attempting to gain control over the wheel that is spinning ahead of the others. Think of it an anti-launch control. Without it, the open diff in the front would just spin the crap out of one tire. In most applications, as the rear-end squats on a launch, the rear tires (with torsen diff) should be able to plant the power but as the front diff spins, EDL will be applied.

There, statement fixed

If you know so much about EDL, tell me how to disable it on a 2001 S4 w/o disabling ABS?

LOL, you expect me to know something that Bosch's own technicians can't even explain to you??? haha I know exactly how the system works, but that doesn't mean that I know how to physically pick apart the various components and isolate and disable certain parts in the system. I drive an '00, so it doesn't much matter to me, but I wish I could help you out!

[jaybquick@JHM]

Do a search for EDL defeat on here or audiworld.

There is a lot of info on it out there.

You can wire up a switch to trick the ABS into thinking the brakes are applied. Since the brakes are on supposedly it WILL NOT kick in the EDL. This is the safest way to do it. If I had a link I would post it, but I am sure people will find plenty of info.


Hope this info helps and gives another alternative.

[SmokinS4]

Do a search for EDL defeat on here or audiworld.

There is a lot of info on it out there.

You can wire up a switch to trick the ABS into thinking the brakes are applied. Since the brakes are on supposedly it WILL NOT kick in the EDL. This is the safest way to do it. If I had a link I would post it, but I am sure people will find plenty of info.

Hope this info helps and gives another alternative.

I am aware of the EDL defeat mod, but I am waiting to see how the fuse pull works. There has been much speculation that EDL can't be defeated on the 2001-2002 models because of the tie-in to ESP.

I have two days on the track next week, so I plan on testing the #42 next week. If EDL doesn't bother me, I won't worry about chasing it down.

The only time I think EDL would bother me is in a launching/dragging situation, which I don't do too often...and pulling fuse 16 or 41 will kill EDL (and abs/biasing too)

I'll report my findings in the end. I'm also trying to find out how to reprogram the ABS computer, but more on that later. In the end, I'll end up compiling all of my research in the Tech Section of AW.

[SmokinS4]

I just got back from two days at NHIS. ESP didn't kick in once. It appears that my trailbraking issues is resolved.

I will probably try to hunt down disabling EDL, since I no longer have the front and rear open diffs, but in the meantime, I'll just pull the abs fuse if I do any drag racing.

I don't reccomend disabling EDL for anyone w/o the rear LSD, since EDL is designed to prevent excessive wheelspin, but the rear LSD will do a better job at managing the power.

[jaybquick@JHM]

I am aware of the EDL defeat mod, but I am waiting to see how the fuse pull works. There has been much speculation that EDL can't be defeated on the 2001-2002 models because of the tie-in to ESP.

I have two days on the track next week, so I plan on testing the #42 next week. If EDL doesn't bother me, I won't worry about chasing it down.

The only time I think EDL would bother me is in a launching/dragging situation, which I don't do too often...and pulling fuse 16 or 41 will kill EDL (and abs/biasing too)

I'll report my findings in the end. I'm also trying to find out how to reprogram the ABS computer, but more on that later. In the end, I'll end up compiling all of my research in the Tech Section of AW.

Looking forward to see if you find out how to reprogram anything in the ABS computer. In my S4 an 01.5 that I went 11.1 with, I have never noticed any edl and just hit the ESP button. Even my launch video I just hit the button and felt nothing. I have driven customers cars and I definitely notice the EDL, it is very obvious. So cars with ESP are night and day better at launching if they have EDL kicking in, it must be about 10% of what the 00 cars do. Just a thought.

[superdug_17]

What if you killed all the systems and just readjusted your brake bias back to 70/30 or what ever you wanted it se to. Couldn't technically you plum in a vave into your front and the rear lines and control your bias from there. I know all racing vehicles(off road trucks, nascar, indycars, etc...) all have brake bias you control from within the car.

[superdug_17]

http://www.stockcarproducts.com/pedassy.htm check this stuff out.

[jaybquick@JHM]

What if you killed all the systems and just readjusted your brake bias back to 70/30 or what ever you wanted it se to. Couldn't technically you plum in a vave into your front and the rear lines and control your bias from there. I know all racing vehicles(off road trucks, nascar, indycars, etc...) all have brake bias you control from within the car.

You can do anything you want if you want to eliminate the ABS alltogether. Just yank the ABS and hook the lines up right then get an adjustable proportioning valve for like $80 to $100 from willwood to put inline to the rears. Just go old school with it basically. Just some plumbing and you would be perfectly fine with the stock Master Cyl.

I personally wouldn't do that coming from racing mustangs without ABS, I love the refined control of the brakes in the Audis.

But to each their own. Going full race is always a viable and lowcost approach.

[SoEvoL]

EDL that much of a hassle in drag racing?

[jaybquick@JHM]

EDL that much of a hassle in drag racing?

Yes on the 2000 cars, it sucks bad dude and kills the 60ft time. You can totally feel the brakes and it bogs the car bad. Not good for the clutch or axles either since it is trying to resist their movement. On a 2001 to 2002 with the ESP button it is no problem.

[BastardS4]

how many times have i forgotten to hit that button, lose a race, then try to explain what happened.... exuses excuses.... lordy. stupid audi.

[jibberjive]

how many times have i forgotten to hit that button, lose a race, then try to explain what happened.... exuses excuses.... lordy. stupid audi.

Ha, I feel you