Hey Everyone,

I don't spend as much time around here as I used to, I'm lucky that a friend of mine mentioned this to me, or I might never have known about it.

I tried pulling fuse 7 (ESP) as suggested in <a href="https://forums.audiworld.com/s4b6/msgs/170387.phtml">this post</a>, to disable the undesireable DBW programming. Note that Audi bought my B6 S4 back for those who don't know, and I replaced it with a B6 A4 3.0 6sp. I have to say that I'm astounded with the results.

The simplest description I can give is "now it behaves like a sports car should." And this with a 3.0 and not a 4.2. There are no longer any cases where the engine delays acting on my inputs for any reason whatsoever. This makes rev matching "a dream" (read: predictable and something you can actually learn), and it makes driving in traffic and getting what you want, when you want it, the norm.

Interesting side effects that were not previously mentioned: When engines are warming up, their power delivery is naturally not completely stable. Back in the day, it was normal in manuals (particularly sport-tuned engines), for you to have judders during acceleration, with a cold engine. DBW enhancements fix this, and this fix goes away when you pull the fuse. It's not terrible, just noticeable, and makes the car feel more raw than it used to ;-)

Second is that if you are at a cruising throttle position, and make a sudden throttle movement, you will almost certainly induce an oscillation - or "bucking". This has always been normal behavior in traditional manuals your body bounces, your foot bounces, the car bounces, repeat - until you break the cycle (e.g. lift completely). As with everything else, this is something fairly easy to learn to control. It's just that I had no idea how frequently the DBW software was doing this for me before (it didn't always succeed though, but it was about 99% successful).

Another previously unmentioned side effect is that the red line gets artificially reduced to 5000 RPMs. I didn't notice this for a long time b/c the car is so much fun now to drive below 5k that I never went above it.

The upshot of all of this for me is that I am guessing that this is exactly the same engine behavior that EsFourMe gets from his DBW clutch sensor mod. Esfo - can you confirm? Except of course he doesn't get all the blinking lights or fault codes, and I would have to imagine that he doesn't get a 50000 RPM redline either.

Anyway, I am now <b>very</b> interested in trying the clutch sensor mod on my A4. As implied above, my suspicion that there was some DBW programming going on that related to real engine management rather than "driver correction", turns out to be true (cold behavior). But the flip side is that it really does seem that it just makes the car behave like cars always used to, so I'm not concerned that it's particularly dangerous or bad for the car.

p.s. if I had known about this before Audi bought back my S4, thinks may well have worked out very differently...

 

So you're killing the ABS, EDL, ESP, EBD, crippling quattro, hosing servotronic, living with a 5,000 rpm redline and poor cold driveability and you're happy?

Sounds like a very poor trade-off to me.

 

So the same person (that's me) was the author of both write-ups. Secondly, yes the behavior exhibited by pulling fuse #7 was the same as my earlier DBW relay mod you spoke of, except for the side affects. Pulling fuse 7 is much more simple to do obviously, but as you and I both mentioned, you lose a lot of useful features. You noticed more than I did (I had the fuse out for a total of only about 15 minutes). I am pretty sure, however, that I did not have a 5000rpm limiter when I pulled the fuse; maybe that's exclusive to the 3.0.

 

Of course it is not an ideal permanent fix, but it will certainly open your eyes up. The transformation is, as Avram said, astounding. Also, it does <b>not</b> cripple Quattro.

 

Sorry, I guess I should have made that more clear. What I am happy with is the driveability of the engine &amp; throttle. I don't intend to drive my car around crippled, I've just done it for a few days to see how I like the engine behavior.

I would not say that it is worth all these drawbacks just to get a good throttle. What I would say is that it is worth <b>trying this</b> to determine if you like how it drives, and therefore whether you want to go through the trouble of EsFourMe's/Captain SheetMetal's clutch sensor relay mod.

IMHO, the relay mod was too much trouble just to find out if you liked it better or not. This is not too much trouble to decide that. And I'm fairly convinced that anybody who liked the way good german mechanical throttle response worked back before we got stuck with this over-intellegent DBW/ETC behavior, will also like it better with this mod.

As for "poor cold driveability," that is a gross exaggeration. The minor judder you get under hard acceleration with a cold engine is well worth all the predictability that you get all of the time. If I had to rate driveability on a scale from 0-10 (ignoring the redline limit), I would say the driveability of the normal B6 platforms DBW program is about a 5. With the DBW uber-logic disabled, I'd call it a 9.

 

Traditionally, high performance cars were frequently considered difficult to drive, especially exotics. The first ones to achieve a given performance level typically don't get alot of refinement along with it. I remember a road test between the Lamborhini Countach and the Ferrari 512 Berlinetta Boxer, where they hired professioinal race car drivers to test them in R&amp;T. Anybody can drive a B5 S4, and if it's chipped, it is as quick and fast as both of those cars.

Then the B6 S4 comes out and most of us feel it is really hard to drive, or at least to drive well. And eveyone chidded to anyone who thought it was hard to drive that it must be "too much car" for him.

Well, the B6 S4 isn't "too much car" for most people, it is "too much logic" even for people who can handle a Lamgorghini Countach.

So the irony is that with the direct response DBW mods, the car is now "harder to drive." That is to say that it is hard to drive for the reasons that a high performance car ought to be hard to drive - it is a lot of power to have to be careful about manipulating. But if you are a good driver, you can learn to do it, and the reward is well worth the effort - an extremely responsive and controllable high performance car.

 

This mod does nothing if not clue you in as to why Audi filtered our throttle response so much. It is a B-E-A-S-T without the filtering--more so than any other car I've driven. It's strange because the engine is not <i>that</i> big, and it's not just the accelerative power, it's the <b>de</b>celerative power that is alarming. Without the filtering, the amount of compression braking this engine immediately generates just defies logic.

So I can understand the goal of smoother driving that Audi and Bosch were shooting for; I just wish they had done a better job. I still maintain, however, that if the throttle map weren't so nonlinear, most people could handle the unfiltered throttle response without a problem. It's the fact that the first 25% pedal travel controls so much of the throttle butterfly travel that makes things difficult in the first place.

 

..caution, because disconneting fuse #7 you don't disable only the ESP (which is not too bad), but you also lose ABS and EDL (which is worse). Furthermore, you lose the electronic brake limiter for the rear axle, so if you hit the brakes hard enough you'll lock the rear wheels well before the front ones, with the imaginable consequences.

Elfer

 

a) nobody is recommending this as a brilliant way to operate your car on a normal basis. As stated already, this is merely a simple way to see if you like how the engine behaves with a directly proportional DBW/ETC program as compared to the standard one.

b) All of these features are only to help you out of an emergency situation. Most of them didn't even exist 10 years ago, and none of them existed 20 years ago. Anybody who is an unsafe driver without these features is also unsafe with them - especially if it is to the extend that a 1-3 day trial without them has even a measurable impact on his long term accident probability.

 

As far as A goes, I was not intending to criticise you or your experiement - even though if it was indeed just an experiment, you can obtain the same effect by slightly depressing the clutch pedal to activate the clutch microswitch - but simply to make you aware of a potential risk that might have escaped you - see below.

As far as B goes, perhaps my explanation was unclear: if you remove the ESP fuse, you do not disengage only the ESP and the related functions (ABS, EDL etc.), but also the rear brake limiter, which is the mechanism that prevents the rear wheels from locking before the front ones due to the heavy weight transferral during heavy braking. This has nothing to do with ABS and has been implemented with a mechanical device since before the war. Were it not there, indeed, it would be almost impossible to keep the car straight during intense braking. With this said, feel free to run all the experiments you wish - I have done so for other reasons - but try not to put yourself in a situation where heavy braking may be needed, if you have the fuse out.

Finally, as far as I am personally concerned, I used to drive until recently a thirty-plus year old 911: when the car was built, ABS, ESP and even power brakes and power steering were not avaolable. Because of this, I believe I can still drive fairly safely without these devices and I also believe I am fairly aware that these are only an aid, not things you can't do without.
However, I do not count among the simple 'aids' the rear brake limiter, which for over fifty hears has been a necessary device from Geo Metros all the way up to Ferraris... as can be proven by the fact that there are no cars without it.

Elfer