torsen differential project [Archive]

Audii-Dudii

01-25-2008, 12:45 AM

i'm confused about HOW this will alter the torque bias....

is it kind of like shimming a DV?

i might need someone to explain to me how a torsen works first lol.

The Torsen center diff varies the torque split between the front and rear wheels by limiting the difference in rotational speed between the front and rear driveshafts. Torque from the engine causes the gears inside (in simplistic terms, half of which are connected to the front driveshaft, half of which are connected to the rear driveshaft, and all of which are in-mesh with each other) to jam together as the front and rear driveshafts attempt to rotate at different speeds, almost -- but not quite -- locking up solid until one of the driveshafts overcomes the gears' resistance to rotation (i.e., the designed bias-ratio is reached) and they begin to rotate at different speeds.

When a car goes around a corner, the front wheels travel a longer distance than the rear wheels. With an AWD car, this requires the front driveshaft to rotate faster than the rear driveshaft. Whereas an open center diff can fully accomodate a difference in the driveshafts' rotational speeds but always splits torque 50-50 between the front and rear wheels, and a locked center diff can't accomodate any difference in rotational speeds but can split torque 100-0-100 and everywhere in between, the Torsen center diff behaves like a hybrid of the two: It's never fully "open" (which is why it can vary the torque split between the front and rear wheels over a limited range) and never fully "locked" (which is why it can accomodate some percentage difference in rotational speeds between the front and rear driveshafts).

To increase the Torsen's bias-ratio -- from the OEM setting of 66-34-66 (~2:1) to say, 80-20-80 (4:1) -- all you need to do is make the gears jam together more tightly (which is what the modification discussed herein does, by replacing a needle bearing or Teflon-coated washer with a hardened steel washer, thereby increasing the internal friction that resists differentiation) and thus cause it to behave even more like a locked center diff. The tradeoff, though, is that the more you make a Torsen behave like a locked diff, the less it behaves like an open diff. In other words, by increasing the bias-ratio, you're _reducing_ the Torsen's ability to accomodate differences in the rotational speeds of the front and rear driveshafts. [I won't go into it here, but if you think things through, you'll see that under power and with all other things being equal, a Torsen biases the torque split toward the rear wheels whenever the steering wheel is turned away from straight ahead and toward the front wheels whenever it's turned back ... ponder the implications of how _this_ might affect a car's behavior while going around corners, especially if you have to apply opposite lock to catch a slide or if you keep the power on and left-foot brake!]

As an aside, it's interesting to note that with its first generation of Torsen-equipped cars (Type 44 chassis), Audi set the bias-ratio at ~3.5:1 (78-22-78) versus the ~2:1 it used with its later chassis. I don't know if this reduction in the bias-ratio was done to address NVH issues or performance/safety concerns -- some people believe the higher bias-ratio resulted in quirky handling with the Type 44 chassis under certain conditions (aka as the "Spider Bite" phenomenon) -- but there's no doubt this change did reduce the amount of "shuddering" people experience as they drive around in parking lots.

Anyway, the bottom line is that what you gain on one side of the equation, you lose on the other, and Audi chose to set the bias-ratio of its second-generation Torsen (i.e., the one with one-piece housing) low enough so that most people never experience any shudder, even if this also means settling for a less than optimal bias-ratio so far as outright performance is concerned.

(Note that there are some Audi enthusiasts -- among whose number I tentatively include myself, although I've never driven an A4 with a locked center diff so I have no actual basis for comparison -- who believe that even the 4:1 or 5:1 bias-ratio of a modified Torsen isn't high enough, preferring instead the infinity:1 bias-ratio that a locked center diff offers, not to mention the consistency/predicability of a torque split that varies in sync with front-to-rear weight transfer rather than differences in the front and rear tires' slip angles.)

Alex@GMS

01-25-2008, 01:37 AM

^^^ are u trying to say that this will handles like shit and is not safe?

Audii-Dudii

01-25-2008, 01:45 AM

^^^ are u trying to say that this will handles like shit and is not safe?

Not at all (at least not as regards the B5 and B6 chassis cars, anyway ... had a few scary moments in a 200q way back when that I'm fairly certain were due to the Torsen's quirky behavior, though.)

I'm just saying that for out-and-out performance, I'm not totally convinced a Torsen center diff is a better choice than a locked center diff...

Papachristou

01-25-2008, 06:00 AM

well, the people who have them sure like them... but i would need to point out, most of us who are doing these types of things are fairly experienced drivers.. audi could have changed it for the common person, not car/race enthusiast

skeeball

01-25-2008, 06:11 AM

manhertm

01-25-2008, 06:24 AM

I've heard that the RS4, has a 4:1 torque split. Is this true?

Audii-Dudii

01-25-2008, 07:04 AM

well, the people who have them sure like them...

Actually, this isn't completely true, as there's a small group of people who don't like them at all. There's even an internet forum dedicated to exploring the subject (although it hasn't seen much traffic over the past few years)! Truth be told, I wasn't much of a Torsen fan back in the day. It's only been since 2002, when I acquired a B5 A4 1.8TQ, that my feelings about the Torsen used as a center diff have moderated somewhat...

but i would need to point out, most of us who are doing these types of things are fairly experienced drivers.. audi could have changed it for the common person, not car/race enthusiast

As I pointed out, I believe this is exactly what has happened. Let's also not forget that Audi designs its chassis with AWD in mind from the start these days, which was not the case with the early quattros, all of which were adapted from FWD chassis, and this could be a factor as well since Audi (presumably) has become better at understanding the dynamics of AWD handling and designing its chassis accordingly...

Audii-Dudii

01-25-2008, 07:50 AM

I think you got your diffs backwards. An open diff is going to send the torque to whichever wheel/axle has the least resistance. A locked diff is going to split the torque by the designed amount every time. Usually 50-50.

No, I haven't got it backwards. The open diff doesn't "send" torque to "whichever wheel/axle has the least resistance," it splits torque equally between the axles ("50-50") and the axle which has the least resistance to rotation determines how much torque the engine is able to develop, not the other way around. In other words, if the axle with the least traction can support only 10ft/lbs of torque, then the engine will develop only 20ft/lbs of torque and 10ft/lbs of torque is all the axle with the most traction will see, even if it could support 50ft/lbs or more.

A locked diff, on the other hand, knows nothing of torque splits and doesn't "send" torque anywhere. It simply insures the two driveshafts rotate at the same speed and lets the torque split fall where it may, based upon the relative amounts of traction available at each end of the car. So, if the axle with the least traction can support, say, 10ft/lbs of torque and the axle with the most traction can support 50ft/lbs, the engine will develop 60ft/lbs of torque and it will be split 5:1; likewise, if the numbers were 10ft/lbs and 100ft/lbs, the engine would develop 110ft/lbs of torque and it would be split 10:1, with the ultimate limit being infinity:1...

And Quattro GenV is higher bias. So it looks like Audi is moving back in that direction.

Perhaps, but don't forget that this is only true for the RS4 (and possibly the latest version of the S4?), both of which also have a static torque split of 40:60 and are aimed at enthusiasts, who (presumably) are more willing to accept the negative consequences of the higher bias-ratio.

On the other hand, the plain-jane A4s and A6s still get the 2:1 Torsen, along with the 50:50 static torque split, so it appears Audi is actually mixed on this subject...

Papachristou

01-25-2008, 07:52 AM

the RS4 does indeed have the 4:1 center bias... but its set up as 40/60 stock and can send up to 88% to the rear...

our lowly (comared to the rs4) a4s arent designed for the track like the rs4 is... they are just AWD underpowered 4 door cars, great for a nice entry level luxury commuter car, especially up north....

i am very confident i will love my stasis diff (especially after talking to MChammered) and i will be posting my personal reponse to it in a week or two depending how long my FE SS takes to break in, i hear the FE needs as much as 1000 miles to break in.... however im not the average driver and i definitely put my car through the paces, especially in corners so we will see... i do not believe this mod is for your average daily driver, nor would a DD waste $500 on something that wont affect him at all..............the cars from audi that are getting the 4:1 split are hard core car enthuiast type vehicles, not daily drivers..........i will revive this thread, upon installing mine!

k0mpresd

01-25-2008, 08:01 AM

..........i will revive this thread, upon installing mine!
you and me both ;)

Audii-Dudii

01-25-2008, 08:02 AM

i do not believe this mod is for your average daily driver, nor would a DD waste $500 on something that wont affect him at all..............the cars from audi that are getting the 4:1 split are hard core car enthuiast type vehicles, not daily drivers..........

I agree completely! FYI, I modified the Torsen in my A4 track/play car some time ago and in combination with the modified 944 LSD rear diff, I'm quite happy with the present setup. Which is not to say I don't have other ideas to explore, which explains why I'm picking up a 3.73:1 rear diff from a Tiptonic A4 this weekend ... stay tuned!

Papachristou

01-25-2008, 08:04 AM

i cut a nice uturn the other day after a nice rain and as soon as i slide it sideways via the ole ebrake, i punched the gas and it just spun and pulled out of it, thats good and all but i would have preferred to stay sideways a little longer.... !!!

of course the fiancee wasnt fond of any of it but, oh well

k0mpresd

01-25-2008, 08:48 AM

fwiw..my car is a daily..it also makes 300awhp on a bad day and im not normal

i also wasnt doing this mod for performance..i am attempting it because ive never modded drivetrain parts before

B6Lovin

01-25-2008, 09:25 AM

so what you were saying in that really long post is that the car will have more of a tendency to act like a rwd car entering a corner, but if it started to slide and i had to counter-steer it would act like a fwd?

or were you saying that when cornering at all it would act more like rwd, and in straight line acceleration it would be more like fwd?

Papachristou

01-25-2008, 09:28 AM

k0mpresd

01-25-2008, 09:36 AM

or call torsen and they will explain it to you as well

B6Lovin

01-25-2008, 09:41 AM

lol either way works for me. just clarifying for my own knowledge.

if this mod works out well, i'll buy a "kit" from you if you're willing to piece them together.

317ssayzarc

01-25-2008, 09:50 AM

where are my washers? [;)]

k0mpresd

01-25-2008, 10:05 AM

trying to source them :(

i want some 83mm supertech stroker pistons...trade ? haha

317ssayzarc

01-25-2008, 10:09 AM

trying to source them :(

i want some 83mm supertech stroker pistons...trade ? haha

no but i can get you a killer deal on some JE's in whatver bore, stroke or cr you want [;)]

k0mpresd

01-25-2008, 10:14 AM

pm me a price please

83mm bore, whatever cr..thinking of throwing an aeg crank/awm together or aba crank/atw ..prob the aba crank/atw and then just transfer all my parts over to that block since my car is external water pump already

i was talking to issam on aim last night about the supertechs

Audii-Dudii

01-25-2008, 10:38 AM

FWD when entering corner (on brakes/nose dive, power needs to be on front wheels
AWD through middle (weight is spread throughout car)
RDW when exiting (under power, weight and power is on rear wheels)

Unfortunately, the analysis isn't that simple. While it's convenient to discuss the torque split between the front and rear wheels in percentage terms, it's the absolute values of that torque that determine how the car behaves.

So, if the engine isn't making much torque (as is typically the case under braking), the performance of the car won't be much affected regardless of how the torque is split between the front and rear wheels. In other words, if only say, 50ft/lbs of torque is being developed, the difference between an 80:20 split and a 20:80 split, while significant in theory, may well be negligible in practice. This is especially true since the Torsen's behavior under engine acceleration and braking can be adjusted independently of each other.

Lastly, of course, because the Torsen "sends" a multiple of the torque that can be supported at the end of the car with the least traction to the end of the car with the most traction, if the inside rear wheel lifts at corner entrance (a common problem with at least the B5 chassis cars ... not sure yet about the B6 chassis), the absolute amount of torque the front wheels will see is zero, as anything times zero is zero.

The bottom line is that analyzing the Torsen's behavior at any given point in time is a complicated, multi-variable, interrelated project that can be mentally taxing, to say the least.

Papachristou

01-25-2008, 11:02 AM

Audii-Dudii

01-25-2008, 11:14 AM

i understand its not making much power but when you first get back on the gas, it will transfer power throughout the drivetrain from front to back and you pass through the curve and weight is shifted from front to back on the car was well

Which is exactly the same thing a locked diff does, except that it has no limit on how much torque it can "shift" from the front end to the back end, and it's not "confused" by slip angle differences between the front and rear tires, either...

Again, don't get me wrong: I have a modified Torsen in my B5 A4, plan to install one in my B6 A4, and am not (for now, at least!) looking to replace it with a locked center diff. However, I have driven/autocrossed/raced Audis with locked center diffs and properly setup, I'm still not convinced this isn't the optimal way to go so far as out-and-out performance is concerned. That's the only point I'm trying to make here...

Papachristou

01-25-2008, 12:28 PM

i see what you are saying... you know better than i do,ive never driven anything with a torsen diff.. but i loved my RWD cars.... so im looking forward to seeing how my car drives bu i doubt the average driver would enjoy, appreciate or understand this mod

k0mpresd

01-25-2008, 12:33 PM

youve never driven anything with a torsen diff ?

your car came stock with torsen center diff....

B6Lovin

01-25-2008, 12:34 PM

i think he meant modified torsen diff

Papachristou

01-25-2008, 12:34 PM

well, not a modified one is what i was getting at!

Papachristou

01-25-2008, 12:37 PM

i just talked to andy@southbend, my flywheel arrived this morning and they are fixing to resurface it and they are doing the diamond resurface on it... he said it should only take a few hundred miles of city driving to break it in... i think ill drive up and down poplar avenue stalling it out[:D] once i get it together

k0mpresd

01-25-2008, 01:34 PM

southbend is good stuff...my stg3 clutch has gotten a work out and still holds like a champ

k0mpresd

02-04-2008, 12:20 PM

1 reassembled modified torsen differential [eek]

http://i22.photobucket.com/albums/b301/k0mpresd/photo-89.jpg

http://i22.photobucket.com/albums/b301/k0mpresd/photo-88.jpg

Papachristou

02-04-2008, 12:24 PM

ive reinstalled mine but waiting on southbend to send my clutch and flywheel back! they sent it to california! WTF?

Alex@GMS

03-15-2008, 12:15 PM

1 reassembled modified torsen differential [eek]

http://i22.photobucket.com/albums/b301/k0mpresd/photo-89.jpg

http://i22.photobucket.com/albums/b301/k0mpresd/photo-88.jpg

are you putting some kits together? how does it feel?

let us no. i want one.

dirtybrd

03-15-2008, 02:02 PM

So the washers go on top, between, and under the gears?

absolutegtr

03-15-2008, 03:35 PM

bump....i need to know [evilsmile]

dirtybrd

03-15-2008, 04:03 PM

Alex, you need to get a DIY together on this, with parts etc.

k0mpresd

03-17-2008, 07:18 PM

http://audizine.com/forum/showthread.php?t=197354

is confirmed working and hasnt exploded yet...*knocks on wood* haha

put ~70 miles on the diff tonight

oversteer + ass end sliding was quite the feeling

thank you jerry koch ! you made it possible

absolutegtr

03-17-2008, 07:29 PM

/\ I just opened that link in a new window, (have not read it yet) so excuse me if I repeat something....

But are you going to get a DIY together and possibly offer the parts to teh community...DEFINETLY interested!

apexslider

03-18-2008, 12:38 AM

18tboost

03-18-2008, 01:22 AM

cool...too bad not for TIP cars'

k0mpresd

03-18-2008, 07:58 AM

I've driven my 4kQ on pavement with both diffs manually locked and have had issues with breaking axles. Is there any concern with newer generation Quattro's having this same issue? A locked center diff and a posi rear...
2 members on this same site have been running basically the same mod

when i talked w/ them neither of them mentioned the concerns you spoke of

one of those members will more than likely see this thread/update and comment

dougyfresh

03-18-2008, 08:22 AM

I am interested in the parts kit when you're comfortable with selling it to the masses.

Edit. I sent you a PM.

Papachristou

03-18-2008, 08:27 AM

Well, i made a video of me sliding around in the snow but my computer is fried so i was waiting to get it uploaded before i did my review... all these people running around here with 1+ programs thinking its going to have their car sliding the ass around like a 335i are crazy... i can get it sideways in the rain but i still get some wheel hop when launching though... i nailed it out a wash bay and got it way sideways but the front end still pulls it out pretty quick (lack of power) but i can also snatch second gear (barks the rear tires only) ill do my review this week, but its not worth it for the average person

i think people with BTs will enjoy it

apexslider

03-18-2008, 12:14 PM

2 members on this same site have been running basically the same mod

when i talked w/ them neither of them mentioned the concerns you spoke of

one of those members will more than likely see this thread/update and comment

How does modifying the B6 torsens to infinity:1 and an lsd in the rear compare to the factory gen 1 quattro? Will it offer the same feel, or a little less harsh?

k0mpresd

03-18-2008, 02:07 PM

no clue

i have only driven b5 and b6 cars...never had the pleasure of driving an old skool audi quattro

Papachristou

03-18-2008, 02:31 PM

how much power are u making kompresed?

k0mpresd

03-18-2008, 04:29 PM

last dyno...20psi

http://audizine.com/forum/showthread.php?t=188255

Audii-Dudii

03-18-2008, 07:35 PM

I've driven my 4kQ on pavement with both diffs manually locked and have had issues with breaking axles. Is there any concern with newer generation Quattro's having this same issue? A locked center diff and a posi rear...
I suspect I'm one of the people referred to below as I have a modified Torsen with a modified 944 LSD in my B5 A4 and have had no problems whatsoever with breaking anything.

I'm not sure why you'd want to drive with both diffs locked on drive pavement (I always found my '85 UrQ understeered hideously setup that way) but I regularly autocrossed it with the center diff locked and running sticky Hoosier tires and I never had any problems breaking anything on it, either.

apexslider

03-18-2008, 08:12 PM

I suspect I'm one of the people referred to below as I have a modified Torsen with a modified 944 LSD in my B5 A4 and have had no problems whatsoever with breaking anything.

I'm not sure why you'd want to drive with both diffs locked on drive pavement (I always found my '85 UrQ understeered hideously setup that way) but I regularly autocrossed it with the center diff locked and running sticky Hoosier tires and I never had any problems breaking anything on it, either.

I usually dont drive it like that on dry pavement, its normally reserved for rallycross. But I cant stand the front wheel bias of these new'ish quattro's and would like to get the rear end a little (read *A LOT*) more involved with things.

When you say a modified 944 LSD...are you talking about a Porsche 944?

317ssayzarc

03-18-2008, 08:18 PM

yes he is [;)]

B6Lovin

03-18-2008, 08:30 PM

how did you modify a porsche rear dif to work? its got a transaxle...
i never took mine apart or anything - i refused to really fuck around with that car... way too many old things to break that cost wayyyy too much to replace. does the audi drive shaft bolt right up to where the "torque tube" or w/e is [was]?

or did i miss something

i'm asking because I'd be interested in doing it on my a4 if it's cheaper than the rear LSD option stassis offers

k0mpresd

03-18-2008, 08:32 PM

so he doesnt have to type it again..

no..im referring to modified 944 diff :)

What about it? The 944 LSD will fit the rear case of a B5 Audi with only minor machine work (you have to clearance a few spots on the case casting ... a die-grinder works fine, nothing fancy is needed) and, of course, you have to get the shims right so the ring-and-pinion mesh properly but any good driveline shop can do this fairly inexpensively (although the shims from Porsche are a bit pricey).

FWIW, I've experimented with balancing the preload against the ramp angles. It's my conclusion the OEM setup Porsche used for its RWD 944 isn't optimal for an AWD A4, so I swapped the OEM Porsche thrust plates with those out a mid-70s E12 BMW LSD, which has different ramp angles, and increased the preload on the friction plates by installing thicker plates and stiffer belleville washers (both Porsche and Guard offer a variety of thicknesses and stiffnesses.)

My current setup works well for me because my car's acceleration is NOT power limited (at least not yet!) and I only need the rear LSD to keep the inside rear wheel from spinning when it's in the air and not to keep it from spinning while it's on the ground ... i.e., I wanted more initial preload and less additional clamping force added by engine and brake torque at corner entrance and exit.

Did that answer your question?

Audii-Dudii

03-18-2008, 09:07 PM

how did you modify a porsche rear dif to work? its got a transaxle...

See an older post by me as quoted above ... and just to make it absolutely clear, you remove the differential from the 944 transaxle and install just that portion into the A4's rear diff case.

317ssayzarc

03-18-2008, 09:12 PM

does it matter if its turbo or NA 944?

k0mpresd

03-18-2008, 09:17 PM

id go w/ no

its the same option code either way...m330 or something like that

317ssayzarc

03-18-2008, 09:18 PM

so i want a locking diff from a 944, cool... the search is on!

apexslider

03-18-2008, 09:19 PM

guess I'll stick with stasis...

k0mpresd

03-18-2008, 09:28 PM

so i want a locking diff from a 944, cool... the search is on!
http://pelicanparts.com ..check the forums..should be easy to find

SilverB5A4

03-18-2008, 09:36 PM

so audii dubii you only have exchanged out the rear diff for a porsche 944 locking diff, you havent modified the center diff?

B6Lovin

03-18-2008, 09:43 PM

See an older post by me as quoted above ... and just to make it absolutely clear, you remove the differential from the 944 transaxle and install just that portion into the A4's rear diff case.

ahhh sorry guys -- that wasn't earlier in this thread was it? i'd feel twice as dumb if it was. (guess i just figured nobody had gone into detail on that subject yet)

only thing im still confused on is the whole using something from a bimmer? you started using all kinds of terms i've never heard hahaha. I know engines, and im learning more about trannys daily... but the rest of the driveline is my real weak point (differences between various types of LSD's, which is best for what, etc)

for instance -- i'm about 99% lost on why you did what you did to your car (with the higher preload? ramp angles? yeahhhh...)

all i know is that on my 951, when it was on a lift - i could spin one rear wheel, and the other one would spin with it... and that that's good for traction.

now on an awd car i'm assuming all the rules change drastically depending on your intended usage... so educate me -- what's best for power/acceleration out of the gate (that's what you said yours was right?) what's best for handling? would creating a balance between the two be more or less how the car is setup now? (03 B6 quattro 5spd) when altering the rear torque bias by modifying the center diff, is it necessary to have a rear LSD to see the most benefit? or would having a rear LSD in addition to the modified center diff create other issues? to me it seems that to keep from losing traction excessively you'd need a rear lsd to keep that potentially greater ammount of torque in check -- again, that's only if i'm understanding this correctly

sorry for all the randomness... there's just good knowledge and info in this thread already - we might as well get it all out here so that people researching this topic will get it all in one shot.

B6Lovin

03-18-2008, 09:46 PM

also -- i'm pretty sure i understand how the center diff works.. or atleast how ours is supposed to react in different situations, my main confusion is with the rear diff, and how it functions in conjunction with the center.

Audii-Dudii

03-18-2008, 09:56 PM

so audii dubii you only have exchanged out the rear diff for a porsche 944 locking diff, you havent modified the center diff?

I did both to my '99.5 A4 1.8TQ some time ago. More recently, I helped both K0mpresd and UCFQuattroguy work out how to mod their Torsens themselves. Why do you ask?

Audii-Dudii

03-18-2008, 10:39 PM

only thing im still confused on is the whole using something from a bimmer?

A large number of LSDs supplied in european-manufacturers cars were made by ZF and as a result, many of their parts are interchangeable. If you learn enough about LSDs, you'll eventually come to understand why different cars use LSDs with different operating characteristics and also how you can take advantage of this by tuning the operating characteristics to better suit your particular application by mixing-and-matching parts, which is what I've done (or at least hope I've done!) by swapping BMW thrust plates for Porsche thrust plates.

for instance -- i'm about 99% lost on why you did what you did to your car (with the higher preload? ramp angles? yeahhhh...)

I started to write an explanation but it's late and I'm tired, so I went searching the internet instead and found this on wikipedia: http://en.wikipedia.org/wiki/Limited_slip_differential ... it glosses over a few of the details but provides a pretty good basic overview.

now on an awd car i'm assuming all the rules change drastically depending on your intended usage... so educate me -- what's best for power/acceleration out of the gate (that's what you said yours was right?) what's best for handling? would creating a balance between the two be more or less how the car is setup now? (03 B6 quattro 5spd) when altering the rear torque bias by modifying the center diff, is it necessary to have a rear LSD to see the most benefit? or would having a rear LSD in addition to the modified center diff create other issues? to me it seems that to keep from losing traction excessively you'd need a rear lsd to keep that potentially greater ammount of torque in check -- again, that's only if i'm understanding this correctly

I've discussed all of this in other posts, both here and at www.audiworld.com, so forgive me if I don't feel like rewriting it again. I'll dig around a bit and see if I can find some of them and will post back with links tomorrow.

I will say, however, that the primary reason I wanted an LSD is not so much to increase traction under acceleration but to prevent the car from changing from AWD to ZWD -- that's Zero-Wheel-Drive, which is what you get when you lift the inside rear wheel of a car with a Torsen center diff off the ground -- in the middle of corners. Every Audi that I've owned and/or driven over the past 20 years will lift its inside rear wheel under hard cornering and when this happens in a car with a Torsen center diff, all forward drive ceases and the car coasts until either 1) it slows enough for the wheel to drop back to the ground or 2) EDL kicks in. As you might imagine, coasting around corners is not the quick way around a track or an autocross course (!) and by making sure the Torsen always "sees" some resistance to rotation at the rear wheels, a clutch-pack LSD prevents the car from switching back and forth from AWD to ZWD.

Anyway, like I said earlier, it's late and I'm tired, so I'll try to dig up some of the information I've posted previously and link to it from this thread over the next few days, if not tomorrow.

k0mpresd

03-19-2008, 05:15 AM

^ thanks again btw

B6Lovin

03-19-2008, 12:20 PM

^definitely, my understanding of drivetrain technology just increased 10 fold.

Audii-Dudii

03-19-2008, 02:31 PM

^definitely, my understanding of drivetrain technology just increased 10 fold.

Okay, I did some digging and here's a thread you should read: http://forums.audiworld.com/s4/threads/573306.phtml#2252562 ... mind you, I just skimmed through it quickly and believe I may not have worded some parts as clearly or technically correctly as I should have (as I noted at one point during the thread, I was really, really busy at work that day) but overall, I think you'll find the discussion about LSDs and Torsens useful.

B6Lovin

03-19-2008, 03:08 PM

^again, thanks so much. i definitely want to understand all that stuff before i start messing with it.

k0mpresd

03-19-2008, 06:22 PM

absolutegtr

03-19-2008, 06:28 PM

just want to update...this is def confirmed working

it was a little wet tonight in nc and we made sure to test the rear bias..on a closed course, of course (aka cul-de-sac) ...if there was enough room, the car would drift w/ ease

Im sold [evilsmile]

Please inform of us when it you can sell a kit

dirtybrd

03-19-2008, 07:04 PM

^Agreed!

Papachristou

03-20-2008, 06:31 AM

just want to update...this is def confirmed working

it was a little wet tonight in nc and we made sure to test the rear bias..on a closed course, of course (aka cul-de-sac) ...if there was enough room, the car would drift w/ ease

i made a hard left turn launch from a stoplight yesterday in the rain and it got so sideways it caught me off guard[:D] if i just had enough power, i know it would do it in the dry with ease!

k0mpresd

03-20-2008, 07:00 AM

my "testing" in the dry was a quick/sharp left hand turn @ a high enough rpm in 2nd gear to where when i hit the throttle the car should in theory have enough power to kick the back end around. i made this turn several times over again. same procedure each time...

but it seems (and justin's experience is the same. he is actually the one who mentioned it) that in the dry when the rear starts to loose traction, the torsen sends power back to the front to keep the rear from spinning even more. which is what it was designed to do.

he also mentioned his experience in the wet was the same as mine and yours

Audii-Dudii

03-20-2008, 07:44 AM

but it seems (and justin's experience is the same. he is actually the one who mentioned it) that in the dry when the rear starts to loose traction, the torsen sends power back to the front to keep the rear from spinning even more. which is what it was designed to do.

Actually, what's happening is that when the rear wheels start to "loose" traction, the amount of torque they can support is reduced. Because the Torsen's a torque-multiplier design, this means the amount of torque that can be developed at the front wheels is likewise reduced and it's reduced by a multiple of the reduction in torque that can be supported at the rear wheels. So even though the torque split between the front and rear wheels is now biased toward the front percentage-wise, the total amount of torque that can be developed at all four wheels of the car has been reduced on an absolute basis. Therefore, it's the combination of these two factors -- a reduction in the amount of torque that can be developed overall, along with biasing the torque is developed toward the front wheels -- that prevents you from being able to kick the back end out under power and keep it there.

[Edit: As an aside, the fact that an event that happens at one end of the car necessarily affects both ends of the car is one reason why some of us diehards still believe a locked center diff is a better choice than a Torsen center diff for racing and/or high-performance driving. This is also the reason why modulating the throttle when cornering at the limit isn't as effective on a Torsen-equipped AWD car as it is a FWD or RWD or AWD with a locked center diff and in turn, why slow-in, fast-out is generally the best way to drive an AWD Audi...]

The solution? A rear LSD, of course... [>_<]

k0mpresd

03-20-2008, 07:48 AM

^ thank you for the explanation

a rear lsd has my name all over it...now if i just had a check in my name for the same amount of an lsd id be set haha [:o]

Papachristou

03-20-2008, 07:50 AM

ive had trouble doing it sometimes, othertimes it does it with ease... i cant figure it out but sometimes it gets so sideways i have to get off the gas, other times i cant get it sideways ??? but it seems the front end does pull it out but it still gets a lot more sideways than it used to (never) and it feels much more planted it hard turns and doesnt understeer like it used ot either

absolutegtr

03-20-2008, 07:52 AM

so is it really WORTH it without a LSD?

Or is it really made to be in combo with a LSD?

k0mpresd

03-20-2008, 07:53 AM

from the fun i was having last night..totally worth it

Audii-Dudii

03-20-2008, 07:58 AM

so is it really WORTH it without a LSD?

Or is it really made to be in combo with a LSD?

It's sort of like sex: Having sex with a condom is better than not having sex at all but having sex without a condom is better still... [>_<]

Papachristou

03-20-2008, 07:59 AM

yeah, if you drive hard. but i wouldnt do it if you dont at least have a fully done 1+ SETUP, k04 or BT, you wont have the power to make it come around or torque to feel it plant itself in turns. You have the clutch already!

absolutegtr

03-20-2008, 08:54 AM

You have the clutch already!

HAHA...true.

Big turbo is next!

dougyfresh

03-20-2008, 09:06 AM

I think I'm going to do this. Modify the diff myself. Gotta do some more reading this weekend when I have some more time. Doesn't look like its out of my abilities. If not, I'll learn [:D].

Audii-Dudii

03-20-2008, 09:20 AM

I think I'm going to do this. Modify the diff myself. Gotta do some more reading this weekend when I have some more time. Doesn't look like its out of my abilities. If not, I'll learn [:D].
Honestly, it's not difficult at all. The only tricky part (after you get the Torsen out of the tranny, as the bolts on the driveshaft and/or center diff cover can be very difficult to remove in some cases) is timing the gears on reassembly, but even that is easy enough to figure out with a few practice runs.

As for me, the more I think about all this, the more I'm tempted to sacrifice one of my spare Torsens to the great god Heliarc and weld it up solid. Then I can finally determine one way or another which works better on the track: A locked center diff or a high-bias Torsen. We'll see...

absolutegtr

03-20-2008, 09:48 AM

When timing up the gears in the diff, are the marks for reference....or is it more like matching everything up the EXACT same way it came out.

Sorry for all the newb questions....but I would assume that if I had it laying in front of me, I would be able to take it apart and put it back together [up]

Papachristou

03-20-2008, 11:11 AM

the bolts for the torsen housing are pretty easy, the top ones can be hard to get to but nothing bad. they are torx, t40 i think... However im sure you have heard of co avants rear driveshaft bolt woes... you will need a 3/8 drive allen key socket and a 3/8 drive breaker bar and cheater bar to put on the end of the breaker bar to allow the allen key to sit perfectly straight in or you WILL strip them, then cry a lot.

k0mpresd

03-20-2008, 11:27 AM

or a 3/8" impact gun works well too

317ssayzarc

03-20-2008, 11:47 AM

or a 3/8" impact gun works well too

yea thats what i was gonna say lol... you read my mind ian [wrench]

k0mpresd

03-20-2008, 11:50 AM

what is the saying ? great minds think alike [:o]

3/8" impact gun is what i used this time around and what i used in the past to remove those types bolts..works like a champ everytime

Audii-Dudii

03-20-2008, 12:12 PM

what is the saying ? great minds think alike [:o]
Fools never differ? [;)]

k0mpresd

03-20-2008, 12:36 PM

we must all be fools then ;)

Papachristou

03-20-2008, 01:18 PM

co avant stripped his with an impact gun, i wouldnt use an impact on allen key bolts.

317ssayzarc

03-20-2008, 02:05 PM

i do it all the time, its really in how you use it... as long as you have used hand tools and know the concept of making sure the bit is seated, youll have no problems with power tools... plus my job is to make money, not take my time lol

Papachristou

03-20-2008, 02:10 PM

oh i agree, but for me there wasnt enough room with a rachet or impact wrench to seat the allen bit in firmly and since it takes such torque to get them off, i would take my time and do it as i recommended

your average person here isnt doing to to make money but save it and if they just take a few more minutes to do it correctly the old school way it will save them much more time and money in the long run, if you strip one of those bolts + not many people here have your skill, expertise, experience and TOOLBOX... it would suck pretty much if you stripped one for your average joe

317ssayzarc

03-20-2008, 07:27 PM

^^^http://i239.photobucket.com/albums/ff52/crazyass713/cheers.gif^^^

k0mpresd

03-20-2008, 10:30 PM

left some black marks on the pavement...looked like 1 wheel really lost traction when cornering and jamming on the throttle in 2nd gear

the car has never slid on dry pavement the way it did tonight

[up] for quattro..it is a very well built system

apexslider

03-20-2008, 11:13 PM

Does anyone make a locked center diff? I couldn't find a DIY on welding my current one.

k0mpresd

03-21-2008, 05:24 AM

you shouldnt really need a diy to weld your own...as far as i know all you do is weld the outside gears together...im sure audii-dudii will correct me if im wrong

and i have a question for him anyways...what causes tbr to be reached? i realize the axles rotating @ different speeds does it and thats why its 20/80 when cornering..but what happens if i did a high rpm clutch dump from a stand still? still 50/50 or is the torsen going to change trq just based on which wheels are spinning or what?

Papachristou

03-21-2008, 05:37 AM

good question, id like to know as well

apexslider

03-21-2008, 07:16 AM

k0mpresd

03-21-2008, 07:17 AM

edited

k0mpresd

03-21-2008, 07:26 AM

it would be nice since I personally haven't had one apart, like they say, a picture is worth a thousand words.
i think this is what you are looking for...dont quote me though

http://audizine.com/forum/showpost.php?p=2097870&postcount=32

Audii-Dudii

03-21-2008, 07:34 AM

you shouldnt really need a diy to weld your own...as far as i know all you do is weld the outside gears together...im sure audii-dudii will correct me if im wrong

Yes, that's all it takes.

and i have a question for him anyways...what causes tbr to be reached? i realize the axles rotating @ different speeds does it and thats why its 20/80 when cornering..but what happens if i did a high rpm clutch dump from a stand still? still 50/50 or is the torsen going to change trq just based on which wheels are spinning or what?

A Torsen center diff is able to vary the torque split between the front and rear wheels by limiting the difference in rotational speed between the front and rear driveshafts. Contrary to what most people believe intuitively, the Torsen starts out acting like a locked diff and opens up once the bias-ratio has been reached, not the other way around.

Remember, an open center diff can fully accommodate a difference in the driveshafts' rotational speeds but always splits torque 50-50 between the front and rear wheels, and a locked center diff can't accommodate any difference in rotational speeds but can split torque 100-0-100 and everywhere in between.

In practice, the Torsen diff behaves like a hybrid of the two: It's never fully "open" (which is why it can vary the torque split between the front and rear wheels over a limited range) and never fully "locked" (which is why it can accommodate some percentage difference in rotational speeds between the front and rear driveshafts).

So, when you dump the clutch and the wheels spin, you now know two things have happened: 1) The Torsen has already done everything it can to prevent the driveshafts from rotating at different speeds by generating as much internal friction as possible (i.e., the torque split is moving toward the bias-ratio limit) and 2) having failed to do so, it's opened up (i.e., the bias-ratio has finally been reached), thus allowing the front and rear wheels to rotate at different speeds and the maximum torque split to be achieved.

Does that answer your question?

k0mpresd

03-21-2008, 07:40 AM

So, when you dump the clutch and the wheels spin, you now know two things have happened: 1) The Torsen has already done everything it can to prevent the driveshafts from rotating at different speeds by generating as much internal friction as possible (i.e., the torque split is moving toward the bias-ratio limit) and 2) having failed to do so, it's opened up (i.e., the bias-ratio has finally been reached), thus allowing the front and rear wheels to rotate at different speeds and the maximum torque split to be achieved.

Does that answer your question?
so, if i dump the clutch and the car does not have enough torque to spin all 4 wheels, it will stay 50/50?

but if the car does have enough torque to spin the wheels, then it is now running @ 20/80 ?

Papachristou

03-21-2008, 07:42 AM

no, so as the wheels start spinning with my diff, its the rears first what does it do then? send the power away from the rear to the front?

Audii-Dudii

03-21-2008, 08:04 AM

so, if i dump the clutch and the car does not have enough torque to spin all 4 wheels, it will stay 50/50?

No. It will start at 50-50 and then vary continuously within the bias-ratio, as appropriate. At any given instant, the torque split could be 50-50, 73-7, 63-17, etc.

but if the car does have enough torque to spin the wheels, then it is now running @ 20/80 ?

*Ding!* Keep in mind, though, that when a wheel spins, with a Torsen, this will reduce the total amount of torque developed at the wheels overall, regardless of whatever the torque split is, as the spinning wheels determine how much torque will be developed at the non-spinning wheels.

k0mpresd

03-21-2008, 08:05 AM

No. It will start at 50-50 and then vary continuously within the bias-ratio, as appropriate. At any given instant, the torque split could be 50-50, 73-7, 63-17, etc.
......
*Ding!* Keep in mind, though, that when a wheel spins, with a Torsen, this will reduce the total amount of torque developed at the wheels overall, regardless of whatever the torque split is, as the spinning wheels determine how much torque will be developed at the non-spinning wheels.
ok. understood now. thank you very much

Papachristou

03-21-2008, 08:47 AM

i noticed if i snatch second gear it only barks the rear tires... it used to bark the front?

Audii-Dudii

03-21-2008, 08:51 AM

no, so as the wheels start spinning with my diff, its the rears first what does it do then? send the power away from the rear to the front?

A Torsen never "sends" power anywhere. When the rear wheels start to spin, the amount of torque they can support is reduced, but the excess torque is not "sent" to the front wheels; in simple terms, it just disappears. Remember, to create torque, an engine has to work against resistance ... no resistance, no torque. That's why an engine capable of creating 600hp under load doesn't make any significant power when revved up in neutral.

Two things happen when the rear wheels spin: 1) The amount of torque they can support themselves is reduced and 2) the amount of torque developed at the front wheels is now limited to a multiple (i.e., the Torsen's bias-ratio) of however much torque is developed at the rear wheels.

However, because the rear wheels lose proportionally more ability to develop torque than the front wheels do (as a result of the bias-ratio working in reverse), the torque-split (as viewed on a percentage basis) shifts forward, which many people mistakenly believe means the now-excess torque was "sent" there from the rear wheels. What they forget to consider, though, is that on an absolute basis, the total amount of torque developed at all four wheels is now less than it was before the rear wheels spun, which wouldn't be the case if the Torsen had, in fact, sent the now-excess torque from the rear wheels to the front wheels. The torque split may be biased toward the front wheels, which is helpful (an open diff would still be splitting torque at 50-50 in this situation and a lot more torque would have disappeared as a result) but there's less torque developed overall, so in a perfect world, you want to keep the rear wheels from spinning whenever possible.

Rear LSD, anyone?

[I have a long day ahead of me so any further discussions of this stuff will have to wait until later ... sorry.]

Papachristou

03-21-2008, 09:19 AM

well thanks for all the cool info, i feel more educated about my car.

BTW how the hell do u know this stuff?

Audii-Dudii

03-21-2008, 09:36 AM

BTW how the hell do u know this stuff?

I've been driving Audis since the late '80s and am a veteran of the Torsen war that occurred a decade ago on www.audifans.com. I have also been fascinated by the Torsen's design since it first became widely available in the early '80s.

Oh, and while I presently work in the legal field and have never worked a day in my life as an engineer (and have probably forgotten most of what I learned since graduating as one 27 years ago), I have a degree in Mechanical Engineering, which comes in handy occasionally...

k0mpresd

03-21-2008, 09:43 AM

do you like seeing posts like these? i mean..do you think its cool i was interested in and actually accomplished modding my diff?

just curious [:)]

Audii-Dudii

03-21-2008, 10:08 AM

do you like seeing posts like these? i mean..do you think its cool i was interested in and actually accomplished modding my diff?

I guess, but it's easier (and IMO, also less fun!) when you have footsteps to follow than when you have to create your own path. FWIW, I spend my days reviewing documents and digging through accounting workpapers (typically several hundred thousand, if not several million of pages worth of them!) to figure out the who/what/where/why/how of accounting fraud, so I love solving puzzles!

My primary interest these days is learning about shock valving. I have triple-adjustable Penskes on my B5 A4 and while they work well, I'm fairly confident they're setup nowhere near optimally. The trouble here is that this isn't a topic that's widely discussed (at least by the people who really know what they're talking about!) and while it's fairly easy to get a handle on the mechanics of what's involved (what does what and how to make the shocks behave a certain way under certain conditions), the value judgment part (figuring out how they should behave under certain conditions) appears to be more art than science...

And to complicate matters further, I'm a bit of a bottom-feeder and on a fairly tight budget, so while I'm prepared to spend the money when there's no alternative (such as with the shocks, although I bought them used for a fraction of what they sold for new and have since spent that much again tweaking them), I really get a kick out of doing more for less, which is why I spend so much time trying to adapt solutions already figured out by others to the issues I'm facing...

317ssayzarc

03-21-2008, 01:01 PM

just commit fraud lol, youll get alot more money for alot less work...

youd be doing more for less [:D]

Audii-Dudii

03-21-2008, 01:25 PM

just commit fraud lol, youll get alot more money for alot less work...

youd be doing more for less [:D]

No way! The cases I work on are typically large, Enron-type ones (although we didn't get a piece of that one, damn it!) and when we're successful, we collect hundreds of millions of dollars on behalf of our clients.

Although bonuses are never large enough, I will say that over the years, I've bought cars and paid off mortgages with a few of mine, so other people's fraud has been berry, berry good to me... [:D]

On the other hand, I do work long hours, as my typical work-week runs 70 hours and 80-90 and even 100+ hour work-weeks are all too common. [:(]

It's a good thing I live only 10 minutes from the office!

k0mpresd

03-21-2008, 01:46 PM

so which ones do you have?

http://www.startupracing.com/Contents/Products/B5/B5ProductsSuspension.htm

absolutegtr

03-21-2008, 01:57 PM

I chirped my right rear wheel today (while turning right) shifting into second....I was smiling [:)]

Audii-Dudii

03-21-2008, 02:03 PM

so which ones do you have?

http://www.startupracing.com/Contents/Products/B5/B5ProductsSuspension.htm

None of them. Mine are the 8760 model with custom mounting brackets and remote rather than attached reservoirs: http://http://www.resuspension.com/SHOCK-8760-SERIES-TRPL-ADJ-p-15194.html (http://www.resuspension.com/SHOCK-8760-SERIES-TRPL-ADJ-p-15194.html)

You can (sorta) see them in the following photos...

http://members.cox.net/jeffreygoggin/P1000637-06.jpg

http://members.cox.net/jeffreygoggin/P1000673.jpg

For the moment, I have OEM control arms and OEM-dimensioned Hyperco springs on it rather than the usual CPP upper/custom lower control arms and 2.5" i.d. springs.

Papachristou

03-21-2008, 02:03 PM

I chirped my right rear wheel today (while turning right) shifting into second....I was smiling [:)]

i busted a U turn today and got it way sideways[:D]

k0mpresd

03-21-2008, 02:10 PM

i told my girl (i guess shes my girl..*shrug*, might as well be) to hold on, made a left turn, and left black marks :p

k0mpresd

03-25-2008, 02:06 PM

http://audizine.com/forum/showthread.php?t=199202

Papachristou

03-25-2008, 02:33 PM

well, im just what 150-200hp behind you[headbang] no blackmarks for me[=(]

absolutegtr

03-25-2008, 02:47 PM

well, im just what 150-200hp behind you[headbang] no blackmarks for me[=(]

well, im completely stock and have no modified diff [:p]

Papachristou

03-25-2008, 04:25 PM

lol, are you going to be a 1+ flash or what?

k0mpresd

03-25-2008, 05:11 PM

well, im just what 150-200hp behind you[headbang] no blackmarks for me[=(]
haha...you have torque though...i only have high rpm horsepower

apexslider

03-25-2008, 05:44 PM

I think there is some great info in here and would like to see this stikcy'd in the FAQ/DIY for some of us diff noobs

k0mpresd

03-25-2008, 05:50 PM

i think theres a lot of good info in here as well

this is one of my favorite threads of all time

Audii-Dudii

03-25-2008, 06:38 PM

I think there is some great info in here and would like to see this stikcy'd in the FAQ/DIY for some of us diff noobs

Hmm ... perhaps I should go back and clean up a few things I simplified for ease of explanation lest I get criticized for them later?

For example, all other things being equal, the Torsen's initial torque split doesn't really start at 50-50 but roughly approximates the weight distribution of the car. Thus, if the car's weight distribution front-to-rear is 63:37, the Torsen's initial torque split (as well as the locked center diff's torque split) will also be ~63:37 whereas an open center diff's torque split is, as always, forever fixed at 50-50.

Once the car's in motion, of course, the torque split then varies according to the loads "seen" at each wheel, averaged through the front and rear differentials, but there is still a pronounced FWD emphasis, as anybody who's tried to drive a stock quattro quickly has surely noticed. Keep in mind, though, that while torque splits are conveniently referenced on a percentage basis, the tires know nothing of torque in terms of percentages, and respond only to torque in absolute terms. So while a Torsen and locked center diff may be splitting torque at the same percentages, the absolute amounts of torque being developed at the wheels can differ quite significantly in some circumstances!

This is what makes analyzing the effects of a dynamic torque split so difficult, because you have to always remember that, on an absolute basis, 80% of 20 is the same as 20% of 80, and what appears to be a massively front-based torque split percentange-wise, might only be a very mildly front-based torque split in absolute terms, if not very much torque is being developed.

But I'm now repeating myself, as this has been covered earlier in this thread, so I'll stop here.

Alex@GMS

03-25-2008, 07:47 PM

ya im saving this

Papachristou

03-25-2008, 08:50 PM

yeah, i just watched my video from sliding in the snow and it spins the fronts more than the rears it looks like, lack of power is my main problem.

exhaust sounds great though [:)]

k0mpresd

03-25-2008, 09:07 PM

i need more power :( haha

Papachristou

03-26-2008, 06:10 AM

im going to make one more vid of me launching in the dry and upload it then ill put up my review

kiss my b6's ass! you have tons of power! i have just a pinch [:(]

k0mpresd

03-26-2008, 06:18 AM

hahaha [:p]

man...i really need a digi camcorder..i want to make a video

Papachristou

03-26-2008, 06:34 AM

shit, i just made mine with a digital camera and used the video option, its not the greatest but it works ok... its on youtube, search 04 audi a4 1.8t stasis neuspeed, its not that great, i just did a few launches in front of the camera, its amazing how quick the car finds traction in the snow with summer tires, there was some big metal grates under the snow i had to be careful of too so i just kinda played aROUND, i was the off screen too much! im going to make one in the dry this weekend

k0mpresd

03-26-2008, 09:11 PM

you need a camera man haha

make one in the rain..rain is easy to drift and not crunchy like your snow seems to be

you can make a camera mount w/ a piece of wood, a drill, some zip ties, and your headrest

clean car btw

k0mpresd

03-31-2008, 06:58 AM

http://audizine.com/forum/showthread.php?t=200362

..to really rip it in a cul-de-sac. but i dont know of any big, empty, safe to slide through parking lots around where i live. and there was some mud on the right side i didnt really want to go sliding through too.

the first slide is the best on camera...in the car it feels to be sliding a lot more than what it looks like on film. i made a video before this one that i didnt like @ all. when i stopped the first time to get the camera, smoke was coming off the front tires. i would have filmed it but my memory card said it was full when i picked up the camera. [:(]

but hey, whatever. nothing better to do today. so here it is.

right click, save as.

http://www.mycarbl0ws.com/videos/100_2646.MOV

Papachristou

03-31-2008, 07:36 AM

ill watch it when i get home...

its going to rain all week here so ill do one this week.....

yeah the snow was crunchy and my car is supa low! plus there was some of those big metal grates under the snow i kept have to back off for... there was some people that came out from all those stores there and watched me for awhile [;)]

also im afraid to really rip a doughnut because several people have blown their power steering racks like that....

B6Lovin

03-31-2008, 01:30 PM

^add me to the list of power steering failures. i didnt even get to reverse steering lock at all, and i'm replacing my pump next weekend.

Papachristou

03-31-2008, 03:03 PM

what was the cause of the failure?

B6Lovin

03-31-2008, 04:39 PM

not entirely sure - i did a wide sweeping drift through a grassy field (it might as well be the smoothest nicest lawn on the planet -- no bumps or holes in it at all... i go up there every month or so and spin a few to get it out of my system) and i was just doing what i normally do... then later that night no power steering. I think it might be the stress on the pump over time/multiple donuts, and the fact that it was pretty warm out that night (upper 70's), AND that i had my ps cooler all moved around from putting on a FMIC this past week. (maybe a kink or bend in the line somewhere?)

i later examined the cooler and there's a dent in it from what looks like a rock that flew into the front of my car and managed to hit it (front bumper wasn't on the car for a couple days)

either way i'm putting in a new pump, and doing the switch to a small oil cooler instead of that stupid little metal tube. hopefully that'll keep me from running into problems in the future. (cuz i know i cant give up sliding the car around)

k0mpresd

03-31-2008, 05:18 PM

i havent had a power steering fluid cooler in years

my power steering pump has been through hell and back too..i used to have a leak and would just keep adding fluid when it started to scream

i just knocked on my wooden end table btw

400HPA4

04-27-2008, 05:53 PM

Trust me when I say this...if you decide to do donuts, do not take your steering wheel to full lock...unless you want to buy another rack.

B6Lovin

04-27-2008, 06:00 PM

Trust me when I say this...if you decide to do donuts, do not take your steering wheel to full lock...unless you want to buy another rack.

yeah, that was one of the first things i ever read on AZ -- was that full-lock was a no-no. I think i've gone to full lock maybe once since i've owned my car... and that was 3 point turning in an awkward spot/on a steep hill.

400HPA4

04-27-2008, 06:13 PM

read what stasis says about it

http://stasisengineering.com/Category_Detail.aspx?id=9&YR=2004&MK=Audi&EN=106&PID=176

FWD when entering corner (on brakes/nose dive, power needs to be on front wheels
AWD through middle (weight is spread throughout car)
RDW when exiting (under power, weight and power is on rear wheels)

Im excited about it!

This is only true if you have a limited slip rear differential. Brake proportioning make more difference on the center diff than wheelspin.

All cars are front brake biased since most of the weight is on the nose of the car during braking.

I promise you the high bias center diff is not the "holy grail" as many people seem to think. It is not even likely that you will notice the difference in day to day driving at all.

We could (Tracee and I) only really notice the difference during track time (which is very hard on your car).

One thing I can say about mine (which broke after a track event) is that STaSIS completely took care of me. I towed my car down to Torrance to repair the transmission (I thought the transmission broke, never in a million years would I have thought the center diff would go out).

The guys at STaSIS offered to come down there and pick up my car and fix it, they also offered to pay for the repair at Eurocode. Since David is a great guy and had my car on the lift, STaSIS overnighted a brand new center diff to me and sent a call tag for the broken one to be returned to them.

Once they got the diff back, it was determined that the deceleration side of the differential had sheared the gears off...

Nobody can say exactly how this happened but it did, there was some speculation it could be from a staggered wheel setup but that could not really be it because the rolling diameter of my tires were within 0.9% of each other (235-35-19) all the way around.

It could be that my car is a heavy ass pig and weighs nearly 1000 pounds more than the World-Challenge cars that the differential was designed for.

It could be my bad ass STaSIS/Alcon 370mm brakes and the nearly 500 pounds of torque my car makes fighting against each other as Tracee was entering and exiting the corners.

I am very glad that STaSIS took care of me 100% though, it would have sucked to have had to spend another $500 on a new center differential...keep in mind, I never even had to pay for my first differential, it was included with the a package when I bought my brakes form them.

The only thing I would fear is that if I were to have bought the parts from the dealership myself (everything you need to make a high bias diff is available) I would have been stuck holding the bill.