[A4] Re: Quattro, Torsen, Haldex and others...
b5quattro at shaw.ca
Tue Dec 28 16:08:44 EST 2004
If all 4 wheels are on shear ice with no traction whatsoever, then I can see how a quattro IV can be immobilised. EDL brakes the side that's spinning more, but since the other side doesn't have enough traction to begin with, you're still not going anywhere.
I agree that the 38/62 split offers better balance in the dry, but I still don't like its inability to shift more power to either side.
I believe BMW introduced their new X-drive earlier this year, with the introduction of the X3. I know they've since replaced the old system on the X5 with the new one, but I'm not sure if they ever adapted the x-drive to the e46 3-series, since the new 3 (e90) was just released very recently. They may simply use the new system on the new 3. I haven't read a lot on the X-drive, does anyone has any good info on that?
And speaking of the X3, I've read nothing but so-so to bad reviews on it. It has a harsh ride due to high ride height combined with a stiff suspension for on-road handling. Unless you absolutely need the ground clearance, you'll enjoy yourself much better in a 3-seriew wagon with AWD. It's lighter, faster with better handling, braking and uses less fuel. Also the interior looks kinda cheap to me. I personally think BMW is diluting their image as an exclusive premium sport sedan/coupe maker by introducing SUVs in their lineup. What's next, a BMW pickup and minivan? Sorry for going off-topic!
----- Original Message -----
From: Rocky Mullin <caliban at sharon.net>
Date: Tuesday, December 28, 2004 11:48 am
Subject: Re: [A4] Re: Quattro, Torsen, Haldex and others...
> interestingly, i'm seriously considering an X3.
> At 8:29 AM -0800 12/28/04, Brian J White wrote:
> >"quattro IV - torsen center diff with open front and rear diffs,
> but now it
> >has EDL to keep side-to-side traction in check. This system
> combines the
> >proactive nature of the mechanical torsen, with reactive aspect
> >the EDL. It
> >should in theory able to pass the "one wheel with traction only"
> >Key point up there. The car on which I saw the test applied was
> >99 or so A4 Quattro...obviously having Quattro IV.
> >Either they disabled the EDL (possible as this was a marketing
> >exercise) or the EDL couldn't keep up with absolutely ZERO
> >on the other 4 wheels. It certainly looked like it was trying
> >just couldn't make it happen. My eyes popped out of my
> >was certainly surprised to say the least.
> >The BMW (the new system) AWD on the 330Xi certainly did the
> >There are handling advantages to the 36/66 torque split as well.
> >Biased towards the rear for that rear wheel drive track handling
> >At 08:07 2004-12-28, Brizax at aol.com wrote:
> >>GOOD INFO THERE, SOMEONE HAS BEEN PAYING ATTENTION IN CLASS THE
> LAST COUPLE
> >>YEARS HUH? :)
> >>NYT is wrong!!!
> >>On torsen based quattro system (now version 4, hence quattro
> IV), the
> >>factory torsen is a splitted 2:1, meaning it can transfer up to
> >>of available
> >>power to either the front or rear axle. I've read many
> >>torque split
> >>figures from different sources, ranging from 40:60 to 30:70,
> but I believe
> >>the 2/3 is the most correct. There're other versions of torsen
> >>available, for
> >>example Stasis Engineering offers a 4:1 version, capable of
> splitting up to
> >>4/5th (or 80%) to either end.
> >>All torsen are normally 50:50, whereas the haldex quattro is
> either 100:0 pr
> >>95:5 normally, and it's capable of sending all power to either
> end. Volvo
> >>uses this system as well. So there, NYT got the 2 quattros
> >>Now here's some distinction of the different versions of
> traditional quattro
> >>systems for longitudinally mounted engines (all B and C chassis
> cars, such
> >>as 4000, 80/90, 5000, 100/200, A4, A6, A8):
> >>quattro I - original version. All 3 diffs are open, but the
> center and rear
> >>are manually lockable. It's very simple and reliable, but it
> tends to eat
> >>tires or cause damage to the driveline when people forget to
> unlock the diffs
> >>after they unstuck themselves.
> >>quattro II - introduced in '88 I believe, when torsen replaced
> the old open
> >>center diff. The rear is still manually lockable, but it's now
> operated>>pneumatically so that it'll unlock itself once the car
> >>over 25 km/h. I
> >>have this in my '90 CoupeQ, it works very well, never needed to
> >>lock the rear
> >>diff, but this version will not pass the "one wheel with
> >>only" test.
> >>quattro III - this was only used in the V8, where both the
> center and rear
> >>diffs are torsen. Since this car wasn't sold in large quantity
> I don't know
> >>how well it actually works, but it sure sounds promising,
> almost like the
> >>HUMVEE's system!
> >>quattro IV - torsen center diff with open front and rear diffs,
> but now it
> >>has EDL to keep side-to-side traction in check. This system
> combines the
> >>proactive nature of the mechanical torsen, with reactive aspect
> >>the EDL. It
> >>should in theory able to pass the "one wheel with traction
> only" test.
> >>On the TT, its quattro system has no version because it's not
> an evolution
> >>of the original quattro for longitudinally mounted engines. As
> I've said
> >>before, my brief drive in a TT didn't impress me much. I think
> >>it's mainly due
> >>to the completely reactive nature of the haldex system, ie, it
> >>sends power to
> >>the rear until it detect slips. However I hear that Volvo has
> >>since modified
> >>their haldex AWD on newer cars and they're supposed to be a cut
> above the
> >>original haldex system.
> >>To further continue the AWD topic, BMW's system is not as good
> as quattro
> >>due to its inability of changing torque split between front and
> rear, it's
> >>always at 38/62. However it's brand new x-drive is supposedly
> >>much better than
> >>the old AWD system, which started in '88 in the 325ix and was never
> >>changed/upgraded until just now.
> >>M-B's system is even worse. All 3 diffs are open and it relies
> on their
> >>version of EDL to control wheel spin by braking the spinning
> wheel(s) hence
> >>sending power to the ones that aren't spinning. It's
> >>reactive, much
> >>worse than the haldex system, and it places too much demand on
> >>brakes. If
> >>Audi decided to deactivate their EDLs above 80 km/h due to
> potentially>>overworking the brakes, how well do you think M-B's
> system copes
> >>with this issue?
> >> Although I must say this probably won't be a problem for daily
> driving, it's
> >> more of a problem if you really get stuck or actually to off-
> >>Now to chip in my $0.02 on the center versus rear applications
> of the torsen
> >>diff, they are really quite different. Hence if you've only
> driven quattros
> >>with torsen center diff, you really have no idea how it would
> behave when
> >>is't slapped onto the rear of a RWD car, of the front of a FWD
> >>(I believe
> >>Nissan used to offer torsen on their 240SX and Maxima as part
> of their SE
> >>package). A friend of mine (240SX owner) has told me once that
> having a LSD
> >>(such as torsen) in the rear is great in the dry, but it does
> >>some wierd stuff
> >>when it's wet and slippery, cause the diff seems to be
> distributing power
> >>from side to side as each of the rear wheels lose and regain
> >>traction during a
> >>Anyhow, hope this clears things up a bit, or not... ;-)
> >>'01.5 S4 - quattro IV
> >>'90 CoupeQ - quattro II
> >>A4 mailing list
> >>A4 at audifans.com
> >A4 mailing list
> >A4 at audifans.com
> Rocky Mullin
> "Evil kills those who perpetrate it, and the pastures of
> inequity are harmful"
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