Talk:Quattro (four-wheel-drive system)
|WikiProject Automobiles||(Rated Stub-class)|
|This is the talk page for discussing improvements to the Quattro (four-wheel-drive system) article.
This is not a forum for general discussion of the article's subject.
|This topic is in need of attention from an expert on the subject.
The section or sections that need attention may be noted in a message below.
- 1 Adequately cite sources/clarify
- 2 AAM quattro center differentials
- 3 Subject Revision
- 4 Comparisons
- 5 Fair use rationale for Image:Quattro.jpg
- 6 torsen/haldex comparison dispute
- 7 undoing quattro IV and V off-road behaviour
- 8 dablinks and forced image sizes
- 9 Title
- 10 EDL
- 11 Torque transfer, is it 50% max or 100% max?
- 12 4WD vs AWD?
- 13 development Torque Vectoring System
- 14 Requested move 30 August 2016
- 15 External links modified
Adequately cite sources/clarify
The article suggests that the Q7 uses a Borg Warner system to provide AWD. There is no source cited for this. The specifications suggest that the center diff is a Torsen unit like other Quattros have (see http://www.audiworld.com/model/q7/07/Q7%20tech.pdf). The front and rear diffs are described as hypoid gears, which is identical to the arrangement on the other modern Quattro cars (see http://www.audiworld.com/model/). Perhaps citing a reference and clarifying what you're trying to get across would clean the article up a bit. Epinkert (talk) 04:26, 28 November 2007 (UTC)
The Q7 does use a Torsen-based centre differential, one based on the "T3" planetary design. This give a static torque distribution of 58%:42% rear:front. Note the VW Touareg does not use the same centre differential, this relies on a simple planetary gear set with a clutch lockup. Skiwi44 (talk) 21:11, 2 February 2012 (UTC)
AAM quattro center differentials
Teutonic Tamer: The link I have repeatedly posted (http://www.aam.com/file.php/729/AAM06_AR.pdf) is not an advertisement...it is a Fortune 500 company's annual financial report. Why do you doubt this? UrPQ31 (talk) 04:20, 30 May 2008 (UTC)
I believe that a change does need to occur, regarding this article, 4motion, viscous coupling, etc. Perhaps re-evaluate all of these related articles. My idea:
1. Have a "VWAG Longitudinal AWD Systems" page (have "quattro" redirect here, but mention, for example, that the Audi A3 uses uses a "VWAG Transverse AWD Systems").
2. Have a "VWAG Transverse AWD Systems" page (have "4motion" and "syncro" redirect here).
3. Keep the "Haldex" and "TORSEN" pages, since they are their own entities, but edit to reflect the reorganization of the previous two pages.
Could someone make an AWD comparison page? I'm wondering how the AWD in my Subaru compares to that in Audi/VW and Mercedes. Thanks. - MSTCrow 00:04, 3 November 2006 (UTC)
- Subaru AWD systems vary between Subaru models. There is an excellent overview at http://www.subaru.com, although you may have to dig for it. Subarus may use an electronic center differential, liquid coupling, sprung-clutch mechanism and a few others. A full discussion of this would tout the weight benefits of Subaru's systems over Audi's. —Preceding unsigned comment added by 22.214.171.124 (talk • contribs) 14:46, 26 November 2006
- That's not really what we do here, honestly. What you're proposing sounds like either a significant amount of Original Research or, if such a thing has been published elsewhere (and I'm sure it has been), unnecessary duplication of content. Should you find an appropriate comparison elsewhere, however, you could certainly try adding a link here or on the AWD page.
- User:Fox1 (talk) 22:49, 26 November 2006 (UTC)
For a comparison of All Wheel Drive systems check out: http://www.autozine.org/technical_school/traction/tech_traction_4wd_2.htm. --[D. Evan Kiefer, 8 February 2007]
The last paragraph (the cons of the Haldex system) must be the WORST paragraph that I have ever read on Wikipedia... It sounds like it was written by an 8 year old!: "Full-time all wheel drive is better." <-- wow! that's not a broad, misguided, sweeping statement! "Some say Haldex system has less predictable behavior when cornering in snow than permanent all wheel drive systems. Other say there is nothing wrong with it; it is just a little different." Some say? Others say? Who says? The title to the last section "When Quattro isn't Quattro any more" is also extreme flamebait! --[T. Holm, 6 March 2007
- The entire rewrite that added the generational format, the pros and cons, and the unencyclopedic tone needs to be re-rewritten. There was some good info added (generational format is fine), but style, NPOV and NOR went out the window.
- I'd love to do it, but I'm a bit short of time.
- Fox1 (talk) 19:11, 7 March 2007 (UTC)
Fair use rationale for Image:Quattro.jpg
Image:Quattro.jpg is being used on this article. I notice the image page specifies that the image is being used under fair use but there is no explanation or rationale as to why its use in this Wikipedia article constitutes fair use. In addition to the boilerplate fair use template, you must also write out on the image description page a specific explanation or rationale for why using this image in each article is consistent with fair use.
Please go to the image description page and edit it to include a fair use rationale. Using one of the templates at Wikipedia:Fair use rationale guideline is an easy way to insure that your image is in compliance with Wikipedia policy, but remember that you must complete the template. Do not simply insert a blank template on an image page.
If there is other fair use media, consider checking that you have specified the fair use rationale on the other images used on this page. Note that any fair use images uploaded after 4 May, 2006, and lacking such an explanation will be deleted one week after they have been uploaded, as described on criteria for speedy deletion. If you have any questions please ask them at the Media copyright questions page. Thank you.
BetacommandBot 05:32, 13 September 2007 (UTC)
torsen/haldex comparison dispute
I would suggest to either move the "longitudial systems" and "transverse systems" out of this article to the general awd article or an article about V.A.G. all wheel drive or have them rewritten to talk about Audi only. The comparison of torsen and haldex could stay in this article, but moved to a separate topic. Also, viscous coupling was never used on Audis and sold under the quattro badge - the "viscous coupling" topic does not belong here. the "haldex aftermarket application" should also be moved to the "Haldex" article.
Next, some technical aspects of the torsen/haldex comparison, as to my knowledge:
1. fuel economy of the Haldex system is a myth - decoupled axle and all other shafts rotate at all times, friction losses still exist. there is no proof automatic AWD is more fuel-efficient than full-time AWD.
2. haldex engine-braking issue is a myth - nothing prevents haldex from locking when engine-braking. the clutch gets locked when it senses the driveshafts are rotating asynchronously, either accelirating or decelerating.
3. haldex tyre identical wear issue is a myth - according to haldex-traction.com, haldex allows uneven tyre wear and works with mini-spares. This is torsen that requires all tires to be of the same size and wear.
4. and about torsen-based quattro weight distribution - the most important issue is missing is this paragraph: nose-heavy audis heavely understeer, this is why audi introduced 40/60 torque split to give more power to the rear and make it go around the corners.
- What nonsense. Please cite your sources, and not from a forum.
- Corrections to you unfoundeded tosh:
- your point 1 - although Haldex shafts rotate all the time, when no torque is transmitted to the rear, then they are merely freewheeling. Simple phyisics states that a freewheeling object uses less power than an object which requires being driven.
- Your point 2 - when braking, the Haldex DOES disengage torque to the rear axle. The Haldex works soley on electronics: it takes its rotational speed from the indivdual wheel speed sensors to calculate when to apportion torque to the rear. It also takes a feed from the brake light switch, and when the brake lights are triggered, the Haldex disengages fully.
- Point 3 - Haldex DOES require all four tyres to be of identical wear, because it is NOT torque sensing (like the Torsen), but relies soley on the wheel speed sensors. The Torsen, being entirely mechanical, takes no readings from the wheel speed sensors, and simply relies on torque transmission, hence Torsen CAN accomodate differences in tyre wear.
- Point 4 - modern Torsen Audis ONLY understeer when driven incorrectly. When driven correctly, a Torsen Audi will NOT understeer, and corners perfectly competently. Audi simply introduced the 40:60 Torsen to give it more of a rear wheel drive "feel".
- Kind regards - -- Teutonic Tamer 19:47, 23 December 2007 (UTC)
Dear Tamer, 1. even if you can prove that a freewheeling object uses less power than a driven object, the benefit is almost non-existant. this is still the car's engine power that is wasted on the "freewheeling" parts. besides, audi has proved in 1980's that a driving tyre roll-resistance is lower than resistance of a driven tyre, thus permanent all wheel drive can be more fuel-efficient.
Now, please go back and read again:
2. the article is talking about engine-braking, where brakes (and brake light switch) are not involved. also, you must know, that clutch engagement mechanism is hydraulic. electronics are used to a) pre-tension the clutch b) disengage the clutch. please see haldex-traction.com
3. please visit haldex-traction.com and try to argue with those guys about this issue :)
4. torsen audis have been critisized for their unstable behaviour, changing from heavy understeer to heavy oversteer, depending on which wheels have more traction. a rear wheel drive "feel" was given on some purpose, which need additional investigation, but, perhaps, this issue is beyond this article.
- Oh dear, you seem to have a hang up regarding Haldex!
- 1. Can I suggest you speak to a physics professor. Any object which is freewheeling requires less energy than an object which requires power to drive it. Get on a bicycle and try for yourself. OK, the benefit in terms of fuel consumption may be small on Haldex, but it is certainly measurable. Can you cite this research from Audi you quote? The only way that freewheeling tyre can offer greater resistance over a driven tyre is when you have a "directional" tyre, with an agressive tread pattern, which has previously been on a driven axle (the tread blocks "feather" in a different way between driven and non-driven wheels/tyres).
- 2. You are clearly very misguided. Audi programme their Haldex ECUs to fully disengage when the brakes are applied. This is specifically for the correct operation of the ABS. The "feed" from the brake light switch takes priority (in the Haldex ECU) over the readings from the front and rear wheel speed sensors.
- 3. Erm - Haldex-traction.com are simply a company website- who are trying to "sell" an inferior product. When you check with the actual manufacturer of the car with Haldex, ie Volvo, Audi, VW, etc - it is the vehicle manufacturer which rightly advises the vehicle owner of the absolute need to have matched tyres with matched tread depths. Indeed, in the UK, a few years back, a certain Volvo car failed to state this in the owners handbook, owners were running on tyres of unequal tread depths, and the Haldex units were burnt out. This very story made it onto a highly regarded UK consumer TV programme.
- 4. I really don't know where you are getting your info on the handling of Torsen Audis. Yes, some Torsen Audis WILL understeer when driven incorrectly, but put those same drivers in front wheel drive Audis, or even rear wheel drive BMWs and they will get the same understeer. Torsen Audis are actually praised because of their stability in corners. Maybe you are getting confused with the pre-Torsen Audis, which had the manually locking centre diff. When a centre diff is "locked", and cornering on dry roads, then the natural transmission wind-up can make the car twitchy.
- BTW, I agree with you regarding moving the "Haldex aftermarket section". AFAIK, that is only really used on older VWs. Rgds -- Teutonic Tamer 22:31, 28 December 2007 (UTC)
1. Here is the quote you were asking for: "This happens because, as vehicle velocity increases, the frictional losses for a freerolling wheel become greater than for an equivalent driven wheel." 
However, I agree with the current statement about "a slight increase in fuel economy" of the Haldex AWD and take this question off discussion.
2. According to haldex.com, in most cases, ECU indeed prevents the coupling from locking (i.e. neither it locks nor fully unlocks the coupling) when engine-braking and transfers very little torque to the rear. So the current statement about Haldex front-wheel-drive-like handling when engine-braking can be true, but it seem to depend on the vehicle.
3. Wasn't the Volvo issue you are talking about happening with pre-MY03 Volvos, which had viscous coupling installed?
I read that an expert was needed for this page and I agree. I am not a drivetrain expert but hope I can help out on some of the discussions.
I will start with the Haldex vs Torsen dispute. To start the basic difference is that Torsen is a torque divider (needs one imput and two outputs) and haldex is a clutch (one input, one output) Basically it is a controllable clutch, meaning the amount (not percentage) of torque is passed through. Because it is electronically controlled, it can be programmed to act in almost infinitive ways). It could even behave like a virtual torque divider and that is (without knowing the algorithms) probably what it is doing in cars (probably different for different brands) I can not agree with the persistance of TT regarding the torque split. I will try to explain my thoughts in a simple way: Normally the front wheels are driven and the rear wheels through the Haldex. We can replace this with a rear wheel drive car that is driven on the left wheel and the right wheel is connected with a Haldex. If the clutch is closed, left and right wheel have the same speed and the torque split is depending on the road friction (the basic difference with a diff). If the left wheel (the driven one) is in the air, all torque goes to the right wheel. This is analogue in the (Audi) haldex: If the front wheels are in the air, 100% of the torque goes to the rear wheels. This can never be reached with a diff without mechanical lockup so the Haldex system really is not so bad. Robkraai (talk) 20:10, 11 June 2008 (UTC)
- Normally the front wheels are driven and the rear wheels through the Haldex.
- The rear wheels are freewheeling normally unless ECU decides to lock the clutch because of the road conditions etc.
- If the left wheel (the driven one) is in the air, all torque goes to the right wheel.
- If the clutch is closed, yes, this is correct
- the Haldex system really is not so bad
- Noone is saying Haldex is bad.
- Haldex vs Torsen dispute has 4 topics, which one are you talking about? Or are you disputing the article itself? Give us a quote. Thanks anyway.
- --Zello (talk) 07:59, 4 July 2008 (UTC)
The tyre diameter topic I did not make up my mind about the torsen diff, it may be adjusted to a different ratio with unequal tyres. For sure it will cope with the wheel speed differences without a problem. The Haldex uses electronics and with software you can do anything! I cannot imagine that they did not build a routine for tyre size difference detection. I have been working in the past on DSA (Dynamic Stability Assistance) which also was based on wheel speeds and there one of the first modules was this tyre size detection. If Haldex states that it compensates for that (I did not read the stuff) I believe it until someone has a reason to beleif the opposite Robkraai (talk) 20:33, 11 June 2008 (UTC)
- For sure it (Torsen) will cope with the wheel speed differences without a problem.
- I've seen the Audi quattro transfer box broken a few days after a tire "specialist" installed different diameter tires front and rear
- If Haldex states that it compensates for that (I did not read the stuff) I believe it until someone has a reason to beleif the opposite
- I believe that too and I've got confirmation from a Haldex engineer on that.
- Thank you for your input.
- --Zello (talk) 07:59, 4 July 2008 (UTC)
A Haldex system does have slightly better mpg because it has less rotating mass. This is because a center diff system has 3 diffs, 3 driveshafts (although one is rather short in an Audi) and 4 halfshafts. A Haldex system has 2 diffs, 1 driveshaft and 4 halfshafts. All are spinning at all times in both cases, but just having less drivetrain means you lose less energy both in spinning mass losses and general losses just having to accelerate a mass and brake it again (as you do with any part of the car, including the driver's mass). On a more on-topic note, I think this section should be in the article, but good luck ever getting a version everyone is happy with.Bollinger (talk) 16:55, 17 July 2009 (UTC)
By variation of electronic sensitivities, it is possible for the Haldex system - particularly Gen 4 - to produce a constant torque bias akin to that provided by a Torsen differential. This is contrary to the statement that a 'normal' Haldex provides only a 5% constant rear bias.
The Haldex system is also capable of reacting in less than one rotation of a wheel. This means that it is NOT a requirement for wheels to 'spin' before the Haldex moves torque - it is a requirement that mechanical slip exists between axels. Slip can be induced by variation in tyre size, higher weight over front/rear wheels (causing a different tyre radius) etc. This information is freely available from Haldex if you send them an email and/or read documentation on the after market upgrade ECU's Haldex supply. —Preceding unsigned comment added by 126.96.36.199 (talk) 09:24, 27 July 2010 (UTC)
undoing quattro IV and V off-road behaviour
I changed the description of quattro IV and V off-road behaviour back to where it was prior to Dec 23, 2007 (partially undid the edit of 10:24, 25 December 2007 by Teutonic Tamer ).
Here is the proof that EDL cannot transfer enough torque left-to-right: 
Note that if this car would be on a slope, or towing smth, there is no chance the car would have moved any further.
Teutonic Tamer, you would do us a favor if you stopped vandalizing this article.
- What an absolute load of bollox!!!
- You clearly don't know what you are talking about.
- Is it just YouTube and internet forums where you learn all this mis-information???
- Have you EVER worked on Torsen quattro systems??
- Have you EVER owned any modern Torsen quattro cars??
- You have been reported as a Wiki vandal. -- Teutonic Tamer 19:36, 4 January 2008 (UTC)
- Ok, from an outside perspective - I don't think this is vandalism per se, but YouTube is pretty clearly not acceptable as a reliable source here. If Zello555 (talk · contribs) wants to reinsert this information, then please provide a more reliable source. Please don't simply reinsert the material or edit-war. MastCell Talk 20:39, 4 January 2008 (UTC)
MastCell, would making a video of my own Golf 4motion (with EDL) moving nowhere in the conditions I described in this acticle be a reliable source? I am afraid there will be no other source because no magazine has investigated this issue yet, if they care at all. But the problem is there and people are talking about it  and yes, some of them are posting videos to youtube.
Teutonic Tamer, when will you start actually READING what other people are writing? Where did I say anything about "Torsen"?
Regards, --Zello (talk) 23:16, 4 January 2008 (UTC)
Teutonic Tamer, because this was you who made changes to the original article (the changes I was trying to undo), I want you to support the changes you made with a reliable source. What you need to do is to get an evidence of a quattro IV Audi with EDL driving up a slope with one front and one rear diagonally opposed wheels in the air. Thanks. --Zello (talk) 11:25, 8 January 2008 (UTC)
WP:NAMB is clear about when dablinks are necessary. No user will get to a page called quattro (four wheel drive system) by accident. If they type 'quattro' in a search box they will go to Quattro and be able to navigate there without a problem, and dablinks which do not include a link to Quattro shows a remarkable lack of concern for the readers' intentions. It is double redundant when every dablinked article (Audi Quattro and quattro GmbH) are linked to elsewhere on the page.
Articles are viewed by readers on many different screen sizes, and the facility is in every users preferences to force their own image sizes; that is why the recommendations at WP:IUP#Displayed image size exist. When people want to see the image at a greater resolution they can clickthru and see it full size. Again, that's the point of thumbnails. If YOU want to see the thumbnail at 300 pixels, set it in your preferences, but do not over-ride everybody elses choices. Iamaleopard (talk) 18:12, 2 May 2008 (UTC)
I object to the title of this page. Quattro is not a system but a name used by Audi. In the definition it is used correct but also on several spots in the article the mistake is made Robkraai (talk) 20:20, 11 June 2008 (UTC)
- Erm. . . if you actually read the first line of the lead paragraphs, it clearly states that quattro (meaning four in Italian), is the name used by Audi AG to indicate that four-wheel drive (4WD) technologies or systems are used on specific models of the Audi marque of cars (automobiles). It goes on to state It is important to note that none of the above trademarks, or nomenclatures define the operation or type of 4WD system, as detailed below. - seems pretty clear to me! Furthermore, using the title is notable, and condsiderably more notable than some of the lesser known 4WD tradenames. -- Teutonic_Tamer (talk to Teutonic_Tamer) 08:22, 15 June 2008 (UTC)
You don't seem to get my point, basically I have 2 objections. Quattro as title is OK and some explanation between brackets as well, but it suggests quattro is a system whilst the article makes clear it is a name that is used on Audi's using many different systems) My suggestion: Quattro (four wheel drive Audi) My second problem is that it describes systems not used by Audi, which in combination with the title could suggest that it is a general (and complete) article about 4wd, which it isn't since there are more systems than the mentioned ones. Robkraai (talk) 11:35, 15 June 2008 (UTC)
- On the name issue, I believe you are splitting hairs. OK, the most appropriate name would be "quattro (four wheel drive)" - ie jsut dropping the word "system" (however, being as this article is linked to quite a large number of related articles, fixing the redirects would be a major task in itself). Audi would not be needed in the title, because the word "quattro" is highly recognisable as an Audi term. On your secomd point, yes, the article does describe systems used by Audi, notably those used by Volkswagen, simply because both Audi and Volkswagen are part of the larger Volkswagen Group which naturally share engineering developments and technologies. -- Teutonic_Tamer (talk to Teutonic_Tamer) 12:39, 15 June 2008 (UTC)
The article states twice that all transverse Haldex-based AWD systems only have EDL on the front wheels. This is false at least for the VW Golf MkV and Transporter 4 systems, as documented in VW Self-Study Program circular 333 . I suspect that it is false for all Haldex-based systems, as it would substantially compromise the basic function of the system. — Preceding unsigned comment added by 188.8.131.52 (talk) 04:21, 23 December 2013 (UTC)
I object to the usage of this name. In my opinion it is a name ivented by marketeers (AUdi only???) It suggests that it is electronically controlling the diff. In fact it is just an automatic brake system also known as traction control. Robkraai (talk) 20:24, 11 June 2008 (UTC)
- Oh dear, so you want to delete every single "trade" or marketing name, from every single commercial company from Wikipedia??? For the record, the article does NOT, in any way describe that the diff is being electronically controlled. Furthermore, EDL is categorically NOT a traction control system (traction control applies the brakes to both wheels on a driven axle simultaneously, and/or electronically reduces engine output - EDL does not reduce engine output, and only brakes one wheel on a driven axle). Please try reading the article more carefully, thanks -- Teutonic_Tamer (talk to Teutonic_Tamer) 08:29, 15 June 2008 (UTC)
Oh dear, Tetonic Tamer thinks I don't read articles carefully. I read a lot of articles and have been active in the field of traction control. I can assure that traction control (at least on some but maybe on most) cars works exactly like your EDL, it brakes only the wheel(s) that are spinning. Jeep calles it BLD for instance. Regarding trade marks, they should only be used if they describe a unique product, service or function. EDL does not comply since there are many systems that have the same function (probably with detail differences) I would like to discuss in this manner and hope for some support to convince TT but if discussion is impossible, I will edit the article to the best knowledge. Robkraai (talk) 11:10, 15 June 2008 (UTC)
- I'm sorry but you are factually WRONG. As an Automotive Engineer, with a keen interest in vehicle dynamics, I can assure you that traction control and EDL are operate in two very different methods. All traction control systems monitor differential axle wheel speeds comparing the driven axle to the non-driven axle - any differences outside the scope of the allowed tollerances will ONLY result in either (a) BOTH driven wheels on the same axle being braked, or (b) the engine ECU reducing engine output, or (c) a combination of (a) and (b). EDL does NOT compare differences between front and rear axles, it ONLY compares differences between the left and right wheels on the same axle, and brakes just ONE wheel, there is NO engine power intervention. Whilst they are both "add-on" functions of modern ESP systems, and use the same related hardware and electronics, the software control of the two different systems are distinctly separate, and help moderate/control different aspects of vehicle dynamics. Don't forget, Wikipedia articles are not considered valid references for other Wikipedia articles, so if you have read something contrary on another Wiki article, it doesn't automatically mean it is correct! -- Teutonic_Tamer (talk to Teutonic_Tamer) 12:52, 15 June 2008 (UTC)
It seems we have an argument. As a vehicle dynamics engineer I'm sorry to say that you are wrong. I don't know why you assume my information comes from wikipedia but it does not. It is my personal experience (the Jeep info comes from the Jeep website). I propose to challenge ourselves with a good reference. I am thinking about issuing some measurements from projects I worked on to proove my right (in that case you have to believe it does not come from Audi otherwise there is no sense in this) Do you have ANY source that can support your idea that Audi is the only car that uses -one wheel braking- for traction control? Robkraai (talk) 17:09, 15 June 2008 (UTC)
- I have to agree with Tamer here. EDL and ASR (Traction control) are all part of ESP but work in different conditions and in a different way. In this article we talk about EDL. ASR EDL --Zello (talk) 08:14, 4 July 2008 (UTC)
Finally I agree with everybody now. It is just a matter of naming. Some OEMS mention EDL and in this case it is a seperate module from their ASR. Other OEMS have the same functionality but do not use the term EDL. In that case ASR is working like ASR plus EDL. In caase of Volkswagen you both are right but for other brands I am right. My point is just to say that cars without EDL (not being VW) do have EDL functionality but call it ASR (or use different names) Robkraai (talk) 08:46, 4 July 2008 (UTC)
Can someone please fix this - "Again, due to limitations of Electronic Differential Lock (see quattro IV description above), in off-road conditions it is enough for one front and one rear wheel to lose traction and the car will not move." - Quatro IV description above doesn't say anything about that. justQQ (talk)
Torque transfer, is it 50% max or 100% max?
In short - it is neither. I have made some changes to the article to introduce the Torque Bias ratio, and it's effect on torque transfer for the Torsen (T2). Also to make clear that the function of the Torsen T2 in this regards, and introducting the T3. Skiwi33 —Preceding undated comment was added at 03:16, 1 September 2008 (UTC)
I am copying my conversation with Teutonic Tamer on the torque transfer issue. Currently the quattro article states that max torque that can be transferred to either axle is 50%, while numerous sources state that this should be 100%. We are waiting for an expert's comments. --Zello (talk) 11:55, 4 July 2008 (UTC)
A couple of days ago I have changed the article so it now states 100% torque to the rear axle. I tried to challenge my position but no reply. I think you agree with my clear explanation: Haldex does not split torque, it equals speed between front and rear. If torque front is zero, the wheels do not spin because of the same speed as the rear. They can not put any torque on the ground and therefore all produced torque (excluding losses) MUST go to the rear. Robkraai (talk) 13:33, 4 July 2008 (UTC)
about the torque transfer in Haldex all wheel drive system: please understand the difference between torque and power (google it). when a haldex clutch is locked, power is transferred to both rear and front axles in the 50:50 proportion. this is correct. but if front wheels happen to be in the air, torque, sensed on the front wheels equals 0. if at the same time, rear wheels happen to be on a dry surface, they will drive the car and torque sensed on the rear wheels will be up to 100% of the torque the car can deliver. this is why specialists say that haldex can transfer up to 100% of torque to the rear wheels. Thanks --Zello (talk) 23:09, 23 December 2007 (UTC)
- Hi Zello, thanks for the message :)
- This Haldex lark is getting a little unreal. I'll just state my point of view. Firstly, I'm a very highly qualified Automobile Engineer, and have spent my entire life working on various four (and six) wheel drive systems. I still have all my relevent text books and technical documents amassed over the years. More recently, I have started to specialise in VW group vehicles, so I have a detailed understanding - on both a 'personal' and 'professional' level.
- Regarding the power vs torque comment - I certainly don't need to trawl through the realms of mis-information that Google (or any other search engine) will display. Torque is a twisting force (which effectively is what provides traction), whereas power is merely a measurement of a rate of work (and generaly is in proportion to top speeds). Power has no effect on "tractive effort". It is the transmission of torque which propels a motor vehicle.
- Onto the 'nitty-gritty' of the Haldex unit - so it seems we both agree that when the Haldex clutch locks fully, the torque transmission is exactly front to rear 50:50, so why the disagreement? Your comment regarding the 'front wheels being in the air' - I'm sorry, but I find that a perplexing comment. Firstly, if a Haldex car is driven at a ramp-like object at a rate which makes the car leave the ground, then the rear wheels will be in the air notably longer than the front, due to the fact that virtually all Haldex VWs/Audis are much heavier at the front end (usually due to the heavy VR6 engine). Secondly, I have never, throughout my entire professional life, ever come across your scenario (one axle in the air) to attempt to describe the traits of four wheel drive systems! However, using this scenario, if the front wheels are airborne, and the rears are on dry tarmac, and the Haldex clutch is fully engaged, then the transmission of torque between the front and rear axles is still 50:50. The momentary fact that the front axle is not transmitting the tractive force to the tarmac still does not alter the torque split. Remember, the front axle is driven all the time, and Haldex can not "turn off" or disengage the drive to the front axle.
- Your final comment about "specialists", and the 100% transfer to the rear axle. They are best described as mistaken enthusiasts. They are obviously confusing the clear fact that the Haldex is simply a clutch device, and not a differential. Yes, the Haldex can lock the clutch at a 100% rate, but that simply gives a maximum torque split of 50:50. A Haldex equiped VW/Audi can only transmit upto a maximum of 50% of the 'drive' to the rear axle.
- If you happen to be in the UK (or wish to use Amazon or similar), can I suggest you read "Hillier's Fundamentals of Motor Vehicle Technology" (5th Ed, Book1) ISBN 0-7487-8082-3 (an academic text book), where you can better understand how automotive systems work (without having to rely on the various 'rumour stores' found on many web forums).
- Kind regards - -- Teutonic Tamer 10:19, 24 December 2007 (UTC)
I repeat my point of view. Haldex clutch locks fully. If all wheels are on the ground and spinning (let's say in snow) the torque transfer can be 50:50 indeed. If front wheels are in snow and rear wheels are on a dry surface, the percentage of available engine torque applied to the front wheels is, let's assume, 20%; in this case the percentage of torque applied to the rear is 80%. In an extreme situation, where front axle has zero traction (front wheels are in the air - this is just an example, no matter how it is achieved) the front wheels receive 0% torque; rear wheels get all 100% of the torque the engine can deliver. Why? Because you cannot have torque in absence of a load.
You do state in the article that Torsen can transfer up to 80% of torque to the axle that has traction, why can't Haldex? Do you know why Torsen can't do 100%?
here is some reading: http://www.tyresmoke.net/ubbthreads/printthread.php/Board/VWR/main/402861/type/post
P.S. The torque transfer is not the only issue you are mistaken about. I suggest you to think about it.
- Hi Zello
- I thought we had already agreed that the Haldex locks fully? !! <confused>
- Your comment about the snow is interesting, particularly the bit where both fronts are spinning in the snow and the rears have traction. However, the fact that the front tyres can not transmit the applied torque to the road surface (when the rears can) still does not escape the fundamental fact that when the Haldex locks fully, exactly 50% of the available torque goes to the front axle, and the same to the rear. This simply means that the rears are able to "use" 100% of the available torque. That is the point you are getting confused on.
- The Torsen vs Haldex - firstly, Haldex can NOT transmit more than 50% of the torque to the front axle simply because it is NOT a differential. Regarding the distribution in the Torsen, and the lack of 100% to one axle - well, the reason is quite simple. The original Torsen diffs were specifically engineered to allow a 25% deviation and physically limit torque transfer upto a max of 75% (ie, 25:75 or 75:25) (this was because they get effing hot when working at extremes of distribution). This original 75% limit was probably specified due to the basic mineral oil based gearbox lubes. The current "standard" Torsens (ie, those with the default 50:50 bias) can now go upto 80:20 either end, which is why Audi specify a high grade fully synthetic gear lube. The very latest assymetric Torsen (used on the current RS4) has a slightly increased threshold, but because the "defualt" bias is 40:60 front to rear, that simply means a maximum of 0:100 front to rear, or 80:20 at the other extreme. The Torsen unit is physically quite small (would fit in the palm of your hand), and having to cope with large torque outputs - and working as a "true" differential, put it under a great deal of mechanical stress. AFAIK, no Torsen unit has failed - yet, but these new assymetric ones will be a new test for the future.
- That TyreSmoke article is interesting, but it basically mirrors what I have been saying.
- So what else do you think I'm mistaken with ???
- I've fairly thick skin, so I don't mind a bit of "enthusiastic" discussion ;-) Regards, -- Teutonic Tamer 23:10, 28 December 2007 (UTC)
Have you read the "tyresmoke" article at all? Do you know what torque is? Have you ever heard about 3:1 and 4:1 torque balance ratio of Torsens? Do you know that torsen mechanically and mathematically cannot deliver 100% of torque to an axle? Do you know what and why happens when you raise one wheel of a torsen-based Audi Quattro in the air?
I wanted to give you a link to a good article about Torsens, but no, this is just another marketing stuff, written by "mistaken enthusiasts" wanting to "sell things".
Yes, Haldex locks fully, we have agreed on that.
Hi sorry to butt in as have enjoyed all the information given here as to have a tiguan ... maybe this post may describe some actual results of driving a Haldex, see top post.. http://vagdrivers.net/forums/index.php?s=3181c430c4f601c798a1f067f81d6690&showtopic=11814&st=0&p=99238&#entry99238 —Preceding unsigned comment added by 184.108.40.206 (talk) 08:31, 4 June 2009 (UTC)
4WD vs AWD?
- Yes, it's AWD rather than 4WD. It should be renamed, both the article title and the links within it. Andy Dingley (talk) 15:28, 28 September 2010 (UTC)
development Torque Vectoring System
I added a citation needed tag to the statement that the torque vectoring system is developed by audi. Several sources on the web claim this is a magna system. — Preceding unsigned comment added by 220.127.116.11 (talk) 15:18, 19 December 2012 (UTC)
Requested move 30 August 2016
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