Sisteme AWD, care e cel mai bun? |
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Sisteme AWD, care e cel mai bun? |
Jun 4 2005, 02:14 PM
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specialist Group: Membri Posts: 4.583 Joined: 30-May 04 From: Honda World Member No.: 26.577 |
In 1980, Audi introduced the world to full-time all-wheel drive to volume-produced passenger cars. It was called quattro. Now in its fourth generation, Audi's quattro® permanent all-wheel drive directs power where and when it's needed. Under ideal conditions power is split 50/50 front to rear. But in extreme cases up to 67% of the engine's power can be directed to a single wheel. The benefits to the driver are safety, performance, power, and control in copious amounts. When cornering, all four wheels of a car must cover varying distances. The task of the center differential is to compensate for the differences between front and rear axles, and to distribute engine power between front and rear wheels. The center differential is the heart of Audi's permanent all-wheel driveline. Depending on the driving situation and road conditions, the system automatically regulates the distribution of power within milliseconds. This takes place by means of either (depending on model) the Torsen; differential, Haldex™ clutch, or hydraulic multi-plate clutch. Influencing parameters in the control process include engine speed and torque, wheel spreads, and longitudinal and lateral acceleration. The division of propulsive power between all four wheels is the basis of the excellent handling and safety of Audi models with quattro. The potential of this drive concept is further optimized by a series of control systems for brake and engine management: The Anti-lock Brake System (ABS) Electronic Brake-force Distribution (EBD) Electronic Differential Lock (EDL) Anti-Slip Regulation (ASR) All of the above assist in increasing traction when accelerating or braking. Furthermore, when cornering, the standard Electronic Stabilization Program (ESP) increases directional stability by comparing target and actual physical driving forces. The locking function of the center differential and the Electronic Differential Lock make sure that an Audi with quattro; all-wheel drive can still pull away with only one wheel able to transfer engine power to the road. Here's how it works: If one of the wheels on an axle loses grip and starts spinning, propulsive power has to be diverted to the other wheel by the axle's differential. Previously, a mechanical differential lock enabled this to take place. Now, the Electronic Differential Lock has replaced the mechanical lock, effectively transferring the excess power of the spinning wheel to the other wheels with better traction. On an Audi with quattro, if both wheels on an axle start spinning, the continuously controlled locking of the center differential ensures that most of the torque is transmitted to the other axle. In this way, propulsion is guaranteed in almost all situations. On an Audi with quattro, if both wheels on an axle start spinning, the continuously controlled locking of the center differential ensures that most ( adica 67%) of the torque is transmitted to the other axle. In this way, propulsion is guaranteed in almost all situations. dupa audiusa.com --------------------------------------------- cineva spunea ca diferenta intre 4motion si quattro este Haldex vs. Torsen. Se pare ca e inexact. Torsen este folosit pentru transmisia de la motoare dispuse longitudinal in timp ce Haldex este folosit pt. motoare dispuse transversal. -------------------- Civic Si 2007 2.0l DOHC iVTEC
Acura TL 2006 3.2l SOHC VTEC |
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Nov 21 2005, 04:47 PM
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Subaru Anti-Hero Group: Moderator Posts: 5.323 Joined: 13-May 04 From: F 1 World Member No.: 25.368 |
QUOTE(Mihnea57315) Va recomand acest link http://www.germancarfans.com/news.cfm/newsid/2050714.001
Si da este pro-active. Link-ul imi place...cu toate ca as putea face talente...ca vezi doamne...ghici unde era aceasta informatzie...pe un forum al GERMAN CAR FANS. Dar nu este PRO-ACTIVE QUOTE With BMW xDrive reacting within fractions of a second, the system offers enormous advantages also in terms of traction. When setting out on slippery or loose ground, for example, the time-lag between the loss of wheel grip on the surface and the re-distribution of drive forces to wheels with grip is only a few milliseconds.
O alta chestie care ma face circumspect este acest "few milliseconds". Ultima data cind am verificat...ii lua unei masini de Formula Unu sa schimbe o treapta de viteza circa 170 milliseconds. Formula Unu...cu tehnologie actuala nu de acum 15 ani. Asa ca...nu prea cred in redistribuirea puterii "in only a few milliseconds". O fi mai iute ca la Subaru cu cutie manuala (ca Subaru cu cutie auto cu VTD este mult mai dependenta de senzori si electromagnetzi) dar nici in citeva millisecunde nu poate schimba. Citind mai departe...nu reusesc sa gasesc nimic despre transferul stinga-dreapta al puterii. Ei spun ca sint senzori care detecteaza anumitzi parametri ...inainte de "wheel-spin" ceea ce potzi spune ca e pro-active...dar potzi spune ca este si "early detection". Comparind-o cu Acura, la RL pe uscat in curba...cuplul este mutat la rotata pe spate din exteriorul curbei...pt. a ajuta la tractziune. No wheel spin In continuare vad ca cu cit devin mai sofisticate aceste AWD, in general dispare cutia de viteza manuala si LSD-urile. Uite sumarul lor. (pagina 5) QUOTE BMW xDrive distributes drive power infinitely and fully variably between the front and rear axle. The system immediately recognises the need to change the distribution of engine power and responds extremely quickly, usually before a wheel even loses grip when driving onroad. As a result, xDrive feeds exactly the right drive power to each axle when, for example, taking a bend fast and dynamically, in the process significantly reducing both under- and oversteer.
The electronically controlled multiple-plate clutch in the power divider controls the flow of power to the front axle within milliseconds as a function of individual requirements. In extreme cases the front and rear axles are even fully disconnected from one another or rigidly, firmly connected to form one unit. Oh wow...axele sint deconectate una de alta...adica no traction...adica soferul devine pasager...la mila computerului. Asta...sincer mi-a zbirlit parul pe spate...de ajunsesem un arici Intervening electronically in the brakes, DSC provides the same function as a transverse wheel lock with forced distribution of power to the front and rear wheels: As soon as a wheel starts to spin without conveying power, the brakes cut in to slow the wheel down, the differential in the final drive thus feeding more power to the opposite wheel. EXEMPLU ! Ok si prima referintza la transfer lateral. Pai...tot la parerea initziala ca da...e avansat...citeste situatzia drumului mai repede si poate face ajustari mai repede...dar treaba asta cu pseudo - traction iar ma agita. Pai ma scuzi...asta nu este transfer lateral adevarat...Pur si simplu...daca creierul masinii a decis ca puntea fatza are nevoie de 30% ...iar puntea spate 70%...atunci daca roata dreapta spate dintr-o data pierde tractziunea...inseamna ca frina dreapta spate o frineaza...si deci contributzia ei de 35% (jumatate din 70% cuplu dedicat puntzii spate) este pierdut in neant...iar masina opereaza pe stinga fatza 15% dreapta fatza 15% stinga spate 35% dreapta spate 0% (frinata) Pai I am sorry...dar la Subaru pot trimite pina la 100% la oricare 2 rotzi. Diferentzialul pe fatza la Legacy este deschis (la fel ca la Audi, BMW) deci orice primeste puntea fatza se imparte fratzeste pe din 2. Dar in situatzia precizata mai sus...asa...incet cum este...ca doar masina saracului nu poate reactziona in a few milliseconds...ci in citeva minute....tot cuplul este transferat la roata ailalta. Dupa care sistemul tinde din nou spre 50%-50% fatza spate. stinga fatza 15% dreapta fatza 15% stinga spate 70% dreapta spate 0% (nefrinata, dar fara cuplu) Iar daca amestecam si STi-ul in povestea asta...cu diferential LSD si pe fatza...cu DCCD (driver controlled center differential - electronic by the way, sau automat de creierul masinii)...pot spune ca puterea poate fi trimisa 100% la o singura roata. Asa...cu tot visco-cuplajul asta antic de pe vremea lui Fuji-san si a fiului sau Subarumoto. Pe sosea uscata sau cu ceva ploaie ...as prefera BMW...pt ca fara LSD (centru, spate), pierderile prin transmisie sint mai mici. Dar cind e vorba de business adevarat cu zapada si ploaie serioasa...cred ca imi prefer masina de om de rind. -------------------- Schumi drive it like you stole it !
2005 Subaru Legacy GT ; 2009 Subaru Forester XP ; 2014 Jeep Grand Cherokee |
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