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 22 2005, 12:47 AM
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specialist Group: Membri Posts: 4.583 Joined: 30-May 04 From: Honda World Member No.: 26.577 |
cred ca toti producatorii in discutie folosesc termenul de "pro-active' in mod liberal (adica exagereaza in mod intentionat si in scop publicitar). daca Torsen este "pro-active" in comparatie cu vasco-cuplajul si EDL ( adica franarea electronica a rotilor care patineaza) este "reactive" in comparatie cu LSD ( care este din capul locului si mecanic "pro-active").
pe de alta parte un diferential deschis cu un sistem electronic de franare nu duce la pierderea 100% a cuplului pe roata franata. diferentialele deschise trebuie vazute ca un dispozitiv care directioneaza cuplul catre calea de minima rezistenta ( deci daca o roata patineaza rezultatul va fi ca acea roata primeste, in mod ineficient, mai mult cuplu in timp ce roata care are tractiune primeste mai putin). Cu EDL in momentul in care o roata este franata cealalta ( care are tractiune) este vazuta de catre dif deschis ca fiiind calea de minima rezistenta si cuplu va fi indreptat unde trebuie. deci EDL e o idee excelenta dar ca mod de a pune cuplul motor pe asfalt este mai prost decat un LSD. de ex. daca normal cele 2 roti de pe o punte primesc cuplul pe puntea respectiva 50-50, odata ce una patineaza si este franata cuplul este indreptat preferential catre roata cu tractiune, ceea ce se pierde fiind proportional cu franarea respectiva. apoi aceasta franare este tranzitorie si imparteala 50-50 revine imediat ce roata care a patinat recapata tractiunea. stiu ca C&D a facut un teste interesant in comparo-ul STI vs. Evo masurand acceleratia pe un traseu in care rotile de pe o parte erau pe nisip in timp ce celelate erau pe asfalt. STI a accelerat semnificativ mai repede fata de Evo care nu are LSD pe puntea fata. daca ai pune un A4 in aceasta situatie cred ca performanta ar fi mult mai slaba tinand cont ca ar merge cu rotile de pe o parte franate si o groaza de cuplu ar fi pur si simplu "ars" in franele de pe partea respectiva. in concluzie: Torsen al Quattro permite o distributie mai buna a cuplului fata-spate in timp ce STI ( si Legacy GT) permite o distributie mai buna a cuplului stanga dreapta. am observat de asemenea ca Legacy 3.0R are o acceleratie mult mai slaba (6.9sec) fata de Legacy GT (5.7sec 0-60mph / 5.9sec 0-100km/h). o parte poate fi atribuita cuplului mai mare, iar o alta parte prob. legata de ratiile cutiei de viteze care este in 6 trepte la 3.0R si in 5 la GT. George stii daca 3.0R are si el LSD pe spate? daca nu asta ar mai putea explica o parte din diferenta dintre cele 2. oricum un Legacy GT limited ( cu aprox aceeasi greutate si aceeasi putere) este semnificativ mai rapid ( 5.9sec) decat un A4 quattro 3.2l FSI (255CP) = 6.4 sec si decat un BMW 330xi= 6.4 sec care sunt muuult mai scumpe. e marginal mai putin manevrabil decat un 330xi dar par cu A4-le similar motorizat... -------------------- Civic Si 2007 2.0l DOHC iVTEC
Acura TL 2006 3.2l SOHC VTEC |
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