Sisteme AWD, care e cel mai bun?

Adica exact ceea ce faceau ceilalti, numai ca aici Subaru este din nou inaintea tuturor. Ceea ce "uita" ei sa spuna este ca fragmentul al doilea este valabil doar cu cutie automata (ma rog, este o steluta acolo). Daca in primul caz critica concurenta, in cel de-al doilea caz aduce elogii unui sistem care nu functioneaza decat cu cutie automata, asta in timp ce concurenta ofera acelasi lucru cu ambele transmisii. Adica noi suntem mai tari decat oricine ca oferim ESP pe transmisii automate, in timp ce ceilalti sunt slabi ca folosesc electronica. Pai ce, ESP-ul de pe Subaru e mecanic? Cum ramane cu AWD-ul concuretei compatibil cu cutiile manuale?
Pana la urma intelegi cat de usor poti fi pacalit de marketing?

Pai daca tu pui intrebarea asta...si tzie itzi este neclara functzionarea diferentzia.lelor. Sorry to say it.

It's the poor man's LSD. (Some people dislike my characterization of it, as it can be very finely tuned, but it's still very cheap to implement and has some reliability problems.)

A simple braking trick helps though. (Note, the EDL system discussed above, actually works pretty well with a torsen diff. It activates rarely, but allows for much greater torque transfer when it does.)

It is capable of going from an open differential to say 60% locked differential condition absolutely instantly (zero lag), so many would argue that it's about as close to perfect as it gets for performance driving. There are no clutches to wear out. Several AWD systems like the Quattro system put a torsen diff in the center of the car to control slip between front and rear wheels. This system does not have the problem the VC does with the ABS. A torsen diff only distributes torque when it's under load. When it's freewheeling all the wheels can turn at different speeds as the ABS may desire.
(Note: It looks like the current Audi Quattro system only uses the torsen diff in the center, and some other LSD or EDL at the axles. )

The disadvantages are that the mechanism is a bit heavier, more mechanically complicated thus expensive, and can't be tuned or adjusted dynamically. Plus, it reacts so fast and is so even handed that it literally makes a torsen diff equipped AWD car boring when you'd really like to hang it all out. If you want to go 100mph in the snow nothing beats Quattro. If you want to slide sideways or spin and recover, forget it. I've heard that VW's new 4motion system is much more fun because of its electronic control.

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.

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...

Nu despre asta vorbeam? Torsen este foarte scump, este clar. Poate LSD-ul de pe Subaru face 90% din torsen la bani mai putin, insa cel mai performant tot quattro ramane...

Valentin, ce inseamna performant?

iata ca Legacy GT cu 250CP este mai rapid decat A4 quattro cu 255CP? este intr-adevar mai sigur pentru ca are ESP...

Subaru brings rally car technology to the street
by Jim Kerr
Photos by Grant Yoxon

Some of the technology that makes Subaru all wheel drive vehicles handle so well comes from their many years of World Rally Car experience. Subaru has excelled in this form of racing and recently offered some of their hot technology to us in the form of the WRX STi. This rally-inspired street car features a 300 horsepower intercooled, turbocharged four cylinder engine, a six speed manual transmission and dramatic styling. Another important feature of this quick and fun to drive sports car is its DCCD driveline.

DCCD stands for Driver Controlled Centre Differential. The WRX STi used three differentials. The front axle is a cam type limited slip unit. The rear axle differential is a mechanical limited slip unit, and the third differential is located at the rear of the manual transmission and can be controlled by the driver. This centre differential can automatically vary the ratio of the power split between the front and the rear axles, or the split can be set by the driver with a switch on the console.

Subaru WRX STi

Subaru WRX STi

Subaru WRX STi

Subaru WRX STi

Subaru WRX STi

Subaru WRX STi
Click image to enlarge
With the DCCD selector switch set in Auto mode, the torque split between the front and rear is 65% front and 35% rear. This torque split ratio is a result of the gear ratio of the planetary gear set that makes up the centre differential. Because of the torque split in the differential and the balance of the car, the Subaru WRX STi tends to oversteer. According to Subaru, this car was "built for people who want to drive".

A manual selector switch on the console enables the driver to control the torque split. Set it at 100% and the 100 indicator on the dash display lights up. This represents fully locked which is actually a 50/50 torque split in the centre differential. Several other torque splits can be selected for different road conditions or car balance conditions the driver wishes, all the way down to 0% or completely unlocked.

Inside the DCCD housing, two cam plates with ramps between them and small balls in the ramps are located at the rear of the differential. The Subaru system energizes a computer-controlled magnetic clutch to vary the torque split. When the coil assembly is energized, one of the cam plates is slowed, causing the balls to roll up the ramps, forcing the planetary gear set forward. A multi-plate limited-slip clutch at the front end of the planetary gear set is forced together by the end thrust inside the unit, locking the parts of the planetary gear set together. With the planetary gear set locked, the torque split is 50% to the front and 50% to the rear.

Several inputs enable the computer to calculate the amount of torque split desired and apply the clutch. The main sensor is a lateral G sensor located in the centre of the car. Lateral acceleration or the cornering force of the car is balanced by varying the torque split. The throttle position is also monitored so the differential can be locked during acceleration. The stop light switch sends a signal to unlock the differential so the four channel ABS braking is optimized.

A parking brake switch signals the computer to unlock the differential, enabling drivers to do "handbrake turns" during rally-type driving. Finally, a rear differential temperature sensor is used so that if the rear differential overheats, the centre differential will unlock. During extended periods of driving aggressively with the centre differential locked, the load on the drivetrain can cause differentials to overheat, so the rear axle temperature is monitored as a safety factor.

Let's look at how the system responds automatically if the driver is aggressively navigating a hairpin corner. As the car enters the corner, the brakes are applied and the differential unlocks for optimum braking with the ABS system. As the driver turns into the corner, the differential provides a 65/35% front to rear torque split for optimum traction and continues to vary the torque split until the gripping point of the corner is reached. Then the differential locks up in response to throttle opening for straight line stability and acceleration.

DCCD is Subaru's most performance-oriented All-Wheel Drive system. It provides optimum traction, straight-line stability and enables the driver to adjust the car so it can match both the road conditions and the driver's needs. Rally inspired systems like this make the WRX STi a fun, responsive car to drive.

Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC).

5.7sec 0-60mph este timpul obtinut de car&driver si de motor trend. In USA f. putini producatori pun acceleratiile pe site-urile lor.

chiar si ultima generatie de quattro nu mi se pare chiar asa de convingatoare. sa luam etalonul BMW ( care nu prea e batut de nimeni la rapiditatea masinilor sale la un nr. x de CP):

de ex. RS4 cu 418CP accelereaza numai marginal mai rapid fata de BMW M3 cu numai 333CP. Legacy GT accelereaza la fel de rapid ca un BMW 330i cu 255CP...

parerea mea e ca la banii dati Subaru ofera performante pe care la Audi le iei cu 3-5K mai mult ( nu neg ca banii nu se merita, prob ca da pentru ca sunt si elementele de comfort si rafinament unde indiscutabil Audi "delivers").

valentin , de curiozitate , ai condus un subaru vreodata ?

si TDI urile sunt tractoare ... tzaca tzaca tzaca iti spune ceva ?

chiar si ultima generatie de quattro nu mi se pare chiar asa de convingatoare.

Mai inainte spuneai ca scoate 5.9, acum ai gasit un test in care scoate mai putin? Cand compar timpii 0-100 eu ma iau dupa datele anuntate de producator.

George nu il ai tu ? FLAINE ? Un Subaru STI alb, filmul parea francez ? A aparut prin Februarie 2005 ? Un Sti alb mergind la munte si cobora FOARTE repede un drum acoperit cu zapada ?

Cea mai spectaculoasa si cea mai puternica clasa de raliu a tuturor timpurilor si cel mai de seama castigator al ei:

Este de departe cel mai invidiat sistem AWD care a existat vreodata.

dar este singurul modele de la Subaru care este capabil de asa ceva (sa aiba tractziune numai pe o roata si sa avanseze)

Un film care nu are nici o insemnatate pentru discutia de aici. Acel film nu face decat sa arater maiestria unor piloti in controlarea unei masini pe zapada, dar este un film frumos, fara indoiala.

Despre sistemele proactive:
Asta este o alta inventie a marketingului. Practic nu exista nici un sistem care sa anticipeze cu adevarat momentul cand se pierde aderenta (la fel ca la ABS)

@f1anatic: parerea ta reprezinta un exemplu de ipocrizie transferata de la marca adulata, la tine. Ieri BMW-ul (Haldex-ul si, probabil, multi altii) erau niste fraieri care nu erau in stare sa faca un sistem AWD fara electronica si azi, dintr-o data, Subaru realizeaza ceva magnific, o adevarata opera de arta asistata electonic. You got that right champ. Cuvintzul magic l-ai spus chiar tu ASISTAT ELECTRONIC. Nu este EDL, nu este bazat pe electronica, nu necesita ABS-ul,...este ajutata de electronica. E o mica diferentza
Imi insiri o serie de cuvinte care habar n-ai ce reprezinta, amesteci diferite tipuri de diferentiale intre ele si ma contrazici la fiecare pas si total aiurea. Nu exista post de-al tau in care sa nu aduci vorba de masina saracului, BMW si Audi rulz, tractoare (cum le-ai adus in discutie vis-a-vis de Legacy GT, nu stiu), sisteme fraiere etc.
Acestea sunt ultimele mele cuvinte care iti sunt adresate tie pe acest forum... pentru multa vreme de acum inainte. Interventia mea s-a vrut oportuna pentru a va mai domoli elanul "fanatic" de a considera celelalte sisteme AWD depasite de capodopera Subaru.

Valentin...observ la tine...acelasi caracter de primadona de la baietzii cu BMW: Tu ai "opera de arta" , o "bijuterie" de AWD si asa mai departe.

Mama mama...si eu care credeam ca era Lancia Delta S4 care avea 450 de CP... Si dupa ce au fost citeva accidente soldate cu mortzi, s-au schimbat regulile Grupei B de raliuri. Si interesant...AUDI s-au retras dupa aceea ...si continua sa nu ia parte in Campionatul de Raliuri...si dupa 20 de ani. Cu asa meserie de AWD.

Imi povestesti cu atita zel despre AUDI cistingind Le Mans. Ce legatura are asta cu tehnologia masinilor de strada ? Ah...putem sa le legam cind vorbim despre FSI. In rest esti pe cimp onarabilule...Masinile alea RS-8 nu au AWD.

Ai ocolit subiectul STi cu multa agilitate...

Dar din cite am intzeles nu toate AWD-urile puse de VAG "are created equal". Din cite se pare cel de pe A4 nu e cine stie ce de capul lui. Iar cind il comparam cu Subaru ...brusc nu mai este "fair play" in opinia ta pt. ca comparam ce au ei mai bun cu ceva - si aici incepi sa spui cite ceva despre generatziile quattro - una peste alta trebuie sa ne raportam la S4 si RS4.

Cind spun ca nu am incredere in electronica...nu inseamna sa traiesc ca Amish. Dar nici nu vreau sa aud de EDL. Am diferentziale mecanice al caror miscare/angrenare etc este decisa de catre silicon. Fine. Si senzori de la rotzi am suficientzi de multzi chiar si pe cutia manuala. Pentru mine electronica nu este solutzia la tot ce misca. Tzin ritmul cu ea...dar prefer anumite chestii sa ramina mai clasice cel putzin o bucata de vreme pina se dovedesc a fi fiabile si viabile.

Un film pe care eu/George nici nu l-am pus. Iar acum tu te asteptzi ca noi sa cadem in extaz la link-ul (filmul) pus de tine ? Hai sa fim seriosi... Potzi sa itzi folosesti propriul citat - ca raspuns al meu. Sau ca sa pun sumarul...Nu ma intereseaza...nu imi dovedeste nimic.

Subaru sint ipocritzi cind comenteaza asupra sistemelor altora. Si ulterior ajungi la consensul ca nici un sistem nu este cu adevarat pro-active.

Dar nu te-ai sfiit sa spui asta de-abia cind am aratat ca si Subaru "pretinde" la fel. Cit a fost discutzia despre X-Drive-ul de la BMW nu ai facut aceasta afirmatzie. Double standards ? De ce nu spui pe sleau ca de fapt totzi sint ipocritzi si isi etaleaza produsele sa para mina lui Dumnezeu...iar concurentza e pe malul alalalt ? Well ?

Iar despre referintzele la masina saracului - ce oi vrea sa spun. Cind e vorba de masinile nemtzesti...NU se compara. In astea nemtzesti stai in lux, in sigurantza, in comfort, motoarele sint o bijuterie, sistemele AWD sint invidiate de toata lumea. E clar ca daca nu mi-am cumparat...sint sarac si conduc o masina corespunzatoare. Credeam ca ai citit ultimul thread Subaru vs. Toata viatza am sa-mi doresc sa pipai un DSG ? Remember ? Fii tu fericit cu Torsen... e tot ce imi doresc...pt. mine...it is the little things in life that matter !

Pa si La Multzi Ani ! Si be safe cu Torsen AWD !