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 19 2005, 02:41 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 |
Originally Posted by RobY
There are many types of Subaru AWD systems the most advanced being the 5eat and the STI DCCD which are offshoots of the WRC Rally car. Using a planetary gear center differential slip limited by electromagnetic cam locking clutch packs. The STI having torque sensing differentials in the axles in addition. It is in fact the most advanced and performance oriented system currently available. This system allows individual wheel movement while using steering and yaw sensor to proportion torque front or rear to where it sees fit. In the STI the bias is variable and driver definable through a selector switch. The torque proportion is done through true electronicly variable limited slip differentials and works at all speeds. This is not to be confused with Haldex which is merely a coupling see link below... How does it compare to the current generation quattro AWD? There is really no comparison the above system is better in almost every way. It works completely unloaded the electromagnetic cam locking clutch pack lsd has locking capability. Whereas the quattro has one 2.3:1 bias ratio torsens. If you ever get your front wheels stuck in a low tractive condition the quattro torsens can send a maximum of 2.3 times the force that cause the front wheels to spin. If your front wheels spin at 10lb/ft of torque because you are on ice the maximum your rears will get is 23 lb/ft. The rest of the power will leak out through the front wheels that are stuck. If one set of wheels become completely unloaded the torsens wont work all the power will leak out the unloaded wheels. The newest Quattro system uses brakeforce psudo differentials that simply use the brakes and ABS system to apply brake force to bias power side to side. seems like a great idea but unfortunately these brakeforce psudo diffs only work under 25mph. If you use it too much you will overheat the brakes. Performance wise it can bias power based on computer controlled attributes and is not set to a preset torsens bias ratio. The 5mt subaru is continuous AWD with a 50:50 torque distribution slip limited by a viscous coupling. Brutally effective as it allows each set of wheels to receive an absolute torque split of 50:50 while still allowing each wheel to move independently of each other. Under normal conditions the viscous coupling is stationary and does no work. If one wheel becomes unloaded slip is limited by a viscous coupling differential that works in any condition even if the wheels are completely unloaded. This system works through differentials slip limited by viscous couplings and works at all speeds. This system is NOT to be confused with a much simpler viscous coupling it is very diffrent. Whereas primary torque transfer in a viscous coupling is through viscous fluid. The primary torque transfer in the Subaru Viscous Copling Locking Differential System is through mechanical differentials whose slip is limited BY viscous differentials. Compared to quattro it has a disadvantage because it does not have variable torque distribution through a center torsens. However this system like the above sytem has viscous locking LSD capability and can work with the wheels completely unloaded. Side to side bias in performance models work through real viscous differentials and will work at any speed and completely unloaded. The lower line automatic transmission subarus use a haldex type coupling. Ive commented on this topic before.... http://www.legacygt.com/forums/show...p?t=8474&page=2 -------------------- Schumi drive it like you stole it !
2005 Subaru Legacy GT ; 2009 Subaru Forester XP ; 2014 Jeep Grand Cherokee |
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