Shakal:
But what is reason why Q5 wasn't able to move forward ? Could be ESP turned off ? They wanted to show that when one axle doesn't have grip, the Torsen differential can´t shift torque to the other axle. I don't know it thats true, but in rl driving conditions (snow etc) I have good experiences both with quattro and xDrive.
Don't know, but here is a paragraph from AUDI on the Q5's Quattro:
The quattro® all-season four wheel drive technology distributes lasting power for all wheels of front and rear axles. Compared with an electronic center differential used on cars at the same level, the system is unique as it adopts a self-locking mechanical center differential. The mechanical structure can transmit the power to every wheel efficiently in a more reliable, direct and sensitive manner. The unique worm wheel-worm irreversible drive principle is utilized to realize different self-lock values and help Q5 cope with different off-road conditions easily. The system can distribute power to front and rear wheels based on a 40:60 torque split under normal conditions. With a rear torque bias, the driver will enjoy more fun during driving. In addition, the electronic differentials that are at the front and rear axles can control the wheels which lose traction to avoid loss of power. Even when three wheels lose traction, the quattro® system can still help Q5 get rid of the difficult situation.
What I do know is that in terms of grip on slippery roads specifically, the Torsen are better regarded than electronic differentials. The downside of the Torsen is that they are more expensive ( in the lower class models like A3 platform based AWD versions, AUDI uses a electronic based AWD instead, like the one the X3 uses) and can also be heavier. Also another downside is that in sport driving applications they are not as sporty in handling as say, viscous-coupling center differential or electronic differential, they tend to understeer more. So if you want AWD grip and safety in slippery situations they are great, but there is a trade off too for other appliations (price, sportcars, etc). But in the case of snow or mud for example, the Quattro on the Q5 is superior than a electronic Xdrive.
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