I've read many times in this board that Torsen in A4 will worsen understeer when the car is understeering by putting more torque/power to the front rather than the rear. How does that work? I thought Torsen will send the power to the wheel that grips and not the one that slips. Therefore it should send more power to the rear wheels.<p>I know that limited slip VC differentials WILL send more power to rear when understeering. Therefore, rather than lifting throtle when understeering, you actually step on it. And I thought this is how Torsen worked as well.<p>thanks,<br> john<p>p.s. - I've read the AWD article many, many times.<br>

They are usually talking about Torsen sucking for extreme understeer in a rally situation. They are not talking about understeer on an exit ramp where you just don't have the guts to pull on the wheel hard enough (since the wheels aren't actually losing grip yet). Understeer is when you have lost traction and your front end is going straight, failing to make the turn. It is not called understeer if you fail to make the turn but have not actually lost grip of the road in the process.<p>In a rally situation you know that there is not enough grip to make the turns in the mud without losing traction. Therefore you will begin to understeer big time. The wheels will be turned but you will be plowing straight. With a normal 4X4 diff., there won't be any traction control so power will be sent to the front wheels allowing them to spin wildly. This will help the wheels to grip at some mud and junk and maybe pull around the corner. If you have Torsen and power is only delivered to the wheels with torque, then you would only get power to the rear wheels. The rear wheels would continue to push and plow the front wheels which are not making an attempt to pull the car around the corner.<p>Basically, I think you need that wild spinning of the front wheels that kicks up all that dirt so that it can find something that might help to pull it around the corner. Ort maybe like a rocket, you are getting thrust by throwing all that weighty mud in the opposit direction of your desired turn ;-)<p>Well, how far off am I everyone?<p>Gordon Martin<br>98.5 2.8QMS (Santorin Blue)<p><br>

John,<p>You are right in that Torsen will in normal cornering conditions apply more torque to the rear wheels and allow oversteering force to come into effect. This is due to the fact that the front wheels are turning slightly faster than the rear wheels and Torsen senses more torque in the rear. Therefore in most cases, Torsen will balance the understeering effect of heavy A4 front end.<p>Now, here is my guess as to why in extream cornering conditions Torsen may cause more understeering.<p>During a hard cornering condition, the combination of weight load on the front tires and the friction load of turned wheels PLUS the loose rear end from oversteering (which Torsen started) may cause more torque resistance to appear on the front end. Torsen, sensing that the front now has a better grip, will apply more power to the front wheels.<p>Now A4 will act like a front wheel drive car at the worst moment. The additional power to the front wheels will cause it to slide and now you have a bad understeer.<p>The interesting thing is that the best thing you can do at this moment is not to let up but to apply steady power so the Tosen will (sensing that the rear now has more grip) send power back to the rear. Of course you do not want to repeat the cycle!<p>How was that for a guess? Any comments?<br>

Rear wheel drive cars oversteer when you get on the gas (assuming you have enough power). Front wheel drive cars plow, or understeer in that same situation. It has to do with the slip angle of the front tires vs the slip angle of the rear tires. The pair with the grater slip cange determines which end will lose grip and "step out".