[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index] TSD's, what's with Trg
If you look on Page 7 of the technical paper found at: http://www.mindspring.com/~audidudi/Torsen.htm We can look at a torsen used in a variety of chassis in terms of the Bias Ratio (the amount of torque the slower wheel/Driveshaft can generate in relation to the faster spinning wheel/driveshaft. I would argue, as you reduce Trg (total amount of engine torque) you reduce the likelyhood of the "unlikely" (see page 10), UNLESS the cf of your road diminishes greatly, and slip angle (rear) becomes high enough. That is to say, a 150hp car will transfer less total torque than Dave E.'s 300hp car. Here's the math (very carefully now, scotty:). Assuming dry road, full contact, slip angle only Trg for a 160 ft/lb car vs a 300 ft/lb car. 160 ft/lb, 75/25/25/75 torsen Center T1/T2 = 3:1 T1 = 120 T2 = 40 or T1 = 40 T2 = 120 Tshift = 80 lb/ft What does that mean here. Well that means up to 3 times the torque of the faster Driveshaft can be generated in the slower one. Assuming a dry track that is a "transfer" of 80lb/ft of torque to the opposite driveshaft. Not astounding. KISS, means that 120 ft/lbs can be at the front or the rear, 40 will always be generated to the opposing driveshaft. However, take a ride in Dave E.'s car the transfer becomes more significant. T1/T2 = 3:1 Torque = 300lb/ft T1 = 225 T2 = 75 Tshift = 150lb/ft Wow, that's almost the total Engine torque of the above example. For racing sake let's double that again, probably the high end of audis racing efforts to date. A full race spec audi with the same torsen. T1/T2 = 3:1 Torque = 600lb/ft T1 = 450 T2 = 150 Tshift = 300lb/ft Yikes sakes, batman. So, given a set torsen (all gen II and gen II audis are 75/25/25/75) split, the T-shift is insignificant as the traction cf is high and the HP low. But start messing with the higher HP/torque cars, "a handful" would be an understatement. However, the spider can bite just as hard if you take the cf (page 3) and lower it. Then even that insignificant 80lb/ft becomes a whole lot. Don't think so? Think of this a little further. The above assumes that you have ideal traction, i.e. no other factors affecting torque. But remember BR is figured in terms of traction/torque to the faster spinning wheel/driveshaft. So that means the 80 lb/ft of torque shift is actually LESS with a lower cf of the wheel to the ground. (Example: A spinning wheel on snow in the 160hp car can puts down 20lb/ft of torque, then the opposing wheel can only put down 3:1 times that or a 60lb/ft transfer). So, as cf decreases, so does the Tshift, but as you decrease that cf, Tshift becomes a more significant factor in potential for bite. So, indeed we can see that one can get bitten regardless of power, it's a cf issue as well. A turbo car has a higher potential for Tshift with a higher cf, but all audi center diffs have the Tshift issue to deal with. Plottable? Not sure. Might be interesting to look at. Scott Justusson QSHIPQ@aol.com '87 5ktqwRS2 '86 5ktqw '84 Urq
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