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*To*: quattro@coimbra.ans.net*Subject*: More Torsen stuff - KISS of Trg*From*: QSHIPQ <QSHIPQ@aol.com>*Date*: Wed, 18 Mar 1998 15:47:16 EST*Sender*: owner-quattro@coimbra.ans.net

Now that the KISS theory is out the window, a look at some basic assumptions to discussions of Trg and Tshift. Specifically, looking at the difference between Trg and Engine Torque. My original motivation for this exercise was to look for optimal shift points, but decided to add the Trg and the Tshift in for the heck of it. Very interesting results. For all our prior Tshift equations here, we assumed Trg = Engine Torque. Well, technically that is ONLY correct, when you have a Transmission Ratio (not final drive) of 1:1. That would be 4th gear to most audi 5spd Transmissions. Torque to Drive axles (or in this case Trg) is the Product of Flywheel Torque and Gear ratio. A Gear Ratio is specifically a Torque multiplier. So, if we have 200lb/ft of torque at the flywheel and a 2.125 Gear Ratio in second gear, Trg = 200 * 2.125 = 425 lb/ft. So, with a 78/22/22/78 Center Torsen, the Tshift is <(Tmax - Tmin) * .01 * torque> or simply (78 - 22) * .01 * Trg = .56 * 425 = 238lb/ft. Taking some of Dave E.'s power output numbers to a 20vt Urq, I find that the Tshift is most significant in the first couple gears and less so as you progress. For Example: Car = 20vtq, Stock 217hp, 5spd trans codes (3B, APL,AUM, AOA,AUL) Trg 1st gear (@3.600) = 750lb/ft+ from 2000rpm>5500rpm Tshift 1st gear = 400lb/ft+ 2000rpm>5500rpm Trg Max = 821lb/ft @ 2000rpm Tshift Max = 485 lb/ft @2000rpm Trg 2nd gear (@2.125) = 400lb/ft+ from 2000rpm>6000rpm Tshift 2nd gear = 225lb/ft+ from 2000rpm>6000rpm Trg Max = 485 @ 2000rpm Tshift Max = 271 @ 2000rpm Trg 3rd gear (@1.360) = 235lb/ft+ from 1500>6600rpm Tshift 3rd gear = 150lb/ft+ from 2000rpm to 5500rpm Trg Max = 310 @ 2000rpm Tshift Max = 174 @ 2000 *Trg 4th gear (0.967) = 220lb/ft from 2000>5500rpm *Tshift 4th gear = 100lb/ft+ from 2000>6600rpm *Trg Max = 220 @ 2000rpm *Tshift Max = 123lb/ft @2000rpm *For KISS, this is the closest to what we've been using to date* Trg 5th gear (@.730) = 150lb/ft+ from 2000>5500rpm Tshift 5th gear = 85lb/ft+ from 2000>5500rpm Trg Max = 166lb/ft @ 2000rpm Tshift Max = 93lb/ft @ 2000rpm I just finished the program, but some interesting trends develop. One might say easily to shift up when you want to control Tshift. However, I do find that the torque flattens as you increase in gears (read less peak), so the tshift might be argued to be more significant in the higher gears depending on slip or traction. I'm not sure whether this matrix will help explain spider bites, but it does show some significant torque that is being shifted about in that center Torsen. Add to that some tweeks and the significance becomes monumental. I put the same trans GR above on a model of Dave E's RS2 Torque curve. Trg Max 1st Gear = 1087lb/ft @ 3000rpm, 627lb/ft second gear, and 411lb/ft in third. That's Tshift max of 609lb/ft,359lb/ft, and 230lb/ft respectively. Spider soup anyone? Scott Justusson QSHIPQ@aol.com

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