Stall - Torque Ratio
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From: Tallahassee, FL
Stall - Torque Ratio Example test bed Questions:
1. The stall torque ratio becomes 1:1 @ the stall rpm?
2. Does a 2.5str (example above) decrease until it reaches the 1:1 @ stall rpm, or is it a jump.... 2.5 str until 3500 stall speed?
3. If you make 300 ft lbs of torque @ 1000 rpms, do you multipy this by your str and derive @ your new torque? Meaning 750 ft lbs of torque?
Comparison:
1st launch - Say we were capable of brake stalling to 3500 rpm, which is the stall rpm. The launch is softer because of the 1:1 ratio, correct?
2nd launch - @ 2000 rpm where torque multiplation is greater (2.5).
4. The 2nd launch will shock the tires harder correct?
Help
Torque curve:
300 ft lbs of torque from 1000-3000rpm
350 ft lbs of torque from 3500-4000rpm
400 ft lbs of torque @ 4500
Info:
3500 TC + 2.5str
300 ft lbs of torque from 1000-3000rpm
350 ft lbs of torque from 3500-4000rpm
400 ft lbs of torque @ 4500
Info:
3500 TC + 2.5str
1. The stall torque ratio becomes 1:1 @ the stall rpm?
2. Does a 2.5str (example above) decrease until it reaches the 1:1 @ stall rpm, or is it a jump.... 2.5 str until 3500 stall speed?
3. If you make 300 ft lbs of torque @ 1000 rpms, do you multipy this by your str and derive @ your new torque? Meaning 750 ft lbs of torque?
Comparison:
1st launch - Say we were capable of brake stalling to 3500 rpm, which is the stall rpm. The launch is softer because of the 1:1 ratio, correct?
2nd launch - @ 2000 rpm where torque multiplation is greater (2.5).
4. The 2nd launch will shock the tires harder correct?
Help
Does anyone know the answers to my questions? 
the converter will multiply the torque 2.5 times when the engine is at 3500rpm and the trans is at 0 rpm. thats how its always been explained to me. once the rest of the drivetrain is moving, that multiplication dissappears and is gone by the 60ft mark.
Yank has good information on the website about the STR. Too much can be a bad thing. I had a converter with a 3.0 STR and it launched like a ****. Then, I replaced the TC with a 2.0 STR TC. The 2.0 pulled harder and longer but, had soft launches. The STR Multiplier is when the transmission input shaft is 0 rpm. So, if you have a 2.5 STR and the car is making 200 ft-lbs, you have 500ft-lbs with the transmission at 0 rpm. Notice on some dyno sheets, that with a stall converter, there is a big spike at the start of the pull. Once the car is moving, the STR will fall off quick. Typically, the higher the STR, the more inefficient the TC is over the rated stall speed. So, you will be giving up top end for starting grunt with the same stall speed.
Thread Starter
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From: Tallahassee, FL
Ok, so the str is @ 2.5 when input is at 0. As soon as the brake is released and you nail the gas, the ratio decreases to its 1:1 ratio. Now, you see your "real" power.
I'm wondering.... How much rpm travel is there inbetween s/t ratio of 2.5 - 1.1? None? How quickly does the str drop to its natural 1:1 ratio?
Thanks for the help guys.
I'll try contacting some of the TC vendors.
I'm wondering.... How much rpm travel is there inbetween s/t ratio of 2.5 - 1.1? None? How quickly does the str drop to its natural 1:1 ratio?
Thanks for the help guys.
I'll try contacting some of the TC vendors.
