How to estimate max wtq from 60-100 time
03-17-2011, 05:06 PM
#1
How to estimate max wtq from 60-100 time
alright im goin to show you guys how you can estimate max torque from your hpt 60-100 time using kinematics.
this will be for the ss/tc ppl with the 3.82 final drive. i will be giving alot of constants as 99% of the ss/tc have similar wheel diameter, weight, and aerodynamic drag. so heres the breakdown thats used in the equations:
---curb weight of an ss/tc is 2926 lbs. with one passenger (180 lbs) it is 3106 and two passengers is 3286 pounds. this equates to 1410 kg (1 pass) and 1492 kg (2 pass)
---wheel diameter of a 225/40-18 tire is 25.1 inches. counting for a 3% loss due to weight being on the tire it is 24.3 inches. that makes the effective radius 0.309 m
---the equation for drag is 0.5*drag coefficient*frontal area*air density*volume^2
drag coefficient of an ss is 0.324, frontal area is 2.15 m^2, air density varies but averages around 1.21 kg/m^3 (close enough for most elevations and temps) so the equation we have is 0.421v^2
---the equation for rolling resistance is rolling friction coefficient*gravity*mass of object. the coefficient of rubber to asphalt is 0.015, gravity is 9.81 m/s^2, and mass of a cobalt ss/tc is noted above
now to the nitty gritty:
force = mass*acceleration
-to find acceleration you take the change in velocity (17.9 m/s for 60-100) and divide your 60-100 time. for example 5 seconds is 17.9/5 = 3.58 m/s^2
-multiply that acceleration by your mass noted above to find the force the car must exert to achieve that 60-100 time, for this example say one passenger so 1410*3.58=5048N
-this force is engine thrust - aerodynamic drag - rolling drag
-to get just engine thrust we must add aerodynamic drag + rolling drag
-average aerodynamic drag is 537N in general and rolling drag is 221N
-so engine thrust for our example is 5048+537+221=5806N
-now to convert engine thrust to engine torque we must divide the gear ratios and multiply by the effective wheel radius to isolate the torque of the engine itself
-60-100 are done in 3rd gear which is a ratio of 1.18 for the F35 transmission, final drive is 3.82, while effective radius is 0.309
-5806/3.82/1.18*0.309=398 Newton-meters
-to convert newton meters to pound-feet of torque we must divide by 1.356
-398/1.356=293.5 foot pounds of torque
-up to this point we have a very accurate value for the AVERAGE torque from 60-100 miles per hour, 60-100 mph is from 3740-6230 rpm for a LNF.
-obviously the peak number will be higher than the average but by how much varies with each engine
-i have found the general rule of thumb is with stock turbo lnf, the average is 85% of the peak torque as the torque curve is very flat. for bigger turbos with more lag but more power up top, i would say this number ranges anywhere from 70% to 85% depending on tuning, turbo size, and other mods.
-so for this example of 60-100 time of 5 seconds flat, in a stock turbo lnf, it is a good estimate that the wtq that you would find on a dyno is close to 293.5/0.85= 345 ft/lbs of torque. WALAAAAH!
this is what happens when you are really bored and know a thing or two about physics. anyone that uses their own 60-100 time, post what they calculated it to be. this should account for 99% of ss/tc with the 3.82 final drive
this will be for the ss/tc ppl with the 3.82 final drive. i will be giving alot of constants as 99% of the ss/tc have similar wheel diameter, weight, and aerodynamic drag. so heres the breakdown thats used in the equations:
---curb weight of an ss/tc is 2926 lbs. with one passenger (180 lbs) it is 3106 and two passengers is 3286 pounds. this equates to 1410 kg (1 pass) and 1492 kg (2 pass)
---wheel diameter of a 225/40-18 tire is 25.1 inches. counting for a 3% loss due to weight being on the tire it is 24.3 inches. that makes the effective radius 0.309 m
---the equation for drag is 0.5*drag coefficient*frontal area*air density*volume^2
drag coefficient of an ss is 0.324, frontal area is 2.15 m^2, air density varies but averages around 1.21 kg/m^3 (close enough for most elevations and temps) so the equation we have is 0.421v^2
---the equation for rolling resistance is rolling friction coefficient*gravity*mass of object. the coefficient of rubber to asphalt is 0.015, gravity is 9.81 m/s^2, and mass of a cobalt ss/tc is noted above
now to the nitty gritty:
force = mass*acceleration
-to find acceleration you take the change in velocity (17.9 m/s for 60-100) and divide your 60-100 time. for example 5 seconds is 17.9/5 = 3.58 m/s^2
-multiply that acceleration by your mass noted above to find the force the car must exert to achieve that 60-100 time, for this example say one passenger so 1410*3.58=5048N
-this force is engine thrust - aerodynamic drag - rolling drag
-to get just engine thrust we must add aerodynamic drag + rolling drag
-average aerodynamic drag is 537N in general and rolling drag is 221N
-so engine thrust for our example is 5048+537+221=5806N
-now to convert engine thrust to engine torque we must divide the gear ratios and multiply by the effective wheel radius to isolate the torque of the engine itself
-60-100 are done in 3rd gear which is a ratio of 1.18 for the F35 transmission, final drive is 3.82, while effective radius is 0.309
-5806/3.82/1.18*0.309=398 Newton-meters
-to convert newton meters to pound-feet of torque we must divide by 1.356
-398/1.356=293.5 foot pounds of torque
-up to this point we have a very accurate value for the AVERAGE torque from 60-100 miles per hour, 60-100 mph is from 3740-6230 rpm for a LNF.
-obviously the peak number will be higher than the average but by how much varies with each engine
-i have found the general rule of thumb is with stock turbo lnf, the average is 85% of the peak torque as the torque curve is very flat. for bigger turbos with more lag but more power up top, i would say this number ranges anywhere from 70% to 85% depending on tuning, turbo size, and other mods.
-so for this example of 60-100 time of 5 seconds flat, in a stock turbo lnf, it is a good estimate that the wtq that you would find on a dyno is close to 293.5/0.85= 345 ft/lbs of torque. WALAAAAH!
this is what happens when you are really bored and know a thing or two about physics. anyone that uses their own 60-100 time, post what they calculated it to be. this should account for 99% of ss/tc with the 3.82 final drive
03-18-2011, 01:52 PM
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03-18-2011, 02:06 PM
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WHAT!? I'm dumb-founded at those equations. . .so can i get something a lil' more simple for us highschool grads with no excessive math skills? lol
03-18-2011, 04:51 PM
#8
yes a dyno would be better but if someone wants a good estimate RIGHT NOW for FREE then try this out. anybody calculate theirs yet?
oh and for ppl that dont feel like going step by step, i combined all the constants so you can do it quickly. take your weight in kg and divide your 60-100 time then add 42.346 and last multiply that by 1.0646.
for example: (1492/4.26 + 42.346)*1.0646=418 ft. lbs
oh and for ppl that dont feel like going step by step, i combined all the constants so you can do it quickly. take your weight in kg and divide your 60-100 time then add 42.346 and last multiply that by 1.0646.
for example: (1492/4.26 + 42.346)*1.0646=418 ft. lbs
03-21-2011, 09:10 PM
#14
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I would like to see this math on someone's car compared to their actual dyno. Just out of curiosity.
I'm switching to E85 soon which will require a new dyno and I'll see if it adds up.
I'm switching to E85 soon which will require a new dyno and I'll see if it adds up.
03-22-2011, 01:17 AM
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4.2 sec 60-100? With two passengers? Holy sheeyatt batman! That would be under 4 sec with driver only....well over 400 WHP. I have dynoed at 308 HP and 360 ft lbs (peak Torque is not in the 60-100 range). 60-100 in around 6 sec. BTW..stock is 8.2 sec with 240 Ft lbs (peak torque is in 60-100 range).
Last edited by ronn; 03-22-2011 at 02:00 AM.
03-22-2011, 01:59 AM
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Seems fairly accurate, but a tad low. Stock is 60-100 8.2 sec. Using your math, that's 228 Wheel Torque. It's closer to 240 Ft lbs (flat torque curve stock).
03-22-2011, 12:40 PM
#19
if your using that 8.2 sec 60-100 from a magazine or something you have to remember there was a shift in that pull. so it would actually be a little faster making about 240 
and sundevil i would expect about 328 from a catless dp and 20 psi tune. it was prob hot as hell when u did it too
and sundevil i would expect about 328 from a catless dp and 20 psi tune. it was prob hot as hell when u did it too
03-22-2011, 12:52 PM
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it does pull all the way to 100 yes but with two passengers that weight 215 it was 10.4 and that was just with a stopwatch i know our speedoes are slow
03-22-2011, 01:14 PM
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ya i know it goes past 100 but since i only have to go to 100 it dont really matter