Dyno Dynamics - Shoot out modes
Discussion
Mignon said:
Stan you know how pedantic and OCD I am 
You're not calculating it right. The rolling circumference of the average brand new radial with about 8mm tread is only 97% of the calculated figure. I checked manufacturers catalogues listing actual rolling radii and worked out the equations. For a worn out tyre with only 1.6 mm of tread left it would be 95% so I take part worn as being 96% as the best possible average.
245 x 0.35 = 85.75 mm x 2 / 25.4 = 6.75" plus the 18" = 24.75" x 0.96 = 23.76"
The reason of course is that tyres compress under vehicle weight and the distance from the axle centre to the ground is less than the nominal inflated value. The tread then sort of shuffles round as it compresses and expands again as it goes over the top of the wheel and that's where much of the rolling friction comes from.
Dave,You're not calculating it right. The rolling circumference of the average brand new radial with about 8mm tread is only 97% of the calculated figure. I checked manufacturers catalogues listing actual rolling radii and worked out the equations. For a worn out tyre with only 1.6 mm of tread left it would be 95% so I take part worn as being 96% as the best possible average.
245 x 0.35 = 85.75 mm x 2 / 25.4 = 6.75" plus the 18" = 24.75" x 0.96 = 23.76"
The reason of course is that tyres compress under vehicle weight and the distance from the axle centre to the ground is less than the nominal inflated value. The tread then sort of shuffles round as it compresses and expands again as it goes over the top of the wheel and that's where much of the rolling friction comes from.
Edited by Mignon on Friday 16th November 20:39
Thanks for that bit of information. I do have tire diameter and tire radius as separate inputs to help if tire pressure was low or someone tighten the straps to much and "crushed" the tire.
Stan
Edited by Stan Weiss on Saturday 17th November 14:06
GregK2 said:
I get 1,530 kg/ 3380lbs from various places including
https://www.pistonheads.com/gassing/topic.asp?h=0&...
https://www.1addicts.com/forums/showthread.php?t=6...
If you want to guess your bhp then fine, guess your weight. If you want to know your bhp then get it weighed.https://www.pistonheads.com/gassing/topic.asp?h=0&...
https://www.1addicts.com/forums/showthread.php?t=6...
This is my simulation still at 3600# but with Dave's tire size. Notice there is a reduction in HP and torque from my first go around. Also if I have not stated it before my numbers are at the wheel.
Stan
Stan
Weight = 3600.0# Radius = 11.88 Inches
Rear Aero Rolling Rear W Accele Time Rate
RPM MPH Velocity Wheel dynamic Resist. Elapsed Horse ration Differ Rev Per
ft/sec Torque Drag - HP HP Time Power in G's ential Sec
2434.0 35.355 51.853 0.00 2.228 5.091 .0000 0.00 0.0000 0.0000 0.0
2446.0 35.529 52.109 73.46 2.261 5.116 .1010 34.21 .0787 0.1010 118.8
2458.0 35.703 52.365 68.79 2.294 5.141 .2110 32.19 .0722 0.1100 109.1
2474.0 35.936 52.705 85.23 2.340 5.175 .3230 40.15 .0946 0.1120 142.9
2484.0 36.081 52.919 60.48 2.368 5.196 .4320 28.61 .0607 0.1090 91.7
2500.0 36.313 53.259 87.90 2.414 5.229 .5400 41.84 .0981 0.1080 148.1
2514.0 36.517 53.558 76.73 2.455 5.258 .6520 36.73 .0828 0.1120 125.0
2525.0 36.676 53.792 65.55 2.487 5.281 .7600 31.51 .0674 0.1080 101.9
2538.0 36.865 54.069 73.52 2.526 5.309 .8700 35.53 .0783 0.1100 118.2
2554.0 37.098 54.410 92.35 2.574 5.342 .9720 44.91 .1039 0.1020 156.9
2568.0 37.301 54.708 79.20 2.616 5.371 1.0800 38.72 .0858 0.1080 129.6
2586.0 37.562 55.091 95.05 2.672 5.409 1.1910 46.80 .1074 0.1110 162.2
2602.0 37.795 55.432 87.01 2.722 5.442 1.3010 43.11 .0963 0.1100 145.5
2636.0 38.289 56.157 183.17 2.830 5.514 1.4000 91.93 .2274 0.0990 343.4
2654.0 38.550 56.540 65.19 2.888 5.551 1.5800 32.94 .0662 0.1800 100.0
2710.0 39.364 57.733 263.82 3.075 5.668 1.6900 136.13 .3371 0.1100 509.1
2747.0 39.901 58.521 196.53 3.203 5.746 1.7900 102.79 .2450 0.1000 370.0
2806.0 40.758 59.778 272.83 3.413 5.869 1.9020 145.77 .3488 0.1120 526.8
2855.0 41.470 60.822 260.06 3.595 5.972 2.0000 141.37 .3311 0.0980 500.0
2881.0 41.847 61.376 133.39 3.695 6.026 2.1090 73.17 .1579 0.1090 238.5
2979.0 43.271 63.464 446.32 4.085 6.231 2.2200 253.16 .5846 0.1110 882.9
3055.0 44.375 65.083 353.60 4.405 6.390 2.3300 205.68 .4575 0.1100 690.9
3106.0 45.116 66.169 243.65 4.629 6.497 2.4400 144.09 .3070 0.1100 463.6
3164.0 45.958 67.405 272.50 4.894 6.618 2.5510 164.16 .3460 0.1110 522.5
3229.0 46.902 68.790 337.83 5.202 6.754 2.6500 207.71 .4347 0.0990 656.6
3312.0 48.108 70.558 422.38 5.613 6.928 2.7500 266.36 .5496 0.1000 830.0
3382.0 49.125 72.049 356.36 5.977 7.074 2.8510 229.47 .4589 0.1010 693.1
3423.0 49.720 72.923 241.41 6.197 7.160 2.9410 157.34 .3016 0.0900 455.6
3500.0 50.838 74.563 394.32 6.624 7.321 3.0410 262.78 .5098 0.1000 770.0
3578.0 51.971 76.225 368.39 7.077 7.484 3.1500 250.97 .4738 0.1090 715.6
3648.0 52.988 77.716 327.60 7.501 7.630 3.2610 227.55 .4176 0.1110 630.6
3730.0 54.179 79.463 419.92 8.018 7.802 3.3610 298.23 .5430 0.1000 820.0
3769.0 54.746 80.294 194.44 8.272 7.883 3.4710 139.54 .2348 0.1100 354.5
3854.0 55.980 82.105 427.15 8.844 8.061 3.5730 313.45 .5518 0.1020 833.3
3929.0 57.070 83.702 394.63 9.371 8.218 3.6710 295.22 .5067 0.0980 765.3
3967.0 57.622 84.512 208.03 9.645 8.298 3.7710 157.13 .2516 0.1000 380.0
4031.0 58.551 85.875 303.77 10.120 8.431 3.8820 233.15 .3818 0.1110 576.6
4114.0 59.757 87.644 393.98 10.758 8.605 3.9910 308.61 .5042 0.1090 761.5
4169.0 60.556 88.815 291.80 11.195 8.720 4.0910 231.63 .3642 0.1000 550.0
4246.0 61.674 90.456 395.31 11.827 8.881 4.1920 319.59 .5048 0.1010 762.4
4302.0 62.488 91.649 297.56 12.301 8.998 4.2920 243.74 .3708 0.1000 560.0
4354.0 63.243 92.757 281.08 12.752 9.107 4.3910 233.02 .3478 0.0990 525.3
4420.0 64.202 94.163 343.72 13.341 9.245 4.4920 289.27 .4327 0.1010 653.5
4480.0 65.073 95.441 321.17 13.892 9.371 4.5910 273.96 .4013 0.0990 606.1
4554.0 66.148 97.017 354.04 14.592 9.525 4.7010 306.99 .4454 0.1100 672.7
4604.0 66.874 98.082 246.62 15.078 9.630 4.8120 216.19 .2983 0.1110 450.5
4672.0 67.862 99.531 331.22 15.756 9.772 4.9210 294.64 .4131 0.1090 623.9
4740.0 68.850 100.980 326.29 16.454 9.914 5.0320 294.48 .4056 0.1110 612.6
4806.0 69.809 102.386 320.69 17.151 10.052 5.1420 293.45 .3973 0.1100 600.0
4861.0 70.607 103.558 294.23 17.746 10.167 5.2430 272.33 .3606 0.1010 544.6
4912.0 71.348 104.644 259.56 18.311 10.274 5.3510 242.76 .3127 0.1080 472.2
4974.0 72.249 105.965 331.72 19.013 10.404 5.4510 314.16 .4105 0.1000 620.0
5042.0 73.236 107.413 328.69 19.803 10.546 5.5620 315.55 .4056 0.1110 612.6
5110.0 74.224 108.862 361.93 20.615 10.688 5.6620 352.14 .4503 0.1000 680.0
5134.0 74.573 109.373 147.60 20.907 10.738 5.7630 144.29 .1573 0.1010 237.6
5194.0 75.444 110.652 297.38 21.649 10.864 5.8730 294.10 .3612 0.1100 545.5
5262.0 76.432 112.100 338.78 22.510 11.006 5.9810 339.42 .4169 0.1080 629.6
5323.0 77.318 113.400 300.47 23.302 11.134 6.0920 304.53 .3639 0.1110 549.5
5376.0 78.088 114.529 288.91 24.005 11.245 6.1930 295.73 .3475 0.1010 524.8
5415.0 78.654 115.360 227.76 24.531 11.326 6.2910 234.83 .2635 0.0980 398.0
5470.0 79.453 116.531 273.40 25.287 11.441 6.4030 284.75 .3252 0.1120 491.1
5534.0 80.383 117.895 317.98 26.185 11.575 6.5130 335.05 .3852 0.1100 581.8
5570.0 80.906 118.662 214.30 26.699 11.650 6.6110 227.27 .2432 0.0980 367.3
5610.0 81.487 119.514 230.50 27.278 11.734 6.7110 246.21 .2649 0.1000 400.0
5690.0 82.649 121.218 389.93 28.462 11.901 6.8210 422.45 .4816 0.1100 727.3
5710.0 82.939 121.644 124.04 28.763 11.943 6.9330 134.85 .1182 0.1120 178.6
5780.0 83.956 123.136 380.97 29.834 12.090 7.0320 419.28 .4682 0.0990 707.1
5849.0 84.958 124.606 376.73 30.915 12.234 7.1310 419.55 .4615 0.0990 697.0
5854.0 85.031 124.712 60.64 30.995 12.244 7.2420 67.59 .0298 0.1110 45.0
5912.0 85.873 125.948 292.73 31.925 12.366 7.3530 329.52 .3460 0.1110 522.5
5982.0 86.890 127.439 348.61 33.072 12.512 7.4630 397.07 .4214 0.1100 636.4
6014.0 87.355 128.121 171.84 33.606 12.579 7.5810 196.77 .1796 0.1180 271.2
6058.0 87.994 129.058 236.52 34.349 12.671 7.6900 272.81 .2673 0.1090 403.7
6099.0 88.590 129.932 220.29 35.051 12.757 7.8010 255.81 .2446 0.1110 369.4
Averages 256.87 211.08 0.1069 476.3
Smoothed
Torque
73.456
73.456
68.789
75.101
74.459
75.443
75.803
75.820
78.911
82.030
90.548
98.036
114.228
136.422
158.544
193.720
210.197
235.441
260.129
271.611
299.939
305.874
311.060
324.317
326.936
339.867
345.124
341.539
351.055
344.547
345.087
351.613
333.740
335.192
330.899
315.989
326.027
328.844
326.679
334.185
325.352
320.437
320.424
316.385
317.300
312.601
313.030
309.762
306.513
305.849
306.440
304.514
300.102
295.820
283.467
286.942
288.212
284.765
286.252
274.246
266.762
270.647
261.317
267.067
281.786
268.641
278.160
275.239
250.374
257.082
248.719
171.840
236.516
220.288
.000
Mignon said:
I thought we went through inertia a couple of years ago and I gave you the values to use.
Dave,I know a few years ago we talked about MOI calculations. But with a great many years of run simulations, and some of those simulations is for the same person with yearly updates. It is one those thing where to change the way I do it now is more trouble than I am looking for.
Stan
Well I can give you the nominal extra vehicle mass the inertia calculations give which for this vehicle in 3rd gear is 187 lbs. I'm not sure your method can overcome the data jaggedness needing smoothing to get meaningful results though. My method smooths those out before any calculations start.
Try a vehicle mass of 3787 lbs and see if you get any closer to my bhp numbers.
Out of curiosity where did you get all those heavy maths skills Stan? School or uni?
Try a vehicle mass of 3787 lbs and see if you get any closer to my bhp numbers.
Out of curiosity where did you get all those heavy maths skills Stan? School or uni?
Dave,
The reason that I need to smooth my output is because the input data is all over the place. By that I mean look at the last column rate rev per sec. This is calculated using the logged rpm and time stamp and it is all over the place which in turn causes my calculated HP and acceleration G's column to be all over the place. When I have used the same calculations on data that came from an engine inertia dyno my results look much better.
Stan
The reason that I need to smooth my output is because the input data is all over the place. By that I mean look at the last column rate rev per sec. This is calculated using the logged rpm and time stamp and it is all over the place which in turn causes my calculated HP and acceleration G's column to be all over the place. When I have used the same calculations on data that came from an engine inertia dyno my results look much better.
Stan
Stan Weiss said:
Dave,
The reason that I need to smooth my output is because the input data is all over the place.
Stan
No sh't Sherlock The reason that I need to smooth my output is because the input data is all over the place.
Stan
I knowed there had to be a reason.That's why I summarise the data into 10 mph increments first to even out the jaggedness and then match the power curve to the increments.
Mignon said:
I summarise the data into 10 mph increments first to even out the jaggedness and then match the power curve to the increments.
I did some crude performance measurements using the speedo and a stopwatch a few decades back. This was before I had any data logging available. There was good data there but it wasn't very consistent due to speedo lag, speedo reading inaccuracy and timing inaccurate. I was able to calibrate the speedo at constant speed, and measure the lag at various acceleration rates, but the timing inaccuracy was problematic because each timing error caused positive and negative errors in the adjacent intervals and I needed a way to make these cancel out. The best solution I found was to do a least squares polynomial fit against a couple of dozen runs. This returned a nice smooth speed plot that I could calculate the performance from. I wouldn't claim the results were particularly accurate - nothing like the sort of accuracy you're talking about here - but I was able to get a torque curve that bore a passing resemblance to the rolling road plot and enabled me to see performance gains and losses over time. Anyway, my point is that for me, curve fitting worked better than trying to summarise each interval in isolation.
GreenV8S said:
I did some crude performance measurements using the speedo and a stopwatch a few decades back. This was before I had any data logging available. There was good data there but it wasn't very consistent due to speedo lag, speedo reading inaccuracy and timing inaccurate. I was able to calibrate the speedo at constant speed, and measure the lag at various acceleration rates, but the timing inaccuracy was problematic because each timing error caused positive and negative errors in the adjacent intervals and I needed a way to make these cancel out. The best solution I found was to do a least squares polynomial fit against a couple of dozen runs. This returned a nice smooth speed plot that I could calculate the performance from. I wouldn't claim the results were particularly accurate - nothing like the sort of accuracy you're talking about here - but I was able to get a torque curve that bore a passing resemblance to the rolling road plot and enabled me to see performance gains and losses over time. Anyway, my point is that for me, curve fitting worked better than trying to summarise each interval in isolation.
There used to be a gadget you could mount on your dash to do it, wasn't it called Gtech Pro or something? I seem to remember having a fiddle with one about 15yrs ago, it's probably stuffed down the back of a drawer or something....227bhp said:
There used to be a gadget you could mount on your dash to do it, wasn't it called Gtech Pro or something? I seem to remember having a fiddle with one about 15yrs ago, it's probably stuffed down the back of a drawer or something....
Yes, I have a similar collection of old data loggers from GTech and Race Tech that must be in a drawer somewhere. I remember the G-Tech one was very sensitive to pitch attitude changes and relied on you to enter the right fudge factor - I never had any confidence in the results. The race tech ones were better because of the GPS compensation - pretty cool to be able to see lane changes in the data logs.Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff