If you haven't noticed yet, I use a lot of physics and math to with my modifications and projects. Usually I'll use a formula or derive one for whatever I am doing, but often it is easier for comprehension of something to view it in a data table than to read a formula. Other times I record observations and data which have no formulas and all that ends up here on the data tables page.
Weight Loss to Horsepower to 1/4 mile time conversion (@ 2850 lbs)
|1/4 mile||+ - .1 s||total hp||+ - 10 lbs||lbs:s|
|20.5 s||1.23 hp / .1 s||85 hp||0.3 hp / 10 lbs||41 lbs = .1 s|
|19.5 s||1.51 hp / .1 s||98.76 hp||0.35 hp / 10 lbs||43.14 lbs = .1 s|
|18.5 s||1.85 hp / .1 s||115.65 hp||0.4 hp / 10 lbs||46.25 lbs = .1 s|
|17.5 s||2.31 hp / .1 s||136.63 hp||0.47 hp / 10 lbs||49.15 lbs = .1 s|
|16.5 s||2.92 hp / .1 s||163.61 hp||0.57 hp / 10 lbs||51.23 lbs = .1 s|
|15.5 s||3.75 hp / .1 s||196.64 hp||0.69 hp / 10 lbs||54.35 lbs = .1 s|
|14.5 s||4.9 hp / .1 s||240.2 hp||0.84 hp / 10 lbs||58.33 lbs = .1 s|
|13.5 s||6.52 hp / .1 s||297.63 hp||1.05 hp / 10 lbs||62.1 lbs = .1 s|
|12.5 s||8.86 hp / .1 s||374.93 hp||1.32 hp / 10 lbs||67.12 lbs = .1 s|
|11.5 s||12.34 hp / .1 s||481.48 hp||1.68 hp / 10 lbs||73.45 lbs = .1 s|
|10.5 s||17.74 hp / .1 s||632.57 hp||2.22 hp / 10 lbs||79.91 lbs = .1 s|
|9.5 s||26.41 hp / .1 s||854.09 hp||2.99 hp / 10 lbs||88.33 lbs = .1 s|
The first column (1/4 mile) is your 1/4 mile time in seconds, the second column (+ - .1 s) is how much horsepower is needed to increase (or decrease) 0.1 seconds off your 1/4 mile time. The third column (total hp) is how much horsepower you would need to have to get the corresponding 1/4 mile time in that row (so to get a 15.5 second 1/4 mile with a 2850 lbs vehicle you will need about 197 horsepower). The fourth column (+ - 10 lbs) is how many horsepower you will gain (or decrease if adding weight) for every 10 lbs of weight you remove (if I had a 200 hp car, and I removed 200 lbs, I'd look at the total hp column, see that at 200 hp every 10 lbs you remove nets you 0.69 hp, so I just gained 12.8 hp). The fifth column (lbs:s) shows how many lbs you will have to loose to get 0.1 seconds faster on your 1/4 mile (using the same 200 hp car that I took 200 lbs off, that extra 12.8 hp would give me a 0.37 second faster 1/4 mile, because every 54.35 lbs takes off .1 seconds from my 1/4 mile).
The old adage is that if you remove 100 lbs from your car, you will run the 1/4 mile about 0.1 seconds faster, which corresponds to about 10 hp (100 lbs=10hp=0.1s). This is an okay rule of thumb, but it is not that accurate, so the above data table is the exact calculations for removing weight from a 2850 lbs vehicle (the weight of my Shadow with a 200 lbs person in it). The numbers work within 2% if you go all the way up to 3500 lbs or down to 2200 lbs, so this table is pretty accurate for determining horsepower and 1/4 mile time changes when removing weight.
Please note, I used the 'Approximate 1/4 mile equations' posted in the Formulas section, but I altered the ET equation. I used 6.357 instead of the 5.5 as the weighted constant in the ET formula because I felt it reflects a more conservative scale for weight loss and 1/4 mile times.
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