# Thread: Find the equation used in this calculator

1. ## Find the equation used in this calculator

Hey guys

This has been really bugging me as I can't figure out how to do it. I've just completed 1st year of my motorsport design engineering degree course so it shouldn't be much of a problem!

Alas...

We have these numbers which represent BHP and weight, inputted into a calculator which give an output which supposedly represents a 0-60mph time. I want to figure out what equation is being used, mainly for fun as it's annoying me that I can't figure it out

Here is the data we have

BHP, Weight, 0-60

500, 1000, 2.9
600, 1000, 2.9
200, 1000, 4.8
323, 1356, 4.5
223, 1256, 5.7

I have more data if it's needed.
How can I go about coming up with the equation for these outputs?

2. ## Re: Find the equation used in this calculator

Inputting your data into ms-excel and using the regression function in the data analysis suite I get,

Time = -0.006091194 BHP + 0.001961836 Weight + 4.27146484

More data would be helpful to get a better fit as the p-values for the regression parameters are not all significant.

3. ## Re: Find the equation used in this calculator

More data:

197 bhp, 1150 weight, 5.8 time
402 bhp, 905 weight, 3.1 time
373 bhp, 961 weight, 3.3 time
665 bhp, 1008 weight, 2.8 time
90 bhp, 800 weight, 10.9 time

Thanks for the help so far mate. More data?

4. ## Re: Find the equation used in this calculator

Give me all the data you have, but in the format in post #1, just the commas in between.

5. ## Re: Find the equation used in this calculator

500, 1000, 2.9
600, 1000, 2.9
200, 1000, 4.8
323, 1356, 4.5
223, 1256, 5.7
197, 1150, 5.8
402, 905, 3.1
373, 961, 3.3
665, 1008, 2.8
90, 800, 10.9
800, 1150, 2.7
264, 1439, 5.4
148, 1301, 8.5
128, 1287, 9.8
119, 1244, 10.0

All I've got

6. ## Re: Find the equation used in this calculator

No worries, here is the output,

Parameter $\displaystyle ~~~~~~~~~~$ Coefficients $\displaystyle ~~~~~~~~$P-value
Intercept 8.856424987 0.020317672
X Variable 1 -0.010798898 0.0004769
X Variable 2 0.000272509 0.920580742

7. ## Re: Find the equation used in this calculator

Ok cheers mate. I'm going to run some more numbers through the formula and see how it works out. Hopefully the 0.92 p value doesn't mean that times are going to be too far out from the original calculator.

8. ## Re: Find the equation used in this calculator

Doesn't work too well :-/ e.g. the 197, 1150 car gives a time of 7.04s, it should be 5.8s

9. ## Re: Find the equation used in this calculator

The 119, 1244 inputs give 7.9 when it should be 10.0
What do you recommend? More data?