I'm working with a stock ford MAF slot sensor. Used in many newer vehicles. You install it in your own custom intake piping.

Pro-m (I think) makes a HPX slot sensor. You get a spread sheet with it called the HPXtool. Input your pipe diameter and it calculates a flow curve to use in your tune.

I've made a sheet for the stock ford sensor and it works great.But instead of just being able to manipulate the pipe diameter I want to also change the voltages. I drag race and I want more resolution in the transfer curve at WOT. My intake pipe is 108mm so for me I want more points in the 3.9v to 4.25v range.

Here is where it gets hard. Or easy for someone who knows this stuff. I unprotected the HPXtool sheet and found you can in fact change the voltage points. It is using a 9th order polynomal equation. But that equation is specific to the HPX sensor not the ford sensor.

I found an addon for excel that dose exacly what I want but it is not free and dose not show the equation it comes up with. I have MATLAB also but am a noob using it.

If anyone could help I'd really apreciate it. Thanks

yeah, uhh, connect the watchamadinger to the whichimacallit and tune it for hoodly-doodly.
dude your fucked, put a carb on it.....

what color is it? what did you run?

white 92 lx mustang. Best run last summer ended up being 11.2 @ 120. Breaking some stuff while doing it.

ohhh, you must be the guy with the nitrous in the back...

No nitrous here. Maybe someday. All motor pump gas small block.

Alright so you want to know what the 9th order polynomial is? I need a little more info. The 9th order polynomial is a huge equation and its going to be hard to work with.

It is definitely not easy. But like I said I did find an EXCEL addon that did do it just fine. Acually did it to the 15th order. But it didn't show the equation it came up with.

If I knew MATLAB better I'm sure it could do it. I have my stuff at work and can email what I have so far.

Just to break it down a little. It is a 30 point curve. X is voltage 0-5v for 30 points. Y is the flow. I know both of these. I want to solve for new X or voltage.

Thanks.....

I am a little confused, maybe I should read closer but.... are you trying to fit a line to your curve and then get the equation for it?

I know matlab can do it for you, but it has been a few years since I messed with it so I won't be any help telling you how to do it. I assume the shape of your curve is similar to HXP curve that you know is 9th order. If my memory is right at all use the help function on matlab and search "line fit" or "best fit" that should tell you how to do it. If my memory is correct you get a dialog box that has several options for the types of curve you have and one option is Polynomial and you can enter "9" it will then solve your equation.

google: "matlab line of best fit" if I am reading your question right seems like it has some helpful info.

another thing to do might be graph just the section you are interested in having a higher resolution (3.9v-4.2v or whatever) then you might be able to use a simple equation to graph the line (not sure how complex the curve is) if you are lucky that section may be linear.

The other option you have is interpolating the data. Do you need to do lots of calculations for several different points or just a couple? If it's only for a couple, interpolate the data you have and you should be as accurate as using a line of best fit equation. Google will tell you how to interpolate if you are not familiar with the equations.

Playing with MATLAB and really not knowing what I'm doing at all I came up with.

Linear model Poly9:
fittedmodel1(x) = p1*x^9 + p2*x^8 + p3*x^7 + p4*x^6 +
p5*x^5 + p6*x^4 + p7*x^3 + p8*x^2 + p9*x + p10
Coefficients (with 95% confidence bounds):
p1 = 0.003684 (-0.0008107, 0.008178)
p2 = -0.09019 (-0.1937, 0.01331)
p3 = 0.937 (-0.06738, 1.941)
p4 = -5.363 (-10.7, -0.02342)
p5 = 18.35 (1.425, 35.27)
p6 = -37.97 (-70.51, -5.425)
p7 = 46.74 (9.874, 83.6)
p8 = -28.73 (-51.18, -6.278)
p9 = 9.475 (3.662, 15.29)
p10 = -0.2856 (-0.5445, -0.02669)

Now to try and get it into excel and see what it will do.

The things I do to try and go faster..... Good fun anyhow.

that will be a fun one to enter into excel. What are the numbers is paranthathese to the right of your "P" values?

Are those just (x,y) coordinates?

I'm pretty confused as to what you are trying to accomplish...

I haven't read the whole thread but I assume he is making a voltage curve for the new MAF sensor. You would need this in order to tune using a new sensor. Any changes in MAF or the diameter of piping his MAF is in will require a new voltage curve.

you should bring your lap top ( if you have one) to the meet at city brew tomarrow and we will see if we can get you fixed up. if you dont have your lap I will have mine, im gonna do some more tuning on 05judges car.

I thought you got it figured out. weren't you trying to get the polynomial and you posted it above... I assumed that was the answer to your question.

i think he just need to figure out how to put his equasion into excel.

thats the easy part. It will take some time to not make a mistake but just enter it just like he has it entered above. I assume if he made it this far he knows how to enter equations into excel. If i am wrong feel free to tell me what you are struggling with and I will walk you through it.

are you talking to me or him at the end there.

I did get it into excel but it isn't right. Close but not right. There are so many options in MATLAB I'm just going to have to play with it more.

When I finish it I'll let you know and email to anyone wanting to see it.

Thanks

1.84632391485613E-03*x^9+-4.34592107284094E-02*x^8+0.439653659999447*x^7+-2.49378649016453*x^6+8.62714758057054*x^5+-18.4044561274264*x^4+24.1884610185043*x^3+-15.2843912494105*x^2+6.37956766566941*x+-0.195238786521244


There it is in all its glory. Spread sheet is done. I'd love to post it for all to see but I don't think I can.

If anyone wants to check it out let me know and I'll email it to you.