custom field formula for slip angle of VSS1/VSS2

[nismoautoxr]

How do i create a custom field that will show the slip angle (%age differance) between VSS1and VSS2 to be used to tune SPK:traction retard for use with MS3 1.3alpha9

[LT401Vette]

Try this Formula:

([VSS1] > 0 ) ? 100 * (([VSS1] - [VSS2]) / [VSS1]) : 0

[nismoautoxr]

Here is what I get when I put that formula in...what I do wrong?

[nismoautoxr]

Ok got it to take . I missed a bracket and a parenthesis and had a underscore in the name but the calculation is off based on calculator math when you divide VSS2 by VSS1 in this screenshot. At the point in the log it should come out to 57% I thought ...am I right?

[LT401Vette]

That looks good for what I was thinking, the percentage of slip. But looking at your field name slipangle you might be shooting for something different.

Is it the cumulative angle of turn lost you need?

[nismoautoxr]

what IM trying to get it to display is the speed diferance in % between the rear wheels and the front so that I can tune the traction control parameters such as slip threshold etc. For instance if the front wheel speed is 52 and the rear wheel speed is 57 then the formula as it is now is calculating around 9% slipangle and the calculator says .9% so theres an inaccuracy somewhere but the higher the ratio gets the the calculation is low rather than high....that make sense?

[LT401Vette]

If you have 52 and 57, the 9% or more precisely 8.8% slip would be correct.

(57-52) / 57 = 0.088
which is the fraction slip, to turn it to percent multiply by 100

0.088 * 100 = 8.8%

[LT401Vette]

If you just want the % difference, you can do like you are on the calculator and divide VSS1 / VSS2, that will give you the fraction of VSS1 is of VSS2, then if you want that in percent you will need to multiply that by 100 as well. That would not be a percentage slip though, more of a percentage of not slip.

Formula:
100 * ( [VSS1] / [VSS2] )

So then your example of 52 and 57 would be:
52 / 57 = 0.912

then to turn the fraction into a percent:
0.912 * 100 = 91.2%

[nismoautoxr]

well see now Im not sure what I want LOL. I am not sure how the FW calculates it but Im sure I want to represent it in that way.

[jsmcortina]

I'm guessing you are trying to understand the MS3 traction code.

The code does this:

Code: Select all

            long lt;
...
            lt = ((outpc.vss1 - outpc.vss2) * 100L) / outpc.vss2;
            if (lt > slipth) {
                slipxtime = (unsigned int)lt - slipth;
            ....
            }
...
    slipxtime = slipxtime * (sliptimer / 10);

That final slipxtime is used as the X axis in the "reactions" curves. sliptime is a timer.

James

[nismoautoxr]

what Im really after is to be able to prevent unwanted traction control from happening like say I have the slip % threshold set to low yet not set it so high that its not going to begin reacting soon enough. Im really just getting my feet wet with traction control and have not yet learned all the ins and outs yet and thought that if I could log the slip% I could get a feel for it without doing alotta calculations but its becoming pretty evident to me that my threshold is going to be in the neighborhood of 5-10% before I want to allow corrections to be made.

[nathaninwa]

Im not sure if there is a workaround, but %slip is kind of broad. If 10% is selected, then its only 3mph at 30, but 10mph at 100. I use 15% slip in my case, and use the launch revlimiter for any 1-2 gear pulls. I worked with suspension a lot to get traction in the higher gears, so even tho its cold out and wet (dry roads tho) I can make a 3rd gear pull at almost 750whp and slip.

[nismoautoxr]

well its kindof moot right at this moment because spark is not being retarded right now for me so Im waiting for the alpha 11 code to be released for development...just working ahead a little so I can make sense of logs when it does work. I could use spark cut but I largely do not care for all the pop and bang stuff. If it was smooth like a msd 6al is it really would not bother me but so far i have not been able to do that with MS without a bunch of backfiring.