I have attached a screen shot of my vehicles speedometer configuration.
I am running a TH350 transmission now and using the Autometer speed sensor which puts out 16 pulses per revolution. I don't understand how I calculate all the fields required to correlate with my new VSS signal.
Could someone point me in the direction as to the formula required to figure out my values?
I imagine that I would change "vss pulses per rev-trans" to 16....but how do I calculate the rest of the fields?
Alright....so after thinking about this logically for a while and trying a few different methods, I believe I answered my own question. I am going to post my method so hopefully in the future if someone looks up a similar issue, this post should be able to help them out. I searched a lot of web sites and could not come up with a solution so here it goes....
Figuring out values for VSS conversion
If you look at my attached thumb nail above, you will see that my primary issue was converting the VSS to 16 pulses per revolution versus 40. The part I found difficult was determining what this would translate to in the "VSS Pulses Per Mile" field.
In order to do this conversion you need the following information:
-Rear gear ratio
-Tire size and circumference
-Pulse count from VSS
The first thing I did was take my tire size and figure out the circumference.
So for example:
-My 30" tire has an area of 706.85
-Using this value, my tire has a circumeference of 94.24"
-Now we know that for every rotation of the tire, we are covering 94.24"
Now that we have the tire information, we need to know how many tire revolutions are covered under a mile:
63360"/ 94.24"= 672.32 tire revolutions per mile.
We also know that my rear gear ratio is 3.73:1. This means for every full rotation of the tire, the VSS is pulsing it's total count 3.73 times.
3.73x40= 149.2 pulses from the VSS per tire revolution
We can now take the pulses per tire revolution and multiply that number by the total amount of times the tire rotates within the mile.
149.2x672.32= 100,310.144 pulses per mile
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The above example is using a slightly taller tire then the number in the HP Tuners Screen Shot which is what lends itself to the very slight difference in total pulse count per mile when compared....however, I thought it still shows that the formula is correct and will get you into the ball park. In my case, I am using a 16 pulse per revolution VSS from Autometer so my table should include a 40,124.06 VSS Pulses Per Mile Count.
I hope this post makes sense and helps someone out down the road.
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