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Old 12-23-2014, 07:31 PM   #70 (permalink)
BrickHouseVX
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Join Date: Apr 2011
Location: Lake Charles, LA
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RedVX92 - '92 honda civic vx
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How to calculate Pulses per mile.

Ok which of the following is the correct way to calc Pulse/Mile?
As you can see the answers are vastly different.

Method1:
To determine the number of pulses per km the ECU requires in the speed sensor calibration field, we first need the number of teeth that our trigger wheel, transmission, wheel hub teeth, etc., has. For this example, we'll keep things simple, we'll pretend we've got a wheel sensor with 16 teeth around it.

We also need to determine the circumference of our tire, in order to know how many pulses per km the sensor will read. So, on this example, lets make it a 22.7" tire diameter (as per Tire Rack for Michelin Defender 175/70/13).

Our formula for calculating the pulses per km can be summed up like this:

P/Km = 1000 (meters in 1km) / [ (pi * diameter) / # of teeth on sensor ]

So, in this example with our 22.7" tire we must convert 22.7" to meters to keep things in the same unit system (metric), so multiply inches by .0254 to get meters.

P/Km = 1000m / [ (3.1415 * .57658m) / 16 ]
P/Km = 1000 / 0.113208
P/Km = 8833.298 <<<< This is the number you will put in your pulses per km field in the Calibration tab for the vehicle speed sensor.

Method2:

(Tire revolutions per mile) * (axle Ratio) *( number of teeth in speedometer gear)= PPM
Example: Michelin Defenders(175/70/13) 917 revolutions per mile
x 3.250 (final gear ratio for VX ??)
x 16 teeth in speedo gear as seen in Manual drawing.

==> 917*3.250*16= 47,684

Last edited by BrickHouseVX; 12-23-2014 at 07:38 PM.. Reason: clarify
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