How to calculate Pulses Per Km to set Speed Sensor

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Claudio
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How to calculate Pulses Per Km to set Speed Sensor

Postby Claudio » Tue Sep 07, 2010 12:28 am

Greetings all, i felt like posting this to give people a little bit of insight on the calibration of their speed sensor inputs. All it takes is a little math.

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 8 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 27" tire diameter.

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 27" tire we must convert 27" to meters to keep things in the same unit system (metric), so multiply inches by .0254 to get meters.

P/Km = 1000m / [ (3.1415 * .6858m) / 8 ]
P/Km = 1000 / 0.2693
P/Km = 3713 <<<< This is the number you will put in your pulses per km field in the Calibration tab for the vehicle speed sensor.

Remember when we said in highschool that math will save your life someday?! Boy where we wrong to say we never would need it again! :twisted: 8)
Claudio
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Independant Haltech Sales & Tech Support

jasaircraft
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby jasaircraft » Wed Sep 08, 2010 10:32 am

good, should this solve the issue on the E8 on subarus about km/h not going down to zero when you stop?
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Claudio
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby Claudio » Sat Sep 11, 2010 3:57 am

jasaircraft wrote:good, should this solve the issue on the E8 on subarus about km/h not going down to zero when you stop?

What do you have the # of pulses in that set to, do we know the number of teeth its reading, what would be your tire diameter, lets do some math and figure it.
Claudio
tuningtechnology@gmail.com
Independant Haltech Sales & Tech Support

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Claudio
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby Claudio » Sat Sep 03, 2011 9:40 am

Just thought i'd bump this. Admins, can this be stickied!
Claudio
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Independant Haltech Sales & Tech Support

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Claudio
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby Claudio » Sat Mar 14, 2015 3:06 am

Bringing this back to life, since we now live in a very advanced technological world and everybody has a GPS on their hands, you can basically run any GPS app that gives you speed, and start inputting numbers in the pulses field until you match the speed on your GPS read out on your celphone with the speed in the software. Then test it by increasing speeds and seeing if they still match all the way through.
Claudio
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Independant Haltech Sales & Tech Support

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HaltechMatthew
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby HaltechMatthew » Fri May 01, 2015 4:17 pm

On the dyno is much easier :D

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Claudio
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby Claudio » Tue Sep 26, 2017 10:56 pm

HaltechMatthew wrote:On the dyno is much easier :D

Sometimes there's no Dyno Matt! ;)
Claudio
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jasaircraft
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Re: How to calculate Pulses Per Km to set Speed Sensor

Postby jasaircraft » Wed Nov 01, 2017 1:20 pm

Great tip Claudio, i guess this works on the platinum and elite series too?
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