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Wheel Speed

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So I have added two wheel speed inputs to the ecu. I have added non driven from the front wheels via the standard bmw e30 vr type wheel speed sensor with a calibration figure of 2350 to get the speed to be correct. Then the driven wheel speed sensor from the rear wheels via the differential sensor which then goes the instrument cluster which then as a digital output meant for the cruise control which is where I have wired the ecu too with a cal figure of 445.

The driven wheel speed sensor works fine, reads wheel speed nice and low but the front one only reads as low as 24kph for some reason. I was hoping to use these inputs for boost by gear and traction control but im concerned it wont work properly with the non driven wheel speed input only working from 24kph.

Any help with why its only working from 24 kph would be great


log and map attached





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It will be around the voltage coming off the VR sensor. The faster you go the bigger the voltage gets. At low speeds you will be below the 1.5volts required to trigger the Di. The best sensor for low speeds in this case would be a hall or optical sensor. 

Closing up the sensor gap might give you a little gain.



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As well as the arming threshold issue that Simon mentions, judging from your large calibration number on the front I would say your frequency (tooth count) is too high also and you are going to "top out" the frequency before you reach max speed of the car.

One of these connected to each front wheel should take care of both issues:  https://www.vems.com/vr-to-hall.html

These have an adaptive arming threshold so work right down to about 0.25V and they have a 1/8 frequency divider built in to effectively reduce the tooth count. 

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