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t vago · 12-18-2016, 02:50 PM

Yah, I set the number of bits for the VSS pulses/mile count to 16. That results in a maximum value of 65535. That is part of the issue you're seeing.

The other part is that the MPGuino code currently cannot handle raw VSS pulse frequencies higher than about 187 Hz. In contrast, using a tire size of 225/45R17 (which I think is the stock tire size of your Mercedes), and a VSS pulse/mile setting of 166770 pulses/mile, I have calculated that your VSS is sending a raw VSS frequency of about 926 Hz to your MPGuino.

I think I have found a way to beat this within the MPGuino code, and allow your speedo to output the correct speed, but I will need your help to verify whether this fix will actually work.

12-18-2016, 02:50 PM	#2 (permalink)
t vago MPGuino Supporter Join Date: Oct 2010 Location: Hungary Posts: 1,808 iNXS - '10 Opel Zafira 111 Anniversary Suzi - '02 Suzuki Swift GL Thanks: 831 Thanked 709 Times in 457 Posts	Yah, I set the number of bits for the VSS pulses/mile count to 16. That results in a maximum value of 65535. That is part of the issue you're seeing. The other part is that the MPGuino code currently cannot handle raw VSS pulse frequencies higher than about 187 Hz. In contrast, using a tire size of 225/45R17 (which I think is the stock tire size of your Mercedes), and a VSS pulse/mile setting of 166770 pulses/mile, I have calculated that your VSS is sending a raw VSS frequency of about 926 Hz to your MPGuino. I think I have found a way to beat this within the MPGuino code, and allow your speedo to output the correct speed, but I will need your help to verify whether this fix will actually work.