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      11-11-2008, 05:48 PM   #99
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lucid's Avatar

Drives: E30 M3; Expedition
Join Date: Apr 2007
Location: USA

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I had also assumed that you would need to differentiate the vehicle velocity data to get at instantaneous acceleration, and use the mass info and add theoretical drag values at the given speed to arrive at torque at the wheels. The main piece of information one can get from the OBD tool is the vehicle velocity data. You need the RPM data to plot the obtained torque figures against the RPM range the data were collected in. If you know the gear and final drive ratios, the RPM data is linearly related to vehicle velocity data, so it is not a new piece of information. So, you can simply process the RPM data, but you'll still need to get at vehicle speed and differentiate to determine instantaneous acceleration.