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Old 03-24-2010, 11:35 AM   #64 (permalink)
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Originally Posted by tasdrouille View Post

This is only 5 days worth of driving for my wife in her Elantra. 17000 unfiltered raw data points and 150000 individual values logged on my CAN OBDuino. Things are starting to look interesting. I just need to take the car and spin it in RPM/loads regions it's not usually used to get a better picture.

XYZ you have RPM, BMEP in kPa and BSFC in g/kWh

Fuel flow was calculated from the MAF sensor reading corrected with the equivalence ratio from the stock wideband sensor.
Brake torque was estimated from the Calculated engine load % (airflow/peak theorical airflow. I need to figure out if peak airflow is adjusted from baro pressure or not in the Elantra.) mapped against the max engine torque curve from the manufacturer.

What I like about this method is that fuel flow does not depend on the repeatablity of fillups and calibration of external sensors, but it assumes the MAF and WB02 sensors are accurate. Even though torque is grossly estimated, I kind of like the fact this method does not care about the car's mass, rolling resistance or air drag, all of which can greatly vary in time.
Hey, that's quite neat. How did you find the CAN codes for the Elantra? I'd be quite interested to know how that stacks up against my predictions. It'd certainly be a good way to improve the model. At what speed are the samples coming?

For calculating torque, are you just multiplying the normalized airflow times peak engine power? I'm not sure how much you can trust the torque measured that way. If you could put it on a dynamometer once you could calibrate it, though, and that'd be quite nice.
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