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Old 03-24-2010, 02:59 PM   #66 (permalink)
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Join Date: Jan 2008
Location: Mirabel, QC
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The Guzzler - '08 Hyundai Elantra GL
90 day: 33.12 mpg (US)

Got Soul? - '11 Kia Soul 2U
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Originally Posted by kubark42 View Post
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?
The CAN OBDuino was designed by member Magister here. He'd have the answers about the CAN codes. Samples are coming in at roughly one PID every 25 ms. There is some error inherent to receiving PIDs asynchronously and using them to computes instantaneous values. I don't know if this is significant or not, but I believe I'll be able to easily throw out errors from rapidly changing conditions so everything averages out in te end.

Originally Posted by kubark42 View Post
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.
Yes, I generated a torque/rpm table from peak torque curves of stock elantras dyno runs, and I estimate torque from airflow/peak airflow. This is based on the fact that torque is proportional to MAF/RPM*Lambda. I have not considered lambda in the torque estimation yet as I'm more ot less at 1 all the time, but I have the data at hand. I have not verified if peak airflow in the elantra is adjusted for barometric pressure or intake air temperature, but again I have the data logged to account for that too. Ignition timing is the other factor I did not account for that affect torque production when estimating from MAF. I will have to investigate that. My car does not have EGR so this is at least one thing I don't need to worry about when estimating torque.
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