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ok, had a chance to log more data this weekend. still dealing with some choppiness to the ECU output. for whatever reason, the OBDII data is only pulling roughly one data point per 0.8s. this isn't too big an issue if one pulls 3rd or 4th gear runs. i can't do that on public roads; i'm stuck with second gear. in second gear, i can pull 1500 RPM to redline in about six seconds. that's not too many data points.
i talked with a guy in australia who used the same hardware to log data on his early 996. his pulled a lot quicker for some reason. FYI, he has OEM spark and fuel maps for the 3.4L 996 on his website (oz951.com). he does lots of slick tests & checks. good site.
i am a data guy. i decided to take what i have & make it workable. i ran the 'choppy' data to get some maximum points & used smoothing and scaling to develop workable curves. i then performed several runs on the identical section of road in the same conditions. the goal was PRECISION, not accuracy. i am most concerned with the ability to compare one change to another.
here are the parameters i used. the HP / Torque calculations use SAE correction factors. drag is considered.
Weight: 2890lb (includes the car, me, 1/2 tank of gas + the spare tire)
Tire Diameter: 25.5" (NT-01 275/35/18)
Gear Ratio: 2.117 (2nd gear)
Final Drive: 3.889
Frontal Area: 19 sq. ft. (WAG)
Cd: 0.40 (WAG based on the fact that i have my top down)
atm press: 29.92 inHG
Temp: 68F
Driveline loss: 15%
Logworks smoothing factor to RPM channel: 0.90
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