I went to the track yesterday, and this time I datalogged a few of my runs. I was monitoring 8 PIDs - RPM, MPH, Throttle position, KNK ST, KNK Fuel, Intake Air Temp, Open Loop FA and KNK LT.
I wanted to examine how much time my car 'coasted' without power while I clutch and shift. I was boggled by the results, since they were consistent among all three runs.
To calculate the time it takes me to shift, I look at the last frame which shows acceleration. Then I count the frames until I see acceleration again, meaning a return of power to the wheels. In my case, one frame is 88ms.
Look at the blue line on this chart:
On all three of the runs I logged, here are my results:
1-2 shift: 623ms (that's over half a second!!!)
2-3 shift: 445ms
3-4 shift: 445ms
Add it up -- On a 13.85s run, that's 1.5 second of time the rear wheels are not being powered. I'll admit that I could be more aggressive with my 2-3 and 3-4 shifts, but my 1-2 shift is quite poor.
If I can reduce my shift time to 300ms for 1-2 and 300ms for 3-4, that alone would reduce my ET by at least .4!
My father in law has an R/T auto. I'll 'borrow' his car later and log the time the auto takes to shift so I can compare.
Another thing that is useful with the logged data is to see how badly your wheels spin in 2nd gear. Look at this mess:
The track was absolutely horrible and on this run, and I managed a 2.8 0-60ft. Awful. Look at the purple line at marker '1' ... I was feathering the gas throughout first gear. Notice how I finally just slam it at the top of first and get massive wheel spin (marker 2). A sharp rise in MPH (blue line) followed by a sharp decrease, then coast, is a sure sign of spinning before the shift. Into second gear, the MPH increase is brisk, but again the wheels are only slipping for a few tenths until the curve settles.
As a side note, with all the work I have done with the DataViewer, I have learned that
a) data logging works by polling the ECU for one PID at a time. It doesn't say 'give me the values for all these 12 PIDs'. It sais 'what is RPM now?' ... 'RPM is 1050'. 'What is Intake temp now?' .. '79' really fast.
b) it takes 11 milliseconds to poll the ECU for one PID and get one result
In my case, I have 8 PIDs, so by the time my device polls all the PIDs, 88 ms have passed. So if you want more precision, reduce the PIDs to the absolute minimum. I'll be removing Open Loop FA and KNK LT, reducing my sample rate to 66ms.
I do want to drive the car home, though.
Linear Mode
