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I got many comments and questions on that video and on a FB group post I made and I felt that a deeper dive in to the PDR data would be helpful.
With the help of forum member Poorsha who analyzed my data and me also looking at the data using Cosworth PI I made a follow up video.
It would be wonderful if we could get a conversation going on this type of track data analysis using the PDR Toolbox and more deeper analysis with the Cosworth PI software.
BTW Poorsha has some very helpful videos and information on his site so if you’re interested I would highly recommend you start there:
https://www.hipodriver.com
Nice video, and great analysis and presentation. I love diving into the Pi data, although like you, do find it a littler hard to learn, thankfully have Poorsha's videos. It is amazing what we can learn after-the-fact.
Think you can ignore the e-diff stuff. There is one youtuber cuckoo who insists the e-diff is so broken as programmed by GM, that anyone who tracks a C8 with an e-diff is going to crash and die....
The braking chart makes me wonder. I’d like to figure out what the asked for torque(pressure) is on the different models. There are also the four actual line pressures somewhere in there. It’s in the CAN data at least. GM trying to hit the best stopping distance for Car and Driver etc is screwing us in the aftermarket world. I’m going to have to take a brake module apart so I can solder in a resistor to have the pressure read lower. Or perhaps in PTM off it behaves differently.
Another thing I just noticed while editing my next video, my PDR displayed Speed is around 5MPH off, it displays a lower speed the actual.
The cluster and HUD do display the correct speed (verified against a 10Hz GPS lap timer). This is on OEMish sized Vitour P1's (285/30/20 - 345/25/21).
The weirdest part is that there is a GPS speed in the data stream that you can pull up on PI
Went to look at some data because this is curious. I have no idea what the cluster and HUD show. I'll have to see if I can pay attention next time. However, I do notice the PDR speed seems to match the speed channel in Pi Toolbox. That channel seems to be consistently less than GPS speed AND the 4 wheel sensor speeds. For me it is about a 2 MPH difference across the track/lap I looked at. No idea where the speed is coming from, does seem off a bit. White is the speed channel that seems to match PDR video. Blues are GPS speeds and individual wheel speeds.
Went to look at some data because this is curious. I have no idea what the cluster and HUD show. I'll have to see if I can pay attention next time. However, I do notice the PDR speed seems to match the speed channel in Pi Toolbox. That channel seems to be consistently less than GPS speed AND the 4 wheel sensor speeds. For me it is about a 2 MPH difference across the track/lap I looked at. No idea where the speed is coming from, does seem off a bit. White is the speed channel that seems to match PDR video. Blues are GPS speeds and individual wheel speeds.
Ok well at least is not just me…
So odd that they chose to use a channel that’s under reporting the actual speed for the PDR video.
Having read the raw PDR data, the MP4 is drawing the data from aprox 1/4 seconds ago. I haven’t figured out the exact number of frames but it apparars to write out the latest it remembers and doesn’t go back and fix things at the end of the recording.
The metadata is time stamped so the Cosworth software is reading that and not what Chevy wrote to the video. So that is a bit of confusion at least. Hth
Having read the raw PDR data, the MP4 is drawing the data from aprox 1/4 seconds ago. I haven’t figured out the exact number of frames but it apparars to write out the latest it remembers and doesn’t go back and fix things at the end of the recording.
The metadata is time stamped so the Cosworth software is reading that and not what Chevy wrote to the video. So that is a bit of confusion at least. Hth
Hmmm ok, great info
So why does everything else seem to line up?
First, I think you treat e-diff data as 1.0 = no differential speed L<->R axles
So, if you are not at 1.0, the differential is "doing it's thing".
Secondly; yes, you blew the turn before you dialed in any steering input (coming too low creates an arc that takes you off the paved surface and there is nothing you (or the stability control logic) can do about this as it is purely traction limited.)
Third, Going to maintenance throttle would have delayed leaving the paved surface, or maybe allowed only 2 tires to leave the paved surface.
Going to maintenance throttle would have delayed the onset of the yaw acceleration.
Fourth, I think you touched more of the curb than you remember.
But really, the second point is why the spin happened. 3 and 4 are just along to explain why 2 was the culprit.
C8Z track spin out data analysis
