CRUZ1NN

I agree that Dragy is detecting motion from the 19 to 32 satellites. On the Dragy website is does mention the following:For those that care about my methodology of posting the PI Toolbox numbers... It is not something that the Toolbox provides as a calculated value. I have to do the calculations.

For my PI Toolbox calculations,

1. I analyze the PDR's mp4 data at every 1/100th of a second. I am not talking about the video display timers, but the data within the mp4 file.
2. I determine the 0 distance at the 1/100th mark that is just before the distance increases > 0 (at the next 1/100th of a second).
3. I determine the 1-foot rollout at the 1-foot distance mark and start the time from there. Obviously the 1-foot rollout does not occur at exactly a 1/100th of a second data point so I use a formula to estimate at what fraction of 1/100th of a second it occurs by looking at the 1/100th time before and after the point it reaches 1-foot.
4. I do the same calculation for a fraction of 1/100th time mark at the end point or 60-foot mark.

Could my method be flawed? Yes, by just a bit. There are times that I posted where Dragy and my calculations from the PI Toolbox screens are off. I could revisit those calculations to see if I made an error.

JerryU

Agreed, GM could state as the car mags do, "we subtracted rollout." And rollout does vary. Remember when dragsters staggered the front wheels!

I understand those drag racing when testing changes other than the strip need a "number" with whatever they are using to measure. That is not my case at all. I am posting for the majority who will buy E-Ray's that DON"T Track or go to drag strips. Makes no difference what GM is using for rollout. The fact that I and others can take a Pic of the Dash Test Result is why I started this Thread. I can see the Doubting Thomases questioning my G-TechPro result as "That is not your car!" BTW I pulled out the 23-year device from Tesla Electronics and importunely it has a broke wire, missing the suction cups. Thought about buying a new one as like VBOX they say they use an array of 3 accelerometers (X, Y, Z positions and they are calibrated.)

As I have said it's a relative number. I have done many 0 to 60 Launches optimizing my ProStreet Rod 23 years ago. Don't know what GM is using BUT they have an array of accelerometers used for control input to the MRC (probably have 4 arrays one at each wheel.) Those must be accurate and very quick response. IF that is what they are using for a start signal may be very repeatable.

Understand it's not what frequent drag races need. But find for my purposes. I have seen differences charging the EV battery to 100%, which I did in the last test, versus it's normal 80%. As expected there are differences heating the tire tread versus not. That is all I am concerned with NOT an "actual" number- whatever actual means!

JerryU

 Thanks for the clarification re PI Tools!
If you are correct, "I agree that Dragy is detecting motion from the 19 to 32 satellites" and that is what is starting the 0 to 60 mph test, could be an issue with measurement differences. G-Tech and VBOX both say they use and array of 3 accelerometers to start timing (positioned at X, Y and Z directions and calibrated.) They can be very sensitive as I'm sure the ones GM is using for control input for MRC. IF (and I don't know) that is what GM is using to start the Dash Test it would detect a minute initial movement.

My 23-year-old G-TechPro used and only used an accelerometer. No GPS as the current Tesla Electonics G-TechPro device. I have the instructions from my old one (bit of a squirrel which is why I still have the now non functioning device!) It doesn't say how many accelerometers it has but does have some interesting statements. In Read This First it states: Accuracy is close to equipment that cost $10,000! Now that was 23 years ago and unlike today's device it does not include GPS.

On another page it states the internal 0 to 60 mph tests are 1/100 second accurate. Fun to see how they calculate everything from acceleration and time: "G-TECHPro measures speed and distance traveled by integrating acceleration over time." Yep, given the two variables all can be derived!

Would appear to me, IF looking for very accurate 1/4 mile, 60-foot times when evaluating changes when not at a strip to gain that extra 0.1, I would include a measurement device that based starting using an array of accelerometers and compare! Just Sayn'.