Minnesota Test Drives

[Vexar]

Good times, J! I think the "under our nose" announcement could be: there's mounts for autopilot sensors in the nose cone (look around in the forums here, you will find it), or the Superchargers which are being found by contacting city planning offices to find permits for "Tesla Motors" in weird cities that are mid-points on popular drive routes. I hope everyone understands the acceleration curves J is showing now. I think an overlay of the regular 85 and the 60 would help. The mass difference between the 85 and the 60 is really what's going on here. F=MA, right everyone?

 

[J in MN]

My P85's dashcam logs (24 days of data, but with some holes) report a maximum deceleration of exactly 2G [256 units] and maximum acceleration of 1.109G [142 units].

@brianman, I've been thinking about how to respond to you without going into a lengthy lecture about experimental error, statistical error analysis, Signal-to-noise ratio, instrument accuracy and calibration.

The graph you posted shows that your data is EXTREMELY noisy. This could be because the BlackVue mounting is loose, or maybe the sensor is just inherently noisy. About the only conclusion you can draw from your data is that the acceleration is greater than 0 g.

When data is that noisy, you cannot pick a single data point and call that the "peak", because you are not reporting just the signal, but also the noise.

You also need to test your result for reasonableness. If acceleration was really 1.1 g, then your 0 to 67 km/h time would be just 1.7 s. We all know from the numerous video clips posted that this is not the case.

Next you need to test your result for consistency with other observations. From the Edmunds track test we know that maximum lateral acceleration with PS2 tyres is 0.86 g. It is unlikely that forward acceleration (with only two wheels driven) is going to be better than this.

So, to get a meaningful measurement from your dashcam, you will need to eliminate the noise. Make sure the mounting is perfectly stable. If still noisy, you will need to make multiple test runs (more than 10 or 20), then align the data and take the mean at each time interval. Then you will find that the result is pretty close to what I posted.

Just eyeballing your graph, I would say that the first 3 seconds is somewhere between 0.5 and 0.8 g, in other words, consistent with my results.

 

[brianman]

If acceleration was really 1.1 g, then your 0 to 67 km/h time would be just 1.7 s.

I said peak, not sustained.

But yes, much of the rest of your post I agree with.

 

[lolachampcar]

Extreme example of noise coupling on the lateral G plot (from a CrossBow 3 axis unit).

http://www.lolachampcar.com/images/Motec Data/Motec Road America 2.jpg

perhaps a better example

http://www.lolachampcar.com/images/Performance/Road%20America%2004%20Qualifying.pdf