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Old 05-04-2020, 03:39 AM   #31 (permalink)
JulianEdgar
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Quote:
Originally Posted by 2000mc View Post
Have you tried testing with a scangauge or other similar device? Measuring to .1mpg should give you around 7x the resolution for an insight vs kmph.
When i tried testing wheel covers my results kept trending upwards, which I think would have been lost along with any result, if not for greater resolution. https://ecomodder.com/forum/showthre...tml#post418212
Do you have thoughts as to why in this more recent test, windows down produced 101kmph from a baseline of 103.5, while in an earlier video showed 98 from a baseline of 104?
I have a full MoTeC data logging system. I can measure mileage to basically whatever resolution I want at whatever frequency I want. But I don't think short-term mileage testing tells you anything much.

I think the problem with both short term mileage and coast downs is that the test occurs over a period. Any change at any point within that test period will give you an error. A change in yaw angle, a gust of wind, etc. With throttle stop testing, you just get to that speed and then it holds. It's a settled, single number recorded at that point.

Yes, I have a very good idea at the reason for the change in maximum speed with the windows down this time. It was dead calm. The other test, it was blowing a gusting crosswind.

Finally, I think that chasing maximum resolution is the wrong fundamental approach. I don't think any on-road testing (including acceleration, etc) has the repeatability to require high resolution. In those circumstances, high resolution gives you a false sense of data accuracy. If I can't see a change of well over 1 per cent (and usually higher), for me the aero modification is not worth pursuing.

(The parallel is performance testing. A few decades ago I used to run dozens and dozens of stopwatched 0-100 km/h road times on my cars, doing runs after every modification. Say the car was typically doing 0-100 in 6.4 seconds. I'd want to see 6.2 seconds as the average of the runs before I figured I'd made any improvement. That's 3 per cent.)


Last edited by JulianEdgar; 05-04-2020 at 06:00 AM..
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