Quote:
Originally Posted by jedi_sol
Tools: Torque pro app, used a graph to measure speed (y axis) vs time (x) axis. Then after each run, I used the graph to see how many seconds it takes to go from 40-20.Very useful!
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From my experience, phone/car type GPS isn't accurate enough to pick up small gains. If you watch your GPS speed it will often jump 5km/h at a time. Even in gentle coast down tests 3km/h jumps are typical.
I have a bicycle Garmin unit that will log and stamp at selected intervals down to 0.1km/h. I've used it before in AutoX because I can actually see my lines through corners with it along with terminal and apex speeds. Only now do I realize it would be a great way to do both real world and coast down tests.
I did my first coast down testing last week just to play with the method, I used the Scangauge numbers because it was easiest (these also jump at 3km/h intervals in coast down testing). To my surprise, when I ran the numbers my calculated cd matched the factory figure (although my bigger tyres should have made it worse).
I also tried mirrors folded and could find no difference (these are big mirrors too). It's worth noting that some cars like the Ford Falcon AU were reported to have a lower CD
with mirrors than without. The mirrors were designed to help deflect air away from the B pillars. I imagine this is the case on 90% of new cars.