Testing wheel skirts A-B-A

[California98Civic]

Originally Posted by ConnClark

The best coast down tests are done by coasting down a hill from a chalk starting line. That way you can always have the exact same energy to deal with for each test.

I have the perfect hill. A mile and a quarter or more, no lights, no stops. Right next to campus. I'll mark a spot. Record speed at a specific second spot. A "coast-up" test. I'll do that first, being the less costly option in terms of time and gas.

Originally Posted by Frank Lee

I ran skirts over a year. Results didn't show up in tank-to-tank records. Skirts are now off. I prefer to be able to check and air up the rear tires without the hassle.

I hear you, Frank. But I can deal with the slight hassle of the air pressure check, and I actually like the look a lot. As long as they are not a net loss aerodynamically, I'll keep at it until I have a good looking, well-fabricated pair of 'em.

[ConnClark]

Originally Posted by California98Civic

I have the perfect hill. A mile and a quarter or more, no lights, no stops. Right next to campus. I'll mark a spot. Record speed at a specific second spot. A "coast-up" test. I'll do that first, being the less costly option in terms of time and gas.

For accuracy it would be best to start from a dead stop and coast to a dead stop and look at the distance. Do maybe 3 test for each configuration.

[Krayzie]

but starting from a dead stop would require a large hill to get speed up enough to affect aero.

[California98Civic]

Originally Posted by ConnClark

For accuracy it would be best to start from a dead stop and coast to a dead stop and look at the distance. Do maybe 3 test for each configuration.

Rolling to a stop from highway speeds won't be an option around here. Too many lights and stop signs. What I have is a hill that gets me from a total stop to 55mph in 0.5 miles. That's 10mph above the posted speed limit with half a mile of hill still to go. I would have to brake to avoid going farther beyond the speed limit. That's not good enough? I figure I pick a spot and compare the speeds I reach by the time I get there. That's too inaccurate?

[Krayzie]

I've never done a coast test before but 55mph should be fast enough to notice a change.

[ConnClark]

Originally Posted by California98Civic

Rolling to a stop from highway speeds won't be an option around here. Too many lights and stop signs. What I have is a hill that gets me from a total stop to 55mph in 0.5 miles. That's 10mph above the posted speed limit with half a mile of hill still to go. I would have to brake to avoid going farther beyond the speed limit.

Start lower down the hill then.

That's not good enough? I figure I pick a spot and compare the speeds I reach by the time I get there. That's too inaccurate?

Yes that is too inaccurate. It involves too much human interaction and relies on your ability to time it right.

If want the test to prove conclusively that you can go farther on the same amount of energy then you want to measure it directly by going farther on the same amount of energy.

[Frank Lee]

In college I did on the road aero experiments and testing. I found that a gust of wind, passing truck, anything could screw up the results. Statistically, one needs to make hundreds of runs to mitigate environmental effects. Good luck.

[Blacktree]

Originally Posted by California98Civic

Rolling to a stop from highway speeds won't be an option around here. Too many lights and stop signs. What I have is a hill that gets me from a total stop to 55mph in 0.5 miles. That's 10mph above the posted speed limit with half a mile of hill still to go. I would have to brake to avoid going farther beyond the speed limit. That's not good enough? I figure I pick a spot and compare the speeds I reach by the time I get there. That's too inaccurate?

That sounds perfect to me!

But like Mr Lee suggested, it may take several runs to get a good sample group.

On a side note, you could use a stop-watch to measure the amount of time it takes to go from zero to the speed limit, to avoid law enforcement issues.

[Superturnier]

I would think that, the higher the speed, the more you can see differences in aero mods?
Yes, I know that an true ecomodder don't want to ruin any tank mileage by some high speed testing.

[ConnClark]

Originally Posted by Frank Lee

In college I did on the road aero experiments and testing. I found that a gust of wind, passing truck, anything could screw up the results. Statistically, one needs to make hundreds of runs to mitigate environmental effects. Good luck.

Maybe he could do it at 3am when the winds are calm and there is no traffic.