Scion xA aero mods

[3-Wheeler]

Originally Posted by aerohead

....I've been compiling data from a 1.1-mile coast-down I do in the T-100 when traffic permits.
My terminal velocities are all over the radar screen,especially when I do the short commute to town with long stay,then cold restart and commute back home....

AeroHead,

It's nice to see you attempting this again.

There were several times when I was tempted to give up on the coast down testing with the Insight, but I have somehow stuck with it!

I use a hand-held GPS, and my readings are also "all over the place" because of the uncertainty of the unit. Especially when you start looking at delta-V and delta-Acceleration data.

I have spend literally weeks (maybe longer) working on this stuff, and "some day" will figure out how to properly process my raw data and make real-world sense out of it.

It may be possible to program a microcontroller to take Hall-effect readings from the rotating tires and store these for accurate coast down readings. Just have to figure out how to program them. Ordered a book and development kit to get started.

Keep us posted on your findings.

Jim.

[NeilBlanchard]

Thanks!

Originally Posted by alohaspirit

shes looking great

remind me again why the wheel skirts are angled like that?

Well, there is a 1/8" steel rod in the bottom edge, to hold a slight bow, so it can clear the tire. If the bottom edge is level, my butt-o-meter said this was not as good. I think there may be air coming out from underneath and/or getting behind the skirt? I did contemplate having them extend lower, but they did not look as good to me.

Another thought I had was, the bottom of the wheel is (more or less) moving in the same direction as the air that the car is pushing through. And, on cars like the Mercedes Bionic, the skirts are slanted...

So, the bottom line is they are slightly slanted because I had decided this was best; and I don't have enough big pieces of Coroplast to try anything else.

[aerohead]

Originally Posted by Sulfuric

I've been taking a lot of really short "cold" (in FL) weather trips, and I noticed a serious drop in FE. It's only a guess, because that's all I have, but my gauge is at 60 where is should be at about $100

Sulfuric,it will be after the holidays before I can put a post together about short trip mpg and temps.
If you have some trip data recorded and can post before this coming Thursday,I'll try and remember my graph and give you some numbers to look at.
When doing my coasts I'm using a non-contact laser pyrometer to record vehicle skin temp,road temp,tire temp,differential temp.As soon as I get the 1-mile to the house,I turn on the National Weather Service TV broadcast to record air temp,% relative humidity,barometric pressure,wind velocity,and direction.
By knowing the dry bulb temp and baro pressure I can calculate the current air density.
If I didn't have the bellypan I'd also be recording the radiator temp, oilpan temp,and transmission temp.
With all this data I'd have a pretty good idea of the environmental factors affecting the coastdown.

[3-Wheeler]

Originally Posted by aerohead

....As soon as I get the 1-mile to the house,I turn on the National Weather Service TV broadcast to record air temp,% relative humidity,barometric pressure,wind velocity,and direction....

Hi AeroHead,

I know that I have mentioned this before, but the broadcast barometric pressure is not "the real barometric pressure".

The local TV stations and such always correct the "real" barometric pressure to sea-level, which makes the baro higher than it really is.

There is hope however.

Knowing your elevation, you can subtract the elevation above sea-level to get the "real" baro.

In Wisconsin where I live, the "standardized baro" is 30.00 inches or so on any given day, but the real baro is actually 1.00 inch Hg less than this, since our "average" elevation is 1000 feet above sea level, which lowers the baro by 1.00 inch Hg.

If you don't correct for this, your air density readings will be off by about 3.5%.

Jim.

[NeilBlanchard]

It is probably mostly due to my Michelin X-Ice winter tires, but it is partly because I repaired the rear wheel strakes and put a smooth wheel cover on the left front wheel -- my FE has jumped up 2-3MPG, even though it has snowed and my driving patterns have not changed.

[aerohead]

Originally Posted by 3-Wheeler

Hi AeroHead,

I know that I have mentioned this before, but the broadcast barometric pressure is not "the real barometric pressure".

The local TV stations and such always correct the "real" barometric pressure to sea-level, which makes the baro higher than it really is.

There is hope however.

Knowing your elevation, you can subtract the elevation above sea-level to get the "real" baro.

In Wisconsin where I live, the "standardized baro" is 30.00 inches or so on any given day, but the real baro is actually 1.00 inch Hg less than this, since our "average" elevation is 1000 feet above sea level, which lowers the baro by 1.00 inch Hg.

If you don't correct for this, your air density readings will be off by about 3.5%.

Jim.

Thanks Jim! I guess it's too much for people to just leave things alone for simple-minded people like me.
I hope they never begin to report temperature in degrees Kelvin.Folks will be afraid to walk out the door.

[Weather Spotter]

Do you have any pictures of the rear tire strake off the car? I am looking for rough dimensions as well.

[NeilBlanchard]

I thought I had taken pictures, but I can't find 'em. Darn. I'll measure it. Obviously, mine are shorter (from the tire back) than the one Darin made. The height is working pretty well for me -- most curbs are not an issue (yet).

[Weather Spotter]

Distance off of the ground would also be nice to have, thanks!

[G2TDI]

Originally Posted by NeilBlanchard

I think outside will be much better -- at night, the infrared LED's would cause a glare on the inside of the glass, I think. Also, in the rain, it is a very good thing having the cameras outside, because then they are not affected by the water drops on the outside of the window, or the mist/moisture on the inside.

They need to be slightly away from the side in order to "see" straight behind the car. Since mine are mounted on the stock supports for the mirrors (I can still mount the mirrors for inspection, or if I sell the car) they show me vehicles that are directly behind me. When a large truck is right behind me -- I can see it in all three mirrors (both video mirrors and the rear view optical mirror).

Do you experience much "glare" into your eyes at night from the monitors?