Interesting stuff. Things like tarmac heat's influence on adjacent air temperatures are often taken for granted in the absence of the real world variables like those mentioned above. A simple measurement of external air temps at different heights taken on a moving vehicle and compared to static temperatures at the same heights would shed light. I'd be curious, but even then results would only be applicable to the conditions in that place on that given day.

Mike, I understand that you don't want to get into details and technicalities about your build at this time, but it's very intriguing stuff and people will naturally want to see and hear more (myself included). I hope you change your position on sharing more thoughts, details and photos.

I figured both this and the rad were dead issues. With 500 hours of development I assume you have it worked out but I am not aware of a modern sports racer that draws intake air from the bottom so "agree to disagree" is in play and it has worked for thousands of years. :)

My Mustang has the inter-cooler HE mounted at the bottom and without boxing, larger heat exchanger, dual fans, and manual switch we could not keep it cool. The ECU would pull timing and spoil the day. The air cleaner is boxed in the front fender and I pull air from the bottom thru the factory brake duct opening in the bumper cover. The last time I ran it, ambient was 95 and IAT1 would run as high as 118. It did not shut down, so we have made significant progress, but I am going to move the air intake to the head light or use a NACA duct on top of the fender next year.

One should keep in mind when Smiths books were written - to imply his work is not based in empirical data is simply not right. Katz, McBeath, and Stainforth all use emperical data, but are much more current publications.

The high down force configuration. I am interested in its integration to your bottom and front clip.

Morris built a full aero rocket, but was sent away :(

x-chr

Forgive the reply within your quote, seemed easier.

Thanks for posting more images :)

How much speed do you need to overcome the engines air consumption and start building pressure?

Come on ERA, don't give up on me. You wanted to call my work into question and I'm not seeing much rebuttal at this point.

No sweat, I'll just continue without you.

Step 1 was to measure the actual heights that matter to me. While coming up with a nice temp gradient with multiple data points would have been great for educating the world, I don't actually give a crap about the world's collective ignorance, so I'll only take data points that matter to me. We also need to remember that the actual temps don't really matter as we are only concerned with the temperature gradient, so let's not head down the road of humidity affecting readings.

The heights above tarmac that matter to me are the ram air inlet (oil cooler opening), radiator duct (just in case I want to pull air from the top), just above the top of the radiator inlet (this is the air that will go into a normally positioned scoop, and finally at throttle body inlet height (this covers getting stupid and doing a snorkel inlet). Here is the heights above tarmac being measured with a laser level.
http://dynashield.com/sitebuilder/im...99-600x450.jpg

The final measurements work out to as follows:

Ram air: 7.4"
Radiator: 14.75"
Upper lip above the rad: 22"
Throttle body top: 29.75"

So the challenge now at hand is taking accurate temp measurements. My thought is that the biggest threat to accurate readings are:

Multiple measuring devices
Rapid measurement times
Radiant heat altering probe temps
Heat being conducted from objects contacting the temp probes

As a result of the above, I decided the fastest way to rapidly take multiple temperature readings from one device was to use a non contact thermometer. Lucky for me I already own a nice Raytec unit. The problem with non contact thermometers is that the target's reflectance can cause wide variations from actual target temperature. They get the most accurate readings from flat black surfaces. My solution was to make test coupons for the readings from .032 6061T6, and coat them in flat black on one side. To keep coating reflectance and thickness variances from influencing the outcome, each coupon was coated on one side with .002" thick cast flat black vinyl.

http://dynashield.com/sitebuilder/im...95-600x450.jpg

Next issue was insulating the coupons from any heat transfer though either radiant or unwanted conductive heat transfer, but also allowing maximum air contact for an accurate air temp reading. The solution was to make coupon mounts from 1" thick eps foam and coat that foam with foil to prevent radiant heat transfer.

First some hot wire action.
http://dynashield.com/sitebuilder/im...96-600x450.jpg

Then bonding on some foil.
http://dynashield.com/sitebuilder/im...97-600x450.jpg

Then cut into 4"x4" blocks.
http://dynashield.com/sitebuilder/im...98-600x450.jpg

To keep the test coupon from touching the foam, a toothpick (insulating wood) was epoxied to the back of each one, then it was positioned in the center of the foam mount .25" above the foam. To ensure consistency, the .25" measurement was maintained with shims until the epoxy was fully cured. The foam mounts were then positioned onto a rod and onto a base plate. Each mount could then be positioned where needed for a measurement.
http://dynashield.com/sitebuilder/im...01-600x450.jpg

Now that the test coupons are protect from radiant heat from the tarmac, I needed to protect them from the radiant heat of the sun, so I made a shade with cardboard and foil backing. Here is the entire assembly getting a proving run with the IR heater. Note that each foam mount is positioned so that the coupon is at the correct height, plus one coupon 1.25" above the tarmac.
http://dynashield.com/sitebuilder/im...00-600x450.jpg

Once all the test fixture proving was completed, it was time to take it out and do some real world testing.
http://dynashield.com/sitebuilder/im...04-600x450.jpg

Due to the varied reflectance of the tarmac, a test coupon was laid directly on the tarmac for temp sampling.
http://dynashield.com/sitebuilder/im...05-600x450.jpg

So ERA, you ready for some real test data, or will having your illusions shattered send you off the deep end?

You are welcome, but be warned that the answer will start another debate.

Pressure is all relative. When you use pressure readings taken at the airbox as reference, you will begin building pressure at pretty much anything above idle, even without forward motion. The reason for this is the nature of a divergent system. At the risk of oversimplification, the divergence will cause the higher velocity air at the inlet to begin "packing" the air as it slows. Also think Bernoulli's principal, as the air velocity decreases, it's pressure will increase. On a proper divergent ram air system, the combination of these two forces will result in a "less vacuum" reading as compared to no system at all, which can be counted as a pressure increase.

Without counting the effectiveness of the divergent system, pure ram air will net ABOUT 1.2psi at 200mph.

ERA,
You want the full excel spread sheet or just the meat? C'mon, take it like a man.

Is this something you just did? What was the ambient temperature? What was the temperature of the tarmac?

Nice work - what were the results?

Your dam looks great -

You seriously need to relax. :)

x-chr

I'm very relaxed. Testing was already conducted way back. The laser front pic is current as demonstration of what was accomplished.

Keep in mind that I wanted to avoid debates. I'm quite comfortable with the ignorance and think no less of you for it. What I do have little tolerance for is people rudely criticizing my work using their ignorance as justification. You may consider my absolute lack of respect for the opinion of internet experts as arrogant, but you would once again be mistaken. I have total respect for you as a person, even if you do base your opinions of other's repeated unsubstantiated crap. You also seem the think that I should be in awe of this forum's size and the resulting diversity of total ignorance, but as before you are mistaken.

You ready for some test results? Last chance to get me banned before I post them.

Here you go. So what would you like to debate next?

Test data,

Air temperature testing was conducted as follows:

Testing was done with a test fixture that mounted test coupons at the desired height and insulated aluminum test coupons from outside heat sources. Testing was accomplished on both concrete and asphalt surfaces, and during cloudy, partly cloudy, and sunny conditions. Each test was accompanied by a control coupon mounted in the shade and with its radiant barrier towards the sun.

Test coupons were set as follows:
1. Reference coupon. Mounted coupon under a shade tree with reflective foil towards the sun.
2. Bare coupon directly on tarmac
3. 1.25” above tarmac
4. 7.4” above tarmac
5. 14.75” above tarmac
6. 22” above tarmac
7. 29.75” above tarmac

Results for all tests were consistent regardless of surface being tested or level of direct sunlight, with the only difference being the temp gradient spread from coupon 2 vs. the others. Wind speed made no significant difference with the exception of normalizing temperatures of coupons 2 and 3.

The following test was taken in early afternoon on a calm day. The readings are an average of 20 samples taken over a period of twenty minutes after a 15 minute soak. High and low readings were eliminated for each.

1. 73
2. 104
3. 74
4. 73
5. 73
6. 73
7. 72

Looks like you need to keep your intake off the tarmac.

Oh wait.... you are.

"There's none so blind as those who will not see."

Like many, I've spent a good portion of my life dealing with people who are so sure they're correct they find it impossible to consider other possibilities. More often than not it's because they heard it from someone they know and trusted, so it must be true, right? The Internet has only compounded the problem, allowing near-universal access to a great wealth of incorrect opinions and misinformation - especially if they 'Google' it using terminology that's stuck in their tiny little brains.

Notwithstanding the foregoing, it is entirely possible to use the Internet to find correct and accurate information, but it takes more than technology and an Internet connection, it also requires an open mind. If only there were more of them.

I have to admit that when I decided to do this testing that I would be focusing my energy on mitigating factors such as the effects of traffic, crosswinds, and recovery times. I was blown away to find essentially no temp rise over tarmac at all. I was expecting somewhere in the area of 20% of tarmac differential temp, not 0%.

My favorite quote in the world is: "The larger the circle of light becomes,the greater the perimeter of darkness around it." Albert Einstein.

Like this?:3DSMILE:
http://www.joblo.com/newsimages1/heavy_metal3xx.jpg

Wow - 30 degrees in 1.25" and no significant change after - that is amazing. Regardless of belief, I would not have expected it. 75 is a fairly cool condition. Did you ever run it in hotter conditions? Not debating, just surprised and wondering the affect of radiant off the surface at higher temps i.e. as temp rises the differential zone rises too and is it linear? It has been my experience on a hot day (90+) I can instantly feel the difference in temp when walking from the grass onto the track. It would be interesting to test at Phoenix or Riverside in August.

Appreciate your work -

How much pressure do you expect @ 100mph with divergent?

I don't think you ever told us the intended use of your car? I assume by the aero, road race.

Will you run a splitter?

x-chr

.....

Not to be a smartass, but with a projected weight of about 2,000 and over 700hp on tap, I'm more worried about traction at 100mph and ram air at about double that.

weird, double post.

It will be very interesting to see the net static pressure at the engine box when you get it running. Do you have a ballpark guesstimate?

I'm not clear what you mean by static pressure.

Edit: Doesn't really matter, I run out of fingers and toes long before those types of equations get solved.