Wind tunnel testing on the S30

[TomoHawk]

Do you mind to remind us what cD, cLF, and cMY are? I forget...

[hls30.com]

Cd-Coefficient of Drag

Clf Coeficient of lift

Cmy Coeficient of yawning moment (it is late after all!)

Will

[26th-Z]

Carl, I just wanted to get the slang out in the open and alert the crowd to the fact that Nissan offered aerodynamic devices on the Z. I think Car and Driver missed the boat on the "chin" spoiler. Obviously, no matter how small, it has some effect. So I don't subscribe to what they said. Poor journalism, in my opinion.

Glad to hear that headlight covers decrease drag. How many miles of driving do you think it will take to pay off the amount I paid for them?

[Carl Beck]

Glad to hear that headlight covers decrease drag. How many miles of driving do you think it will take to pay off the amount I paid for them?

Hi Chris:

A few possible answers to that question come to mind.

1. You won't live that long, even if the car runs that long..

2. Far less miles at $2.75 per gallon, than it took to pay for it when C & D conducted their tests!!

3. It is not so much a matter of the improvement paying for itself - as it is a matter of you being willing to pay whatever is necessary to make your Z Car even MORE GREEN (so to speak).

A 0.2 mpg increase in the efficiency of your Z at 70 mph, over time might result in some poor student in China being able to add a gallon of cheap gas to his Toyota, or someone in India being able to get to the Customer Call Center - in time to take your calls on a Customer Hot Line...

0.2 of a mile per gallon increase, means that on a 15 gallon tank of gas - instead of running out of gas 3 miles from the nearest gas station - you can coast up to pump.

FWIW,

Carl

BTW - at Post 7 Chris mentioned Ben's article - and by mistake I quoted Arne's reference to the C & D article.... da... hope everyone figured that out...

[Carl Beck]

Members at hybridz including myself are putting togther donations to take the S30 to a wind tunnel I thought I would let the fellas here at classiczcars know. BJ Hines and a few others from the North Carolina area have gotten together with the owner of a windtunnel and are planning to rent the windtunnel for some basic testing/ data collection on the Zcar, both in stock trim, and with a number of spoilers/airdams/aerodynamic devices to see what really helps, what really doesn't and what cause and effect can be measured.

This is VERY important to each and every one of you who drives an S30. We all thumb thru the pages of each vendor catalog, trying to decide which air dam looks best, or which rear wing provides the most function along with form. Don't you want to know WHAT TRULY WORKS? After this testeing is done will be be able to finally end the debate on what works and what doesnt. All the information gathered from this will be free and open to the public, it will be posted on hybridz.org in the form of video, pictures, and graphical information from the wind tunnel. here is the link to the thread on hybridz http://forums.hybridz.org/showthread.php?t=116938

Hi datsun40146 (everyone):

First let me say that I applaud your efforts. I like the idea of having the results of a day's work in a wind tunnel. My problem is I don't know "why" I like that idea!

I have read the thread on HybridZ... and

Personally, I have no idea what specific tests can be conducted in a wind tunnel, nor how the effects of air flow over, under, around the car are actually measured. (what instruments?, how is the car connected to them?). Because of that lack of knowledge, I have no real idea of exactly what data or information will be reported.

For example - aside from viewing the air flow over , around or under the body, and then guessing at their effect - what test instruments are attached to the car in the wind tunnel, that actually measure down force, lift, or drag? What instruments are in the wind tunnel that actually measure air speed at various points along the car - or are there any?

In the Car & Driver road test done years ago - they hooked up test equipment that measured changes in the ride height of the car as it was running on the road, and thus computed pounds of lift or down force at the wheels. Is that type of equipment used in the wind tunnel?

Isn't the coefficient of drag simply calculated based on the profile of the frontal area of a car? It's not actually derived from measurements taken in a wind tunnel is it? Are Down Force and Lift actually measured?

Aside from viewing laminar flow and turbulence, then identifying areas of high or low pressure based on observation - maybe a little more detail about exactly what information or data would result from a wind tunnel set up would be helpful. That is to say, what is actually measured there and how is it measured - as opposed to being calculated.

Maybe some real details would help raise the contribution levels.. It is not so much a matter of what works and what doesn't - as it is a matter of knowing that something works well enough for either your intended purpose, or well enough to justify the expense of adding it.

I thing VaGus510 ask a good question related to the cost benefit of a wind tunnel vs. a CFD model as well.

FWIW,

Carl B.

[datsun40146]

Carl copy and paste what you have written here over at hybridz in the post pretaining to this. They will answer your questions in full to the best of thier ability. I can't answer your question for sure but I think they use a stream of smoke to see how the air is flowing over the body to creare drag.

Here is the link http://forums.hybridz.org/showthread.php?p=714796#post714796

[Go240Zags]

Glad to hear that headlight covers decrease drag. How many miles of driving do you think it will take to pay off the amount I paid for them?

There's two sides to that coin. The higher gas prices go up the sooner you'll pay for the covers. A hidden benefit to gas price increases maybe? .

Edit: Guess I should have read Carl's response first.

[John Coffey]

Glad to hear that headlight covers decrease drag. How many miles of driving do you think it will take to pay off the amount I paid for them?

It also depends on how fast you drive. They do offer a useful drag reduction at speeds over 100mph.

[hls30.com]

I just went through the HybridZ thead on this, and it looks like the test will take place in March, they are exploring the option of a second day of testing, and are evidently going to be checking for aerodynamic tuning-meaning seriously altered bodywork. I hope some of the members here who are on that thread will elaborate on what is going on, as I am certain the actual plans for the testing are being concluded off thread.

Will

[dspillman]

Hi datsun40146 (everyone):

{What instruments are in the wind tunnel that actually measure air speed at various points along the car - or are there any?

.. Are Down Force and Lift actually measured?

- as opposed to being calculated. }

FWIW,

Carl B.

HI Carl,

For those interested.

I've been told that car rests upon 4 pads measuring a multitude of inputs.....Should be quite accurate.

David

[hls30.com]

I hope every change will be photo graphed, or the session videotaped for study.

Will

[LEB]

I've been looking at the wind tunnel post from time to time. I've been involved in car testing a number of times over the years in a number of tunnels. I was the guy making the changes.

They basically set the model on supports under the wheels without the wheels actually touching the ground plane. There are then very sensitive gauges attached to these mounts called strain gauges. Thus whatever loads that are put on the four corners are measured by a thing called a balance. The car can be run at yaw angles as well as straight forwards. It's usually difficult to change the ride height quickly.

I'm not into the actual math used but by using the frontal area of the model and the area of the tunnel they compute blockage and then ultimately the drag. By doing it this way you can compare different cars, trucks, etc using the same scale. It's possible for a v an to have a better drag coefficient than a sports car.

The speeds that are used are usually determined by trying different speeds and making a graph to see where the top of the curve is where it levels off and becomes reliable. The lowest speed that works is where they want to run because of the heat generated by the moving air. It takes a lot of air conditioning to keep the temperatures down.

Basically you start at the front and work towards the back. Any changes that are upwind of other changes can make you start over. The biggest improvements are usually at the front. There they have the potential to affect more surface. I have made headlamp covers only to find that they didn't help.

Finally, I'm only knowledgeable with working to achieve the least drag. If you want to go racing, you have to use a completely different set of goals. (That's where I don't think their wind tunnel exercise will be too effective. For everyday driving there's a lot of leeway in what the loading can be. If performance is considered it has to be coupled with tires, power available etc. The more power available the more you can trade off for performance. The variables are endless.

Larry