Tuft testing
This article used to be paid access only, if I'm not mistaken. Looks like a free for all now:
https://us1.webpublications.com.au/st...108656_5lo.jpg https://autospeed.drive.com.au/cms/A_108656/article.html Hopefully they'll re-publish the next parts freely as well. |
Aero Testing Part 2
I have been impressed with the work I have seen done at AutoSpeed.
They seem to have a good grasp of what they are trying to accomplish and make it easy to understand. I think I have additional parts of this story, will post them later. https://autospeed.drive.com.au/cms/A_1055/article.html |
The extra parts are free too. But the navigation on it all can be kind of tough.
Very very good article. |
Aero Testing Part 3
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Thanks guys!
Two good way to save these: 1) save as html {or] 2) Highlight the article itself with pics - not the web page border etc. etc. Then copy and paste into a word processor document and save that. The "Printer Friendly" link wasn't as good as the word processor method, it bunched all the pics at the top of the first page. |
Aero Testing Part 4
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More.....I need more ..... wahahaha !
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Aero Testing Part 5
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https://autospeed.drive.com.au/cms/A_1080/article.html |
Thanks for the post. It has been a great help!
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I'll post pictures of my '93 Civic hatcbacks tuft test when I get around to it later.
I would post the video, but I would have to block out my number plate frame by frame .... which while I'm at it I'd like to ask ..... why DO people ( and magazines ) block out the number plate ? Can people get some kind of classified info about you from your plate ?? |
I have wondered that too. I mean, if I want plate numbers, I don't need to go look on the internet...
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Paranoia.
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>>I would post the video, but I would have to block
>>out my number plate frame by frame .... Post the video. You don't think people see your number plate when you are driving down the road? "-) |
I'll post some stills. I notice even the magazines block out the plates.
There has to be a reason. ;-) ( Also the video is VERY shaky - almost useless really ) |
I uploaded some pictures at : https://www.flickr.com/photos/82006403@N00/
The tuft testing images are further down the bottom. There is atotal of maybe fifty or so. |
Cool stuff. Thanks.
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Very, very, very interesting..... partly because I hav a Civic, but still.....
Some observations, let me know your thoughts and between us all we might get some interesting conclusions. - Kammbacl works on the side, but not the bottom (the bottom needs to be.... on the bottom. Where it is just introduces an additional voids and turbulence area - Look at the back bumper.... flow down, under, and forward? Makes no sense if you think wind tunnel. Does make sense if you think about the car travelling down the road over stationary air, pulling some with it, leaving a vacuum to fill in from the sides, back, front, etc. - Rear wheel well sicking in.... see previous - Front wheel well not sucking in.... maybe that really is brake dust on the front rims :-) - Serious cowling into hood flow... bet the vent works well - Texan eh? Not an Aggie I hope. - Something you have good that I did not... no flow into the front hood seams. I had to beef up the weather stripping there. - Interesting that you have a belly pan,,, and also the rear bumper reverse flow... thinking it would be worse without the pan, or the pan did something unexpected. - Yeah, my mirror sux too Wow... thx for the shots.... very enlightening. Gives me some clear ideas on changes. |
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Great photos. Very instructive. |
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This is one of those counter intuitive things. I think it helps to not think wind tunnel and think staionary air with car moving through it. The air under the car for example, on one hand gets battered around with a net forward momentum add. Contrasting this is the air up front which is rushing below and under the bumper picking up speed towards the rear. Messing it all up even further is the stuff exiting the engine compartment. So you likely end up with a pressure increase under the car up front, and a decrease near the rear. Note that the data in these pictures has me thinking of this explanation, not independently, but this explanation would describe the observed behavior.
If all this is correct, the following should help (let's see if the recommendations are consistent with other observations): - Less air into the engine compartment means less backward velocity increase and turbulence underneath..... grill block. - Smoothing out the underbody imparts less forward momentum into the stationary air..... underbelly pan. - Deflectors underneath diverting air around remaining appenditures, like lower control arms would help in addition (but should be teardrop shaped completely.... just a parabolic front is not enough. - Deflectors in front of the front wheels to divert air outward would help. - Wheel skirts (exterior) in the back to keep air from rushing into the rear vaccuum would help. - Wheel skirts (interior) in the front would keep the flow underneath the car - Vertical lengthwise channels would keep air flow uniform and.... but here is an anomoly... a diffuser to reduce velocity in the back would be counter to the data.... want to speed up in this case? - Any spoiler up front that moves air up instead of down should help (smoother streamlining above). - Lowering the car should help. This is starting to make sense :-) For the coup de gras, a properly channeled underbody with an electric fan assist in the rear, velocity driven by delta air pressures between the under rear and the behind.... equalize ???? |
Whuuups !
Well... now that I am sure that the images - can actually be viewed - I'll have to add some notes. About the test : This test was done some time ago. At the time, I did not have any sort of belly pan in place ( sorry to mislead ) I installed an underbody covering a few months ago which extends to just behind the engine compartment. This should get rid of any 'parachute' effects happening back there. |
How can I link to one of those images folks ?
( Thanks for posting Bill - I guess I wasn't selecting the corect url thingee ! ) |
Bill - it worked . Thanks ! I'd post some images and make some observations ( and ask some questions too ) but I don't want to hijack this thread.
I'll have to create my own thread. |
Let's see what happens when you expand an image, right click on it, click "properties" and copy the url and paste it into the image dialog box that you get when you click the little mountain and sun button...
https://farm2.static.flickr.com/1376/...c76445.jpg?v=0Yep, that worked. |
]Very, very, very interesting..... partly because I hav a Civic, but still.....
Glad you could get some use out of it. It was really embarrasing, and I felt like an idiot when people were laughing ( including my parents who were my drivers for the test ) Now you guys have all the hard work done for you.:) " - Kammbacl works on the side, but not the bottom (the bottom needs to be.... on the bottom. Where it is just introduces an additional voids and turbulence area" Are you talking about the cardboard junk that I have taped to the side of the car ? Nevermind that. I originally had a cone shaped extention sticking out that I intended to test ( I have an image of the idea with the rest of the images ) I wanted to have one side with the extention and one without, but it all started to fall with gravity and rain was on the way, so I just took it all off except for the side piece. I plan to do a better test next time I visit my parents. " Look at the back bumper.... flow down, under, and forward? Makes no sense if you think wind tunnel. Does make sense if you think about the car travelling down the road over stationary air, pulling some with it, leaving a vacuum to fill in from the sides, back, front, etc." It should be interesting to see what effects that my underbody cover has on the airflow of the car in comparison to these images. ( The only aero mods at the time of the test were the mirror pull back and the partial grill block using my liscense plate ....and that cardboard junk on the back ) Any special areas that you would like to see tufted on the car the next time that I run a test ? " Rear wheel well sicking in.... see previous - Front wheel well not sucking in.... maybe that really is brake dust on the front rims :-)" I never noticedthat - I'll have to check that out better ! " Serious cowling into hood flow... bet the vent works well " Actually, just the opposite ! It is horrible ! Do any of you other Civic owners have this problem too ? It just barely blows ..and the air is warm. The vent isn't clogged either ) " Texan eh? Not an Aggie I hope." Nope but I'm surrounded by them ...I live in Austin now ! " Something you have good that I did not... no flow into the front hood seams. I had to beef up the weather stripping there." I would think that the hood seam would not be a problem at all. I'll have to create a post on a Hot Rod article that I read that completely changed my thinking about aerodynamics. They got an basically stock looking '81 Camaro with big rear tires and a brick flat cow-catching front end to a .20 drag coefficient . No side skirts, tires hanging out in the breeze, a big honkin hood scoop and they didn't even make the door handles and window trim flush. I was shocked ! Small stuff doesn't really matter all that much apparently. " Yeah, my mirror sux too" Actually I did that on purpose - it decreases the cars frontal area by a small amount . So nice of Honda to let us be able to pull the mirrors back ...and if you notice , it almost looks intentional - the mirrors profile is streamlined when pulled back :) Wow... thx for the shots.... very enlightening. Gives me some clear ideas on changes. No problem ! |
I started a new thread here : https://www.gassavers.org/showthread....0864#post60864
I posted the pictures that I have from a Hot Rod article that blew my mind. Seeing stuff like that just makes me want to throw up my hands and say forget it . Air moves in strange ways and you would think that it would flow a certain direction only to find out that it goes completely opposite. |
Yeah my vent is no good either. i am studying it now and have concluded that the air pressure cushion at the cowling is not all that high. For example, opening the window helps a lot (very low pressure outside the window) but opening up the hatch actually hurts.... how the heck the air pressure at the back of the car could be higher than the cowling amazes me but that is what i am seeing.
I was suspect of the camaro claim of .2 until I looked at the pictures.... if you want a low Cd you want to get all the air moving around the object in a streamlined fashion and avoid separation in the back by a shallow long slope. it may look like a brick from one perspective, but i see something that will really slip through the air in those pictures I am a former Austinite.... great great town. Every time I come back I go straight to Taco Cabana for the fajita's..... sounds crazy, but that is what I miss most. Oh, and yeah on the Kammbach cardboard rear.... i was pointing out that the lower extension being half way up the rear of the car really does nothing, as the problem is the air turning the sharp corners (which is why the sides do work). |
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( By the way ) I too have thought of an electric fan system which would blow air from the back of the car*. It could be powered by you cigarette lighter / AC outlet . It would really look stupid though. Imagine driving behind someone with a fan blowing back at you.:D ( * To get rid of vacuum at the back of the car. ) |
Based on the Autospeed articles, I bought a couple of Dwyer magnehelic gauges off Ebay. I have 0-0.5" H2O, 0-5" H2O, and 0-30" H20 gauges. Between the three I am getting some very interesting information at quite low speeds on my '98 Saturn. Using inexpensive gauges like this can add a lot to the knowledge gained from tuft testing. It's really nice for determining if the pressure behind your radiator increases (bad for cooling flow) or decreases (good for cooling flow) when you add a belly pan, and that sort of thing.
Bman |
Interesting.... what sort of pressure deltas do you see around the exterior of the car at speed? versus inside of the car, etc?
Let is have a look at some of the data... it would be interesting. |
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Show us your Photoshop image of your car.
Nerds laugh at me, You did all the tuft testing that you showed us all. Now show us the projected outcome of the changes you intend to make on your car.
Thank you, CO ZX2 |
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Also, any slim chances that I might one day go on a first date ( I'm now 34 ) will become even slimmer. Am I being sarcastic ..... sadly no ( really ) :( Oh ... you mean aero-wise ? I don't drive fast enough to see a real difference. I only use my car to drive the 7 miles ( exactly 7 ) to work and back. ( 7+7 miles back) Average speed is about 42 MPH ( speed limit is 45 MPH ) I have a hill that is just under one mile that I get up to 50 MPH and shift into neutral on. ( yes - the car is automatic. ) ( speed limit there is 55 ) I tried killing the motor a couple of times while coasting, but that doesn't work too well on an auto, since the car must be in 'park' before it can be restarted again. ( You have to pull the car over to the side of the road. ) I have several stoplights, and most are under a minute. I think what kills my mileage is rolling resistance and weight more than aero ( by a long shot really ) Since I must be to work by 4:00 AM, I do all my driving stunts early in the morning when there is little to no traffic. I drive like normal on the way home. I ride the bus as much as I can, and would like to bike to work, but I'm a little leary of new things like that. ( How will I be affected by 100+ degree temps while trying to pedal up that hill and rain... and criminals at 4 in the morning .... and ...and .......AAAAHHHH !!!! ) BTW, The next time that I visit my parents, I plan to do some more extensive tuft testing, including ........... well give me some time, since an illustration will do more than words ( I'll have a piece of cardboard dangling from the back of the car covered in tufts to show the flow a several feet behind the car ) I'm hoping that some of this can be beneficial to someone, but for me it's just couriousity ( and boredom ) I plan on adding a cardboard extention like this :https://farm2.static.flickr.com/1153/...73c55cd1_b.jpg It would just be a flat piece of cardboard that would stand out straight from the back of the car and be secured by some bracing attached with the bumper bolts. It would be mounted just top the right of the plate so as to be legal and have the required safety flag. The purpose of the thing would be to show the pattern of the air flow behind the car ( vs. just on the surface of the body ) much like what you would see in a wind tunnel using a smoke wand. Do you filks think this would work, or do you think that the airflow would be disrupted by the device ? |
N.l.a.m.-you are getting serious. They will quit laughing when you get 75 mpg. They will cry and kiss you when you get 100 mpg. Your cardboard will come to a point at the rear, right? What will you do at the bottom, cover it?
If you don't mind me asking, what do you do for a living? You honestly do have exceptional ability in drawing and design. I didn't see the rest of your post before I started writing. Heck, if you're gonna go that far, duplicate from your pattern for the other side and bring it to a point in the rear. Maybe taper the bottom up some, and cover the top. Duct tape will hold the pieces together. Then you will be testing something that may be out of this world. |
[QUOTE=CO ZX2;62748]N.l.a.m.-you are getting serious. They will quit laughing when you get 75 mpg. They will cry and kiss you when you get 100 mpg. Your cardboard will come to a point at the rear, right? What will you do at the bottom, cover it?
My car is a Civic DX automatic. The best I have ever seen was 56 MPG with the car ( but MetroMPG and I think it a fluke ) The average is just over 42 MPG highway - around 35 - 37 city. So 75 MPG .... uh.... no. Not unless I found some mountains like yours .:) As far as what you were talking about above , Actually, I think you misunderstand.( Or perhaps I misunderstood you ) That piece of cardboard is just a flat piece of cardboard with tufts all over it. Seen from the top it would just be a flat piece of cardboard turned on its side. The purpose of it would be to see the airflow several feet behind the car. Hopefully this would show any vortexes and spinning eddies. Do you think it will work, or actually effect the test ? If you don't mind me asking, what do you do for a living? I'm a gigello. ( Yah ... sigh. It gets a little boring sometimes with all those beautiful women. All they want is to make love all day. Oh well at least they pay me exceptionally well .) * You honestly do have exceptional ability in drawing and design. Thank you ! I need tons of practice. I didn't see the rest of your post before I started writing. Heck, if you're gonna go that far, duplicate from your pattern for the other side and bring it to a point in the rear. Maybe taper the bottom up some, and cover the top. Duct tape will hold the pieces together. Hmmm - again not sure what you mean. I plan to tuft test the car with, and without wheel covers ( maybe very temporary front ones too that would come off at the slightest turn of that wheel.) and with a couple of other add ons as well, such as my doublely-stuped-shop-vac-lookin-cone-headed-double boattail-extention. All of this would involve both my mom and dads time( the drivers of both the car and the chase vehicle - with me as the camera man) , so I don't know how much I can realistically get done in an hour or two. Then you will be testing something that may be out of this world. Nah ... people will just laugh and say "What the heck did you do that for moron ."[/QUOTE] * Actually, I work at your favorite store - or rather it's clone - Lowes. |
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