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Originally Posted by aerohead
The Kamm-back car is based upon a 1/2-streamline body of revolution.These bodies cannot produce separated flow due to their perfect sectional density.Drag coefficient is simply a function of body elongation.
The notchback car is a mutilation of the ideal form and technically,is 'challenged',as far as drag goes,and will not (cannot) react to boat-tailing as will a K-form.
It is true,that up to a point,the notchback can have little penalty as far as drag goes,compared to the same car with a K-form greenhouse,but after that,you'd need the K-form to get the drag lower.
It may have been MetroMPG who modified a Honda similar to your's with a K-form addition,only to see no real drag reduction after all his effort.
You might want to select a Cd target,then inspect vehicles(especially Honda's) which already meet that target,and see if your car might benefit from some of their features.
Research by Audi,on their Audi-100 III demonstrated 'saturation' points for specific mods,whereas some part would respond positively to a certain alteration,after which,no additional shape change could produce additional benefit.This is exactly what 'optimization' is all about.
There are production Honda's of Cd 0.27,and Honda concepts of Cd 0.20.Honda solar racers as low as Cd 0.10.
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Makes me wonder why people react negatively to kammback shaped vehicles such as the CRX and Prius when they're so much more streamlined...after all it isn't that hard to produce an aesthetically pleasing fastback car.
Quote:
Originally Posted by 19bonestock88
I did vortex generators on the Malibu that I had and water tested the back glass before and after... I copied the formula from the Evo, and had them about 4” above the glass... beforehand, there was flow separation in the center of the glass, that showed itself in water(dew in the morning) taking forever to run off if at all on my commute... after I added the vortex generators all the water run off as soon as I got up to 50mph, but I couldn’t detect any net improvement in drag... it took the same(or within a window of error) throttle/load to hold 55mph on flat ground as it did beforehand... now I never did a true coastdown test to produce more accurate data than just engine load at cruise, but eventually I removed them(after two tanks I think) both because I didn’t think they were helping and because my then wife was starting to refuse to ride in the car...
The visor isn’t a half bad idea(might use on my build), and they can be found for $30-50 for the Civic... a shame I can’t get one made specifically for my car, I’d have to cut up one for a Corolla or something... like mentioned earlier, cut a slot near the leading edge(about 2” wide(est.) and almost as long as the whole visor) to allow an air fence and I’d really think of using thin Plexiglass to extend the trailing edge to about where the trunk lid comes up to when open... if you follow the template shape, it *should* help
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The description of the ebay visor SAYS it helps with FE....but then again practically every exterior vehicle accessory claims to help with FE, even the ones that obviously don't.
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Originally Posted by freebeard
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cringes Yes, lol.
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Originally Posted by kach22i
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That is an AMAZING chart. Saved it for reference!
Quote:
Originally Posted by kach22i
If you are a " if it's not broken - then don't fix it" type of guy, then why are you posting here?  |
A Civic is broken if it can't easily beat 40 MPG on a tank, and my Civic is down to 36-37 even with hypermiling (due to short, cold engine trips). Therefore my Civic is broken and I need to fix it.
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Originally Posted by kach22i
Enough talk, just build something.
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Just waiting to get my timing belt replaced before modding.
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Originally Posted by Ecky
A good example is a pickup truck bed. It's usually the case that drag is lower with the tailgate up, rather than down.
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I know my Civic isn't a pickup truck, but just curious, is this because having the tailgate up creates an enclosed area that contains the airflow more?
Long post, I know..hopefully y'all can find all my responses to your posts in here.
