EcoModder Forum Which mass produced car is closest to a teardrop shape ?

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 11-17-2008, 01:24 PM #51 (permalink) Civic 4 Life     Join Date: Jun 2008 Location: USA Posts: 229 Civics Lesson - '08 Honda Civic LX Team Honda 90 day: 40.53 mpg (US) Thanks: 0 Thanked 2 Times in 1 Post I think the force of drag is (1/2)(Cd)(frontal cross-sectional Area)(fluid Density)(Velocity^2), so Cd is separate from the area in the equation. __________________
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 11-17-2008, 01:48 PM #52 (permalink) Moderate your Moderation.   Join Date: Nov 2008 Location: Troy, Pa. Posts: 8,919 Pasta - '96 Volkswagen Passat TDi 90 day: 45.22 mpg (US) Thanks: 1,369 Thanked 430 Times in 353 Posts except when you compare overall drag to complete frontal area of the vehicle, you get a true indication of exactly how aero it is. You could potentially make something shaped like this | | | Have a Cd of .40.... Or you could have a shape like this \ .| ..\ With a .46, but the second shape is still more aerodynamic, when you compare the Cd to the overall frontal area That's what I meant when I said that. __________________ "¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"
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Quote:
 Originally Posted by Christ except when you compare overall drag to complete frontal area of the vehicle, you get a true indication of exactly how aero it is.
But Cd is not the overall drag, it's purely a function of shape. A toy model of your van will still have the same Cd. To get total drag, you multiply the Cd by the cross-section area.

 11-17-2008, 09:20 PM #54 (permalink) Master EcoModder   Join Date: Feb 2008 Location: belgium Posts: 663 vectra a - '95 Opel Vectra GLS 90 day: 37.51 mpg (US) Thanks: 14 Thanked 61 Times in 44 Posts simply put its about the amount of air a car needs to push aside and how smoothly is can do so. a brick is less aerodynamic than an ev1 but it still has less overall drag as its smaller. __________________ aer·o·dy·nam·ics: the science of passing gass *i can coast for miles and miles and miles*

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Quote:
 Originally Posted by jamesqf But Cd is not the overall drag, it's purely a function of shape. A toy model of your van will still have the same Cd. To get total drag, you multiply the Cd by the cross-section area.
SO, while I mistyped exactly what I was trying to say, you clearly understood it enough to argue with it.. essentially making less sense.

I'm well aware that Cd is not overall drag, and I'm also aware that CdA is the overall drag figure.

What you've stated here that is not entirely true is that a toy model of a vehicle will have the came Cd as the full-sized vehicle. It will not, even when built to scale, as a direct result of manufacturing inefficiencies.

But I digress, we're taking this off topic.
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 Originally Posted by metroschultz Hey Phil, I'm thinking take my Metro/Swift engine /trans and put in a stripped out Probe rolling chassis. I would play the devil getting the weight out (and for the suspension I would not be able to remove weight), but what about the possabilities for aero on something like that? Schultz
NOOOOOOOO!!!!!!!! Would be very unwise. The Probe weighs over 1000 pounds more. And for the suspension, Metro parts probably weigh half as much.

Makes much more sense to leave the Metro engine in the Metro chassis and do aero mods, such as basjoos and others have done.

 11-18-2008, 12:18 AM #57 (permalink) 93 Metro Streamliner   Join Date: Oct 2008 Location: Oregon Posts: 180 AeroMetro - '93 Geo Metro Thanks: 1 Thanked 14 Times in 7 Posts Imagine this car with all the wings, mirrors, etc shaved off, and front and rear wheel skirts.
 11-18-2008, 12:34 AM #58 (permalink) Moderate your Moderation.   Join Date: Nov 2008 Location: Troy, Pa. Posts: 8,919 Pasta - '96 Volkswagen Passat TDi 90 day: 45.22 mpg (US) Thanks: 1,369 Thanked 430 Times in 353 Posts Metroschultz - think of putting 1,000 lbs of bricks in your metro... or 7 average guys. That's what it would feel like still trying to drive that thing. Noone said you had to sacrifice power or speed to get gas mileage. It helps though. What you'll probably end up doing, is getting further into the pedal trying to accelerate safely (without impeding traffic), and end up getting worse mileage. Unless you can take about 800 lbs off that car, don't bother. __________________ "¿ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"
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sputnik - '93 oldsmobile silhouette
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Quote:
 Originally Posted by Christ The Silhouette is not that bad.. except, again, the hatchback rear config... It could also benefit from a Kammback or boattail with some pretty extreme benefits... When GM says the Cd is .30, they're not giving you the proper figure... what's the actual frontal area of your nearly 7 foot tall van? When you figure that in, you're not getting that great of a deal. Swapping a Metro/Swift 3 cylinder into that van could be relatively easy though.
yes i know the difference between cd and cda

so the van is a whopping 5'6" tall, 5'7" wide at its widest (not including mirrors,still counting airspace under car) actual frontal area is pretty close to 30sq ft.

depending on your needs, it is a good shape. do you want to bring 6 friends in your metro, depends on your friends i guess.
i can fit full sheets of plywood inside the van, compaired to a pickup, or stacking them on the roof of a car. aero is going to be much better.
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 11-18-2008, 12:37 PM #60 (permalink) Ex-lurker     Join Date: Apr 2008 Location: Jersey Posts: 571 Skeeter - '05 Toyota Corolla LE 90 day: 35.55 mpg (US) Thanks: 2 Thanked 8 Times in 6 Posts Nissan 350z is the closest I see regularly Attached Thumbnails   __________________