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Old 11-21-2009, 05:44 PM   #102 (permalink)
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Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 55.97 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

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Originally Posted by Cd View Post
would be interesting to see how much turbulence is on the very back and underside. ( like behind the wheels )
I think we know there's going to be turbulence behind the wheels!

But I am planning to tuft the bottom boat tail surface and see what it shows. I'm expecting turbulence over all of it, with no belly pan.

When do you plan to add minitails to your mudflaps ?
Ummm.... Tuesday, June 21, 2011.

I don't know! Eventually. After I lower the car... eventually.

Also, I know that you didn't get good results with your bellypan test, but as you mentioned, the cardboard was drooping down during the test. Do you ever plan to redo the test ?
I had that one botched test (the one with the droop), then I re-did it with just an A-B comparison, 3 bi-directional runs each. It showed about a 2% improvement at 90 km/h (56 mph).

Since I have the prototype boat tail built, I'm going to put the belly pan back on, fair the rear control arms into it (they stick waaay down below the plane of the floor pan), and then test the works.

I suspect the bottom of the tail is useless without the belly pan, so might as well see what all the bits are worth together. I suspect the effect of belly pan + boat tail (assuming the bottom angle isn't too steep) is greater than the sum of the individual mods' effects.

Originally Posted by Nerys View Post
quick shot of BLACK spray paint and it will even have a nice 20ft finish.
I thought about painting it, but this is just for testing. The "good" version will be black.

Originally Posted by Bicycle Bob View Post
Will we see little fairings behind the mud flaps, too?
Yep, eventually. See above.

The thing about the concave rear is to encourage a single large vortex to form there.
A little confused about that. How can we have a single vortex shed off the rear of a vehicle... unless you mean one that's rotating on an axis parallel to the "transom"? (As opposed to parallel to the direction of travel, which would necessarily mean a pair, wouldn't it?)
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget
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