View Single Post
Old 02-04-2010, 05:07 PM   #5 (permalink)
Batman Junior
MetroMPG's Avatar
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,313

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.8 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 73.57 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)
Thanks: 3,086
Thanked 5,964 Times in 3,089 Posts
Cool! Subscribed.

The underside of the Flea's boat tail angled up to 6.5 degrees, and retained attached, if turbulent flow to the trailing edge, documented in the tuft testing video.

I think basjoos is right: you can get away with steeper angles if you have adequate radii between sides/top and sides/bottom plus taper in both plan and profile. That would permit pressure recovery from the sides, and the bottom angle can be increased.

My taper used predominantly straight lines on the top & sides, but if you arc gently through the taper, you can go up to 22 degrees and retain attached flow, says Mair (says Phil). The Insight has decent enough upstream aero that I bet it's possible on your cars.

The challenge in construction for you guys will be the unusual cross-sectional shape at the rear of the car. You've got a lot more taper already in progress in the greenhouse at the transom than you do at the height of the rear wheels.
Latest mods test: 15 mods = 15% MPG improvement: A-B test, 2007 Honda Civic 1.8L, 5-speed
Ecodriving test:
Manual vs. automatic transmission MPG showdown: Nissan Micra 1.6L

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