One of the biggest aerodynamic problems with the majority of bluff body vehicles (most hatchbacks, vans, wagons) is the amount of pressure drag / size of the trailing wake. In other words, the rear of the vehicle is where the big gains are to be made.
That said, a hatchback configuration isn't automatically an aerodynamic death sentence. Several of the most slippery production cars in recent years (1st gen Insight, 2nd gen Prius, Audi A2) have used "Kammback" shapes, where the roofline tapers downward, following a particular shape (a "chopped" teardrop).
It's possible to retrofit this shape onto existing vehicles and gain a measurable improvement in fuel economy.
Instructions for mod
Information required: How do people perform this modification, pictures, problems, what to look out for
Information required: A listing for different ways to do this if its different on different types of cars
Please enter your user name and any relevant data in the table
|User Name||Car Make, Model, Year||Cost of Mod||Time to Perform Mod||MPG Before Mod||MPG After Mod||MPG improvement guess||Instruction Link|
|Weather Spotter||Toyota, Matrix, 2006||$15 USD||12 hr||45.06||45.98||1.98% (.91 MPG) ABA testing 2.34% better aero (coast down testing)||Weather Spotter's Data and How To|
|3dplane||94 Mazda Protege DX||$34||8 hr||limited testing showed that the particular design hurt MPG||3dplane's Kammback how to|
|wyatt||94 Suzuki Swift 5MT||$10||12 hr||48||50.9||6% (2 1800+ mile trips) 12% better aero (coast down testing)|
Problems / Consequences of mod
You might reduce your rear view, most states require a certain distance behind your car to be viewable. You also might add to the length of you car (parking issues).