Effects of a slightly open Hatch?

[GasSavers_TomO]

I am curious as to the effect that having the rear hatch open along with the front windows rolled down all the way have on the drag of a Civic Hatchback.

I have a nifty little device that can hold open the rear hatch of almost any car. I've used it on my CRX's hatch and now my VX Hatch. It was originally designed for 4th and 5th Generation Corvettes, but the guy made one up special for me so he could branch out his application list. Corvette Gadget Man is the site I got the item from.

Anyways... With the windows down (when extremely hot and humid out as well as my daughter not being in the car) I would put this in the hatch glass latch and VIOLA!


When in this configuration, I don't get any cross-winds or turbulence inside of the car. I do get a small whiff of fumes when taking off from a stop, but nothing horrible. Does this configuration reduce some of the negative pressure behind my car, make it worse, or no change at all?