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Originally Posted by JeffD
California98Civic: Thanks for the link to your thread, seems like we were going down the same path. I'd be curious for a picture of yours. That is where the 100mm number came from.
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Thanks for checking out my test. I have the pics but have been missing the cable. I'll try to find the right cable and post them.
Quote:
Originally Posted by JeffD
Xist: thanks for the link, I had found a different presentation by the same person and subsequently lost it. ...
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If you want the PDFs I have them. PM me if you want them with an email address. I'll email the attachments. You are right that the box cavities that start at the outer body edge angle inward and those that extend from the tail lights and such are straight, expecting the flow to "skip" over the corners. The goal was apparently to raise base pressure a little by reducing turbulence a little. The tests satisfied the designers, eventually--or so they claimed.
Quote:
Originally Posted by JeffD
... Several of the box cavity examples that extend from the trailing surfaces have slanted or curved walls. The ones with straight walls are inset from the side surfaces. I wonder if that inset acts like a slanted surface to the air flow. I think maybe I'd be better off if I moved the half bed cover forward 4" and made a 15 degree sloping extension for the top wall (interferes with the utility since you wouldn't be able to open the tailgate w/o opening the cover though). The side walls having to be inset due to the tail lights could remain straight. Can't do much about the bumper on the bottom...
Sound right?
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Safe bet to assume aerohead has it right when he says that the box cavity will need very clean flow before it will work. (Props to Frank Lee also, who pegs it in one of his posts above.) So your first efforts could be to work on the flow from the front backward. You might start with an air dam and maybe the mirrors. Then the aft portion of the cab. I wouldn't move your half-tonneau, but maybe make it a full tonneau. Wheel well covers. THEN the box cavity.
The studies we are both referring to made it clear that a sedan shape benefited even less than the hatch, and in each case they observed that the state of the flow (especially under the car) mattered a lot for the effectiveness of the box cavity. So you and are are making the same mistake at the same time: we need to do more for the flow that approaches the back end if a smaller measure like this (instead of a long kamm or boat-tail) is going to work.