diffusers

[2007 ion2]

does anyone know of any guidance/science as to the placement of diffusers on the rear bumper cover/belly pan?

[wyatt]

Hucho has done some work on diffusers, and has said that 3 degrees is about right. Depending on where the slope is started (and probably other factors) that slope may need changed. I personally think the slope could be increased if you were willing to add a set of ground effects on the sides of the car to reduce the amount of air escaping, thus putting more flow over the diffuser. I have a "diffuser" belly pan from my rear axles back, and it just attaches to the bumper and the axles (with no thought to the angle). Not much air gets under it, since I have had it on for about 15,000 miles with not so much as a zip tie pulling loose, but all cars are different, so your testing is up to you.

[nmgolfer]

IT really hard to prevent flow from separating (thereby defeating any hope of pressure recovery) in an adverse pressure gradient even with nice diffuser inlet flow conditions let alone the messy air between pavement and car under-body. Your efforts might be better directed elsewhere but Good luck with your project should you proceed.