rear diffuser build thread

[wdb]

75mm is a touch under 3 inches. My STi has more clearance than that underneath, and Subaru engineers still found reason to put a front undertray and two center smoothing trays on the car. Later models also had a rear diffuser installed from the factory It was a pretty ugly little thing so I sincerely doubt they put it there for looks!

I'm not saying that rock crawler 4x4's should expect much benefit, but I am confident that vehicles sporting normal road car ride heights will benefit.

Interesting to me is the benefit side skirts play in keeping the air under there until it can do some good exiting the rear of the car.

Speaking of diffusers, apparently they also do some good at the trailing edge of front splitters. Here's a sample image:

[Deezler]

Any progress? This thread got me to go look under my rear bumper for a while the other day.....

[LeanBurninating]

Yah I have been thinking about it more lately...

I think I should make an under belly tray first... but I can't decide whether to go with coroplast or aluminum sheet metal... I think aluminum might actually be cheaper but coroplast is probably easier to work with.

Any tips on finding the cheapest coroplast around? Should I bother at the hardware stores? I have tried contacting local sign companies.

[aerohead]

with respect to mpg,the diffuser embodies the very rear portion of a complete belly pan,which begins its upsweep as underchassis components permit,rising vertically at no more than a 2.5-degree angle for attached flow.No vanes would be necessary,unless at the extreme outboard position,to form a rear wheel fairing as well as an undercar horizonatal stabilizer for center of pressure control(crosswind stability)as invented by Dr.Alberto Morelli.Vanes of any orientation other than parallel would probably see separation on their leeward side.Spanwise divergence between the rear wheel fairing/diffuser dams could sustain 7-8 degrees,well within the limit for a divergent nozzle in fluid mechanics.Again,the vertical component of the diffuser upsweep is limited to 2.5-degrees.---------- Not sexy,not racy,but it works.

[LeanBurninating]

ok ok ok ok

I know traditionally diffusers work vertically. Or in some cases, vertically and with the aid of the outward sweeping veins then the diffuser functions cross sectionally.

In this case I want to keep things simple, I want to work with only flat surfaces for easy vein application, and to keep it cheap and easy to make.. blah blah blah. Im only going to make it function horizontally. Flat surface, and veins.

Perhaps Im just an idiot.

Thank you for your input, I will plan on maybe using 7 degrees of seperation between the veins then.

I definitely need to get off my rear and build this stupid thing.