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F'ing fast.

Go to solution Solved by TobyB,

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1 hour ago, visionaut said:

Flatbottom generally aren’t very effective without accompanying aero mods (splitter/skirts/diffuser).


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2002 -73 M2, 2002 -71 forced induction. bnr32 -91

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I suspect it wouldn’t be that hard to make a rear diffuser, or more to the point make something that looks like a rear diffuser,  template it out and use someone like Send-Cut-Send.  But without actually testing it,  it may be pointless. 

"Goosed" 1975 BMW 2002


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While wind tunnel can  be the most effective, real- time data logging

(from a gopro looking at strings to pressure sensors linked to an inexpensive logger)

can be equally as informative, and a small part of the day-of work for a track day.

I did a low- effort real- time tire temp monitor, and we learned a LOT, later, from having the data.


It looks to me like the biggest bang for the buck is just a tall rear 'spoiler', a la Nascar.


That said, I run a very lightweight rear shell of a decklid, and if the rear trunk surface was generating

much lift, it'd distort that lid a LOT.  I guess I should video the thing to see for sure, but I've never seen it lifted

noticeably in other people's video of my butt...




not photogenic

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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1 hour ago, Dudeland said:

I suspect it wouldn’t be that hard to make a rear diffuser,

Great read by Willem Toet, former Head of Aerodynamics at Ferrari F1.




Diffusers are simple in principle - a shaped piece of bodywork containing a venturi with a throat, tunnel and strakes that creates downforce from accelerating the flow of air, lowering its pressure to generate downforce - but complicated to design to fit under a given car. It’s tricky to a) increase volume along the length while b) maintaining attached flow along the tunnel geometry.


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Where we goin’? … I’ll drive…
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