MINI Cooper S rear diffuser w/ underpanel

[Ladogaboy]

That's good. I'm just concerned because some people have actually melted our stock diffuser after switching to an aftermarket/custom exhaust.

[lama]

Originally Posted by curv872

After almost a year on the car its holding up very well. No problems with heat, since the top side is covered with an application of aluminum duct tape.

It would be very helpfull if you could give me the length of each side of the diffuser you made(don't know if I explained in right!)!
I also have a mini cooper S and I am looking forward to construct the same diffuser,as well as the front body panel!Any photos you have from the front one,would be helpfull also!

[curv872]

Originally Posted by lama

It would be very helpfull if you could give me the length of each side of the diffuser you made(don't know if I explained in right!)!
I also have a mini cooper S and I am looking forward to construct the same diffuser,as well as the front body panel!Any photos you have from the front one,would be helpfull also!

Which side? The underpanel is just a 4x8 sheet of coroplast cut in half and trimmed to fit, it wedges under the side sills and exhaust tunnel heat shield...front lip if folded up under the wheel liner & heat shields (aluminum tape was applied to the edge that comes in contact with the heat shield). The trailing edge is secured with aluminum C channel which also attaches to the front edge of the diffuser...so it becomes 1 piece.

[TXwaterdog]

Thanks for posting the rear diffuser howto.. I might add one to my ride as well (not a mini).

[jime57]

Originally Posted by InsightfulRay

Not a big fan of A/B drag tests. Personally, I don't trust short distance A-B-A testing

I agree with you on this score. I am particularly skeptical of A-B-A testing on an Insight 1 on which it is very difficult to keep fuel consumption stable. I have become a fan on moderate length "standardized" test circuit. Mine is about 20 miles one way and fairly flat. I test at least 3 times, averaging both directions.

I was able to get fairly consistent results on a Toyota Echo on which I had added an after market cruise control, but again the course was of moderate length, about 5 miles.

[jime57]

Reposted as thread.

[rainagain]

Originally Posted by johnf36

side skirts

How are those attached?

[h3ll]

what's the book name in your first post about the CD and CLR?

[curv872]

Not sure exactly, but J. Pottoff's work is mentioned in various sources.
2 to check out - "Aerodynamics of Road Vehicles" as well as "Race Car Aerodynamics"

Mentioned here to on pg 10 - aero

[aerohead]

Originally Posted by curv872

From the rear valance, my design extends back 26" to the rear subframe and is nearly 4ft wide. From the subframe, the underpanel begins a gentle rise at the same angle another 12" back. So we are talking about nearly 12 square ft of area acting on the air.



A and B of diagram above, the best angle for drag reduction (CD) is from 2 and 4 degrees.

A (like mine), the best angle for reducing lift (CLR) is 6 degrees.
B, the best angle for reducing lift (CLR) is 11 degrees (at the expense of increased drag)

Made out of black coroplast, total weight with strakes, just over 4lbs.




Visual indication of how far back the 6deg rake goes back to combine with the flat underpanel:



Now for the shocking results!

I drive the same commute to work everyday and usually average about 26-27mpg. After logging 106 miles with the diffuser, I filled it back up with 3.538 gallons....that's now an avg of 29.9mpg!!!

Joe

the Mini,should have a squareback wake,which doesn't produce lift.