Quote:
Originally Posted by tvbd56
would the full belly pan with integral diffuser be 12% on it's own or would it be 5% on top of 7%?
|
I don't have everything with me to give you a decent answer.
*Hucho is showing Potthoff's research on diffusers.
Pothoff's test vehicle started at around Cd 0.256,and then with the 2.5-degree diffuser dropped to 0.231 or thereabouts,for around a delta- 0.025 improvement.
That's a 7.9% improvement on top of whatever the bellypan gave him (which isn't given).
*Hucho gives Carr's research on pans but I don't have it.(Members?)
I think that Carr gave 0.07 for a complete pan,but I need to verify if the tailpiece was just level,or a diffuser.(And 0.07 needs to be given a context as to the test vehicle analyzed).
*I'll get that,but maybe in the meantime another member will catch this and chime in.Sorry for the delay.
--------------------------------------------------------------------------
I got to my materials and here are some additional numbers
*Both Carr and Buchheim et al came up with a delta-Cd 0.045 for a full bellypan.
*Buchheim's test vehicle was a 1982 Audi 100 III,Cd 0.30.
*With the full pan the Audi's Cd falls from 0.30,to 0.255 (which agrees with the table for the diffuser.
*With the diffuser added,the Cd falls to 0.23 (which is in close agreement with the table.
*So in this particular instance,the Audi's drag is reduced 23.3% with a 2.5-degree diffuser and complete paneling.
-------------------------------------------------------------------------
*The Ford Probe III had Cd 0.22 with active valance and full belly pan.
*The production Sierra/Merkur had Cd 0.34 without these features.
------------------------------------------------------------------------
*R.G.S.White indicated a delta-0.038 drop for a smooth belly pan on a higher drag (Cd 0.58 ) car (6.57% drag reduction ).
-------------------------------------------------------------------------
*CAR and DRIVER reported that NASA got a 15% drag reduction on their Ford Econoline van with a carefully executed belly pan in the mid-70s.
-------------------------------------------------------------------------
*University of Wichita showed a 6.3% drag reduction in early research.
--------------------------------------------------------------------------
*University of Michigan showed a 5.8% reduction likewise.
--------------------------------------------------------------------------
*In 1933,Fachsenfeld showed a drag reduction,from Cd 0.40,to Cd 0.27 with a scale model Omnibus intercity bus.
--------------------------------------------------------------------------
*In 1963,Walter Korff showed up to a delta-Cd 0.12 difference with a full pan on a car with exposed frame/axles,springs.
--------------------------------------------------------------------------
*Ford Motor Co. showed delta-Cd 0.04 for a full pan on a 3/8-scale sedan car model in the University of Maryland wind tunnel.
--------------------------------------------------------------------------
*Chrysler belly-panned their 1934 Chrysler DeSoto Airflow aerodynamic test mule,which helped it achieve Cd 0.244,but did not present the numbers in such a way as to isolate the pans individual performance.
--------------------------------------------------------------------------
*On my 1970 VW Transporter,I estimated a 1.038 mpg improvement with a full pan ( 8.726% drag reduction).
--------------------------------------------------------------------------
I looked,but couldn't find any additional info just for skirting.It's out there somewhere,but probably only as internal memos in corporate labs.