View Single Post
Old 06-02-2021, 11:16 AM   #8 (permalink)
Aero Wannabe
COcyclist's Avatar
Join Date: Dec 2007
Location: NW Colo
Posts: 696

TDi - '04 VW Golf
90 day: 47.98 mpg (US)
Thanks: 625
Thanked 196 Times in 154 Posts
Originally Posted by vianney View Post
here are some pics of w/o undertray

and with undertray. purpose of the undertray was to avoid having the large transverse bar facing the flow, so the udnertray is composed of two parts, one kind of deflector in front, and the bottom diffuser.

my plan for this is to perfom tuft testing to check attached flow on the diffuser. (once i will have the boat tail attached to the end of the car this will be even more important!)
Like this from another thread.

The back end is trickier on rear wheel drive. The fuel tank is pretty smooth and the driveshaft needs some room to move up and down. You may have to stop the front part of the belly pan at the back axle and build another frame and belly pan section behind the axle. Try to seal this section all around the sides to keep air and mud/slush/snow out.
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun

Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 06-02-2021 at 11:35 AM..
  Reply With Quote