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      11-26-2019, 09:44 AM   #152
First Lieutenant

Drives: 2007 Z4 M Coupe
Join Date: Oct 2012
Location: Woodstock, GA

iTrader: (0)

Flat panels and diffuser

Finished up the mid panels and installed the diffuser. Came out pretty good. Would love to get it to a wind tunnel, but seat of the pants tells me it works. Data does as well.

The mid panel will run close to the exhaust, so I had the mid section of the exhaust ceramic coated to keep the temps down. I also molded in several naca style ducts to keep air moving down the pipes and through the diff fins.

A lot of effort went into measuring the height and rake of the panels. I then made frames to suspend it under the car. I used Tinnerman fasteners for a flush mount so as not to disturb the airflow. I also made sure not to use fasteners in the all important throat of the diffuser. Smooth airflow is key!

You can see here that the airflow will be nice and smooth without interruption. The key to a diffuser is not the expansion chamber as much as the flat area in front of it and having a smooth airfoil shaped transition. This is where the air is made to speed up and create the low pressure (Bernoulli principle). This diffuser has a 10% angle.
The placement of the exhaust will likely have a bit of a turbo charged effect drawing air out the diffuser.

View that the oncoming air will have...

Four panels in all. Splitter is CF over 3/8" foam. All other panels are CF over 1/8" foam. Vacuum bagged for strength. Unbelievably light and rigid!

3002 tii1352.50