Quote:
Originally Posted by COcyclist
Welcome nexus. I have done some aero mods to my Mk4 Golf. I did not really want to change the look of the car so I have done a full belly pan with an open section for the catalytic converter. The exterior of the car from VW is pretty good (except the back end).
This shows a CFD of the Golf so unless you do some serious boattailing, the underside is the way to go, and perhaps rear wheel skirts. You can try smooth wheel covers but I have not noticed much difference with or without.
Your gasoline exhaust will be much hotter than the diesel so you will need to leave more open areas.
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Thanks for the comparison, that is very helpful! I believe my mk6 and your mk4 have similar stock Cds (.34 on the mk4 vs .32 on the mk). Does that CFD include your underbody mods as shown in your picture, or is it for stock? How did you get the CFD analysis done?
Also, I'm a little confused about something. To reduce the low pressure behind the car, I should be looking at box cavity/flow separator kinds of shapes, right? Or should I be looking more at getting flow to wrap around via rear diffuser, slotted spoiler, etc? Or does the rear airflow really not matter at all until I get the underbody cleaned up?