Quote:
Originally Posted by JulianEdgar
You cannot just ascribe Cd reductions to a car based on what the change did on another car. (Same as you cannot just add Cd reductions together to get an assumed total reduction.)
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Of course, this is why I didn't add them together and quote a precise number, just assumed a serious drop in Cd.
VAG judged, due to late-2000s experiments with eco versions of Audis and Skodas, that underbodies and suspension control arms fare much better if covered / plated over to achieve a surface as smooth as possible. Even if the suspension arm moves all the time, they still thought it needed a "fish-flipper" surface, compared to usual shape of suspension arms.
For Mk7 Golf there is a set of underpanels similar to my own, which can be retrofitted also to "non-eco" versions:
How to retro-fit skid trays, aerodynamic under trays, & stone guards to a MK7 Golf
They also
covered the exhaust bend before rear axle, which I didn't do - my pipes were too big and still needed some airflow under them to be safe.
2020 Audi A3 version of undertray set:
My setup is similar, but without the mid-car side panels, since the floor is "mostly" smooth.