Aero features for a custom rear bumper

[viio]

I've just taken delivery of a spare rear bumper for my polo which I intend to modify for aero before fitting it. I'd like some help from the assembled boffins to decide what features to build in. I'll be using mainly fiberglass to build the parts, and I'll be testing some CFD using solidworks before I start making anything.

So, what do we think?

Here are some of the things I'm considering (inspiration pics below):

• Some sort of Rear diffuser if it will help fill in the wake
• Larger bumper with Lower edge to keep it near to the ground
• Integrated mud guards
• Sharp sides like the Chevy Volt

[Frank Lee]

The "diffuser" in that first example doesn't look to me like it could be effective. I think that one is all about styling.

I like the "Volt" sharp edges. At a minimum, they shouldn't hurt anything.

[viio]

Agreed. I'm thinking that if I set up a diffuser shape on the bumper, I can continue the shape underneath the car with flat ABS plastic or similar. It'll need to extend underneath to be effective.