Do any Prius aero mods actually reduce drag?

The CD on the Prius III is the best it can be in the market for the retail price of the vehicle.
Can it be improved, yes a little bit......
Solid wheel covers, enclosing the rear wheels body panels.
Full covering the front grill.

 

Yes there are little modifications that will reduce cd but will it be worth it? 1st aero mod is to keep the body clean free of rough spots like fall out by clay baring. It and keep it waxed! This will reduce the air friction, protect the paint and looks better. Won't reduce cd by much but every bit helps! Next lowering springs this will reduce cd a little and improve handling will affect ride quality!

 

Short answer: Yes.

Longer answer: According to Gary Eaker, former GM aerodynamicist and owner of the A2 wind tunnel, the following almost always reduce drag on cars they've tested:

-Lower the ride height
-Block the grill
-Add a front air dam
-Seal the back of the hood to the cowl
-Remove outside rearview mirrors

And, mods with no effect on Cd:

-Wax/smooth paint
-Golf-ball dimples
-Taping seams
-Smoothing rivets

Ideally, you should tweak the car in a wind tunnel to get the best results, as different designs can have complex interactions and downstream flow can affect upstream flow and vice versa. But there are lots of modifications that get very predictable results. On my Prius, I have solid wheel covers (pizza pans bolted to the stock wheel covers), lower grill blocked, passenger mirror removed, and lowered on Tein H-tech springs. I think it would be great fun sometime to take my car to A2 and see just where it is now and what can be done to improve Cd further.

 

The answer is probably yes, there are things that can be done at a cost of many dollars that will yield positive results saving many pennies.

 

Just brainstorming:

1. Remove the antenna (assuming you're not needing it).
2. Remove rear wiper.
3. Remove front license plate. (or do some sort of aero mod to the holder?)

 

I've removed the passenger side mirror, and only recently put the driver side mirror back on the car for some upcoming road trips through states that require it. Most states do not require exterior mirrors at all; a small convex mirror mounted on the A-pillar will eliminate any blind spots if aimed properly and is much cheaper and easier to set up than a camera system. You can check your state's mirror laws on the Ecomodder Wiki (should come up on a simple Google search).

I've been using this setup for the past year and a half:

 

I removed rear wiper. Removed antenna, replaced with $7ebay unit (functional) =), and no front plate. I plugged holes with BMW parts. Painted them silver.





I have two more mods on my car since then.. i'll post updated pics soon =D

 

I used the H&R Sport Springs to lower it a bit and it seemed to help ever-so-slightly in the mpg department. Probably wouldn't have done it if I hadn't been doing the shocks/struts. Honestly though the ride didn't seem any worse than stock. Plus it looks a lot better (imho), and the handling is definitely improved. Makes on/off ramps much more fun.

Untitled by Ryan Kokesh, on Flickr

 

I'd be worried about having a mirror explosively launched into my face by the airbag right behind that pillar.

Otherwise seems like a great idea for reducing frontal surface area.

 

Alternatively, you could mount a mirror to the top of the door panel, right next to the window, but you'll need something more complex than a simple L-bracket. If I take the driver's mirror off in future, I'll probably go that route.

 

Check out the images tab after googling automotive boat tail mod.