Adding Rear Wheel Skirts

That seems like a fantastic idea! It certainly will reduce drag. WHEN your side skirts become available, I'm sold! :0)

 

The Force,

I don't know why, but I have some deep-seated afinity for rear wheel skirts. I just like the way they make a car look. So, its exciting to see your efforts.

Yet, I don't think it can be assumed that they will reduce the car's Cd or aerodynamic "slipperyness." I've been doing a lot of reading on aero mods around the 'net. And reports are mixed on rear wheel skirts. Where there are possible positive results, they are often small, or unproven. Abysmal MPG increases have also resulted.

The Prius is aerodynamically very slippery as it comes from the factory. It is the second slipperyest car you can buy. The car has all kinds of subtle aero refinements that are for the most part unrecognized by us plain folk. I have to believe that if skirts made an appreciable difference, they'd be OEM.

There's already something weird going on at the back of the car. It has to do with the black plastic trim piece across the back of the car at the lower edge of the bodywork. To a casual observer, it looks like a skirt or dam. But if you feel up behind the tires, there are tapered boxes. From its shape, the boxes are fairings there to smooth the airflow aft of the tires. What's weird is, it is generally understood that it is far more effective to have a fairing behind the front wheels. Yet they are not there. I have to conclude that there is some subtle yet very troublesome aerodynamic condition at the rear end that the fairings are meant to correct/reduce.

That being the case, It wouldn't surprise me that wheel skirts are going to screw things up, How? Well you got me there. Without a wind tunnel which allows for testing with the wheels spinning we'll never know. But there's no doubt in my mind that the designers at Toyota do, and those fairings prove it.

Here is the result of a google search on "wheel skirts" at ecomodder.com:
wheel skirts - Google Search
There's a lot to be thought about in these threads.

Here is a thread from GasSavers.org where wheel skirts caused a 10 MPG reduction. Yikes!
Wheel Well Covers Greatly Disappointing - GasSavers.org - Helping You Save at the Pump

Every discussion of wheel skirts that I've read deals with full skirts. It's whole-hog or nothing. Aerodynamics it turns out is a science of great subtlety. The size and position of the little air dams in front of the Prius' tires is critical. You can bet they have been sized and placed for maximum effect. So, just because a full skirt doesn't work, it cannot be assumed that a half or even quarter one will not. Or maybe the skirt should stand proud of the body at its rear edge creating a slot so that air thrown out by the wheel acting as a centrifugal pump can exit rearward along the bodywork, and then help fill in the "hole," low pressure area, behind the car. Who knows? Not me. But I'm waiting anxiously for a proven answer.

You know what? I would still like to have skirts -- I prefer half skirts actually -- but first I'd have to be convinced that they wouldn't play havoc with my FE/MPG.

Such is life!

 

Jay,

What happened to your aero hubcaps?

 

Rear skirts look terrible on the Honda Insight and they will on the Prius. Just say no.

 

on the pictures your can see t stick out.
is that going t produce More drag then it will help?

maybe make a opening in the back to let the air get out!

 

I bet Toyota didn't add skirts like an insight only because of customer perception.
Toyota went to huge lenghts to make this very different vechicle drive and look normal. Even so there was huge resistance to the Prius back in 04.

This is why there is room for enthuiasts on this site to modify their prius away from the compromise Toyota sucessfully achieved.
Anyway i think Rokby's suggestion for letting air exit at rear is a great idea.

For mounting these Skirts could i suggest a Light bar slightly bowed across the outside of the wheel center with L shaped ends fixed to the bolt in the bumper and the other end fixed to the wheel arch where it is rolled into the wheel well liner. Once you have a good fixng here there are a number of ways to fix to this without damaging the car. Also if you remove this bar later, your car is back to stock for resale.

An idea i had for aerodynamic testing is to find a long long descent and freewheel from a certain speed under set temps and wind direction and see how far the car will freewheel in neutral with and without Aero Aids attached. The higher the speed you start with might give better results for testing as i think drag is exponential to speed.
P.s. see my lightened Prius Thread.

 

See what these guys have achieved here with home made aero aids
Prius aero mods (undertrays, grille block, mirror delete...) - Ecomodder.com Fuel Economy Forum

 

I have sucessfully manufactured a set of Rear Fender Skirts for the 2010 Prius, made of Fibreglass and easily attached. Can be ordered directly from me and I will post pictures of them installed on my 2010 Prius. They will be available painted to match or in black jellcoat. Each pair will be custom fit to your car. Delivery within 15 days as each set will be made to order..
Satisfaction guaranteed.... I am trying to find out how to create a Posting showing these skirts on my car.

I am manufacturing them and they look AWSOME...

Bob Knight

 

Resurrecting a dead thread.

I made some out of sheet metal because it was easier.