Aeromodding my 2003 "Classic" NHW11 Prius. - Page 7 - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 02-16-2010, 01:42 AM

Quote:

Originally Posted by orange4boy

That's a Homer quote.

Touche.

orange4boy · 02-16-2010, 02:54 AM

Percentage of Total Drag of a .29 CD Volvo:

Cooling package: 33.4%
Exterior: 31.7%
Wheels: 20%*
Floor: 6.9%
Rear Axle: 3.1%
Engine: 3.1%
Front Suspension: 1.4%
Exhaust: 0.7%

*Front wheels: 13.1% Rear wheels: 6.9%

From: Modifying Under-Car Airflow, Part 1

Discuss...

tasdrouille · 02-16-2010, 08:27 AM

Nothing new. 20% is on the low side. But that's probably due to the poor results from the cooing package. The wheels and wheel wells can make up to 35% of total aero drag in passenger cars.

Don't forget to look up the product number for the airdam material next time you are at HD.

MetroMPG · 02-16-2010, 11:46 AM

Yes please, a product number that applies in Canadian stores would be swell.

Topher: kilts = classic!

orange4boy · 02-16-2010, 03:59 PM

Quote:

Nothing new. 20% is on the low side. But that's probably due to the poor results from the cooing package. The wheels and wheel wells can make up to 35% of total aero drag in passenger cars.

It does seem on the low side. Perhaps it was tested in fixed floor wind tunnel. I always remember the Hucho drawings of basic car shapes at ~.07 and when wheels are added it jumps to ~.16.

Does this mean the once the grille is 100% blocked the wheels suddenly account for almost half of the drag?

aerohead · 02-17-2010, 08:01 PM

Quote:

Originally Posted by Jethro

All of this inspiration is really making me wish it wasn't 30 for the high this whole darned weekend. Grrr!

I think an air dam is the next mod for the HotRod.

Wouldn't that be ColdRod?

aerohead · 02-17-2010, 08:06 PM

Quote:

Originally Posted by orange4boy

Fantastic image of the wheel fairings on the original 1 litre Volkswagen

The front ones curve outward sharply from the centre.

If the law were changed to allow it,these wheel fairings could be made real ground-huggers and move to clear obstacles.
They might be worthless in a 4-season environment,but boy would they cut drag away from the snow and ice.
These are the reason some of the solar racers score such low Cds.
Great photo,thanks!

orange4boy · 02-19-2010, 04:14 AM

Here is a shot of the car while we were shopping.

I added the wheel deflectors yesterday. They are made from rubber baseboard. I attached them with 3M "automotive acrylic plus attachment tape" 1/2" x .045" And hey, It's NASCAR licenced. Woo hoo. For ultimate ecomod attachment, If ductape is somehow tragically, not available, this is the stuff. It's what is used to attach emblems and plastic body panels. I paid $44 <Ouch!> for 20 yards. You can buy smaller quantities from auto parts stores and body shop/paint suppliers. I got 10 feet of base"board" from the roll ends bin for $5. It's meant to be a consumable.

I calculated the area of the space between the wheels to be about 268 sq. in. and the space under the air dam to be 252 sq. in. I figure that way there is a balance there so less air will be forced to go through the wheel wells. I don't know if it's a sound theory but it's all I have for now. Since the rule of thumb is to have the air dam no lower than the lowest part of the underbody, I'm just including the wheels into that rule. Makes sense to me.

It seems to work. It's certainly not worse. The butt-o-meter is reporting better. Hmmm. Is 10 fans at the end of a carport a wind tunnel?

Quote:

Originally Posted by aerohead: If the law were changed to allow it,these wheel fairings could be made real ground-huggers and move to clear obstacles.

Speaking of the law... here the minimum ride height is determined by the wheel rim. No part of the car can extend be below the lowest part of the rim with the exception of flexible mud flaps. So I'm good.

Below is a view of the back of the air dam. I plan to close in the underside so it's flush with the hard airdam and run another rubber baseboard on the inside to create a full fairing for the front wheel.

Below is a shot of my coroplast bending technique. Crease the inside then bend inward.