Ford Fusion aero mods: Cd from 0.34 to 0.21

[MetroMPG]

OK, so it's a Bonneville car. But it's instructive about the basics what to do to improve aero:



- grille blocking
- smooth wheel covers
- narrower tires
- deleted mirrors
- deleted wipers
- lowering, in conjunction with...
- full undertray
- rear decklid extension (improved roof to trailing edge angle)

[MetroMPG]

PS - judging from the photos at ABG, the exterior sheetmetal is stock. Nothing else is.

PPS - It's a hydrogen fuel cell powerplant.

[MetroMPG]

Quantified:

0.34 - original Cd

-.08 - lowering (that's massive! and it's the only time I've seen it quantified)
-.025 - full grille block
-.015 - mirrors deletion (doesn't mention wipers though)
-.01 - full belly pan

I suspect they couldn't mod the door handles or add skirts in order to keep within the "stock" definition for bodywork. Probably a class thing.

EDIT: the slide isn't exactly comprehensive. It doesn't address the decklid extension or the smooth wheel covers...

[MetroMPG]

Why is the original car's aerodynamics so terrible to begin with? Some thoughts...

- High off the ground . It's as high (or higher, depending on the source) as my hatchback Flea!

- The bodywork around the rear wheel arch is terrible. The wheel sticks out dramatically - looks like the edge of the tire is exposed for as much as as 2/3 of its height. Which means any attempt to boat-tail the bodywork after that point is a wasted effort since the air is already disturbed (and further churned up by the chunky alloys).

- the wheel arches are also pretty large, with a big gap between the tire & bodywork.

[MetroMPG]

If you look through the ABG Fusion 999 gallery, you can see they used wheels with a different offset (and narrower tires) that let them completely "hide" them (from airflow from the front) within the wheel wells.

Obviously the overall shape of the car is fine if they got it down to .21. It's on the details where Ford messed up.

[technoshark]

If you look at the pictures in the ABG 999 gallery referenced above, the front nose piece is pretty much completely smooth - the frontal features are apparently decaled, a la NASCAR. A production Fusion, even with grill blocks, still wouldn't be this sleek. However, the rest of the body appears to be standard production pieces, which interests me - the front fenders have a sharp crease at the top leading down to the nose, as does my Focus. Apparently there isn't much of an aero loss with this, since it would have been relatively easy to put a mild radius on the fenders/nose to eliminate this character line & smooth out the airflow even more. I wonder how much the fences on top of the roof are worth, too...

[MetroMPG]

Originally Posted by technoshark

If you look at the pictures in the ABG 999 gallery referenced above, the front nose piece is pretty much completely smooth

Good point. Much smoother than stock, too.

Here's a good pic that shows it - note the lovely radius...
http://www.autobloggreen.com/photos/...esting/313361/

The fences on the roof aren't there to contribute to reduced Cd - they're safety features meant to prevent lift from airflow across the roof should the car slew sideways at high speed.

This Mazda doesn't appear to have them, for example. And as a result we get a nice look at its wonderfully smooth undertray... several times!

[YOUTUBE]http://www.youtube.com/v/SWgWk_evROk[/YOUTUBE]

[Cd]

Metro, after looking at the gallery, I assumed wrongly that they ran at Bonneville with those stock door handles.
The door handles were flush at Bonneville.

[technoshark]

That's a great flat full-length underbody pan on that Mazda - nice of him to flip his car & show us.

[aerohead]

Originally Posted by MetroMPG

Quantified:

0.34 - original Cd

-.08 - lowering (that's massive! and it's the only time I've seen it quantified)
-.025 - full grille block
-.015 - mirrors deletion (doesn't mention wipers though)
-.01 - full belly pan

I suspect they couldn't mod the door handles or add skirts in order to keep within the "stock" definition for bodywork. Probably a class thing.

EDIT: the slide isn't exactly comprehensive. It doesn't address the decklid extension or the smooth wheel covers...

This is the first ever for me time that the effect of lowering had been assigned a numerical value.Its new grist for the mill.