Focus wagon (.30) vs hatchback (.35)

[tru]

my zx3 shows some mean vortices rolling while driving in the rain. I have tried adding some trips to the rear to help out but havent settled on anything permanent. I really think a box on the rear of the vehicle that utilizes the bumper would do the most good...

[LocoJason]

screenshot of a small tuft test at 65mph. Not much movement, but it's interesting to see how the air is moving laterally across the back window and collides with the air coming off the side of the taillight. The tufts coming off the lip on the trailing edge of the roofline are also pointing straight at the taillight...

[redorchestra]

is that a box cavity? good job! do you also have a diffuser?

[HydroJim]

Originally Posted by redorchestra

is that a box cavity? good job! do you also have a diffuser?

The screenshot is from a stock Ford Focus zx3. The taillights just stick out above the hatch to create what appears to be a box cavity in the picture.

[Cd]

Originally Posted by GRU

Yes. If people only didnt buy cars based on the looks.

But cars don't have to look "jelly beans" to be aerodynamic !

Just look at the Lexus LS430 with its' .25 drag coefficient !



I see a LOT of area where stylist can improve drag, and still have cars that look nothing like one another !

When the 2nd generation Insight came out, I read articles that gave the reasoning for the Prius like style as having to do with aero.

Hogwash.

[Cd]

BTW, here is a tuft test of the back of my hunchback Civic

[redorchestra]

I just completed a shallow diffuser for the rear of my focus. Today will be the test drive to see the changes and whether it will hold on. I also filled the spaces on my rims with some chunks of an aluminum serving tray. I had some black spray paint that I wanted to paint them with but it clogged up so they went on brushed aluminum. I will make and test a cavity next.

[morphector]

I think that another reason for the better aero of the wagon is the sides, you can clearly see that the wagon is narrower on the back.

[ShadeTreeMech]

I know this is a massive thread bump, but I bought a 01 ZX3 and while driving it noticed a couple things. The 2 liter engine seems nearly too powerful for such a light body, and when driving at less than highway speeds she's a spritely little car. But at highway speed, she seems ungodly slow to accelerate such as when passing. The wife and I could figure it out until I researched the drag coefficient and boom, a forum I haven't visited in years!

I now own a Volvo v70 that I love as well as the focus and my still running van. The maxima died sadly a few years ago.

If anyone wants to chime in on suggestions or improving the aero on this car it would be great. I noticed a member with a kammback on his focus that netted much improved economy over the 30 mpg we've gotten on longer runs. But we generally only drive the focus on short runs so losing the practicality of the hatch is undesired.

Oh how I miss my 83 Sentra station wagon. That 1.6 liter car gave me 35 mpg when I hammered it mercilessly with the ac on and I'm betting it was due to its very aero rear end. The air flow was such that the rain didn't touch the back glass at highway speed and snow would miss the windshield at moderate speed. It was quite a remarkable first car