Belly pan or vortex generators?
 

This is the underside of my Toyota Matrix.
http://i17.photobucket.com/albums/b5...g?t=1204167343
What concerns me is the big step down from the subframe to the factory floor pan.
Should I try and smooth this out with a new floorpan or put vortex generators on the subframe?
Or just leave well enough alone.
I do plan on closing the holes with stainless steel tape.

Your thoughts will be appreciated, Thanks

I would go for the full belly pan in this situation, I would think.

Welcome to the site!

Belly pan.

Vortex generators WILL NOT fix the turbulence you have down there ;)

I agree with them both. Come summer my Matrix will definitly be treated to belly pan in front, and hopefully in back too.

The full length body pan is unquestionably the better option. And vortex generators on the subframe will do little.

However, here's something you can try. If you've got a smooth pan under the nose of your front end, and it extends back to/under the engine compartment, and it's LOWER THAN THE SUBFRAME (and anything else in the area), you can place some VG's at the trailing edge of the pan to energize the airflow under the car. It doesn't keep air totally away from the rough surface of the underbody, but it will provide some deflection at speed.

^true that

Instead of vortex generators, why not try flow fences? Some L angle aluminum of ~2" height, or equivalent in plastic, would tell us. Or, PVC 2" X 2" square rain spout from Home Depot, cut diagonally along its length into two L pieces, then screwed or glued to the belly of the vehicle, would work.

yea.. you should see mine. clumps of dirt fall off when working under there... oh wait what's this... A LIVE POSSUM!?!?!?!?!

OK so I am taking your advise on the full belly pan.
So far I have covered from the front bumper to about 4" behind the front wheels. I used lexan. Reasonably easy to work with and durable. Difficult to photograph, I will work on better pictures.

http://i17.photobucket.com/albums/b5...o/Bellypan.jpg

I also am using a grill block. 3" grill block. OK it is actually 3" wide tape. I have left one row of openings free in the top grill and 2 open in the bottom grill.

http://i17.photobucket.com/albums/b53/edbso/Bottom.jpg

http://i17.photobucket.com/albums/b53/edbso/Top-1.jpg

Around town the underhood temperature is around 120F and goes down to ambient temperature at highway speeds.

I figure that I am good to go to the rear axle but over it and on to the rear bumper????


EPA mpg Highway 28 mpg

Recently observed on the highway with cruise set at 70 mph 31.5 miles per American gallon.

37.87 miles per Canadian gallon.

ac was off.

The proces continues
 

So I have decided to do the area between the front pan and rear axle with screen that is glued and screwed in place.
http://i17.photobucket.com/albums/b53/edbso/sc1.jpg

in process and after ...

http://i17.photobucket.com/albums/b53/edbso/scy.jpg

With all of the screen in place I painted it with a couple layers of paint with a roller and have sealed 1/2 or so of the holes.

Tomorrow or soon I will hit the area with under coating.

Next the area from the rear axle and back bumper. I think Lexan will be the best answer there.

Wind noise is reduced .
The car also feels "lighter" and only slightly a bit darty. Could be my imagination or simply different road surface influencing the driving feel.