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.

Why paint it? The naked screen should be adequate to smooth the air flow, while allowing the exhaust system to vent heat. And, aluminum screen being about the world's best heat conductor, it will dissipate heat from any contact with mufflers, etc..

Or, you could use Coroplast along both sides, with aluminum screen just to cover the central tunnel and exhaust pipes/mufflers. The Coroplast could act to clamp the screen in place, nice and taught.

I could only speculate that the paint might make the screen hold better. Isn't tearing of the material the main problem with screen bellypans?

An area under the cat,muffler and pipes was left unpainted.
The paint cost nothing as it was on hand, hence the "kitchen yellow" color.

AND it probably does improve airflow. Adequate is not enough for anything but Gov't work.

Please keep us posted regarding before and after fuel economy, noise, etc. I'm seriously considering modding my BMW 325is in similar fashion.

BTW, what kind of glue did you use?

I hope you're working with that thing on stands - not just supported by the jack o.0

Looks promising though

Thanks for looking out for me.

I use a 3 tone jack and stands with a wheel block.

Observation:

The car is quiter.
Wind noise reduced
as well as induction and or exhaust noise is decreased.

I also have found the CleanMPG.com and entered my recent gas log.

To me, noise reduction alone would seem to make this a worthwhile experiment.

The screen, in addition to making smoother airflow under the car and less noise in the first place, probably also reflects and absorbs noise by acting as an acoustic barrier of sorts. A smoother screen with better acoustic absorption would probably work even better.

Your aluminum windowscreen fabric is a great idea, and the price is right. To make it super-smooth after fitting it to the car, you could then use a flat table covered by smooth glass or plexiglass: Pour plastic resin such as polyester on the flat table and spread it evenly. While the resin is still fluid and before it sets up, secure the pre-fitted aluminum screen to the table, such that the resin penetrates and forms a matrix with the screen fabric. (A vacuum bag would help lots with this.) Once the resin hardens, peel the matrix off the table, and the hardened but flexible resin will retain the smooth texture imparted by the table top. Put the pre-fitted screen back on the vehicle for a super-smooth finish.

you have pics of the vacume bagging ???

There are some nice tutorials at the WISIL site, including one on vacuum bagging at http://www.wisil.recumbents.com/mars...FS00intro.html

cool :thumbup:

The work continues
 

http://i17.photobucket.com/albums/b5...g?t=1211228073

The belly pan is continued with lexan from the rear axle to the back bumper.

I want to do some work around the wheel wells. Likely will use some spray foam to tidy up the openings.

On the now much shorter list are front wheel diffusers, before and behind,
Smaller rear wheel diffusers,
Rear wheel skirts, and
Fresh fill of Amzoil transmission fluid.

I also wand to do some work with vortex generators to smooth the air coming off the back of the car and coming off the rear view mirrors.

I can't wait to get a tank of gas through the car on a highway roadtrip.

So I have a tank of gas through the car average 65 mph
got 41.39 miles per CDN Gallon. EPA is 36
I am satisfied. Was also running into a headwind.

:thumbup:

Well I have the back side of the trip in.
Had the cruise set on 65 mph, 379.5 miles

Fuel Consumption
Litres per 100 Km .......... 6.66
Miles per Imperial Gallon .. 42.42
Miles per US Gallon ........ 35.32
Kilometres per Litre ....... 15.03

17.8% over the Highway EPA at 65mpg. I continue to be a happy puppy ;-)

Do you plan to measure your catalitic convertor temperature? If the temperature gets high enough the ceramic honeycomb inside will begin to erode. The erosion may partially block some of the honeycomb.

here is one of the possible part numbers for the matrix cat and front pipe from the factory:
174100D170
here is the price from 1st toyota parts $842.28

Though with the price of gas maybe your answer is "don't care".
Thats OK too. :)

Belly Pan and Aero/Ecomodding
 

Thanks for your concern.
I think that there is enough air around it to keep it in the operating range.
Additionally no one ever, except under warranty replaces a cat with a Toyota stock cat. Not even a lottery winner.
MagnaFlow Catalytic Converter 94105 at $65.10 is the part all the enthusiasts use.

Okay, I did not mean to be a wet blanket. :)
If you are willing to cut and weld the exhaust system, then an aftermarket cat is a better deal.

Reason I mentioned it was that I once was a passenger in a very old honda civic which had some water in the gas, and the car was misfiring and putting raw gas into the cat.

The car ran poorly, but it ran, and the driver just wanted to get it home. It was only when someone passed us to say we had orange hot and molten things falling from under the car that we found out that the cat casing was melting away and falling on the road. I would have never believed that was possible if I had not seen it myself. When we opened the hood the cat (it is right on the exhaust manifold in that car) was glowing very bright red. It was a sunny day in the winter, and you could see the cat just glowing very plainly.

So now I have a lot more (excessive?) caution about cats.

Dramatic reduction in wind noise!!!
 

I have added Zig-Zag Vortex Generators aka a Turbulator on my side rear view mirrors.

http://i17.photobucket.com/albums/b53/edbso/zig-zag.jpg

Frankly I don’t feel or hear anything different and do not expect to find a measurable effect on the mpgs. I also do not see the potential for any large or measurable negative effects.

Then I added Zig-Zag Vortex Generators aka a Turbulator on the front A Pillars and there is a dramatic reduction in wind noise. There is still some left but it is dramatically reduced

Given that Toyota has used Vortex Generators on the Tacoma outside rear view mirrors and there is some excellent glider data for the Zig-Zag Vortrex Generators I thought that I would go for it and am much more than pleased at the results.

where did you get that ???

Ditto!

BTW, if you can find or make tape of the right thickness, you can easily make zigzag tape with pinking shears.

The guys who sell zigzag tape to the sailplane crowd will only sell it in compete rolls, or so they say.

Maybe you could make dimples by making spots of clear silicone bathtub caulk from a tube, dabbed on. This might effectively duplicate the dimples that BMW and others cast onto their mirror housings, as seen in the E36 325i et al.

Heh, the missus has a slew of crafting scissors that can make any type of zig-zag imaginable. I'm making me some of this ;).

The stuff they use on sailplanes is pretty thick, maybe 0.030" or more. You might want to layer the tape to that thickness, then cut it with pinking shears.

FWIW, the sailplane stuff has the innie and outie zizgags parallel, if that makes any difference.

The little turbulator bumps on my Bimmer 3 Series mirror housings are about the same height, i.e., ~0.030".

I suppose the turbulator has to be a given height to trip the flow optimally.

what kind of tape are you going to use ???

Don't know. What's weather resistant and sticks to auto paint?

Why not use the pinking shears and tape to make a zigzag stencil, then put on some clear silicone bathtub caulk as the turbulator, peeling off the stencil before the caulk firms up. That caulk is transparent and has a ~50 year life, so you wouldn't have to paint it. Build up in layers to desired thickness. Tough stuff.

and how thick does it need to be to work ??? also want to be able to wax ??

Hi Edbso,

I think that is a good idea. Even the Prius has the vortex at the top of the A-pillar. I can see the swirling/stagnation of the rain on the driver's window there. Some concept next generation Prius have shown side dams there. But, that is allot of extra drag possibly, due to the air going sideways, and not up over the roof axially. So, putting in a turbulator is probably just the thing. It will chop up the big vortices into little ones, which have less cross-section (boundary layer height). At least that is my guestimate of why its quieter.

Came from the glider sail plane area.
 

So I found this interesting piece about work being done on the airflow over a glider wing

What particularly impressed me was the lightness of the material, Zig-Zag tape. AND it works.

http://www.wingsandwheels.com/images/zig%20zag.jpg

I also took the opinion that if I made a big error in placement there likely would not be huge negative effects.

To help visualize how the laminar bubble would look during qualitative wind tunnel cession the testor used vaseline plus TiO2 mixing as a surface liquid for visualization. The result could be clearly seen thanks to UV light.


The before shot of disturbed air flow over the wing.
http://i17.photobucket.com/albums/b5...otreatment.jpg

Now the attempts and final fix.

Starting with straight tape...not much result.

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

Now Zig-Zag tape placed on a diagonal too test for positioning. Big improvement in areas.

http://i17.photobucket.com/albums/b5...pePosition.jpg

And the final result.

http://i17.photobucket.com/albums/b5...g?t=1212356890

I think that the results are dramatic and IF one makes a huge error in placement I don't think that there will be a huge negative effect.

When I put the tape on the rear view mirror I couldn't tell that there was a difference. When I put it on the A pillar the reduction of the air aka wind noise was dramatic. A huge improvement.

So in summary...
It appears to work...
It is inexpensive (Dymo tape) cut with pinking sheers...
It is light and
I like that it is "quirky".

This is the airflow that I have over the A pillars.
Basically horizontal so I placed the tape perpendicular to the flow.

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

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

I hope that I have energized the air across the side windows. Should be able to tell during a rainy day.

I also have to wonder whether a positive effect can be had by placing the Zig-Zag tape at the trailing edge of the Matrix?