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The Free Mod Series - Part 6: Acing Aerodynamics

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Aerodynamics. What can't be said? If they're better, you get better gas mileage (less resistance to moving through the air) while having the ability to accelerate faster...


A stock Camry/ES 300 is pretty good from the factory.

Gen 1 ES 300 has a .32 drag coefficient, while having 21.88 ft ^2 of frontal area

Gen 3 Camry is .40 drag coefficient, while having 22.27 ft ^2 of frontal area

Good, but could be better!

ES 300's HP losses at X mph:

55mph = 7.8 horsepower

60mph = 10.1 horsepower

70mph = 16.0 horsepower

100mph = 46.7 horsepower

120mph = 80.7 horsepower

140mph = 128.1 horsepower

Camry's HP losses at X mph:

55mph = 8.4 horsepower

60mph = 10.9 horsepower

70mph = 17.3 horsepower.

100mph = 50.5 horsepower

120mph = 87.2 horsepower

140mph = 138.5 horsepower

Anything we can do to cut resistance is going to and increase gas mileage, and increase top speed (if you don't have an ECU limiter)

Roughly 1/3 of the drag on a modern car comes from the undercarriage! Ever seen your undercarriage??? Next to NOTHING has been done to help it out!!!

Percentage of Total Drag

Cooling package (including radiator, intercooler, oil cooler, etc) - 33.4%

Exterior - 31.7%

Front wheels - 13.1%

Rear wheels - 6.9%

Floor - 6.9%

Rear Axle - 3.1%

Engine - 3.1%

Front Suspension - 1.4%

Exhaust - 0.7%


Face it... The large front air damns on most body kits don't do crap for aerodynamics. (Let alone many people don't like how they look); while lip spoilers simply look ridiculous if you're not a Porsche running a 24 hour endurance race!

Let's decrease that by a big chunk!

Anyone that's ever changed their oil will recognize these as the stock under trays:


We are going to replace those. You have a choise to make:

Plastic sign material (i.e. the large, fluted yard sign stuff) = $2.50, easy to make. Cut it, tape it together, bolt it up. Good to just "see if this crap actually works"

A sheet of ABS plastic (1/8" thick) = $50-100 Much stronger. This is actually a permanent solution. Cut to fit, use a heat gun and bend it into the shape you want.

Fiberglass Epoxy = $20-30. Many, many times harder to use. You must build a form first, then lay your fiberglass down, then epoxy it. One chance, but nothing is going to bust this!

Both fluted Plastic, and a large sheet of ABS can be found at sign shops. Just ask for any scrape 2' in depth, by whatever the width of your car is.

The easiest way to start, is to tape a large sheet of paper under your car, and trace out the general pattern. Transfer this to the material you are working with.


At this time there is an aerodynamic warning.

¡¡¡DO NOT go farther behind than the front cross member!!!

If anything leaks from your engine, the plastic will be melted.

More importantly, what you do here DOES AFFECT your engine bay's ability to expel air. Run no covers and the temperature RISES because less air is able to pass through the radiator. Make too LARGE of a cover, and the same thing happens. Remember that some 90-95% of the air that enters your engine bay is expelled at the BACK-BOTTOM of the engine bay!


Be sure you leave extra material around the outsides. You want enough so that you can tuck it under the bottom of your body/bumper, that is rolled back plastic.

Tape the plastic signs together... WELL...

If you have ABS simply take a heat gun to the ABS and get it hot. You can then bend it evenly with something like a broom handle for even leverage.

I suggest re-using the stock bolt locations on any mounting method. No need to re-use them all. That's all the more you have to take back off during a fluid change!

(I'll skip fiberglass epoxy, because it takes a lot of practice... PM/IM/EMAIL for questions/tips on that. *Definitely* create an ABS Plastic one first so you have a ready-made mold.)

Here is my fiberglass epoxy one:




It is not visible to anyone at headlight height, or above.






Shape plays a very important part. If you form the thing down LOWER at the edges (in front of the tires), and roll it inwards. It will deflect air from part of the tire (from looking in front of the car) you can take a good chunk of drag away from the front tires. The trade off will slightly decrease stability in high wind. (Not enough for me not to go back and do it later)

(Unless you're a lucky, or smart; you'll want to remake an ABS one a few times, or make a few sign versions to find a "sweet spot")

Gas mileage on a 350m one way, all highway trip improved 4mpg at 75-80 mph, while top speed improved roughly 5 mph. 28mpg trip-average on a 3vz-fe that was previously never getting more than 24mpg under it's best highway day is a huge difference.

Now for the most important question! Why it is blue!?

Simply because I didn't have enough black model air plane covering, and blue was the darkest color I had on hand. ;)


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WOW , i comend you on your cerativity .

It defintaly can work especially since it will cause lift and acheive decreased high speed drag but by the front end being lifted even slightly it reangles you alignment causing a reduction of steering feel.

After all the reading you have done on this site how many members are going to build a fibreglass rad support funnel ?

To achive hopefully acheive 4 mpg.

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I put none of them down i stated basic fact have i not. You need to reread what i posted if you think that.

Who buys an ES for performance ?

The types of modifications mentioned are interesting but are more inline with a honda or another car with many more modifications with bolt ons.

My opinion but i find it annoying for you to chime in saying i am putting him down when i am not.

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Read your posts again, you put down everything he said in all of them. Some people do like their ES for performance and a lot of the folks on this forum would love to read about performance mods. Annoying is posting after every time another member posts to disdain "performance" posts, so check yourself before you call other members names.

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The ES does not = performance

it equals luxury in a entry level midsized sedan

You could throw all the money you want at an ES and it would never equal a Honda Civic (EF TO EK)bone stock for handling .

Or 1/10th of the money for performance upgrades mainly as it is the #1 platform for the aftermarket.

Telling me to "check myself" is just plain stupid.

Who said anything about reading his posts?

Of course people will like to read them.

The platform is not in that segment for a reason, taking a soft chasiss and engine to extremes is not viable.

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Considering the way gas prices have been lately, the MPG increase alone would make the mod well worth the effort. Performance would be an added bonus. From what I've read of posts here, lots of people are into DIY, so I can see where people would want to try this.

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I'm not addressing any of that.

I'll save you the arguement of drag, lift, and all that.

Because there is over three times the surface area on the modified under tray, laminar airflow is achived where the stock promotes nothing but turbulence.

The laminar flow has a much higher velocity, the pressure differance between the bottom, and top of that general part of the car is much less.

Thus... There is that much less lift.

Anyone familliar with their car at very high speed will know exactly what I'm talking about. On my personal test track (Filled with professional drivers) the nose of the car becomes light at X mph. Because of the torque over of the engine, and the aerodynamics.

I noted the onset of that was delayed roughly 5 mph.

Actual notes I took are against forum rules.

The original article is actually in a published magizine, with testing done on a prius. It went from 44mpg, to 52-54 on the highway. The Prius undertray is the same crappy stuff we have. Slightly worse actually (which is obviously amazing, The pruis is an amazing cross-sectional machine! Yet it achives that with a horrible under-car flow. Amazing.)

SKperformance, the ES 300 actually was sold, and marketed as a sports sedan from 92-96. It was the equal of everything in it's segmant in performance tests at the time. The OEM Goodyear Eagle's gave it enough grip to off-set the massive body roll of the suspension in most testing.

On topic tho you two, seriosuly! LoL! Discussion the performance limitations of any of the family would be something I think that would be a bunch of fun on this particular forum. Start another thread. We all have a lot to learn, and we can all teach ourselves.

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I have to agree, its funny how SK had nothing good to say about any of Toys posts. Perhaps jealousy? In anycase the Ferraris incorporate the same design under the chassie because at high speeds, the air pressure is decreased underneath the car, in turn causing the vehicle to "stick" and pull towards the road. Ferrari even claims if you were to drive the car @200+mph upside down, it would stick to the road.

My 2 cents-

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I have to agree with SK here. The Lexus is not a sport car let alone make a “funnel” for it.

I thought, and I think most do, that Lexus stands for high levels of comfort, convenience and refinement. I do not think speed is top 5 for Lexus on their ES series.

I personally have a Suzuki GSX-R1100 for speed/sport, not a Lexus. Again, the 4 mph increase at 75-80 might be nice but if you drive in the city you can get lets say 2 mpg and have a nice homemade piece on my car (looks nice going to all the management meetings or weddings. Maybe we can make a Wal-nut colored one too??? :D

My old 1998 ES get almost 30 mpg on the highway and 25 in city/work and that is fine with me.

Also who drives the Lexus at top speeds? There is not enough room in most states and I do not condone driving at illegal and dangerous speeds. It is plan stupid and immature.

If you are comparing a Ferrari to a Lexus we are in for a great time of reading. Beside the HUGE delta in thousands and thousand of dollars, the ES stands Executive Sedan not a race car.

Now this and all the other articles looks really/great nice and I am sure some race people will try it, but the vast majory might not. Now I am not saying remove the posts but is there a forum for all the DIY/homemade projects here on LOC?

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I guess thats why Lexus decided to put underbody panels on the IS300 and most of their other cars lately and why they even feature that on their commercials. It's also funny that most car makers have worked really hard to reduce the cd of their cars with the advent of CAFE standards. :D

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I guess thats why Lexus decided to put underbody panels on the IS300 and most of their other cars lately and why they even feature that on their commercials.  It's also funny that most car makers have worked really hard to reduce the cd of their cars with the advent of CAFE standards. :D

I agree but there is much more design put into it then "just mounting" a funnel to your car. Nothing is that simple in the engineering world, ever.

Also was this topic on ES or Camary not an IS.

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I guess thats why Lexus decided to put underbody panels on the IS300 and most of their other cars lately and why they even feature that on their commercials.  It's also funny that most car makers have worked really hard to reduce the cd of their cars with the advent of CAFE standards. :D

I agree but there is much more design put into it then "just mounting" a funnel to your car. Nothing is that simple in engineering.

Also was this topic on ES or Camary not an IS.

Smoothing out the underside of a car to clean up the air flow is not exactly rocket science. In fact, it's not even an IS that Lexus turns over in their commercial. I did mention other models, didn't I?

This statement

Also who drives the Lexus at top speeds?

doesn't imply anything but Lexus, to the reader. But hey, I'm not one to quibble about petty things like that. If I was, I would mention that I've never seen a Camary.

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All I am saying is that if you think bolting on an air funnel to an auto is not going to effect the performance, handling, functionality & reliability of the car, well you are a better engineer then me. Yes, the basic design is not rocket science as you called it, but you have no idea on what other things are effected from it.

You stated other cars. I do not know what that is. I stated top speeds since the original poster did and that is foolish in todays legal issue happy world.

It was Camry, sorry. I am not one to spell very well since engineers can't spell. If they did, they are not engineers.

PS. The CAFE standards are a joke. They state that light trucks (manufactured in the 2005-2007 model years (Mys) to be: The standards for all light trucks manufactured is set at 21.0 mpg for MY 2005, 21.6 mpg for MY 2006, and 22.2 mpg for MY 2007. This rule is effective May 5, 2003.

Give me a break. Fords, Dodge and chevy light trucks are lucky to get 13 to 15 maybe right now….

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Personally, I doubt very much that not many (if any) folks are going to try any of these so called 'mods' on a newer ES (say 2000 & up) that is still under factory warranty (I mean, someone is going to put an 'under tray' made out of plastic sign material on their brand new or nearly new ES? I don't think so :rolleyes: :whistles: ) That's just one example (I don't feel like writing a novel today lol :lol: ) These ideas maybe decent of older ES models no longer under factory warranty & for those that want to tinker with them, but you won't get many folks in the newer models to even consider it. :whistles:


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I never looked at my 2001 ES 300 as a sports car. I see it is as a sofa on wheels. Actually I would hate to really race the car, it just does not have the pepiness that I like when I have the need for speed.

All those mods seem like a lot of work to get a few HP or MPG. Plus it does not look that great. But for each his own. I would spend a lot more time fixing that sagging lip that Lexus has.


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hey if you got the skill and the cash any car can be bilt for performance it all a matter of what you like. any car can have turbos or supperchargers bolted on with the proper bottem end work. I bought the lexus because I like the fact that it is not a honda it is a diffrent car then everyone els dose. doing mods to your car is a way to make a statment about how you are and what you like. and as someone how drives there lexus as a winter car and a big block in the summer i am always trying to get a littel more performance out of my ride. when it come's to car's I have just about seen it all over the years in the shop's bilding car's and i like to see when someone dose on i havent seen before that is why i bought my car

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