The Free Mod Sieres: Part VI Acing Aerodynamics

[Toysrme]

Background:

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...

Theory:

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%



Instructions:
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 tock 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.
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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!
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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:



[IMG]




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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Part I Quicker Transmission Shifting
Part II Adding Airflow
Part III Taking Advantage of Intake/Exhaust Upgrades
Part IV Cheaply Monitoring the ECU & A/F
Part V How to pick up MPG, and sleep with her too!
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[CrawlingEye]

Nice, I like it. I think I may try this with some ABS plastic soon. I have a couple bolts that got stuck so I just tore mine at the couple locations. I figured I'd buy a new one from a junkyard, but instead this seems like a fair alternative.

[brungold]

thanks toys, this is GREAT stuff! i the FMS!

[dna59]

Nice addition to the series.

[ASG14]

Nice, I may have to try that this summer!

[UfoZ]

Very cool write up... I have actually been mulling the aerodynamics of my car over and comparing it to cars that create huge downforce with no spoilers- namely Ferrari. They almost entirely cover the underside of the car with diffusers which help suck the car down onto the road at high speeds.

Toyz mentioned the heat dissipation problem... Why not make a diffuser like this with a few vents to help expel the hot air?

Anywyas, Im just sort of thinking out loud here but this is definitely something that I plan on tackling. Except it will be in true UFO style - carbon fiber.

[Toysrme]

Actually, a larger than stock one can improve cooling, if you have tons of cooling stuff (intercooler, extra oil cooler, aux transmission cooler)


It's the pressure differances created. *to and extint* the faster the flow under the car, the lower air pressure is. Giving the air in the engine bay an easier time to exit, giving the cooling equipment in the nose (where all the airflow for the engine comes from) an easier time entering the bay.


I've scrapped finishing the project until probably well after tax refunds, but at some point, I'll continue this by making tire deflectors (front AND back) and plating the rest of the car. From the firewall, to the rear bumper. That will probably be done with corrigated sign plastic for $$$ reasons.






^^^^^^^^^^


Downforce was one part of this. And other than I'm cheap, one reason to continue to sue the worn out stock suspension. At 125mph, the nose of an ES 300 begins to lift. It's around 1". By 130mph it's raised half it's suspension travel. At over 140mph, it will nearly pull the full 4" of stock suspension in the air.

A stock camry should feel roughly the same thing. Take your car to 130mph, and it's not just steering feel, but you can WATCH the front end of the car raise slightly. It isn't much to worry about. (unlike how it sounds) The stock springs are verw weak. (You can compress them two inches with less than 200 lbs of force.) @ 125-130mph that would be the differance between the wieght of a 3vz-fe in my car, and a 5s-fe in the car.

I've all ready religated adding positive downforce to this car as impossible. Ask MCE, I've computed actually adding a high drag, high lift wing ala R/C airplane type between the front tires, where there will be high velocity. The problem is you would only be making about 20lbs of downforce, to counteract the entire nose of the car wanting to lift.
Splitters would be useless in our case and you can't simply "pull a NASCAR" and add a front air damn to 1/2" off the ground. however yes, the lift is slightly less. probably bumped the affects 3 mph higher.



I would suggest anyone concerned with aero lift, to simply buy springs that take more lbs of force to compress. Those will

[whocares04]

HOLY CRAP!!! i've noticed this at as low as 90mph! like when i get onto a straightaway on the highway at night travelling at like 75mph, i'll take it to 90mph+ then just let off the gas to go back down to 75ish and right after i let off the gas at 90+ the front end drops and i never really thought about why...

gonna have to try this esp. if i can increase top speed!

[Toysrme]

What you feel is the counter-torque on the engine. Everything has an equal but opoosite reaction. Engine spins towards the fron of the car, there-hence-forth, the engine is pushed towards the rear of the car.

The more power the engine is making, the more it's going to lean backwards (this is what the dog-bone mount works to control). As the engine leans backwards more and more, the rubber mounts can't compress anymore (absorbing that energy). That is the point where the engine is pushing on the frame, and actually is able to lift the front of the car.


The car will settle back down as the rpm/speed builds, and you'll actually feel the car pulled back up, as you keep accelerating.

[jackfrost1031]

This engine raising is really pronounced on my longitudinal VW engine, but the entire car weights about 2100lbs. My Camry's nose raising isn't as pronounced since I have stiffer springs and struts than stock.

I think I'm going to try this on my cars and my mom's when I get a chance.

[DrtySthV6SE]

i read, i like, good stuff toys

[CrawlingEye]

I think this weekend (or following week) I'll pickup some sign-material and give this a whirl. I figure I can play with designs more cheaply with the sign material and also once I find something I like, I can use it as a template to make it out of ABS plastic.

[SmokingTires]

I already get 27mpg on highway, imagine what I would get if I did this

31mpg!

[Meperezs]

Save that gas!

[userlain]

This mod is a detriment to front downforce. Think about it, the plastic is angled down like the front of a boat, this causes the air that is being rammed underneath the car to compress, but the air will not compress easily, thus creating lift in the front end like a speed boat on water.

If you wanted to make this mod actually work I would recommend dimpling the plastic panel you are going to put on the underside of your car, and don't angle it down more than you have to to get it to fit.