Project: modding sixth gen Corolla sedan on a budget

[christofoo]

I'm just polling for (dis)agreement here before I finish this up tonight.



BTW, the under-body clearance is about 6", so I'm shooting for about 5.5-6" air dam clearance (probably 6" toward the middle and 5.5" toward the wheels). I'd rather err on the high side if I must err.

[darrylrobida]

See attached photo: home depot styrofoam 4 x 8 x 1.5" gorilla glue
cheese cloth w/latex paint total cost $20, good to 90mph add $8 for
led turn signals.
Last photo of my 88 civic dx conversion to a woody flatbed. It gets 40 mpg

[christofoo]

Originally Posted by darrylrobida

See attached photo: home depot styrofoam 4 x 8 x 1.5" gorilla glue
cheese cloth w/latex paint total cost $20, good to 90mph add $8 for
led turn signals.
Last photo of my 88 civic dx conversion to a woody flatbed. It gets 40 mpg

Your Civic Styrofoam nose looks sweet! If you had posted that before Sat I would probably do it that way, at least on the Corolla if not both my cars. Your design is almost an exact match to my ideal mental aero form.

I've already got a piece of PETG cut and half bolted on the Corolla's bumper, and it doesn't seem like a good idea to jump ships now. I am going to try some hand thermal forming with it and see how close I can get to that shape, but it's probably not going to be as steep of a forward angle.

I found your thread on the pickup conversion, that is also a lot of fun. Before I checked your sig I felt certain you must live in CA. An open form like that would not be fun in a UT winter.

EDIT: I meant to ask, what is the clearance of your Styrofoam nose-piece? does it extend below the stock bumper level?

[MetroMPG]

Glad you tufted the leading edge of the hood. Despite the car's "blocky" front end appearance, those relatively small leading edge radii really work to prevent flow separation.

Originally Posted by christofoo

I'm just polling for (dis)agreement here before I finish this up tonight.

It seems that an angled airdam that lowers the stagnation point makes sense. Haven't seen any hard data or testing against a simple vertical dam though.

BTW, the under-body clearance is about 6", so I'm shooting for about 5.5-6" air dam clearance (probably 6" toward the middle and 5.5" toward the wheels). I'd rather err on the high side if I must err.

Why err high? Do a mockup with cardboard: go aggressively deep (say 3 inch clearance) and compare to 5.5-6 inch clearance.

I went very deep (3 inch clearance) with the air dam mockup I tested on my Firefly which has similar ground clearance to your Corolla. A-B-A coastdown testing seemed to show an improvement. I did not try a shorter version though.

http://ecomodder.com/forum/showthrea...down-9732.html

[christofoo]

Originally Posted by MetroMPG

It seems that an angled airdam that lowers the stagnation point makes sense. Haven't seen any hard data or testing against a simple vertical dam though.

I know, I've been thinking my jacknut installation is well suited to doing a Cd vs angle test suite. Unfortunately I'm not ready for coast-down testing right now, and I don't see any way to answer the question with tufts.

Originally Posted by MetroMPG

Why err high? Do a mockup with cardboard: go aggressively deep (say 3 inch clearance) and compare to 5.5-6 inch clearance.

1) Clearance is desirable. I angled into my driveway and measured 4.5" corner clearance before I put on the dam - the problem being that I was not in the car when I measured (also it's hard to put the tape measure in the right imaginary spot). I put the dam on last night with 5" corner clearance and scraped in 3 different locations, a) my driveway, b) an intersection dip, not even the worst dip I expect to encounter, c) at work, in all cases doing my best to hit the low spot at an angle. Either I'm going to get better at this, or the PETG is going to get cut even higher than 5". SLC in general has some really gnarly dips and driveways. It's a headache.

2) My own personal untested theory: you can either A) push the leading edge of the dam forward until it more cleanly shears top and bottom flows, or B) push the leading edge of the dam down to throttle the flow coming from the high pressure zone in front of the dam going under the car. I expect option A should be the best choice for FE as well as clearance, all other things being equal, since the final result is less frontal area. (Option C would be an underbody airfoil, i.e. paneling and boattail, with a smooth nose but no air dam, like the Aerocivic.)

Again, it's a big hindrance that I'm not ready for coast-down testing... yet. It may even be a mistake to do this type of mod without mockup and coast-down. But maybe I'll get lucky. Or maybe I'll be able to edit the design as I go without making it look too chopped up.

[christofoo]

Here's what I got done last night:



I used jack-nuts (a.k.a. screwdriver installed rivet-nuts) for attachment. This is my first time using them, and I really like jack-nuts, particularly for fastening stuff onto a plastic bumper. Reversibility is not as good as some other fasteners because of a larger drill hole. If I took the mod off I could paint the jacknuts or maybe drill them out and putty and paint (but I'm set against totally reversing a good mod anyway, even for a prospective buyer. Find me someone who likes the mod instead). Jack-nuts are fairly easy to install, easy and quick to remove the mod, they're not too expensive (less than $0.50 per location), and the fastening is really quite strong and durable. I ordered them from McMaster.

Todo:

• Try heat gun to soften corners and then push leading edge even farther forward.
• Add air inlet and ducting.
• Add braces in the middle for rigidity at high speed.
• Maybe add features on bottom to smooth underflow (radius bottom edge, panel to cover underside gap)
• Paint it black (except over the blinkers). Some folks may really dig the stealth look. I'm okay with it, but I'd much rather have a more blatant ecomodder look, as long as it looks smooth and relatively attractive. Because I'm an evangelical ecomodder. Anyways the crystal clear probably won't look that great when it gets mud on it.

[christofoo]

Originally Posted by MetroMPG

Glad you tufted the leading edge of the hood. Despite the car's "blocky" front end appearance, those relatively small leading edge radii really work to prevent flow separation.

I was surprised by the result just because car noses have gotten softer and softer and softer, even since this 89 model. There must be something to be gained, but clearly I'd have to do A-B-A testing to find out how much, again a hindrance that I'm not ready for it.

(The reason, I mentioned earlier, is my rolling resistance problem, most likely drum brakes. Just a question of free time and priority.)

[Sven7]

I think noses have gotten softer because the fashion/design world has moved away from boxy stuff.

Why do you think drum brakes are a problem for RR?

The clear air dam is kinda cool but you're probably right in painting it. Do be sure to cover the hole it's creating underneath, or the air may just swirl under there. Do you know if it stays stable and keeps it shape up to about 90mph? Figuring a 60mph cruise with 30mph head winds...

[christofoo]

Originally Posted by Sven7

...
Why do you think drum brakes are a problem for RR?
...

I can feel more drag when the car is cold. I had a test on my "bullnose" that demonstrated higher drag when cold (rather than finding the aero effect of the bullnose that I was looking for). Sometimes I think I can hear the rear brakes when cold. Can't say I know for sure.

Originally Posted by Sven7

...
The clear air dam is kinda cool but you're probably right in painting it. Do be sure to cover the hole it's creating underneath, or the air may just swirl under there. Do you know if it stays stable and keeps it shape up to about 90mph? Figuring a 60mph cruise with 30mph head winds...

I'm still debating what to do with the hole on the underside. I believe several ecomodders have left the edge harsh and still had positive results, although I doubt that's optimal... I might split some pipe insulation or large rubber hose into half-cylinders and add it to give the bottom edge a radius, then do a little coroplast to close up the bottom. Surely that would help.

I forgot to mention in my todo; you're right that I need a pair of braces in the middle; I'm pretty sure it bends in the wind. I have a little video camera I can strap to the lower grill temporarily to verify rigidity at speed. That should make for some fun shots too, assuming I manage not to lose my camera.

[christofoo]

Originally Posted by Sven7

I think noses have gotten softer because the fashion/design world has moved away from boxy stuff.
...

That's also possible.