5th generation civic hatchback - improving aerodynamics

[AndrewJ]

So in following the footsteps of the pioneer Basjoos before me, I too am setting out on the road of improving the aerodynamics of a 5th generation Honda Civic hatchback.

Goals are as follows:
1.) Improve aerodynamics from Cd: 0.32 to Cd: 0.26 or better (Honda Insight equivalent)
2.) Materials must be Weather, impact and wear resistant with a (projected) life of 5+ years of normal use.
3.) Overall design of components must be removable, with no permanent changes to the structure of the automobile.
4.) Aesthetic considerations play a role, notably in the S.W.M.B.O. test. (She Who Must Be Obeyed cannot object *too* strenuously to the aesthetics of the modifications).

In pursuit of these goals I plan to implement the following modifications, in roughly this order:
1.) Rear wheel fairings (not the most effective, I know, but the easiest, and most forgiving)
2.)Front wheel fairings
3.)Partial front belly pan
4.)Fiberglas front nose/splitter
5.)Boat-tail

And now for a quickly photochopped picture of phases 1-4




Now, to kick-off my little project I acquired a full sheet of 4-5mm (?) thick peice of white one-sided-grained ABS plastic. This actually took about a solid month of trying to track down my local plastics supplier. But today I actually found him and for a mere $75 took home a sheet of awesome white ABS.



ABS seems to me to be the ideal material for making fairings and such because of it's malleability under heat and because it can be "welded" with the right equipment. Luckily my local Harbor Freight store has the welding kit if I ever feel spendy, and they had a heat-gun on sale for $9.99 last week which I fortuitously saw fit to pick up even though I had no ABS at the time.

[AndrewJ]

So I got the first of my aluminum supports for the rear wheel fairings attached to the car tonight. It got dark before I could get the second side on though. Oh well, I have a little time tomorrow. So here's some lovely crappy pics.

Here's the horizontal support brace installed; it's pretty sturdy.




On the back side I've attached it with an "extruded U-clip" to the rear bumper.
In the front I basically attached it with a larger, stainless-steel version of your standard drywall anchor. I unknowingly chose to drill into the body where I can't get behind the sheet metal to get a nut on the bolt. So that's where the big drywall anchors come in.
After having it on the car, I've decided that I'm going to try to find a hinge to put on the front part of it tomorrow. A hinge will greatly facilitate tire removal if (when) I get a flat.




The only other thing I need is a much smaller bracket above the tire to hold up the top of the fairing.

So far, I have spent about $8 on the 1"x 1/8" aluminum bar stock and about $15 on various stainless steel hardware, that seems like a lot for hardware, but it is stainless steel, and I have changed my mind about fasteners about 3-4 times now...

[AndrewJ]

ok, I got all the brackets for the rear fairings installed. There is one horizontal bar running the length of the wheel well opening on the bottom and a small tab on the top of the wheel well opening approximately between the 11o'clock and 12 o'clock position (from the drivers side)
[IMG][/IMG]


Now I just have some template-finessing to do. The initial templates I made for the rear fairings are a little off. I made them before I had the aluminum brackets made or installed, so they're a bit off.

[AndrewJ]

So I got the rear fairings finished up and installed. They need a little bit more coaxing with the heat gun in places. That and the heads of the bolts and the washers need a good coat of white paint.








For all those interested in using ABS in the future please note that it will discolor if you heat it up too much with the heat gun, so heat up the back side of the piece so you wont see the discoloration when it is installed.

[AndrewJ]

So, first off, I'd like to amend my initial "goals" section.

I've decided that I probably won't be converting Harold to an EV. I just don't know what my driving needs will be in the future, and for any foreseeable EV-type range I'd rather just ride my bike.

So, since I probably wont be keeping this car long-term (and it's not worth much anyway) more "permanent" changes are quite acceptable.

So that brings us to today's installment: Airdam Mania!

I've had a crappy cardboard/white-duct-tape grill block on the car for a while now. It's been great, but I decided to make a more permanent combination of grill-block and airdam.

Sure, this will increase the CdA of my car, but it will also take care of two (or three) nasty areas of aerodynamic drag, thereby decreasing my Cd.

Alright, here's a pic of good ol' Harold with the temporary grill block:



I went ahead and cut a 82" x 17" strip out of my ABS sheet and grabbed a screwdriver and a few self-tapping screws. Here's what I came up with.







I've got a bit of driving to do this weekend for work, so I'll have to see how this new airdam effects my speed on a few "calibrated" hills on my drive.

[MetroMPG]

Awesome. Great to see another set of wheel skirts join the fleet.

I have a theory that rear wheel skirts help more on cars where the back wheels are set close to the back of the car - meaning, there's not enough bumper cover behind them where flow can reattach before turning into wake. Typically that means small cars.

Anyway, very cool work & looking forward to watching the progres.

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Housekeeping question: some of the photo sizes (big) are wreaking havoc in my browser - do you have an intermediate size option you can link to @ photobucket?

[AndrewJ]

images downsized sir.

[igo]

Good work on the wheel skirts. That air dam is huge. I would be worried about scraping going around bends fast or hitting bumps.

[Lazarus]

Outstanding. I llike the skirt brackets. Are you planning on a mirror delete? Those are huge. Very nice work indeed.

[XFi]

Looks Great! Glad to see you still making aerodynamic advancements with Harold. (and continuing your GS thread here ). I am definately interested if the front spoiler affects your MPG or coasting at all. I am thinking about something like that for the UnNamed Wagon. To be honest, my feeble mind didn't even make the connection to 'ajohnmeyer' until I saw these pics.

[MetroMPG]

Originally Posted by AndrewJ

images downsized sir.

Thanks. There's likely a function to automatically resize giant ones, even if they're hosted offsite (by dynamically setting width="" in the html). I'll have a look and see, as I'm sure this will come up often.

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That air dam is GIANT! I'll be very interested to see how it compares on your "calibrated" hills. I'll also be very surprised to hear that you didn't scrape it .

Sounds like you're going to be using the same methods Coyote X did to determine which bumper style was best for his car - comparing terminal coasting velocities on an often used descent.

I'm envious - "testing season" has been finished here for over a month due to the weather.

[MetroMPG]

PS: smooth wheel covers?

[AndrewJ]

Originally Posted by MetroMPG

That air dam is GIANT! I'll also be very surprised to hear that you didn't scrape it .

Oh, belive me it scrapes! Eventually it won't be quite so giant as it will be ground down.


Terminal velocity coasting results are in and they're interesting.

So my testing hill starts at about a 3% grade for 1/2 mile then goes to a 6% grade for another 1/2 mile. I usually start by killing the engine at the top going 55mph. By the end of the 3% grade section I've usually slowed to 50mph. Terminal velocity at the end of the 6% grade section is just shy of 65mph.

Today I did the same run with the airdam on and got a surprising result. The terminal velocity at the bottom of the hill was 67mph. But the interesting part was that on the 3% grade section I did not slow down from 55mph.

I think the airdam is a keeper. I'll have some tinkering to do in the next few days to get the final form down.

[MetroMPG]

Any chance of an A-B-A? How many screws on that puppy?

[AndrewJ]

I might do an A-B-A on Tuesday or Wednesday. It's only got 4 screws in it at this point, not counting the 3 license plate screws (there were 4 but one was so rusted it snapped off)
I'll probably do some A-B-A with the wheel skirts then too. Maybe front wheel skirts if I can get motivated to get them done by that time.

[MetroMPG]

That would be very cool.

So here's the other big question... do you feel self-conscious driving it?

It took quite a while to forget about my car's skirts. Lots of people noticed, and I even got a few quick rolled-down-window Q&A's. And that's just with rear skirts!

[AndrewJ]

People seem to take notice of the airdam much more than the skirts. I think it's because the airdam is frickin' loud when it scrapes, that and it's a huge white expanse of plastic. I think it gets the attention of the younger guys b/c of it's almost "racer" appearance.

About a week ago I got the first comment about the skirts from an old guy in a store that I frequently work in. I was passing him in the stock room and he stops me "Is that you're little white car out there?" me: "the civic? yeah." him: "those wheel covers are really neat looking!"

I can't help thinking that they're much more likely to be appreciated by the older crowd, those that grew up around all the Cadillacs, Buicks, Oldsmobiles, etc that had rear wheel skirts from the factory.

[AndrewJ]

So I finally got some motivation to do some more work on the car today.

I took off the airdam and shortened it about 2" so hopefully that will resolve the scraping issues I've been having.
I also took the opportunity to add some front wheel spoilers to the airdam.

Here it is all trimmed up with the wheel spoilers, off the car of course.




And here it is on the car.




And one detail shot of the wheel spoiler.




I also deleted both side mirrors, but it was very much dark when I got them done, so pictures will have to wait until tomorrow.

[MetroMPG]

Nice to see you working on refinements.

Originally Posted by AndrewJ

I might do an A-B-A on Tuesday or Wednesday.

Any news there? (Clearly I'm a sucker for the data.)

If not, I'll settle for qualified subjective observations .

[AndrewJ]

No, still no A-B-A but I'll try to squeeze in some testing on my next day off. I think my data gathering is moving at a Forkenswift pace.