Flat Bonneville-type spoiler

[scottoriou]

I havent done sufficient testing to say that these gains are proven but previous to this spoiler my best average was 47.5 mpg. I ran two ABA tests early this morning before the wind picked up each one was 30 miles long total. I get my car up to 60 on the interstate and hit cruise and then reset my scangauge. Today my average over those two runs was 51 mpg. This spoiler sticks out 10 inches from my rear decklid.

[California98Civic]

Originally Posted by scottoriou

I havent done sufficient testing to say that these gains are proven but previous to this spoiler my best average was 47.5 mpg. I ran two ABA tests early this morning before the wind picked up each one was 30 miles long total. I get my car up to 60 on the interstate and hit cruise and then reset my scangauge. Today my average over those two runs was 51 mpg. This spoiler sticks out 10 inches from my rear decklid.

This looks pretty good, a little more stealthy than what I have contemplated. Thanks. It could significantly change what I try on my car. Could you describe your test method and results in more detail? It would be helpful. Are you saying you got something like your old 47.5mpg during the test when you took off the spoiler? Was it on the A runs or on the B run? Oh!! And what is this spoiler made of, how is it secured (bolted?), and does it have supports on the underside? What angle is it set at?

EDIT: okay... I see the angle in the second shot.

[scottoriou]

my tests go as such. I try to take all human interaction out of it. I have a stretch of interstate that is close to my house. I get up to 60 mph and at a designated point I reset my scangauge. and then 15 miles up the road I look at the scangauge at the second point and record that. I then get off the interstate and turn around and get back on heading the other direction. I get my car up to 60 and resume the cruise and at the same point I stopped the first test I start the second test. I then average all my A-B runs and my B-A runs to find the average for both and then average those together to get my averaged A-B-A. My previous best which was last thursday was 47.5. I added that spoiler on sunday and hadnt had a proper chance to test it until this morning I did two A-B and two B-A runs and the total average was 51.9 for A-B and 50.2 for B-a so the A-B-A was 51.

The wind started to pick up so I wasnt able to take the spoiler off to do runs without it so I'll get back to you.

its fastened to my deck lid with some 1/4 inch bolts through the holes for the stock spoiler. The spoiler itself is made with a sign material thats aluminum with plastic sandwiched in the middle. I actually have like 8 more 4x8 sheets of it if anyone is near Central IL and whats some. Its really light and stiff. Makes awesome bellypan material.
There are no supports. Its plenty sturdy enough without them.

[brucepick]

scottoriou - put up a pic of your spoiler please!
I'm sure I'm not the only one who would like to see what it looks like.

Apparently you're still kinda new so maybe can't post pics. But you can post your pics on something like photobucket.com and just write the link into a post here.

[brucepick]

I'm still stumped.

The posts I'm reading here fall into several categories, none of which help my understanding of this thing.

Does this thing need a downward angle or a level panel??

Thanks indeed, to any here who can clarify this for me/us.

[Pendragon]

Scottoriou,

That is an interesting choice of materials. I do not recall anyone using it before. Mounting it through the existing holes for the factory spoiler is a slick idea.

I am not sure if it is the photo or whether the lip actually has a small upward angle (5 degrees, perhaps?). Could you clarify that and what your thinking was in selecting that angle? Is the angle adjustable (shims between the trunk lid and the lip)?

Have you considered putting some end plates on it for stage 2 testing? That would be very interesting.

Thanks for posting the pix.

[California98Civic]

From aerohead, pendragon, brucepick, and scottoriou I took some advice and tips as to the design of a quickie flat spoiler and a quick test. I built the below in about an hour out of remnant cardboard in the garage. It "clips" into the trunk with three cardboard "tongues" reinforced with duct tape. It can be removed easily and quickly, and it fits in the trunk without taking it apart. It extends two feet behind the trunk lid and follows the angle of the trunk lid exactly. Oh, and I tapered in with the taper of the trunk lid. Then I waited for traffic to quiet down and took a ride along the Pacific Coast Highway out here. My speeds were kinda slow, but the convenience can't be beaten and frankly I was kinda nervous the thing might fly off on the freeway. Also, it was getting late and so I only got an A/B in (sorry). Nonetheless, I did six bi-directional lengths for A and six for B. The average speed for all runs was about 52mph. The average mpg for A (not modded) was 46.87 and the average mpg for B (mod) was 47.32--the spoiler seems possibly to have produced a gain of .45mpg. But of course this was not a full test.

I'm confident that the spoiler will hang on in the higher speeds now, and I really should try a better, higher speed test. Maybe tomorrow or the next day.

But... reactions?

[Frank Lee]

Originally Posted by brucepick

I'm still stumped.

The posts I'm reading here fall into several categories, none of which help my understanding of this thing.

Does this thing need a downward angle or a level panel??

Thanks indeed, to any here who can clarify this for me/us.

The required angle is going to be quite different from vehicle to vehicle and even between the fabricators' preferences... so the answer is "yes".

The car/person that wants to minimize the trailing wake area and is not concerned about how far out the rear the spoiler sticks will go with a downward angle. The car/person that balks at having a spoiler sticking out that far will opt to compromise a bit on ultimate trailing wake area reduction and angle it straight out, or up (up to a 30 degree max according to aerohead). In all cases the spoiler has to intersect (or close to it) the aero template, which should allow the airflow over the roof to "pretend" it's attached all the way to the rear of the vehicle.

[brucepick]

Thanks Frank. I think you're saying the rear edge of spoiler should meet the aero template line? I'm thinking, if it extends beyond that line (which represents a curved plane) that would be detrimental? And of course if it doesn't extend to meet the line, it doesn't intersect.

[EVDRVR]

Originally Posted by California98Civic

I have been seeing those little "flips" all over town now. But I think I need something bigger for this purpose. And I agree the rear spoiler on that "Bonneville Civic" looks easy to mimic. I think the trunk lid is the key to securing the spoiler ultimately. I could create little flaps in the spoiler that close into the trunk lid. The supports featured on the Bonneville Civic could rest against the lid, or under it, without adhesives or drill holes anywhere. Cool pics, btw.

Oh! And aerohead, thanks for the tip on the tape... I'll check it out for sure.

Have you considered attaching a spoiler using commercial suction cups to test your design? Here is a link to one particular brand, many are available. Industry swings plate glass through the sky with these things so I feel that following reasonable cautions and a safety strap you might find them useful.

Wood's Powr-Grip Co., Inc. | Vacuum Cups | Mounting Cups | 3" Concave Vacuum Cup with Threaded Stud