2006 Civic Coupe Aero Mods

[JacobLeSann]

So, I’ve had an ongoing thread about this, but it’s been pretty quiet in the “Success Stories” forum. I figure I’d get more advice here.

https://ecomodder.com/forum/showthre...-new-post.html

I bought the car in 2022 I think, and have been tinkering with it since. I’ve gone from 38 up to 47 MPG. I’ve reduced high speed instability, improved top speed, and done lots of testing. It’s been running a front undertray, partial grille block, rear Bonneville-type spoiler, wheel discs, and an airdam. I want to take it even further.

The main design constraint is that I want to sell this car down the road. All of my modifications must be reversible. So hood, trunk, bumpers, wheels are all fair game.







This is where I’m at currently. I used tuft-testing to observe airflow over a trunk extension I made. This is designed to capture an air bubble and create an artificial fast-back roofline.

From my photos, you can see that there is ~2” spacing between the trunk and the longer tuft. There still seems to be attached flow along the surface of the extension.

I wanted some opinions on this design. Let me know.


12/2/23: Here is a summary of this thread up the current date, for those who want an abbreviated format: https://youtu.be/ouDkptwDQMs?si=pa5OQiFCoUDyBqr0

[freebeard]

Get some of those Volvo station wagon tail lights that run up the D-pillar, Swap sides, turn them upside down and put them on the ends of Cruiser skirts. Where the duck duct 100-mile-an-hour tape is now

The ledge below the back window is a reasonable alternative to shortening the gla$$.

If the spoiler had the same perimeter but a shallow concave center, you might net some downforce.

[JacobLeSann]

Haha, I was genuinely surprised how well the cruiser skirts held up at those speeds. Red Green wasn’t wrong about duct tape.

Volvo tail lights are cool…maybe a more primitive reflector setup could do the same job. I was leaning more towards having faux ducts ala Toyota. If anything, I’m designing the rear to have a box cavity in the vein of the Porsche 935 Kremer (non moby dick).

Concavity…hm. I could check it out yeah. I’ve found the convex shape to be much easier to produce. I just laminated styrofoam boards and used a hardwood flooring sander.

[freebeard]

Reflectors won't replace the tail lights. The tail lights stand in hte way of a reasonable boxed cavity.

One might make a perimeter frame with saggy fiberglass cloth and let gravity find a catenary curve.

[JacobLeSann]

Oh, no I meant using the Volvo tail-lights in the rear of the cruiser skirts. I figured it would be cheaper to use reflector tape instead. Furthermore, I would just turn them into fake vents like the modern Toyota Camry. I don’t want to do a full tailight swap.

The car is meant to run all stock equipment, except for stuff I can swap out. That would be the trunk, bumpers, fenders, hood. I have spare parts for all those items. I plan to sell the car down the road.





Some examples of inspiration for rear box-cavity design I have. I could make some cut-outs in the rear panels for tail-light visibility, and use clear plastic to fill in the gaps. I did that on my Aprilia scoot and cops don’t mind.

[aerohead]

For low drag I recommend that you investigate the roofline of the late-1984 Porsche 962 sports prototype racing car, and 1996 Porsche 911 GT1, both by Norbert Singer, head of Porsche Racing.
This roofline is what aerodynamicist, Dr. Hermann Burst recommended as the 'solution' for the 1972 Porsche 911 Carrera RS 2.7, but was shot down by Harm Lagaaij, head of Porsche Design because it didn't satisfy the 'look' of Ferry 'Butzi' Porsche- III ( designer of the 911 ) 'falling tail line' of 1959-60.

[freebeard]

images.fineartamerica.com/images-medium-large-5/1996-porsche-911-gt1-morio.jpg

That's an entertaining difusser.

[JacobLeSann]

Aerohead, those are both very cool cars, and I can see the effectiveness of the roofline. I’m a big fan of the chop-top look on the 1996 GT1. Unfortunately, it doesn’t really fit into my requirements for this car (removable, and attached only to the trunk or bumper cover). I want to be able to keep this car with solid mods for a while, and return it to stock and sell it when I’m done with it.

Nonetheless, I’m actually starting at the front of the car right now as I research the rear more. I found I’m having cooling issues at low speed. I’ve noticed from the get-go that this car does not like any form of grille block. It likes to kick in the rad fans at stop lights, which isn’t correct (imo) in this fall weather. I will deal with this first, and move towards the rear of the car.


Edit: Has anybody determined if covering the manual transmission can cause overheating of the MTF? I’ve been thinking about this. No oil cooler on it. Last time I changed my fluid it was pretty black.

[freebeard]

Remember that green Colani Beetle body from ecomodder.com/forum/showthread.php/there-no-single-best-aerodynamic-shape-41112.html#post688113.

The Julian Edgar video convinced me there is some benefit to 'boat-tailing' the front of the car. Smaller stagnation point, the pressure cancels out side-to-side, and bonus front wheel skirting.

[JacobLeSann]

(Source: NASCAR)

Boat tailing the front? I guess it makes sense, really. The front of this car seems efficient enough, though. I found while tuft testing that the front of the car didn’t have any big flow problems. The grill openings and radiator airflow are fairly unoptimized, and I feel that’s the only concern I have with the front end.

In that picture above, they have shrunk the grille opening to 20% or so of what it would normally “need” to be. Using proper ducting, airflow is spread out from the small opening to pass through most of the radiator. I’d like to test something of this nature on my car. I understand I will be operating at much lower speeds than a NASCAR (except on Monday mornings ).

After that, I think the “exhaust” airflow (coming out of the back of the radiator), is restricted. So far as I can see, it’s expected to just tumble out the bottom of the front bumper. My front skid plate blocks that off, and the OEM engine bay is so packed that it may be causing pressure buildup. Optimally, I would want this airflow to dump smoothly out behind the front wheels. I think this will induce less lift.


….These are assumptions, though. Testing is key.