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Old 07-25-2014, 10:40 PM   #1 (permalink)
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I have a few aero questions.

So I finally did the aero template and these were the results





So I have a few questions about that and some that are unrelated. Anyway here they are, first did I use the template correctly?

Also is the spoiler going to affect anything? I was wondering because it seems like the back end is bad enough that it shouldn't make a difference. I also don't want to take it off because I think it would make a really good mount for a kammback idea I have.

Now the unrelated questions.

Is it better aerodynamically to have a grille block in front of a plastic mesh kind of grille or does it not make a difference either way?

For wheel covers would having them on the inside of the wheels work as well as on the outside like you usually see?

And finally (for now) is smoothing out the back end of a car (like in the area with the spare tire well on mine beneficial without a full belly pan?

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Old 07-26-2014, 08:16 AM   #2 (permalink)
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Quote:
Originally Posted by backpacker3 View Post
Also is the spoiler going to affect anything? I was wondering because it seems like the back end is bad enough that it shouldn't make a difference. I also don't want to take it off because I think it would make a really good mount for a kammback idea I have.
ABA testing.

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Is it better aerodynamically to have a grille block in front of a plastic mesh kind of grille or does it not make a difference either way?
Better to block than not to block. In front or behind probably to small to measure on most cars.

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Originally Posted by backpacker3 View Post
For wheel covers would having them on the inside of the wheels work as well as on the outside like you usually see?
Smoother is better.
http://ecomodder.com/forum/showthrea...tml#post418250


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And finally (for now) is smoothing out the back end of a car (like in the area with the spare tire well on mine beneficial without a full belly pan?
http://ecomodder.com/forum/showthrea...tml#post436970
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Old 07-26-2014, 11:28 AM   #3 (permalink)
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Weird. My browser did not show Nemo's response until the forum told me to reload.

I am all you got? I have a bad feeling about this!

Your images look good to me. Did they not quite fit perfectly, so you made two? Virtually all factory spoilers are only for looks. My HX came with one and so did my dad's Focus SFE. Mine also has lean burn and light alloy wheels. His has an active grill block and smooth wheel covers. I know that one Civic owner swapped trunk lids with someone without the spoiler, but if you simply remove it, you have open bolt holes, which would work great to mount a Kamm-back.

Having the block in front of the grill should be more aerodynamic than behind, although I do not know how much of a difference it would make. I would think that it would be different with wheel covers, since they would spiral in constantly-varying relation to the wind. I imagine that most of the problem is with air swirling around the outer edge of the wheel, not crossing from one side to another.

A partial bellypan should provide part of the benefit of a full one.
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Old 07-26-2014, 01:42 PM   #4 (permalink)
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questions

Quote:
Originally Posted by backpacker3 View Post
So I finally did the aero template and these were the results





So I have a few questions about that and some that are unrelated. Anyway here they are, first did I use the template correctly?

Also is the spoiler going to affect anything? I was wondering because it seems like the back end is bad enough that it shouldn't make a difference. I also don't want to take it off because I think it would make a really good mount for a kammback idea I have.

Now the unrelated questions.

Is it better aerodynamically to have a grille block in front of a plastic mesh kind of grille or does it not make a difference either way?

For wheel covers would having them on the inside of the wheels work as well as on the outside like you usually see?

And finally (for now) is smoothing out the back end of a car (like in the area with the spare tire well on mine beneficial without a full belly pan?
*Ideally,you'd have a long-telephoto image of the car to get all the profile closer to that of a technical drawing,but for what you have the alignment looks real good.
*The spoiler may catch some of the downwash off the roof and kill a bit of rear lift,so it's worth keeping if only for that.
*If the grille block is 'outside' the grille,it can guide the airflow around and over with less local energy loss.
-------------------------------------------------------------------------
With respect to the 'open' wheels:
Pontiac measured -0.018 loss compared to a ventilated cover
...................... -0.024 loss compared to a flat disc cover
...................... -0.027 loss compared to a convex (MOON) type cover
Running a cover on the inside would produce similar results,as the airflow would have zero flow support surface down the sides of the Sunfire.
-------------------------------------------------------------------------
The 'diffuser' area works best when there is a smooth belly up to it.
*Carr showed a Cd 0.015 drag reduction from cleaning up this area in the presence of a belly pan
*When this area was carefully sloped up as a diffuser it netted a Cd 0.04 improvement,but only with a full pan up ahead of it.
*If you can locate a HONDA VX,look under it's tail to see some special smoothing panels.These lowered drag measurably.You can compare its belly to the Pontiac.
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Last edited by aerohead; 07-26-2014 at 01:43 PM.. Reason: spelling
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Old 07-26-2014, 01:58 PM   #5 (permalink)
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Quote:
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*Ideally,you'd have a long-telephoto image of the car to get all the profile closer to that of a technical drawing,but for what you have the alignment looks real good.

Lacking a long telephoto get lower when you take the picture. Center the lens top to bottom in reference to the vehicle while keeping the camera perpendicular to the ground with the face of the camera parallel to the car.
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Old 07-26-2014, 09:50 PM   #6 (permalink)
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Thanks for all the replies. There are two images because I took two different pictures because I wasn't sure which would be better. The top image is the one I took while standing back from the car and trying to keep the lens at about the center of the side of the car.

I am going to be putting in a block on the smaller upper grilles I wanted to see which would be better though. I was going to take the easy route and put it in behind cause I can use the screws that hold the plastic mesh thingamajigs in I'll put it on the outside though based on what aerohead said.

I think I'll probably just leave the spoiler as is for now. I considered doing ABA testing but since I lack a scangauge and because the spoiler houses my third brake light it's kind of an involved process to remove it and having the holes it leaves behind to let water leak into the trunk isn't too fun either.

Thanks for the advice on the wheel covers too. I was wondering because the way my wheels are it would be easier to mount covers to the back side rather than the front.
I wonder if having covers on the front and back would make even more of a difference? That way the air behind the tire would be smoothed out as well?

I'll have to see if I can find a VX next time I'm at the junkyard and take a look.
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Old 07-28-2014, 05:31 PM   #7 (permalink)
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front and back

Quote:
Originally Posted by backpacker3 View Post
Thanks for all the replies. There are two images because I took two different pictures because I wasn't sure which would be better. The top image is the one I took while standing back from the car and trying to keep the lens at about the center of the side of the car.

I am going to be putting in a block on the smaller upper grilles I wanted to see which would be better though. I was going to take the easy route and put it in behind cause I can use the screws that hold the plastic mesh thingamajigs in I'll put it on the outside though based on what aerohead said.

I think I'll probably just leave the spoiler as is for now. I considered doing ABA testing but since I lack a scangauge and because the spoiler houses my third brake light it's kind of an involved process to remove it and having the holes it leaves behind to let water leak into the trunk isn't too fun either.

Thanks for the advice on the wheel covers too. I was wondering because the way my wheels are it would be easier to mount covers to the back side rather than the front.
I wonder if having covers on the front and back would make even more of a difference? That way the air behind the tire would be smoothed out as well?

I'll have to see if I can find a VX next time I'm at the junkyard and take a look.
Hot Rodders have used inner and outer wheel covers as a speed trick
since Bob Rufi introduced them to dry lakes racing in 1939.
Danika Patrick's Indycar had beautiful carbon fiber inner covers.
You'd want to be mindful of brake cooling.
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Last edited by aerohead; 08-01-2014 at 06:02 PM.. Reason: correct date
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Old 07-28-2014, 09:46 PM   #8 (permalink)
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I was thinking more of one that would be similar to a brake dust shield on the inside of the wheel itself. Since the inside of the wheel also has the same pattern from the spokes or whatever you want to call them it would smooth out that surface too.
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Old 07-29-2014, 05:38 PM   #9 (permalink)
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I was thinking more of one that would be similar to a brake dust shield on the inside of the wheel itself. Since the inside of the wheel also has the same pattern from the spokes or whatever you want to call them it would smooth out that surface too.
Since the wheel must clear all the brake components during install and removal,it seems like you could have no more than a 'ring' on the inside,or else it would interfere with all the brake hardware.
If you attached your streamlining fairing to the back side of the spindle it could effectively seal that area while not interfering with the wheel/brake system.
And you're impacting brake cooling and also wheel bearings,so be mindful that you don't create a heat trap for expensive bits and pieces.
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Old 07-29-2014, 06:50 PM   #10 (permalink)
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I think we might be thinking of different things or maybe I'm not explaining my idea correctly. This picture is pretty similar to what I was talking about

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