CR-V underbody - need advice (many pics!) - Fuelly Forums

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Old 11-16-2007, 12:39 PM   #1
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CR-V underbody - need advice (many pics!)

So I finally did fluid maintenance of my CR-V, and now running full sythetic, hoping to get FE out of that.

Now I'm back to looking into the aero mod topic and would want opinions as to what to do how for the underbody.

I am thinking of soundproofing while at the same time improving aero, by using MLV (vinyl) instead of coroplast for covering.

So I'm posting a few underbody pics and my goal is to do minimal mods for maximal gain.

I am warry of just doing an air dam, as it increases frontal surface and changes aero. I am not sure it's the best way to start.

Front:

Underbody seen from the front bumper: It looks pretty flat, and like air flow would not disrupt too much, except neat the back wheels.

- Would the small dimples and bolt holes make a difference in the front?
- I could block some of the vents.




Front wheels:

- I think I need to do something to dam the air out of the wheels. Any idea on how I could build and mount an air dam there? The surface is already there so a dam makes sense to improve aero, and avoid the air from trapping into the wheel well.




Moving forward a little:

- The back of the engine is not covered. We see part of the tranny on the right, and the beginning of the drive shaft.
Should the cover be extended? I would think I'd want the air to flow out from there.



Front suspension.

Not sure what to do there. I need that to move.





Mid section:

- We see most structural parts follow the body: chassis beams, exhaust, drive shaft.
Should I cover these recesses and make a flat surface, or leave them to "channel the air, so it keeps flowing instead of escaping to the sides?
I kinda want to cover the hole between the 2 beams, if just to protect the brake lines running. There are a few holes I can use to rig some sort of holders.



Rear axle:

Ouch, there's the gas tank that sticks out like a brick! You see the drive shaft left of it going to the read differential,and full left, the exhaust pipe and the suspension.

- I want to cover the gas tank somehow, and make a more aero slope in front. Ideas on how to make something solid, yet not weld stuff?

- The drive shaft, top left of photo sits on a cross beam that I think might cause turbulences there. However I'd take ideas as to how to fix that?!

- Should I worry about the suspension's aero, and if so ideas on what I could do? This is a SUV so they need to travel up/down. I do go offroad!

- What about the tires? Should I put a deflector in front? A lot of the aero drag comes from tires! If so what shape and size? The '07 CR-V has a deflector which is a small vertical piece of metal, nothing fancy nor aero.



More views:



Sides:
Here's the side of the CR-V, near the moldings under the windows. I am not sure I need to do anything. I probably don't need to put covers there. At most put duct tape?



The wheel well... Anything to do there?




Rear

Some photos looking now towards the front of the car.

This is the rear bumper and wheel. Yo can see the suspension and the sway bar, as well as the spare wheel compartment.


And the other side with the muffler and mud flaps.


Misc:

Feel free to comment for ideas on those.

The wiper blades



Mirrors sticking out




& #65;
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Old 11-16-2007, 12:57 PM   #2
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2007 Cr-v

Here's a few studies on the 2007 CR-V's underbody.

My rough drawing of aero flow, and the air dams in front of the wheels:



The air dams are prettu small and the underbody doesn't seem much smoother than the 2nd generation CR-V.



From the side, a few interresting aero things, noted from I to V.

I - bumper advance
II - roof shape/spoiler
III - front wheel air dam (shaped)
IV - underbody
V - rear wheel air dam (not shaped)



And the rear view that shows stuff sticks out some still.

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Old 11-19-2007, 04:37 PM   #3
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If this were mine I would lower it to look like the altered pic above. I would also build a belly pan to follow the yellow line. Im building a similar design bellypan/diffuser on my rabbit. I will report the gains when I know how much it helps. You could also build or buy if they make a cusp spoiler on the back. Air diverters in front of the front tires should help as has already been shown
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Old 11-26-2007, 12:45 AM   #4
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The 2002 CR-V is not like the 2007. The underbelly is not as smooth, and the gas tank sticks out, lower than anything else: It's near the rear wheels.

I am making the tire air dams/diverters from ABS plastic: It's somewhat easy to mold with a heat gun, and cut with a blade.

I bought some black vinyl runners from Home Depot for the underbelly instead of corrugated plastic. Dunno how I'm gonna proceed yet, but I expect double duty as a sound barrier. Also less than $2 per linear/ft, and 2ft wide.

I already duct taped all the small recesses and cranies that are molded for bolts etc. to make the bumper and side skirt surfaces smoother. That was quick simple job.
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Old 12-06-2007, 11:45 AM   #5
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ever give it a shot?
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Old 12-06-2007, 12:04 PM   #6
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I've got a roll of vinyl sitting in the stairs, with expansion bolts, PCV home made reverse-mud flaps for the rear and all. It's been too miserable the last week-end to do it and before I was out running around.

i did get a quick fix in: a new clarion CD player, and just right there the ride is already muuch better. Also took me long time to find where to recycle tune-up car fluids in my county.
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Old 12-18-2007, 07:14 PM   #7
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Rear wheel air dams

With the bad weather settling in and the need to use the SUV, I haven't done much. However...


Mods:

- I did install the rear air dams for the rear wheels. Heat molded from black PCV pieces. $2 mods. Holds with a bold and a screw. It looks like a reverse mud flap. I installed that and rotated my tires at the same time.
- The fluids are new (tranny, 5-20 mobil-1 synth oil but not EP and filter, rear differential, air filter)


MPG report:

I am not certain I get better gas mileage, though I did get 26~27MPH last week-end with the scan gage, using cruise control at around 70~75MPH on a highway with rolling foothills (I280 from I85 to I92 intersection for those in NorCal).

The thing I noted is I seemed to hit 30MPG more often on flat spots or low inclines... It seems the SUV is more sensitive now to drafting. So I wonder if the aero mod on the tires unlocked potential but it is not fully tapped yet.

WRT to stock flaps, mine are bigger covering the whole width of the tire and have the sides bent at an angle instead of being small flat pieces covering 1/2 the tire. They extend down a couple of inches...
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Old 03-16-2008, 05:38 PM   #8
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Update:

Web page with air dams/deflectors for the wheels
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Old 03-18-2008, 11:16 AM   #9
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The underbody of that CRV looks like an undertray might be more work and less efficient than a decent air dam and side skirts.
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