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I'm wondering if I can improve the aerodynamics of my brick like 99 Honda CRV..

There are some large openings in the upper bumper and a smaller air input above them.

I'm thinking of blocking those air-inputs with a screen mesh.

The reason I'm thinking screen mesh might be the right stuff is, slow moving air sucked in by the fan would not be affected.
But, when driving at highway speeds, the mesh will act like a solid blockage, since high speed air can't penetrate a mesh screen. (Due to surface turbulence).

This would force most of the air normally going into the openings to find a new path around the car. Making the nose act like it's more streamlined.

Does this sound logical?

Thanks..

http://i46.photobucket.com/albums/f147/Xringer/CRV/Skidplate.jpg

I have heard that screening will act like that. You could probably get away with blocking the entire upper grill without problems even if it is a solid block. Just make sure you have a scangauge to monitor coolant temps.

I'm on the list for this SGII group buy. Maybe I'll have it in a week or two.
At the same time that I placed my order, I also put a Ebay bid on a Skid-plate. The Skid-plate will be here tomorrow!:woot:


You might be right about solid blocks. I once had a car-bra on my old Laser RS. The air input was blocked by a nylon mesh.
The holes in the mesh were petty small, but I never saw the temp gauge go higher than normal while making long runs on hot days.
And, the AC worked exactly the same with or without the bra installed.

The screen blocking will help. I did it with my Civic (see gallery section for pics) and I saw a boost of 1-2mpgs from it with no other changes. The only thing you need to do is watch your engine temp. Right now my temperature covers the wavy water line icon on the temperature guage (a little less then half). I think I could block even more of the grill so long as the temperature goes no further than the half way point.

I saw a FE report on TV the other day and they said to insulate the underside of your hood.
Since a hotter engine gets better FE..

Is that true? If it is, I could add blockage and maybe move the temperature up to a more optimum range?

---------

One other thing I was wondering about. There are couple of deep air-intakes on my lower grill (upper bumper).

I know the best way to block them would be to seal them over on the outside surface of the grill.
But, what if I went inside the rear of the grill and placed the blocks at the back ends of these air tubes.
Looking at it from the front, would be like looking into a big 6" deep coffee cup..

Would 'bottom' blocking be as effective and 'outside' blocking?
My half-baked theory is, if it's like a cup, higher air pressure inside the cup will not allow new air to push into the cup.. Since the cup will be overflowing..
A full cup should act about the same way as the 'outside' covered cup..?.

Does it sound crazy, or am I on the right track?

It'll be good, but not quite as good as a flush block. It's what I have. Click on "my rides" for pictures.

It'll be good, but not quite as good as a flush block. It's what I have. Click on "my rides" for pictures.

Interesting pics. Cleaner than my duct tape. Another guy on the ecomod forum cut some plexiglass and fitted it right in front of the grill. At first glance you wouldn't even notice that it's there. The surface is smoother so I'm guessing his aero drag would be even less.

Thanks. Those are good pics. Did you put coroplas behind some of those openings?
I make RC airplanes out of Coroplas and I still have some in stock! :woot:


Got my Honda OEM SkidPlate today.
http://i46.photobucket.com/albums/f147/Xringer/CRV/D116.jpg
http://i46.photobucket.com/albums/f147/Xringer/CRV/D114.jpg

Not a big one like I wanted, but just might help a little with the underbody air flow.

I've been thinking more about using mesh material for Grill blocking and I'm wondering if
a Car Bra might be the way to implement putting the mesh over air intakes.

This style of Covercraft full coverage bra, should have about the same coverage on my CRV.
I once had a similar bra for my 91 Plymouth Laser RS and it worked very well.
http://images.autoanything.com/images/products/large/car_bras/covercraft_full_mask.jpg

If I could get a fairly tight mesh over these holes, it might make the front end a bit more aerodynamic.
http://i46.photobucket.com/albums/f147/Xringer/CRV/Skidplate.jpg
If the mesh wasn't real tight, it should be pretty easy to insert a second layer of mesh inside the bra.

Anyone ever hear of a car bra helping out with grill drag?

I would start with blocking off the two openings on each side first and see how much it helps. Then I'd look at covering the lower half of the middle opening.
Just do it in increments until to you find the happy medium.

I'd do an angled "wing" (diffuser?) inside the bumper on the outer openings to direct the air away from the radiator support (just don't direct it into the skid plate)

I would look and see what kinds of front bumpers are available after market. (it looks like anything but that one might be better, lol)

some of that "ricer" stuff is inspired by real race cars in japan...
you could also add to the rear of the short skid plate with some sheet steel.
or that chloroplast you were talking about.

I would start with blocking off the two openings on each side first and see how much it helps. Then I'd look at covering the lower half of the middle opening.
Just do it in increments until to you find the happy medium.

I will do that, but I think blocking off the upper half of the middle input would work better.
Since the plate is already causing problems with the top half getting a direct shot of air..

I've looked at the path in, and the bottom 1/2 looks very promising.
Maybe bringing my blocking shield forward in the middle, so it's up near flush with the backside of the plate,
will lessen the low pressure behind the edges of the plate and bring down it's overall drag just a tad.. Maybe keep strong swirling air off the surface of the radiator..?.

I'd do an angled "wing" (diffuser?) inside the bumper on the outer openings to direct the air away from the radiator support (just don't direct it into the skid plate)

I would look and see what kinds of front bumpers are available after market. (it looks like anything but that one might be better, lol)

some of that "ricer" stuff is inspired by real race cars in japan...
you could also add to the rear of the short skid plate with some sheet steel.
or that chloroplast you were talking about.


I was looking at that wide support in the center of the bottom 1/2 yesterday.
My first thought was to use a wedge shape (like a piece of cake) with the pointed
end forward and the base just wide enough to cover the width of that radiator support.
That should put a 'cleaner' pressure front on the surface of the radiator surface.
----

I've seen three different styles of CRV Import 'race' noses. They appear to be lower where it counts.
http://www.grounddynamics.com/Templates/frmTemplateq.asp?SubFolderID=486&SearchYN=N

But there are some problems with them. All of them have big openings for fog lamps, very large air intakes and are also upper intakes.
So,a lot of mods would have to be done before even installing.

Since the 'race' bumper is larger overall, I think the extra drag it will cause, outweighs the positive effects of the air dam. I think they are for 'looks' more than cd.
I wish they made one that's smoother, with less extra stuff all over it.

I think maybe if I get good blocks in place on the OEM bumper, all I would have to do is add a forward-curved wheel-to-wheel Air Dam and have a much better cd.
That way, when the snows come, I could quickly pull the air dam off for a few months.

----
I've reviewed the idea of adding an extension to the TE of the skid-plate. Since, in it's stock form, it just covers the (plastic) bottom engine Splash-guard TE.

I'm guessing, but I think the chopped-off TE of the skid-plate will cause low pressure swirls to flow up in back of the radiator. Which might be good for cooling anyways.

So, the extension idea is on the back burner until I get the grill blocks in and take some temperature readings on the road.

I think that bottom-center opening should be enough for all your needs. I'd go ahead and block the upper.

I was looking at that wide support in the center of the bottom 1/2 yesterday.
My first thought was to use a wedge shape (like a piece of cake) with the pointed
end forward and the base just wide enough to cover the width of that radiator support.
That should put a 'cleaner' pressure front on the surface of the radiator surface.
----

I've seen three different styles of CRV Import 'race' noses. They appear to be lower where it counts.
http://www.grounddynamics.com/Templates/frmTemplateq.asp?SubFolderID=486&SearchYN=N

But there are some problems with them. All of them have big openings for fog lamps, very large air intakes and are also upper intakes.
So,a lot of mods would have to be done before even installing.

Since the 'race' bumper is larger overall, I think the extra drag it will cause, outweighs the positive effects of the air dam. I think they are for 'looks' more than cd.
I wish they made one that's smoother, with less extra stuff all over it.

I think maybe if I get good blocks in place on the OEM bumper, all I would have to do is add a forward-curved wheel-to-wheel Air Dam and have a much better cd.
That way, when the snows come, I could quickly pull the air dam off for a few months.

----
I've reviewed the idea of adding an extension to the TE of the skid-plate. Since, in it's stock form, it just covers the (plastic) bottom engine Splash-guard TE.

I'm guessing, but I think the chopped-off TE of the skid-plate will cause low pressure swirls to flow up in back of the radiator. Which might be good for cooling anyways.

So, the extension idea is on the back burner until I get the grill blocks in and take some temperature readings on the road.

you are right all those "race" noses stink...
and I agree with the idea of blocking the upper opening mentioned above this post...

(the techno R thing looks good but is useless.)

you may be right about the cooling of the shorter skid plate...
hmm

I would agree with Pale and go for a flush surface type block, and also agree with ALS to do the side openings, monitor temps, and then go for the bottom of the two center openings. The bottom would go a longer way towards cleaning up the bottom "curve" of the bumper to the underbody, and you would be surprised how little opening you need under normal driving conditions to maintain cooling. Just keep an eye on your stabilized temps (find out what temp your thermostat is first) and also watch for unmanageable temp rises after shutdown that your electric fan (if there is one) can't deal with in short order.

I listed some of the issues I have run across working with coroplast over the last few months in another post if you're interested.

http://www.cleanmpg.com/forums/showthread.php?t=11445

you are right all those "race" noses stink...
and I agree with the idea of blocking the upper opening mentioned above this post...

(the techno R thing looks good but is useless.)

you may be right about the cooling of the shorter skid plate...
hmm

I was able to find one pic, in wild..
http://memimage.cardomain.net/member_images/6/web/726000-726999/726067_57_full.jpg

It looks like there is so much flat area in front of the headlights, they won't be able to
light up the road very close to the car..
Those bottom intakes are a tad on the JUMBO size... :(

When I suggested the outer openings I was implying that you could cover all four of the individual outer slots at the same time. Then look at the upper and lower larger center openings for more coverage later on. If no cooling problem came about over the blocking of air in those four smaller locations.

What ALS said!

Okay guys. I think we got it nailed down. Smooth surface blocks on all but the bottom 1/2 of the center.

But, before I start closing up holes, I would like to get a good idea of the normal running temps on a hot day. So far, we have not had many hot days.
I see we have a 79 degree day coming up on June 7... :(
(I'm starting to hate how cold this global warm is getting).

I also want to run up and down Route 3 and get some MPG readings at different speeds.
Once I can get a good idea of what the 'V' can do in it's current form,
I'll have a better idea if the cd has made any dramatic change.

I have a feeling that the blocking will help, but the change might be so slight as to not be easily measured.
Maybe adding other changes will add up to a longer glide one of these days.

Thanks,
Rich

I had some spare time this evening, so I taped up the intakes. (including the upper slots & Honda Logo).
http://i46.photobucket.com/albums/f147/Xringer/CRV/M018s.jpg

The horizontal center (plastic) cross piece is set back a bit, so the tape is angled
back towards the rear. That might drive more air into the lower intake,
but the plate blocks a lot of the upper section.
http://i46.photobucket.com/albums/f147/Xringer/CRV/M013s.jpg

Tomorrow I'll make the divider wedge to stream the air around that center radiator support.
That should increase the positive pressure a tad.

I took a 15 mile test run up Rt3 and back to see what the coolant was going to do.
It's running about 10 degrees hotter. Yesterday's ave was 185f and after the tape job,
it's running at about 195f ave. The outside temp dropped during my ride to about 70f.

Once I was back in my drive way, I waited about 2 minutes and the fan(s) came on.
(There are two, one or both came on).
The SG2 displayed 202f and dropped towards 190, turning off the fan in about 30 seconds.
I'm guessing the trigger point is 200f. This was typical fan operation before the tape.
Now, I have to wait for a hot day and do some more highway miles.

I figured this trip would have a low MPG, since I stopped at lights etc at least 15 times.
Did one :Banane54: jackrabbit start, drove 55 ave on the highway parts, used CC going up the hills
& didn't coast until my driveway, (I wasn't trying) but still ended up with 30 MPG for the trip..
Which kinda surprised me. The real-time MPG display seemed like it was running a tad higher on the highway.
But, there wasn't much level roadway, so it was most likely placebo effect.. :eek:

Cheers,
Rich

that will look cool made out of the right materials
(already looks kinda cool)

your factory thermostat is most likely a 190 so your temp seems fine to me.

X - Really nice work on the tape job, looks good. Are you going to fabricate coroplast blocks once you are comfortable that you have a working configuration? Looks like you used Gorilla Tape or some other type of black duct tape, and judging by the neatness of the work you did, you may not be happy with the weathering of the tape after a few hundred miles or so.

It appears that your thermostat is now wide open since your seeing higher stabilized temps with the tape in place, and your getting close to your fan threshold temp, so keep a close eye on your temps (as I'm sure you're going to). You probably don't want your electric fan having to run continuously to keep temps down.

Just a note of caution -- you may find that the car runs hotter around town than on the highway because of reduced airflow due to slower speeds. I saw some of this in the Elantra but it was more than counteracted by the extensive FASing I began doing at that point.

The black tape is from 3M and it seems to a little better than the silver stuff I have.
Unless I start parking outdoors a lot, the tape might last all summer.

I did the streamlining of the intake.

http://i46.photobucket.com/albums/f147/Xringer/CRV/inside.jpg
The nose piece is a 3"x6" piece of folded coroplas.
I couldn't figure out any easy way to do the false floor, so it's just tape for now.

The intake path isn't enclosed very much, but maybe with things much smoother on the bottom,
the positive pressure in the lower area of the radiator might be a bit higher. It just might help a little.

It's raining today, so the V will stay in the garage. This weekend is going to be hot,
so I'll get some testing done.

Update:
I have not yet done the SG2 Fillup offset adjustment yet (I want to burn off at least 3/4 a tank first).
But, prelim numbers are looking promising. I've done a couple of mileage runs, and the temp never varies much from 180-185, even in this high 90s heat wave.
It will get up to 202 max, whenever I'm stopped in traffic after warmup.

My first mileage run came out at 33 MPG highway. That's very close to what I expected to see.
Deleted the mud-flaps this morning and took another run before noon. Got 34.6 MPG with an average speed around 52 MPH.

If I use some DWL, I'm sure I can hit my goal of 35 MPG highway easily.
I can't wait until I get back in for another fill up, so I can see what the offset is going to be.
I'm hoping that my current numbers are close to accurate.

Has anyone done calculations to see what impact running the fans more has on FE? There must be some downside there, I'm just wondering if it negates the positives. OTOH cars are designed for extreme conditions -- that hole in the front of the CRV has to work in Death Valley CA as well as Fairbanks AK -- so I'm sure there's wiggle room for those of us who live somewhere in between.

The fans are going to use some power off the 12V supply, but as far as I can tell, the fans
are working exactly the same now as before adding the grill block.
They only come on in stop-and-go traffic. Or when it's 92 out and I'm waiting at a long light.
They come on and go off about 20 seconds later.

So, I get faster warm-ups, a more aerodynamic nose & no change in fan operation..
The only down side I can see so far is the cost of 3M black duct tape.. :)

Wait a sec.. Now that the air has to come in via a smaller intake, the motors may be drawing
little more current. Maybe a few more watts.?.

Next time I'm in traffic, I try to remember to watch the TPS when the fan comes on.

Ping for updates. Have your averages gone up, down, stayed the same?

http://i46.photobucket.com/albums/f147/Xringer/CRV/uppergrill.jpg

The tape is still hanging in there and I'm slowly working on a new fill-up..
But, since almost all my driving has been in the city, it's killing my MPG.
I think it's around 25 or 26 MPG right now.. :(

I'm going to cover up the holes in my rims before I try anymore highway test runs.
I want to see if I can hit 35 MPG on flat roads at 50-55 MPH..

I've also been thinking about how I can use some VGs to negate some of the drag from the rearview mirrors. (If that's even possible).

When I get some more MPG data, I'll post it.