Grand Caravan Grill Block
 

I've decided to take SVOboy's advice and make a grill block for my van. The only question is I'm really not sure where to start. I've taken some pics of the front to get some ideas. I'm planning on using foam and corrugated plastic as SVOboy suggested. Also I live in Southern Mississippi where it can get pretty hot. I"m not sure if I should cover the top and bottom middle portion. Both lower sides will definately getting covered because the openings serve no purpose without fog lights. I called a sign shop and they have
4' X 8' corrugated plastic for $15 and 18" X 24" for $1.50. How much do you guys think I will need?

Maybe I should have posted this in the Aero Mod section.

Moved it to the aero forum for you.

Get a big sheet and do some rear wheel well covers too!

My grill has a vertical-slotted design. I don't know if your grill has long slots or something else. I got some dark gray foam pipe insulation from Home Depot and cut it to fit the slots.

Some pieces keep falling out. I'd glue them in but I'm planning on a complete new front grill from corner to corner. If not for that I'd be hot-gluing them in. Duct tape can help too.

I'd block the upper half of the grill and see how it works out. With the upper half blocked, the blocked air should tend to wash up over the hood and stay out of trouble that way.

i'd try to see where the radiator actually is. the grill may not represent the actual radiator surface, for example i only recently found my radiator is offset to the right. so try to figure out wich areas of the grill are most effective and block everything else off...

also you might want to try to make a cardboard or tape grillblock first. you can start with a small portion and add more surface untill things get to hot. so you don't waste any material and once you've determined what works best you can make an extra effort to make it look good.

If you want to give this a test before you make any significant investment, you can. On the van, their is a plastic cover over where the radiator and condensor are located. Their is a gap of about 3/4 of an inch between the two. You can remove the cover and put a sheet of cardboard in it, to block off the air's ability to pass through the radiator.

When I had one on my wife's van, I had to leave about 1/4-1/3 of the radiator unblocked, in order to keep the temperatures from climbing beyond their normal 25 percent point. I was pretty surprised at how much of an improvement it made. I took it off because it is primarily driven by her and I didn't want her to experience any problems because of my tinkering. I do think it was effective, on the order of 10-20 percent improvement in mileage, but you can give it a test run, before you go more permanent, if you want. You may very likely get a little better results with a more elegant approach, but this would give you a pretty good rough cut.

Gary I looked under the hood and there is a descent size gap between the radiator and grill fins. If I were to place cardboard behind the grill fins, then the block wouldn't be flush. Is being flush an issue or is blocking the grill the most important thing?

Well, ... ? I don't know, for sure. From what I've read, mostly here and my own experiments, it is probably slightly less effective than a gap cover or fill, as you are considering. When the gap's are blocked, the air inside of them doesn't have any place to go, so it creates a sort of mini bubble, which is probably not quite as finished in terms of airflow, as a nice smooth surface. However, from what I experienced, I suspect that it probably addresses better than 80 percent or maybe 90 percent of the opportunity, on a relative basis.

On my wife's Town & Country, 98, the first pass I used Saran Wrap across the whole front of the car. The second pass, I used the cardboard. I haven't done a more finished test, but I would expect it would be as good or better than the cardboard quicky test.

Remember that the goal is to improve the aero, not necessarily reduce cooling.

The engine can probly cool OK with a third of the grill open (depending on the car). If you use the AC in high heat and you have very little air coming through the condensor (sits in front of the radiator), the compressor will have to work a lot harder.

My take is, it's both aero and cooling.
Any air that skips over the hood or is pushed cleanly to the side is better than having it bang around in the engine compartment and under the car. That's the aero improvement. For that to work optimally, you want a nice smooth surface at the front of the grill so the air can slide off cleanly. But even blocking it behind the grill is better than letting it get in, as far as aero goes.

Cooling probably becomes more important in cold weather but it has to have an effect in warmer weather also. Cold air flowing through the engine bay cools the engine so the system has to sap off combustion heat to keep the engine up to temperature. The point is, any air going thru there that's in excess of what was needed to provide cooling at the radiator and for a/c is going to cause some unwanted engine cooling. (Remember the original Beetle was entirely air-cooled).

[QUOTE=brucepick;57519]My take is, it's both aero and cooling.
Any air that skips over the hood or is pushed cleanly to the side is better than having it bang around in the engine compartment and under the car. That's the aero improvement. For that to work optimally, you want a nice smooth surface at the front of the grill so the air can slide off cleanly. But even blocking it behind the grill is better than letting it get in, as far as aero goes.

Very true about bouncing around the engine compartment. In the geo the rad. is off set also. Grill on right side will be blocked. At the same time two panels at the right and left of the rad. will be installed to guide it through just the rad. Under the hood between the grill and rad. core support. Plus the belly pan will act as the bottom of the trap. This hasn't been proved by me yet but I THINK you could get away with a smaller opening if you make sure to maximize the flow. If you have an actual temp. gauge go bold and have something with you to cut away material if you need to. Don't let it overheat all the FE in the world won't pay for a cracked head or two!

I started to do my mod today. I took Gary's advice and removed the plastic covering the radiator. Then I said the hell with it and removed the plastic grill. I think it will be easier to size the whole project with the grill out. I was considering leaving the grill out and making the block flush, but I don't think I'm that good at making things. I'm also considered using foam between the grill fins. I took some pics to get some opinons.
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i think there is an aftermarket company that makes grill blocks? I've seen them on f-150s ,rangers. I'm not sure who makes them , they come in different colors and they have small holes in them to get some air flow to the radiator. I would probably get a cooler thermostat installed to compensate for the lower air flow on the radiator.
Lund is one company they offer a bunch of grill blocks, i was looking at the plastic inserts one with holes, the other is a winter block with no holes.
https://accessory-center.com/Plastic-...ront.1423.stml

Those grill blocks are pretty nice but I didn't see any for Caravans.

Are those grill intakes below the bumper? If so, then the lower openings should be more than enough to handle your cooling needs and you can totally block off your upper grill openings (trim Coroplast to fit and secure with screws, velcro, or clear caulk).

The upper grill openings on most cars is mostly a concession to styling (people traditionally expect a car to have a grill, so the stylists give them one), but they are not really needed for cooling. Compare the grill openings of the new Beetle (mimicking a grill-less rear engined, air-cooled car) and the Golf or Jetta. All three cars have the same ICE and radiator, just different sized grill openings. Ditto the 92-95 Civic and the 96-98 Civic. The earlier generation Civic was optimized for FE and just had a grill opening below the bumper. On the later generation Civic, the stylists had their way and they added a chromed grill intake above the bumper (the highway EPA mileage dropped from 46mpg on the 92-95 to 37mpg on the 96-99 as factors other than maximum FE came to the fore).

The bottom is a grill intake. I was thinking about putting the coroplast behind the grill fins, or do you think I should do it with out them? I'm gonna talk to a body shop tommorrow (across the street) and see what they recommend. I really don't want to mount using screws but clear caulk sounds good. Would the cock ruin the paint? Also what do you think a body shop would charge to close up the grill using fiber glass or whatever else they use?

You could take the world famous test material cardoboardo and use some plastic wireties, to tie it to the grill from the back side. If you threw some econo black spray paint on it, before you attached it, it probably would be almost invisible. The holes in the bumper do allow air flow and they probably would be adequate for driving.

Hey, I might have to try this!

I started working on my grill block today. I decided that I would use coroplast behind the grill fins. Having the grill fins would make it easier to mound and would be sturdier. This wasn't my first choice but it seems to be the best way (to me). I also tried using foam in between the grill fins but I didn't like the way it was looking (maybe in the future). I haven't completed it yet because the spray paint is drying. I decided to skip the black paint and go with red (wanted to be differenet). My only question is how should I mount it? I bought zip ties and some epoxy stuff designed for plastic.

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The white coroplast is my prototype. I'm using it for the measurements. The holes are for the guides that are used to mount the grill to the van.

nice work with the color match. that will look good.
did your wife mind that you painted in the house?

I actually painted on the balcony with that blue plastic cover that you see. I didn't make a mess so she didn't mind. So what do you guys recommend me do to hold the coroplast on the grill fins? I was thinking about using zip ties first, because I have a lot of coroplast and I can always remake if something goes wrong.

Black zip ties. Or black twist-ties.

Nice job.

I'm on my way to test drive with the grill block on. I actually have to get more zip ties. It's coming out better than I thought. I'll post some pics when it's complete. Thanks for the help everyone.

Well I finsihed and the results are pretty good I think. Let me know what you guys think.


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I took the van for a test drive and I liked my results. I drove 50mph and averaged 32.1mpg. I didn't take more pics of when I reached 32, because I didn't want to wreck. I didn't use the AC and I had the windows up. I know this isn't that much especially for the highway, but I haven't been able to achieve over 26mpg at 50mph, so I feel pretty good.
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great job! im just put on a mini grill block to see what it does

I know the red color for the block may not have been the best choice, but I like it.

it looks better then mine just card board

I want to do the bottom corners also, any suggestions? I don't think I'll block the bottom intake because I'm afraid to overheat in this Hot Mississippi weather.

Ohh I forgot to say thanks to everyone that gave me suggestions on how to build this. The project actually changed 3 or 4 times in the making.

For the bottom corners :fill the hole first with pink foam insulation (cut to fit snug) then cover with coro-plast. I'd probably paint the coro-plast body color or basic black for them .

By the way ...Good job !!

That's a lot of zip ties!! I think it looks good. I hope that your results hold up. Good improvement.

Nice job. I'm interested and letting you be the guinea pig. ;)

Did you check the temp reading on the scanguage too?

I did probably go overboard on the zip ties. I even bought the zip ties that were UV rated so they don't deteriarate. The main reason I used so many is because I don't want the block coming off on the highway and messing up the radiator. Better safe than sorry I guess. savoF3 guinea pig away. I did keep an eye on the analog and SG2 temps. The highest the water temp got was 220F. The analog gauge stayed below the half mark. I had exited the highway and I was sitting at idle when I got this temp. It didn't stay there very long and went back to about 192 to 202. The highest I've seen it get before the block was 216F.

MN Focus is there a way I wouldn't ruin my paint when installing the corner blocks?

I like that its simple and gives a neat appearance, great job. Use painters tape?

I'm confused. Where does the painters tape go?

Use the painters tape /masking paper to mask off the Strawberry and paint the blocks on the vehicle OR
Use the tape as a 'host' barrier around the pre -painted block edges upon install .Since the tape isn't super sticky it should peel off easily or you could just leave it on if it isn't real noticeable.

Question could I use magnets to block the corners of my grill? The kind that have ads on them seems like a good idea. I'm kind of stuck on what to use. Tape was suggested, but the holes in the corners go all the way through. Please review the pics and let me know.