DIY - Front Grill Block - 1991 Honda CRX
 

The front grill block is on of the quickest, easiest, and cheapest ways to cut down on aerodynamic drag in your vehicle. While it doesn't amount to much, it does make a difference, especially considering that a large amount of aerodynamic drag is caused by this opening. It's best to leave it only partially blocked so that the radiator recieves some airflow, however, a large block is okay because radiators are typically larger than they need to be, and fuel economy drivers tend not to abuse their engines too heavily.

Many new cars, including certain Mercedes and Hondas use electronically controlled radiator shields that open/close depends on engine cooling requirements. Take a look at this Civic for an idea what this looks like:
http://www.autoblog.com/media/2006/1/103036.jpg
http://response.jp/issue/2006/0103/a...ges/103037.jpg

Purpose: To prevent air from entering the grill to reduce drag as it moves through the radiator and engine bay.

Time: 1-3 hours depending on complexity of project

Tools:
- Hobby Knife
- Hot Glue Gun


Supplies:
- Coroplast
- Spray Paint
- Foam (for modeling)

I chose to repaint the trim on my bumper as well as do the grill block at the same time, so first I removed the bumper. If you leave it on you can get it done much more quickly, but that's up to you. Just follow my mounting instructions with the bumper on the car.
Click here to see how to remove your bumper (as shown in the wire tuck page).
This is my bumper removed, you can see the grill opening as well as the two pockets on the side. The side pockets are not supposed to cause much drag but I covered them anyway just to smooth thing out as much as possible:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00464.jpg
Here's another shot to get an idea of the bumper's geography:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00465.jpg
I used this style of insulation foam to make templates because it is easy to work with:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00466.jpg
One of the templates sitting in a side pocket:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00467.jpg
I then transfered the template to the coroplast, cut some support to place down the side of the pocket to mount the coroplast to, and cut off part of the coroplast towards the center of the bumper so it would mount flush to the bumper where it tapers together:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00469.jpg
The center pieces are just glued to the ribbing on the grill and then glued around the edges from behind:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00470.jpg
I taped up all the painted portions of the bumper so I could respray the trim and the coroplast black:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00473.jpg
Two shots of the finished product remounted:
http://crxmpg.com/edrive-images-crxmpg-com/DSC00492.jpg
I think it turned out pretty darn good, :)

good idea I could not do that on my truck though it would overheat so fast. After I get the front nice and muddy it starts to rise the heat. Not that bad but still noticable. And same when I have the plow on it. How dose a mod like this effect your car tempature.

It hasn't really affected it at all. My radiator was very much over sized to begin with. *shrug*

Looks good to me. :thumbup:

I was wondering though, what did you use to cut the coroplast? I just found a supplier in my area and will be picking some up for some mods to the Matrix soon.

I think I use an exacto knife...which is dangerous. Dunno if I listed it in the DIY but I dropped the knife into my knee about half way through and cut my quad tendon pretty badly, was hobbled for a long time, so be careful, :p

SVOboy, I can see the pics of the new Honda, hosted by autoblog, but not your pics. Your site says the edrive-images-crxmpg-com directory is not found (insert crying smilie here).

The winter weather did a number on my cardboard grill block. So I finally got my permanent Coroplast block installed a couple of weeks ago, when we had some nice 50*F weather. Here's the before
http://www.themillers.us/images/cava...ckTempOld1.jpg
and after
http://www.themillers.us/images/cava...BlockFinal.jpg
shots. I was able to tape a large piece of paper on my bumper. and get the outline of the grill opening by rubbing with a crayon. The perimeter of the block was sealed with black silicone. It's attached using six black wire ties and four black license-plate bolts.

Daox, I used a utility knife to cut the Coroplast, and only ended up with one cut on my finger. But not from the knife, from pointy end of a compass I was using to scribe an offset around the edge of the Coroplast! Much better than a cut tendon. ;)

deadman, my cardboard block had no affect on the engine temps when I installed it last summer. There is a huge opening underneath, between the bumper and the air dam. I added the molding at the front of the hood this winter, and was still running cold. I had to block my radiator with cardboard to get the engine back up to temp.

And no, I'm not going to block the bullet hole on the passenger side. That's a memento from the 'hood. :eek:

s2man -

Grill block looks good!

How about clear packing tape, or a black plastic snap-in cover (they're in the specialty fastener section in most hardware stores)?

Hole Plugs: 3/16", 1/4", 5/16", 3/8", 1/2 inch, 5mm, 8mm, 10mm, 12mm

CarloSW2

good job!! Looks great. I'd have thought it came from the factory that way if you hadn't told me...
But any ideas on how one can do that in a more southern climate and not overheat?? What is the normal daily temp in NH during July/August !?!??
It was 100 here the other day and with nothing blocking my grill, I could notice that my '98 civic was a bit hot :^)

The comment re: mud causing overheating made me realize... maybe people who go mudding should use a grill block and duct air to their rads. Then you'd get the aero benefit AND you'll never get your rad blocked up with mud! I'm going to mention this to my cousin for his lifted Jimmy.

Welcome to ecomodder! A smaller block is definitely a good call for warmer climates. I would experiment and see what works.

Hiya,

Why am I only seeing the two pictures of the Civic? (Which has an awesome adjustable grill block...)

I have an '05 toyota 4runner and would like to build a grill block but also don't want to sacrifice the clean, stock look of the grill. Is it possible to build the grill block behind the stock grill and also the 4runner has an upper and lower grill so if I had to choose which one would I build the grill block on (guessing the lower)? See photo of '05 4runner grill.

Me either was looking forward to block the front grill of my VX. Got already plastic blocking. The only location that wasn't been block was the connector of the block heater. Any suggestions?

This looks like a good place to post this. I started with a piece of Coroplast to block the upper grill on the bluesmobile, but decided to try plexiglass instead -- couldn't wait for the black paint to dry on the Coroplast.

I got the folks at my local hardware store to cut a piece of plexi 7" X 30". Drilled eight holes and secured it to the grill with zip ties. Removing and replacing the grill was relatively easy, and no modifications were made to the grill.

I may end up fastening the black Coroplast to the front surface of the plexiglass to protect it from stones and stuff. The clear look is very cool, but plexi is somewhat brittle, even at room temperature. I found that out the hard way, when I used a center punch to mark my drill holes on the first piece. Fortunately, the second piece was as cheap as the first one, about six bucks.

No photos yet, but this MS Paint job will show how the zip ties are fastened.

Wow that grill of yours look great.. It tempting me to have my old ones replaced already.

I used fiberglass cloth and resin to block mine. Just brushed some resin and spread the cloth, let it dry. Then spread resin over all of it and when it dryed, sprayed paint to it.

We block off grills all the time on high speed tracks - you can buy colored plastic rolls from Speedway Motors to match your car - $12.99 for 10ftx24" - and flexible enough to use almost anywhere. We have constructed it so as the speed increases the plastic deflects more - ideal for highway and restrictive for city.

Hello everybody!
If use something like persiennes and mechanism from central looking doors...When temperature is rising the persiennes go to open,when temp drop down-the persiennes closed.The process will be automatised using tempeature sensor and relais to switch between two positions...Just idea...

$17.99 when I checked today. Anywhere else cheaper?

cool :thumbup:

I cannot see the pics up close, i do not have enough post yet. What kind of mpg gains did you see. I have a 08 Suzuki SX4 sport sedan and it has a huge opening at the bottom of the bumper and has a 3/4 inch honey comb type of mesh grill. I would not want to risk blocking the top one would blocking say 50 percent of it be a help?

Making the grill opening smaller will help you MPG, how much is varies with the car. On mine I blocked just the upper part and saw a .78MPG (1.8%) gain. The wiki has a 2.8% 5 user average (range of 1-6%):
Grill block partial or full - EcoModder

The wiki (Main Page - EcoModder) is full of great ways to improve MPG. It is the collection area for mods, projects, & reference material. I would start there and you should find a few months work of projects to work on!

If you find a mod or two that you need help on start a help me thread. If you do some mods for MPG, please track your MPG and report the data so it can be added to the wiki to help others :)

Ben L.
wiki moderator

Thank you for the feedback for the sake the look of the car if I block the upper grill from behind and not in the front will it still have a positive affect or will it make it worse since the air will not flow in and out of the engine compartment?

Sorry to be a pain if you google images for suzuki sx4 grill 2008 you will see what I am talking about, I would have done it but I am not allowed yet.

Blocking the grill from the front or back will keep air from moving in/out of that part regardless, as that is the idea.

You will get the same warm up benefits, as for Aero, it will still help but it will be a few % less.

This mod would be great in the winter and would allow the engine to heat up faster. However, I would be concerned about the increase in coolant temp. during the summer. Especially since having high coolant temps. would cause the ECU to retard injection timing, which would result in worse fuel economy and less power. Higher under-bonnet tempertures will also promote premature wear of critical electric and mechanical components under the hood.

i was considering that mybe it is just a good mod for the winter.

It works great in the winter, I also keep my upper grill block on all summer to (watching temps on scangauge).

...aren't most of today's radiators "sized" large enough to handle the added heat loading of installed airconditioning unit?

How do you get the plastic to deflect more as the speed increases? I’ve thought of a few ideas, but they’re all pretty Rube Goldberg-esque. I'm sure a track-tested solution is better than my idle musings.

But if wildhorsesracing isn't available, and anyone else has some idle musings, please share.

The plastic we use is stiff but flexible to take any abuse that an off-road excursion can produce when racing on a road course. It will automatically deflect based on airpressure built as speed increases. There have also been more deluxe versions that involve gas shocks from a hatch/hood...

Ah, thank you--I had the impression that it opened up in stop and go driving and closed down at constant cruising speeds, which I think would be better for on-road use.

Awesome DIY i used this to make mines for a 93 honda accord