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Thread: DIY: Coroplast grill block

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    Administrator Daox's Avatar
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    DIY: Coroplast grill block

    This weekend I installed a lower grill block on Swarthy. It was cold out, but I wanted to get something done on the car. I have had the coroplast piece cut out for over a week now, so I figured it was time to finally get it on the car.

    First things first though. Some of you may be wondering what a grill block is. A grill block is a mod that blocks some or all of your grill opening off. The purpose of this modification is mainly to improve the aerodynamics of the vehicle. The more aerodynamic it is, the less power required to push it through the air. The less power required to push it through the air, the better fuel economy you get. Another benefit of the modification is that it helps warm your engine up faster by allowing less air through the engine bay. Arguably, you can probably accelerate faster too and have a higher top speed, but thats really not a big deal unless you're drag racing your Mirage.

    There must be a downside though, right? Otherwise why wouldn't they do it from the factory? Well, actually Mitsubishi did a pretty good job already of blocking the grill off already. Nearly half of the open area on the lower grill is already blocked off. Here is a before picture of my Mirage. You can see the passenger side of the grill is not actually open very much.

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    The real downside of this modification is you need to watch your coolant temperature. Blocking off the grill does reduce the amount of air going through the radiator, and thus it reduces the cooling capacity. The more you block off, the more you need to keep an eye on the temperature. If you go too far, you will notice your cooling fan turning on more often. If taken way too far, you could overheat and damage your engine.

    So, why block off more than stock? Mostly, to improve aerodynamics further and speed up warm up even more. I've done this on enough vehicles to know that even with a 100% grill block (mail slot and all), I would be completely fine on my short commute to work during winter. I know that if I was going to take a freeway trip, I would need to open up some area. I think the mail slot will be plenty of area to cool year round without any issues, even on the freeway. That may seem like a tiny opening, but you have to remember that the cooling system was designed to run through death valley on a bad day running the A/C. Its MASSIVE overkill for Wisconsin weather. If you do this mod, you will have to tailor it to your own climate.



    So, lets get started with the DIY!

    First, get yourself a piece of corregated plastic. The stuff I used is about 1/8" (3mm) thick. I used black because it blends in great with the car. You can buy it from Home Depot or a sign shop. I just checked online and Home Depot has this material in a 4'x8' sheet for $20. It looks like this.

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    I measured the lower grill opening, and cut a rectangle the same size. No need to be super picky. To cut it, I used a drywall square, pencil, and a nice heavy duty scissors. I may have even used my wife's nice kitchen shears, but lets keep that on the down low...

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    With it cut roughly to size, start shoving it in the grill area and see where you need to trim. You can put in as much effort as you'd like here. I honestly just started cutting to what I thought was good. I trim off a big chunk, test fit, cut again, test fit, cut, rinse, repeat. You'll end up with a piece that looks quite similar to this.

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    Now that you have it cut out, its time to attach that thingy to the car. To do this, I gathered a myriad of useful tools including a phillips screw driver and two black zip ties (yes, I know its not a myriad, that was a joke).

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    I decided to use two zip ties to hold the grill block on. The one on the passenger side goes through one of the openings, around the main middle horizontal bar, and back out another opening and then through the holes in the grill block. The other just goes in the open area on the other side. So, I used the screw driver to poke some holes in the grill block.

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    Now, stick the zip tie in one of the holes of the grill block, and fish it through the grill on the car. I recommend starting with the passenger side as it'll be harder to get the zip tie through. I also recommend leaving the zip tie loose while you work on the other side. Once both are through, pull them tight.

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    This is what it looks like just walking by.

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    A bit closer up.

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    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 45.4 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.6 mpg (Imp)


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    Administrator MetroMPG's Avatar
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    This is a good first mod for anybody interested in bumping fuel economy a few more percent.

    Ideally, you'd want a 100% block with a temperature-sensitive servo that would open up based on cooling needs. (Active grille shutters are happening on more and more new vehicles).

    Mitsubishi paid fairly close attention to "passive tuning" how much grille area they left open -- they even have different sized openings on the manual Mirage vs. the CVT (because the CVT requires more cooling):

    Look carefully and compare bottom grill opening:

    CVT


    5-speed manual


    From:
    Thread: Aerodynamics of the new Mirage (0.27-0.31 drag coefficient varies with options)

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


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    Administrator Daox's Avatar
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    Very true. Its very easy to do. Also per the EcoModder wiki, it nets an average of almost 3% increase in fuel economy.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 45.4 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.6 mpg (Imp)


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    Quote Originally Posted by Daox View Post
    ...even with a 100% grill block (mail slot and all), I would be completely fine on my short commute to work during winter.
    ...if I was going to take a freeway trip, I would need to open up some area.
    With the wacky temperature swings this winter, I seem to be changing my grill block on a weekly basis. I have a 100% block in place now...but it was 7 degrees this morning. It's going to be 50 this weekend, so I will open up the lower radiator by 30% then.

    I always have the mail slot blocked...so maybe I should experiment with removing that portion during warmer temps instead of un-blocking the lower grill.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 51.5 mpg (US) ... 21.9 km/L ... 4.6 L/100 km ... 61.9 mpg (Imp)


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    So are the rads wider on the cvts? I guess they must be.
    I was thinking of putting like 1/3 grille block on the passenger side Daox posted to protect the rh side of the rad from being pelted by rocks. I've had to change at least 2 rads that were punctured in the little area where the condenser doesn't protect it. Ironically, I haven't had to change any ac condensers.
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    Fummins, does the CVT have trans oil lines running to the radiator? It must be a bit bigger if so.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage base ES 1.2 manual: 54.0 mpg (US) ... 23.0 km/L ... 4.4 L/100 km ... 64.9 mpg (Imp)


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    Senior Member Fummins's Avatar
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    Quote Originally Posted by MetroMPG View Post
    Fummins, does the CVT have trans oil lines running to the radiator? It must be a bit bigger if so.
    Nope. No tranny fluid in the radiator. It has a little oil cooler on the side of the cvt with 2 coolant lines going to it. looks kinda like this Name:  cooler.jpg
Views: 568
Size:  71.1 KB The cvt has an extra coolant hose from the top and the bottom of the rad that go to the cooler. The cooler is mounted directly to the front of the cvt.
    Last edited by Fummins; 01-16-2018 at 10:38 PM.
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    Quote Originally Posted by Daox View Post
    This weekend I installed a lower grill block on Swarthy.
    What are the possibilities of 3d printing grill blocks? They could either be snap-in along the lines of what Mitsubishi has done for the 5-speed, or further developed toward an automated full opening for any climate condition.

    Quote Originally Posted by MetroMPG View Post
    Ideally, you'd want a 100% block with a temperature-sensitive servo that would open up based on cooling needs. (Active grille shutters are happening on more and more new vehicles).

    Mitsubishi paid fairly close attention to "passive tuning" how much grille area they left open -- they even have different sized openings on the manual Mirage vs. the CVT (because the CVT requires more cooling):
    3d printers are pretty impressive in what they are able to make, but at some point limits are reached - for example size or cost. Can the segmented grill opening help with the size limits?

    Just thinking out loud and offering some thoughts. You know, it's just one of the benefits of public forums.

    Thanks for posting this.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.9 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.9 mpg (Imp)


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    Administrator Daox's Avatar
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    3d printing grill blocks is totally doable, but not very practical I think. To print something that would replace that coroplast piece I image it would take at least 24 hours of continuous printing if not more. Its simply a lot of material to lay down. Secondly, its a curved piece, and there isn't a great way of printing it, and that is assuming that it could be modeled accurately to begin with. How do you measure up the grill so that it can be modeled?

    That all being said, I have 3d printed a grill block insert lets call it. Its even automatically servo actuated as the OEMs are doing. It is a clip together design and mounts inside an existing grill block. I currently have this installed on my 2000 Honda Insight.

    There is tons more info in my thread on EcoModder, but here are a few pictures.

    The basic frame. The pieces snap together to make it larger if necessary.





    Here is the door. Again snap together.





    The full design with servo.





    Actual design printed up.





    And, here it is installed on my Insight.





    Test program being run on it.

    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 45.4 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.6 mpg (Imp)


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    Impressive. Dude you're always more than a step ahead.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.9 mpg (US) ... 21.2 km/L ... 4.7 L/100 km ... 59.9 mpg (Imp)


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