Grill blocking

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flcruising

:
2008 Mazda5 Touring
I was wondering if anyone has thought about closing up either the gaping hole on the lower bumper or the grill to increase mpg? I've been contemplating a method of approach, and it seems that for the lower opening using plexiglas on the outside or black coroplast on the inside would preserve the appearance. I'm not talking about a full block either since there isn't an underbody opening to allow the radiator fan to draw air from, unless of course I decide to cut some.

BTW, this is very common practice over at gassavers.org and ecomodder.com, so don't flame right away.
 
flcruising said:
I was wondering if anyone has thought about closing up either the gaping hole on the lower bumper or the grill to increase mpg? I've been contemplating a method of approach, and it seems that for the lower opening using plexiglas on the outside or black coroplast on the inside would preserve the appearance. I'm not talking about a full block either since there isn't an underbody opening to allow the radiator fan to draw air from, unless of course I decide to cut some.

BTW, this is very common practice over at gassavers.org and ecomodder.com, so don't flame right away.
Click to expand...
I'm all ears. Any direct links to articles on cause/effect? Would be an interesting read.
 
Well, the posts are galore, so it's kinda hard to single them out. Here's some results from gassavers.org

Most of the motivation for a grill block is to speed warm-up, but my motivation is to decrease drag - even if it's slightly. The upper grill is usually determined as the place to start because it disrupts the upward airflow, so I will start there as well. The battery cooler duct is the only thing fed by the upper grill. But the lower grill on this thing seems rather large, so some experimentation will be involved.

As far as the oil cooler is concerned, it's a fluid-to-fluid heat exchanger that is apart of the cooling system. Therefore any slight impact this would have on the cooling system could impact the oil temperature. Let me reiterate though, I'm not saying to block off airflow to the radiator completely, but simply decrease the frontal area that is being diverted through it.
 
Cardboard is best used as a template. I did the grille on my dd this afternoon and found that a great finish material was vinyl tile that can be purchased for about $1 ft[SUP]2[/SUP]
 
I'm a member of ecomodders and have a grill block on my toyota tacoma. I've been using that grill block for a few years, especially in the winter. I also just got a 2010 Mazda 5 last fall and just recently made a 80% lower grill block and a 90% upper grill block. The 20% opening on the lower is right in the center where the ambiant temp gauge is. We are using it on a road trip next week so I can let you know how it goes. I use a Scangauge II to verify coolant temps while driving to make sure the engine isn't overheating. I've had overheating occur in the tacoma with 95 degree ambiant temps and the air condition on full. My blocks are secure with zipties so I can pull over and cut the zips if needed.

I used cardboard as a templete and then cut it out of an old clear plastic bin/tote I didn't need anymore. Painted the plastic cut outs and drilled pairs of holes where the zipties will secure the blocks. I can take a couple pics if you'd like to see what it looks like.
 
Yes, pictures would be nice. I can't figure out how to block off the upper grille and have it look decent. My wife wouldn't go for it if it looks cheap so hopefully your plastic totes are appealing.

A 100% upper block & 50% (or so) lower was what I had in mind, and will be installed full-time. Something clear for the upper would be perfect, but I don't know how well plexi or lexan would bend in the middle...
 
I've always wanted to try this. I thought fixing four bolt points into the stock grille would be a good idea, as with using coroplast for the blocking material. I would probably start off with 30% and work my way up, paying extra attention to operating temperatures on my Ultra Gauge.
 
Back from out trip

Well we averaged just over 30 mpg for our round trip. 5 tanks and over 2000 miles. It's fun to see 400 and more miles on a tank. Typical highway speed was between 75 and 80 mph so I wasn't too light on the foot. Plus we had 3 passengers and a lot of lugguge (couldn't see out rearview). I will get photos of the blocks posted soon. Most people don't even notice the grill block until you point it out to them.

If you do grill block, I recommend getting a scangauge or similar device to monitor engine coolant temps. I could see temps bump up on the long climbs through the hills of Kentucky, especially when pushing 80mph. The Scangauge also helps see your mpg in realtime although my numbers above are from actually tank fills. I will be removing the upper block for typical city driving since the aero-benefit isn't as great.
 
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