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Old 09-11-2019, 05:49 PM   #1
Old Henry
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Default Grill screen air flow

I have always discouraged the use of screens of any kind in front of the grill because it reduces air flow to the radiator needed for cooling, especially at very high ambient temperature. But, I've never tested my theory until today.

I bought an anemometer to use on my boat trip on the Columbia River a month ago and used it to measure air flow from a household fan.

First, I measured the speed of the air coming out of the fan with no screen.



It was 8 mph.

Then, I measured the flow through a piece of standard home window/door screen.



The house screen reduced the flow in half to 4 mph.

Then I measured the flow through what is called a "pet screen" which looked more open to me than the house screen.



That screen only allowed .6 mph flow.

Finally, I measured the flow through a genuine Ford grill screen made for my car.



It was 6.9 mph, 86% of the full flow.

So, even the very open grill screen made by Ford reduces the air flow to the radiator by 13%.

What that means is that even the Ford grill screen reduces air flow through the radiator the same as if 13% of the radiator was plugged with bugs. That's a lot of bugs. I'll continue to drive without a screen and just brush the bugs off of the radiator once in a while when they pile up.
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Last edited by Old Henry; 09-11-2019 at 06:04 PM.
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Old 09-11-2019, 06:02 PM   #2
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Default Re: Grill screen air flow

Good to see you back on the barn!
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Old 09-11-2019, 06:54 PM   #3
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Default Re: Grill screen air flow

Plausible.. or busted... as the busters would say ?
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Old 09-11-2019, 07:32 PM   #4
Joe Immler
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Default Re: Grill screen air flow

Thank you for the research on this. It is good to know. And...welcome back!
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Old 09-11-2019, 08:30 PM   #5
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Default Re: Grill screen air flow

Prof.
Glad to see you back.


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Old 09-11-2019, 08:33 PM   #6
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Default Re: Grill screen air flow

Interesting. Thanks for that, Craig....
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Old 09-11-2019, 08:49 PM   #7
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Default Re: Grill screen air flow

old henry, thanks for the scientific facts, your experiments are always well done, and welcome here. i'm sure we all miss your travel tales, but your new hobby makes you happy and thats what life is about. welcome back, best wishes, and let us know when the old ford goes out touring again
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Old 09-11-2019, 09:09 PM   #8
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Default Re: Grill screen air flow

Glad you're back.
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Old 09-12-2019, 01:27 AM   #9
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Default Re: Grill screen air flow

That air-flow meter blows me away !?!?!?....��.....good to hear from you.... hope all is well... Mark
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Old 09-12-2019, 07:23 AM   #10
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Default Re: Grill screen air flow

Craig: thanks for the info, hope to see some more road trip videos in the future.
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Old 09-12-2019, 09:00 AM   #11
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Default Re: Grill screen air flow

Interesting test results. I do see the screen having a purpose to prevent the occasional rock from damaging the radiator. Pretty much standard equipment driving up the Alcan.

And welcome back to the Barn!
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Old 09-12-2019, 11:27 AM   #12
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Default Re: Grill screen air flow

Quote:
Originally Posted by cas3 View Post
old henry, thanks for the scientific facts, your experiments are always well done, and welcome here. i'm sure we all miss your travel tales, but your new hobby makes you happy and thats what life is about. welcome back, best wishes, and let us know when the old ford goes out touring again
Quote:
Originally Posted by corvette8n View Post
Craig: thanks for the info, hope to see some more road trip videos in the future.
Since I've driven Old Henry everyplace I ever wanted to drive him, I've shifted my interest to "road trips" in my old 1982 17' Silverline Nantucket ski boat "Sharkie" with the original Mercury Black Max 200 hp outboard motor.

My most recent "road trip" in the boat was 400 miles on the Columbia River from The Dalles to the ocean and back a month ago. What an adventure! The anemometer I used for these tests I bought for that trip to measure the wind we were often up against.

Next week I'll take 4 grandsons to Lake Powel for some sight seeing of that most gorgeous lake.





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Last edited by Old Henry; 09-12-2019 at 12:09 PM.
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Old 09-12-2019, 03:48 PM   #13
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Default Re: Grill screen air flow

Have boated the Columbia many times. Your 2nd photo looks like the area where the movie "Maverick" was filmed for the river scenes. Glad to hear from you again!!
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Old 09-15-2019, 08:07 AM   #14
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Default Re: Grill screen air flow

Henry, I found your information interesting but I use screens in every car I own, Why the screen works for me is because I put the screen next to and on the back side of the grille. In Mo. one has to do something for the bugs, especially the grasshoppers, they are messy. Installing screens this way increases my volume of air coming so the radiator doesn't see a flow restriction in my opinion. My radiators all look like new and I don't have any heating problems. This theory doesn't work as well on a 32 Ford grille shell but it doesn't seem to hurt me any either except in stop and go traffic on the 32's. The one 32 even has a chopped smaller radiator and the engine temp usually runs 185 all the time. Sorry if I'm argumentative but results speak pretty loudly too. Have fun with the boating.
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Old 09-15-2019, 01:25 PM   #15
Old Henry
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Smile Re: Grill screen air flow

I got suspicious of grill screens on a cross country trip in a full size dodge van many years ago. I bought and installed the screen that went clear across the front of the van. Eventually the van seemed to be running at noticeably higher temperatures than normal. I suspected the screen was reducing air flow so removed it and the engine temperature returned to normal.

Different strokes for different folks.
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Old 09-16-2019, 06:31 AM   #16
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Default Re: Grill screen air flow

Hey Prof., is that a Tower of Power Merc. on the transom? Heck, i'd tow the boat with Old Henry...a Ford tow'n a "Merc." ....just say'n. mike
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Old 09-16-2019, 07:43 AM   #17
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Default Re: Grill screen air flow

I would think it would be obvious that any type of screen in the airflow path would reduce the airflow.
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Old 09-16-2019, 09:59 AM   #18
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Default Re: Grill screen air flow

What actually causes the reduced airflow is the pressure loss across the screen. The finer the screen the higher the pressure loss.
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Old 09-16-2019, 12:14 PM   #19
Old Henry
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Default Re: Grill screen air flow

Quote:
Originally Posted by mfirth View Post
Hey Prof., is that a Tower of Power Merc. on the transom? Heck, i'd tow the boat with Old Henry...a Ford tow'n a "Merc." ....just say'n. mike
The outboard motor is the Mercury Black Max V6 200 hp.
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