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Dusterbd13-michael
Dusterbd13-michael MegaDork
10/6/19 6:38 a.m.

Pretty much exactly what the title asks. If I was to put a piece of screen door mesh in front of save my radiator how much airflow would I be losing through the radiator?

Woody
Woody GRM+ Memberand MegaDork
10/6/19 6:58 a.m.

At the very least, it should keep the flies out.

stafford1500
stafford1500 GRM+ Memberand Dork
10/6/19 7:18 a.m.

Michael,

You should be fine to use screen door material as long as it is very close to the radiator face. There is a similar material used on NASCAR and dirt cars to keep the rads clean (Outerwear is the brand name stuff). If you put it too far forward, the drag and airflow limitations get really big really fast. Put it at the slowest airflow area (right in front of the radiator) to reduce the effects as much as possible.

All of this goes for wire meshes at the inlets too, just not as badly.

Dusterbd13-michael
Dusterbd13-michael MegaDork
10/6/19 7:45 a.m.

So, right up against the radiator no real problem?

At the inlet to a vent, no real problem?

The space in between it will cause an issue.

Am i understanding the rule of thumb correctly?

stafford1500
stafford1500 GRM+ Memberand Dork
10/6/19 7:53 a.m.
Dusterbd13-michael said:

So, right up against the radiator no real problem?

At the inlet to a vent, no real problem?

The space in between it will cause an issue.

Am i understanding the rule of thumb correctly?

More or less. Try not to put screen at the smallest area of a duct is the better way to think of it.

Dusterbd13-michael
Dusterbd13-michael MegaDork
10/6/19 8:05 a.m.

Cool. Thanks steve!

jfryjfry
jfryjfry Dork
10/6/19 10:55 a.m.

But screendoor mesh against the radiator doesn’t sound like it would offer much in the way of impact damage protection.  

Keeping dirt from clogging the radiator - like a filter - yes.   

stafford1500
stafford1500 GRM+ Memberand Dork
10/6/19 11:03 a.m.
jfryjfry said:

But screendoor mesh against the radiator doesn’t sound like it would offer much in the way of impact damage protection.  

Keeping dirt from clogging the radiator - like a filter - yes.   

It does not have to be right up against the rad core, maybe an inch ahead of the core. Just dont put it at the small cross section area or you get more blockage than having all the fins folded over.

Dusterbd13-michael
Dusterbd13-michael MegaDork
10/6/19 11:08 a.m.

Actually, filter was the idea. Especially after spending all the time cleaning the radiator and ac condenser. Its amazing how much crap was in there.

Also, i was think of using it to make the hood vents as well. Instead of louvers or expanded metal. It would keep crap out of the engi e bay and visually hide giant holes in a green hood allowing white engine bay to be seen.....

reshufflesleep
reshufflesleep
10/10/19 7:05 a.m.

It keeps the flies out.

Nugi
Nugi Reader
2/5/20 8:17 a.m.

Old thred, but I just wanted to suggest nomex honeycomb panels to anyone looking for radiator protection. Get em on amazon, ebay, etc. The 'reject' quality ones are plenty good, this stuff is used in aircraft wings. About 2mm hex openings iirc. Much better airflow, will shrug off golfball sized rocks. Apparently used in dirt track, or so the guy who clued me in told me. I live on a dirt road and hoon like a madman, with no front bumper, or hood... under the honeycomb, the soft chinesium radiator is still minty. Hardest part is attaching the stuff in a way that looks nice. I ended up with small zip ties, and aluminum tape, but one could do better. 

Apexcarver
Apexcarver UltimaDork
4/16/20 9:22 a.m.

I got some screen for the Fmod for similar.

 

Problem is that I need it to keep rocks from going into the sidepods, so it goes in a poor location. On top of that, you pretty much cant have too much cooling capacity on one of these as its a snowmobile motor and wants a water temp under 140* (I have two VW scirocco rads with fans on a 494cc motor and thats the norm)

 

If theres something that would flow better and still keep the rocks out I'm all ears.

 

nderwater
nderwater UltimaDork
4/16/20 9:23 a.m.
Nugi said:

Old thred, but I just wanted to suggest nomex honeycomb panels...

Oh wow that's cool stuff.  How resistant to moisture is this material?

 

Apexcarver said:

Problem is that I need it to keep rocks from going into the sidepods, so it goes in a poor location....

Looks like you could use two stages of screens -- something tough but open like steel hardware cloth at the sidepod inlets, then a fine screen right at your radiators.  What setup do you have currently?

wvumtnbkr
wvumtnbkr GRM+ Memberand UberDork
4/16/20 9:33 a.m.

We tried a fine mesh on our airdam for our champcar.  No bueno.

 

It was at the smallest part of the system.  

 

We had to go to a more open mesh to get the temps back down.

Apexcarver
Apexcarver UltimaDork
4/16/20 9:37 a.m.

In reply to nderwater :

Currently, a shopvac used in between events to suck the pea gravel out, lol

 

The rads are back in the pose and if car is ----> front then they are / in the sidepod at a steep angle. 

 

I bought alum screening thats fairly open to see, but always looking for the best solution. 

 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
4/16/20 11:03 a.m.

The answer seems to be pretty convoluted...
 

There seem to be some extremely detailed and overly complex engineering calculated answers to that, and some grossly simplistic answers like, "Yeah, well it's a restriction, and any restriction..."

Fire departments say window screens can block airflow by somewhere between 50% and 80% when they consider room ventilation.  They knock out screens as quickly as they can.

HVAC engineers recognized and calculate the reductions, but then increase the window size to accommodate for it. I'd say in a car, increasing the opening size also reduces aerodynamics, so I would question that approach. 
 

Note that very few new vehicles ever use mesh that small.

So, how much does window screen door mesh limit airflow?  Enough to matter.  I will resist doing it.

 

stafford1500
stafford1500 GRM+ Memberand Dork
4/16/20 11:35 a.m.

Here are some really simple results of calculating the actual open area for different screen sizes:

  • 2 openings per inch, with 0.063 wire = 76% open area (or 24% blockage)
  • 4 openings per inch, with 0.047 wire = 66% open area (or 34% blockage)
  • 10 openings per inch, with 0.025 wire = 56% open area (or 44% blockage) This is close to window screen
  • 20 openings per inch, with 0.015 wire = 49% open area (or 51% blockage)

Based on the numbers above, large opening screen at the smallest openings will keep the big stuff out and tighter mesh near the radiator face will protect the radiator. For ducts that get bigger as they approach the radiator, the finer mesh will be less of a problem at teh biggest cross-section because the airspeed is lower than the small inlet opening.

Using the numbers above: if you use the biggest screen at an opening, the airspeed will be ~24% higher across the screen than with nothing in place. Drag across a screen increases at the square of the speed, so the extra 24% airspeed would increase the drag ~53% (from 1.24^2).

jharry3
jharry3 GRM+ Memberand HalfDork
5/11/20 10:02 a.m.
frenchyd
frenchyd GRM+ Memberand PowerDork
5/11/20 10:08 a.m.

In reply to Dusterbd13-michael :

In horsepower it cost me 12 on a 303 horsepower engine.  That's for Three 2 inch SU carbs. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
5/11/20 10:18 a.m.

And as a bonus, it also doesn't work very well as an air filter :) Mesh filters like that are a trend amongst some "tuner" circles.

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