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Author Topic: "Aero" screen?  (Read 8300 times)

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Offline Jack Gifford

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Re: "Aero" screen?
« Reply #15 on: August 15, 2018, 12:31:14 AM »
I bought some screen samples, but haven't really tested them yet. One of them is about 60% open area, with nominal .003" openings, that I'll eventually test on the engine dyno. Anybody have a clue about the relationship between open-area-percentage and actual airflow percentage? I think these samples are simply round-wire screen, but I'm not sure.
M/T Pontiac hemi guru (or does guru status expire after 30 years?)

Offline Saltfever

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Re: "Aero" screen?
« Reply #16 on: August 15, 2018, 01:03:36 AM »
You know the drag formula CdA. Often the Cd is far more important than the "A". Meaning that the shape of the wire can create more drag (or reduce flow) than the area! Round wire having one of the worst Cd's. That is why aircraft have teardrop or oval shaped wires for bracing and struts. Even on a slow 90 mph biplane the bracing wire is oval. Thousand$ spent on CFD probably could get you close but lacking that you will have to do your own dyno or flow tests. You could probably set up a drag-differential test in the garage with just a fan. You couldn't quantify the drag but if you keep the area identical on your test samples you will see their difference in drag.  Check out Aircraft Spruce.com for possibilities.

Offline tauruck

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Re: "Aero" screen?
« Reply #17 on: September 05, 2018, 05:50:16 PM »
Add all the screen wire thicknesses together and you'll find you only have half the airflow.
We used a sock made from the same material used in composite vaccuum bag technology
called breather bag on our Mazda Peripheral Port motors and it out "breathed" any commercially
avaible filter. Cheap and excellent. Easy to use and keeps FOD out!.

Offline Bratfink

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Re: "Aero" screen?
« Reply #18 on: July 23, 2019, 02:25:30 AM »
I bought some screen samples, but haven't really tested them yet. One of them is about 60% open area, with nominal .003" openings, that I'll eventually test on the engine dyno. Anybody have a clue about the relationship between open-area-percentage and actual airflow percentage? I think these samples are simply round-wire screen, but I'm not sure.

Aero wise, the relationship is quite linear (10% blockage = roughly 10% drag improvement)... its actually more quadratic in nature, but let?s not over complicate things. Engine HP wise I?m not sure, but I?m willing to bet it?s similar.

Offline Jack Gifford

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Re: "Aero" screen?
« Reply #19 on: July 24, 2019, 12:09:32 AM »
Thanks for the comments.
I did not get to do any comparison testing during dyno sessions. Perhaps when I get to a landspeed track I'll be able to do that.
M/T Pontiac hemi guru (or does guru status expire after 30 years?)

Offline wobblywalrus

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Re: "Aero" screen?
« Reply #20 on: July 24, 2019, 12:11:01 AM »
"Zero power loss using K&N filtration" is a topic discussed on Page 20 in David Vizard's "How to Build Horsepower."  He recommends 7 hp per square inch filter area for K&N's.  That is the area to cause no power loss.   

Offline Rex Schimmer

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Re: "Aero" screen?
« Reply #21 on: July 26, 2019, 11:37:27 AM »
Every time I read this post it reminds me of a build for a big off shore boat. It ran 4 BBCs all of 500+ cu. in. and they ran giant 2-15/16 dia inlet tubes on the injectors. The engine builder was a Brit and he "always" ran the neat domed screens over each inlet tube as that was the "proper" way to do it. So one time he had rebuilt one of the engines and was at the dyno testing and tuning and to his surprise he suddenly had an extra 75 horsepower! Same engine just rebuilt but he had forgot to install the inlet screens! He never ran them again.

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline wobblywalrus

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Re: "Aero" screen?
« Reply #22 on: July 26, 2019, 01:02:41 PM »
One good reason to mount a big air filter over the inlet end is to provide a reservoir of comparatively calm air for the engine to breathe.  This is a big help assure the intake system performs it as designed.