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Author Topic: "Aero" screen?  (Read 2161 times)
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Jack Gifford
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« on: November 20, 2016, 12:59:10 AM »

I'd like to run a screen over the scoop on a blower injector. But I'm guessing that normal screen fabric is quite poor aero-wise, since its made of round-section wire. Anybody know of available screen material that's more aerodynamically optimized? If so, I could use a finer (smaller-aperture) screen that's free-breathing enough, without needing to have a huge screen area.
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« Reply #1 on: November 20, 2016, 06:46:42 AM »

Be careful about how much of the open area of the duct is "blocked" by the wires of the screen.   You wouldn't think it would be much, but some screen types can reduce the "flow area" by 30/40%     Screen mfg's list "high airflow" screen material.

I've had poor inlet screen setups seriously reduce the bhp because of reduced airflow to the engine.     I've also had engines overheat after the installation of "rock blocker" screens in from of the heat exchanger(s)/radiator(s).

 cheers
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Stainless1
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« Reply #2 on: November 20, 2016, 10:58:43 AM »

Jack, let's back up one step... what is the purpose of this screen?  Are you are thinking it is needed to  filter air to your very cool engine, then I'm thinking you may need to rethink it.... too many thinks in one sentence  rolleyes... but if keeping salt out of you motor is the purpose I don't believe you will be able to get screen that fine. 
Hopefully the placement of your intake will be in clean air... if it is not... you need to start thinking filter not screen.  Our NACA intake has to be where it is so we have to filter or ingest a bunch of salt.  The salt we find in our filter is dust.... We use a K&N flat plate filter without oil for our NA motors, and a cone type with our blown motors.  Of course you are presented with one of the issues we face, space limitations, that is why we use different filters. 

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Stainless
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Jack Gifford
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« Reply #3 on: November 21, 2016, 01:30:39 AM »

I expect the scoop to be generally in "clean" air, especially since I may run only pavement LSR. I was planning something like 1/4" screen wire to catch birds, huge bugs, candy bar wrappers, etc. But then I got to wondering about finer screen to catch even smaller stuff. With the small area (maybe 20 sq.in.?) of a forward-facing scoop, I suspect that round-wire window screen would be more restrictive than I'd like. I guess I'll go with the 1/4" screen.
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Peter Jack
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« Reply #4 on: November 21, 2016, 07:42:16 AM »

Jack, I would let the dyno be your friend. Once you've established where you want to be with your engine try a couple of different screens and configurations relating only to filtering and see if you can live with any of them.

Good luck!

Pete
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« Reply #5 on: November 21, 2016, 11:03:48 AM »

There's lots of different style KNN filters if you can work one in. Salt coming off the tires during turn out is something that needs to be addressed.
  Sid.
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Crackerman
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« Reply #6 on: November 21, 2016, 01:41:15 PM »

Dont forget filter prescreens as well. They are a very breatheable bag that slides over filter. Can be cut apart and stretched over inlets and such.

AFE makes a "race day" filter,  for big chunks. Its basically ta mesh filter without cotton media.

And now power driven diesel (www.powerdrivendiesel.com) has come up with some incredibly high flowing filters that out flow and outfilter any oiled cotton gauze filters on market.
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John Burk
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« Reply #7 on: November 21, 2016, 01:59:49 PM »

Jack , you might start by asking how many land speed racers have experienced engine damage from ingested junk .
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Jack Gifford
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« Reply #8 on: November 22, 2016, 01:33:22 AM »

Tlhanks for all the comments.
I'm a new-guy at LSR but in other motorsports I've seen a number of instances of "junk" ingested by the open intake of an engine. Admittedly, most have been off-track; but keeping some sort of screen  in place would have prevented most damage.
Peter Jack- good idea for dyno testing of screens.
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rouse
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« Reply #9 on: November 22, 2016, 08:28:36 AM »

We used to run a screen between the hat and blower, that was back in the 6-71 days and you could by them off the self from anyone that carried GM parts.

It had fairly fine wire on about 3/16 (6 mesh) spacing. Over time that screen saved engine several times, as we found a variety of things caught by the screen, ie. rocks, nuts, trash, you name it, and yes SSS, the nuts were the metal type. 

So; I found that a screen that would stop the big stuff helped, but any finer than what we had would have a very negative effect on air flow.

Rouse

 
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Johnnie Rouse
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« Reply #10 on: November 22, 2016, 08:56:12 AM »

Johnnie, why is it that you manage to get in a shot or two about Texans no matter what you're saying to us?  I assume that when you say that (to me) - you're teasing about restraining that other fine race team from Texas -- Chock Full O' Nuts.

How'd I do?

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rouse
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« Reply #11 on: November 22, 2016, 03:43:45 PM »

SSS,

Just making sure everyone knew I wasn't referring to the organic type, as the engine was behind the driver. grin

Rouse
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Johnnie Rouse
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Rex Schimmer
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« Reply #12 on: November 23, 2016, 02:13:14 PM »

One way of reducing the masking effect of a screen over the inlet is to give the screen a big radius which increases the amount of screen and therefore the number of openings for the air to flow through. You should be able to calculate how much screen you need to provide enough openings to match the scoop area. I would actually add 15 to 20% to make up for the  lousy air flow around the screen wire. Once you have the estimated screen area I would suggest a frame made from small tubing or rod that would allow you to tack weld or solder the screen to it and provide support for the screen. As everyone has said, just covering the inlet with flat screen will restrict the air into the blower. You can buy stainless steel screen from McMaster and Carr in almost every opening size you can image.

Rex 
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Jim Phelps
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« Reply #13 on: December 08, 2016, 04:58:44 PM »

If you google hex airflow straightener or hex airflow straightener design you will see a variety of low restriction honeycomb screens.  Some of these are used in airflow sensor boxes. They have some depth and may not be easily fitted to your inlet.
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