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Old 10-20-2012, 01:58 PM   #1
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Default EVO Extractor hood vent on Miata

I don't really race, but having read a lot here and having personally dealt with cooling issues I wanted to give this a shot. I thought about all of the different options, GT500, Mini and even those Road Race carbon ones. For either liking the looks or the functionality or whatever, I chose to give an Evo vent a try.

I was really reluctant to try this on my really nice condition MSM hood so this mod sort of look a back seat until I found a lovely donor. Overall I think it turned out pretty nice.

Basic install instructions are tape everything off, lay vent down approximately where you want, measure, measure again, make a template, trace it onto the tape, drill a hole and start cutting. I used a combination of left/right tin snips, an air saw and a carbide bit and sand paper for cleaning up edges. Then I put a little bit of a bend in the top and bottom to get it to fit the shape of the hood better. I believe the bottom took a few more degrees of bend to fit nicely.

Lastly you'll need to find a way to hold it in place. The Evo vent has off center mounting tabs and studs that are really weirdly orientated for its original application and I just made some mounts quickly out of 1" aluminum stock. Will get a picture of the bottom shortly.

Does it work? I probably won't go through much personal testing, but I'm pretty sure we all know it doesn't hurt.






Attached Thumbnails
EVO Extractor hood vent on Miata-img_20121018_112054.jpg   EVO Extractor hood vent on Miata-img_20121018_112304.jpg   EVO Extractor hood vent on Miata-img_20121018_143251.jpg   EVO Extractor hood vent on Miata-img_20121018_163113.jpg   EVO Extractor hood vent on Miata-img_20121018_163126.jpg  


Last edited by slmhofy; 10-20-2012 at 04:05 PM.
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Old 10-20-2012, 02:21 PM   #2
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Shame it looks like ***

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Old 10-20-2012, 02:24 PM   #3
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Not bad.
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Old 10-20-2012, 03:13 PM   #4
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I think it needs some sort of front lip to actually extract air from under the hood.
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Old 10-21-2012, 03:31 PM   #5
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I like that. I wonder how it would look on an NA
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Old 10-21-2012, 03:50 PM   #6
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where did u buy the vent?
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Old 10-21-2012, 08:57 PM   #7
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WRC cars duct their radiator fans directly to the hood extraction opening.

Without a lip in front of your opening, and without ducting, I'm not sure you're getting any extraction from the opening. Have you any test data showing any benefit yet? The front of the hood slope is typically a high pressure zone, and this may actually lower the pressure differential pre&post radiator compared to stock.

The actual execution of the installation looks pretty good. Given the color of the hood, I take it you still have your original hood in unmolested condition?
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Old 10-21-2012, 10:53 PM   #8
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For pressure reference. This pic gets circled around here a lot.
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Old 10-21-2012, 11:10 PM   #9
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Have you done any tuft testing yet? It SHOULD flow air out, but... well... it would be nice if you knew it was working or it wasn't.
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Old 10-22-2012, 01:20 AM   #10
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Since the hood is a different color why not strip and polish it?
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Old 10-22-2012, 03:18 AM   #11
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Quote:
Originally Posted by Clos561 View Post
where did u buy the vent?
I don't exactly remember where I bought the hood. I think I got it from either DSMTunners or another Evo forum. Just lurked for a while and did a bunch of google searching. I'd imagine they're not that easy to find jest because if a car gets in an accident, the hood usually gets smashed.
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Old 10-22-2012, 03:22 AM   #12
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Quote:
Originally Posted by Mobius View Post
WRC cars duct their radiator fans directly to the hood extraction opening.

Without a lip in front of your opening, and without ducting, I'm not sure you're getting any extraction from the opening. Have you any test data showing any benefit yet? The front of the hood slope is typically a high pressure zone, and this may actually lower the pressure differential pre&post radiator compared to stock.

The actual execution of the installation looks pretty good. Given the color of the hood, I take it you still have your original hood in unmolested condition?
I'm sure a lip like the Evos have and ducting straight from the back of the radiator to the vent would help, but Torquezombie's picture and this one will show you that that area on the hood is indeed a low pressure zone at speed.



I may, but probably won't do any testing. Tons of other people here have already done it. Hustler, Sav, Brain, they all know better than I probably ever will.

And thank you for the execution comment
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Old 10-22-2012, 04:20 AM   #13
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The vent works perfectly because the hood is low pressure. Look at the picture above (the one of the grey hood with negative pressures written on it) if you don't think it is.
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Old 10-22-2012, 12:19 PM   #14
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A lip in front would greatly increase the extraction of air on such a flat area of the hood, but it well definitley extract air presure from under the hood and increase air flow through the rad. as it is.
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Old 10-22-2012, 11:45 PM   #15
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For the record, I'm not in favor of anyone in this thread getting executed
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Old 10-30-2012, 02:54 PM   #16
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For anyone interested in learning more about how aero works and especially if you are considering aero mods to your car, I found this book to be an outstanding reference:

Competition Car Aerodynamics Competition Car Aerodynamics
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Old 03-05-2013, 06:22 PM   #17
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OP,

I'm thinking of copying this. Can you post up that picture of the underside for the mounting you did? Thanks.
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Old 03-05-2013, 07:32 PM   #18
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Quote:
Originally Posted by wannafbody View Post
Since the hood is a different color why not strip and polish it?
Because that's stupid and you are stupid for suggesting it.
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Old 03-05-2013, 07:36 PM   #19
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Quote:
Originally Posted by hustler View Post
Because that's stupid and you are stupid for suggesting it.
quoted for truth, and + props
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Old 03-05-2013, 07:50 PM   #20
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Quote:
Originally Posted by Mobius View Post
For anyone interested in learning more about how aero works and especially if you are considering aero mods to your car, I found this book to be an outstanding reference:

Competition Car Aerodynamics
And

Race Car Aerodynamics by Katz

and if you want something with both practical and theoretical

Aerodynamics of Road Vehicles (~900 pages)
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