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Old 06-08-2010, 02:02 PM   #1
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Default minor hood mod

So I have been looking at a lot of extraction hoods and from what i get out of it, the moving air over the vents creates a vacuum and sucks the air from the engine compartment out right?

so if I were to remove that black rubber molding that runs along the top of the firewall and seals to the hood, and also put a couple washers between the hood hinges and the hood (raising the windshield side of the hood a half inch or so) would I get the same affect?

your thoughts?

thanks!
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Old 06-08-2010, 02:05 PM   #2
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Googles Cowl Induction Hood. People have known about this happening since the 70s
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Old 06-08-2010, 02:05 PM   #3
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Do more reading. You'll stuff more air pressure INTO the engine bay by doing that.
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Old 06-08-2010, 02:07 PM   #4
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Hood spacers daas not work.

Talk to hustler about pressure differentials, he knows all.
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Old 06-08-2010, 02:13 PM   #5
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Quote:
Originally Posted by rigidbigelsworth View Post
So I have been looking at a lot of extraction hoods and from what i get out of it, the moving air over the vents creates a vacuum and sucks the air from the engine compartment out right?
...yes and no. It creates a low pressure zone which helps to relieve pressure under the hood (it...sucks it out). This in turn creates a greater pressure differential between the mouth of the car and the engine bay -> Greater flow across the heat exchangers.

Quote:
so if I were to remove that black rubber molding that runs along the top of the firewall and seals to the hood, and also put a couple washers between the hood hinges and the hood (raising the windshield side of the hood a half inch or so) would I get the same affect?

your thoughts?

thanks!
I think you need to look into the high and low pressure zones on the car. The base of the windshield is an area of relatively high pressure. If you do the hood riser mod you'll end up increasing the pressure under the hood(as another member pointed out already) This blows *** for cooling.
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Old 06-08-2010, 02:16 PM   #6
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well whether it is pushing/pulling air, either way it should cool down the engine bay right? or am I an idiot :/

EDIT: I posted before i saw jeffs comment.

so basically, I am an idiot and should leave my hood alone..
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Old 06-08-2010, 02:17 PM   #7
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Quote:
Originally Posted by Bond View Post
Hood spacers daas not work.

Talk to hustler about pressure differentials, he knows all.

Are you looking to hang the kid? Don't ask him, search using advanced search and type him as the username you want to search.
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Old 06-08-2010, 02:20 PM   #8
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alright lets just pretend this thread didnt happen.... haha but thanks for the help guys
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Old 06-08-2010, 02:21 PM   #9
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Quote:
Originally Posted by rigidbigelsworth View Post
well whether it is pushing/pulling air, either way it should cool down the engine bay right? or am I an idiot :/
You aren't an idiot, you're just thinking about it the wrong way.

Cooling down the engine bay isn't nearly as important as flow through the heat exchangers. Engine bay heat will lead to slightly higher IATs, which is something you can combat with some clever heat shielding and removing a front turn signal.
Poor flow through your heat exchangers will lead to overheating and EVEN HIGHER IATs.

A small amount of power loss > wrecked cylinder heads from overheating.
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Old 06-10-2010, 12:51 AM   #10
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Won't adding turn signal and NACA ducts increase under hood pressure, and decrease flow through the heat exchangers? Have these changes been checked out with a magnahelic? So confusing.
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Old 06-10-2010, 01:13 AM   #11
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Won't adding turn signal and NACA ducts increase under hood pressure, and decrease flow through the heat exchangers? Have these changes been checked out with a magnahelic? So confusing.
alot of people that add those route it specificall onto the air filter etc. Essentialy yes it will but not to the extent of your hood riser idea. This magna says to just add WI and prosper. The best part of the exraction hoods is that it gives the heat a very short distance to travel before it leaves the engine bay, this coupled with sealing everything off to where it only flows into, where u want it to.
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Old 06-10-2010, 09:10 AM   #12
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Neither the hood riser or extraction hood were mentioned by me.
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Old 06-10-2010, 09:17 AM   #13
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no hood riser, my rubber gasket was just pulled away. at 40mph the strings kept getting sucked into the bay, at 50+mph they just stayed in. The string closest to the inside got sucked into the bay at like 10-15mph and stayed there.

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Old 06-11-2010, 02:03 AM   #14
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so what methods are there to cool down the engine bay area that are either free, just takes some time, or very cheap? I dont want to do the "pop-out-a-turnsignal" intake vent, i want something i can do all the time since this is my DD and i kinda like the use of my signals..
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Old 06-11-2010, 02:20 AM   #15
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TSI's keep your signals working and legal. You can also wire up your side auxiliary lights on your bumper cover to pulse with your turn signals.

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Old 06-11-2010, 11:51 AM   #16
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Quote:
Originally Posted by rigidbigelsworth View Post
so what methods are there to cool down the engine bay area that are either free, just takes some time, or very cheap? I dont want to do the "pop-out-a-turnsignal" intake vent, i want something i can do all the time since this is my DD and i kinda like the use of my signals..
Here you go:
https://www.miataturbo.net/showthrea...ght=mini+scoop
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Old 06-11-2010, 12:00 PM   #17
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who cares how hot it is under the hood? like honestly. for cereal.
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Old 06-11-2010, 07:33 PM   #18
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Quote:
Originally Posted by rigidbigelsworth View Post
so what methods are there to cool down the engine bay area that are either free, just takes some time, or very cheap?
A wise man once told me: "Keep the water cool, and the engine bay will take care of itself." Kind of like "Watch your pennies and the dollars will take care of themselves."

Bottom line: cool the water (and the oil) and all the systems (including the engine bay) will be cool enough. Don't search for engine bay remedies, but rather maximizing your cooling system:
bigger, aftermarket radiator (filled with distilled water with a sip of WaterWetter)
ducting to ensure that all air entering the mouth of the car flows through the radiator
coolant re-route
and, if all that don't do it, aftermarket oil cooler
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