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Discussion Starter · #1 ·
I know there is alot of debate on what style hood scoops actually cool, or are just visual etc.

I currently have a hood made modeled after the old CFX hood that use to be available. I am now looking into something different.

There are quite a few people on here who believe the NACA style duct is the most efficient/effective duct and Im wondering if this would be a good effective hood for a little bit of cooling action with my high turbo underhood temps.

I am thinking about doing a NACA style scoop just about over the turbo and just over the intake mani on either side of the stock cowl....

Can I get some opinions?

Something like the stock datsun turbo hoods, but on both sides and without the "vent" portion (or with if I can find some)



(further towards the windshield than this)

 

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I think the one in the top photo would be very effective if mounted over the turbo. It would look very nice fiberglassed to the hood.
 

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Discussion Starter · #4 ·
well I am a member on a Z car board and can pick up a pair to make it symetrical for a pretty good price....

Just weighing out the options. I want some function but want it to look good too.
 

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That NACA duct shape is more to add air into the car than remove it.

Maybe you'll want to mount those backwards to act as a vent instead of a scoop?

Just a comment because I'm not sure it'll work that way.
 

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I am all for scooped hoods even though mine is not turbo i have seen a deffinant drop in temp while driving.
 

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the most effective vents i've seen for extruding hot air are on the sierra cosworth. they are mounted close to the front of the hood in a low pressure area and do a wonderful job of extracting hot air from under the hood without the nasty results of cramming more air into the engine bay and causing the front to want to lift. it's hard to argue with the most successful touring car design ever.

 

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Im for 2 of those forward.
really moonpie one forward and one backwards:laugh:? your a goof..just teasing.

i would also add the vents. the scoop just in front of the turbo of filter to ram air into it and a vent over the turbo to help expell heat. same for mani. scoop in front to force air over it to cool it then vent over it to expell heat. If i had those. id be putting them in.

isnt there a website you can buy vents/scoops from to get new ones instead of old used/brittle ones?

i know the 5.9L 1998? jeep grand cherokee, cant remember the model, some sort of TSI type word had 2 vents on the hood that looked usable for venting/expelling heat but not for scooping. Good thread btw:thumbsup:
 

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...i know the 5.9L 1998? jeep grand cherokee, cant remember the model, some sort of TSI type word had 2 vents on the hood that looked usable for venting/expelling heat but not for scooping. Good thread btw:thumbsup:
It was the 1998 Jeep Grand Cherokee Limited 5.9

Only offered in '98.

I have one as my daily driver. The vents work well to get the underhood heat out. I'll add pics later.
 

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Scooping air from the hood to cool the engine bay is not reasonable due to the MUCH higher pressure under hood than above. The air will want to come OUT of the vent.

Scooping from the hood to provide the intake cool engine air is reasonable and best done as far back on the hood as possible.

The best pressure locational image I've seen is hotlinked from a swedespeed forum member (thanks!)




--billyM
 

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Nice graphic, Billy. That's some cool information sitting on that hood...

xr4man: is that an intake on the center of the front of the Sierra Cosworth?
Did you modify an XR4Ti or did you actually import a Sierra? Just curious...
 

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Both of these works for me, cooled down the header, and gave me a better airflow for the intake. And it worked well for when it caught fire, I saw the flames and smoke through there....
 

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From my reading and my understanding of how it work this is the kind of hood that gives a good help in cooling without looking like a race car or a monster. It really blend in like a factory option.



And depending on the hood style something like the EVO 6 hood should work great to get hot air out. If I had the guts to cut a perfect Celica hood I would do something like that.


Also raising the hood at the back by putting spacers on the hinges have prooved to cool down at certain speed.
 

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You want max airflo coming in the front thru the intercooler. Then some of this air should be exhausted near the front of the hood so the hot air doesn't heat the intake air and the rest of the engine. Air should be directed per your mechanical configuration and there is no one size fits all for optimum performance. If necessary you might get more performance by porting some air thru 3" dia tubing while avoiding IC. U could even steer the ic/rad output air with a distorted "S" curved sloping member to the hood exhaust. Underhood temp control is a major performance limitation. If possible use a TC to measure air temp at different underhood points at speed as u reconfigure your hood. Also, wrapping IC output tubing (if metal) to keep compressed air cool may be important so ic output air doesn't get reheated. Pressure is always highest at "flat" part of car front and that should be the input. Air flowing across hood (and rest of body) will always be low and should be used as the exhaust. In general the exhaust should slope upward from the hood at no more than a 7-1/2 degree angle and should be wide to keep the exhaust pressure low for lowest exhaust pressure and max exhaust airflo.

Assuming that the ic air flows to the intake plenum u might want to port cold intake air thru a 3" dia tube blowing on the intake plenum. I have a na setup with cai but i wrapped the aluminum intake afm and there was a small improvement.
 

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How about something like this for venting, maybe not as aggressive. Hid in the back outer corners of the hood...
 

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Nice graphic, Billy. That's some cool information sitting on that hood...

xr4man: is that an intake on the center of the front of the Sierra Cosworth?
Did you modify an XR4Ti or did you actually import a Sierra? Just curious...
the opening in the center of the grille is to direct air over the intercooler.
i didn't actually import this car, it was already here when i bought it. and no, it's not built on a merkur xr4ti.

rwdfreak, that's probably the best example for a hood vent on a mk2 i've seen. the evo vents are contoured alot to get the maximum "suckage" possible from their vents. only problem with them is that everyone has copied them and made a carbon hood for every honda and cavalier/cobalt out there so they are a bit played out.
 

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the opening in the center of the grille is to direct air over the intercooler.
i didn't actually import this car, it was already here when i bought it. and no, it's not built on a merkur xr4ti.

rwdfreak, that's probably the best example for a hood vent on a mk2 i've seen. the evo vents are contoured alot to get the maximum "suckage" possible from their vents. only problem with them is that everyone has copied them and made a carbon hood for every honda and cavalier/cobalt out there so they are a bit played out.
Except that it's a MKIII not a MKII LOL. Note that the Hood bulge continues down onto the header panel.
 
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