New Hood Mod! NACA Ducts!

[Triathlete]

Hmmmm! Whats going to keep the water out on those rainy days?

[Ldub]

Hmmmm! Whats going to keep the water out on those rainy days?

I was thinking a chunk of sponge or high density foam cut to fit (HAS to be black, of course), would slow it down to a drip on those rainy days & keep out most of the cold air during the frigid winters we experience way up nort.

[thedutchguy]

Me think you brave man to take two days of !

[iamjacksadrenalgland]

actually, NACA ducts are designed to vent air out from under the hood. there's a pressure difference between air flowing over the hood and air trapped under the hood.

this issue was debated at great length on a porsche forum that i used to belong to when 944 owners considered using hoods set up with NACA ducts plumbed to their intakes.

... and now for today's automotive fun facts ...

in 1979 porsche decided to build a turbocharged version of their normally aspirated 924. in order to accomodate the extra heat generated, they fashioned an NACA duct directly over the exhaust manifold/turbocharger.

in 1981 porsche offered a limited production 924 carrera GT which utilized an intercooler between the turbocharger outlet and the intake manifold. the resulting temperature drop allowed for more boost and more power. in order to provide airflow over the top mounted intercooler, they fashioned a large scoop on the hood.

[Hotsauce]

I was thinking a chunk of sponge or high density foam cut to fit (HAS to be black, of course), would slow it down to a drip on those rainy days & keep out most of the cold air during the frigid winters we experience way up nort.

Cold air= power. Cold fresh air is good, but obviously too much water is bad. My truck makes noticably more power on really cold days.

I really don't think you can get up enough air pressure for any signifigant ram air effect, but the cold air will help.

John C.

[Ldub]

Cold air= power. Cold fresh air is good, but obviously too much water is bad. My truck makes noticably more power on really cold days.

I really don't think you can get up enough air pressure for any signifigant ram air effect, but the cold air will help.

John C.

I'm right there with ya John...to a point, that point being around zero, or a little above.
There's a reason older cars had heat risers ducting warm air from around the exhaust manifold up to the intake, same reason our throttle body is plumbed into the cooling system.
In severe cold, warming the intake (combustion) air a bit makes combustion happen more easily.
On mine, I've plumbed a bypass around the throttle body (using ball valves) that shuts off the coolant during the above freezing months.
My two cents.
SilverBullet, Sorry for the thread-jack.

[Chopper]

I think, maybe, save the costs of ducting... let them be extractors. The location is too far back from the airstream to realize any ram effect and is actually in a low (negative) pressure zone. Notice rams are located at the vehicles leading edge (hood lip or grill in GM cars) a high pressure zone, or near the windscreen base (another high pressure area) Cobras, Subaru, and several GM designs. Think about the huge hole, right in that spot, on an Evo... it's all about getting heat out. They even designed in a little" kick"around the hole to lift the air even more, creating more "suck" I think the piping won't help anything,and if made tight,may hurt. IMO love,Wayne

[SilverBullet75]

My inspiration for the ducts actually came from the Porsche
924 Turbo
968 Turbo S
928 GT - Custom

Even if they don't work quite the way they are supposed to, I'm happy that they look cool and provide even a LITTLE bit of extra cooling during the Nevada summer

[VCrossfan]

Looks nice Bullet...Hats Off ! ! !

[Ruflyf]

The location is too far back from the airstream to realize any ram effect

He could always just supercharge that would make the air flow more of a direct feed to the intake, or better yet let me test the hood out on mine.

[WormGod]

The scoop offers little airflow, so even cooling is minimal. The slope of the hood appears to raise airflow over the scoop more than in. Sometime back I taped some ribbons around the hood and near the scoop. All airflow is more to the front of the hood, so the scoop would need to be positioned more at the very front of the insert. There is SOME airflow at the scoop location, but I dont think it would be enough to utilize as a proper ram air. I went through this way back when, when I decided to try a ram air mod, but it simply wasnt enough to work with. We suffer the same issues that the STi hoods suffered pre- '06. The scoops were enlarged for more air to be scooped in to the TMIC. I am thinking that a pre- '06 STi hood scoop size on the VX would look insanely silly.

Our best bet for good ram air is through the grill or better yet, mod through the round parking lights in the front cladding.

[WormGod]

Looks good and clean. Killer work!

I would love to do a sort of Evo style insert mod to suck some heat out. Unfortunately, that would mean losing some stability in the hood from the cutting needed, but damn, would that look good.

[SilverBullet75]

Thanks!

Question...
For those who have the CF Hood Scoop... Is there any other function built in than just cooling? The scoop is placed even further back than my NACAs!
Just curious.
Thanks!
---JIM---

[AlaskaVX]

Thanks!

Question...
For those who have the CF Hood Scoop... Is there any other function built in than just cooling? The scoop is placed even further back than my NACAs!
Just curious.
Thanks!
---JIM---

Mine is only used for cooling and it works better then I would have imagined. It blows cool air directly on my supercharger and after a 300 mile trip with hard driving I can put my hand on the top of supercharger and it is almost cool to the touch.... it used to be quite warm after the same trip.