vent/scoop opinions

[myREDcarMAN]

So i mostly lurk on here, but i couldn't find a suitable answer.
I plan on doing a shortened ram intake (much like Alex frost) and was wondering if a small vent or scoop would be in any way beneficial? I was envisioning something just behind the light. I would likely add some additional heat shielding. Or would the fact that the summers here only get up to mid 80's negate the need for one? Help me out guys still a bit of a NOOB here.         

[DirtyGaze]

Can definatly be done, and colder air is always more beneficial...but I really dont see a need for it.  IF you were to see HP gains, they will be very small and might even be pointless due to the drag coefficient of your brand new scoop, lol. 

Try the short ram, see how you like it.  If it works for you and you still want to try the scoop, go for it.  I wont hate on it...mostly cuz you could hate on my car all day long and I have no defense...Im just saying dont expect to much of a change.

[SlickS12]

How about this one from the 280z? 

[iceageg]

+1 for the naca duct design.  Especially if it is near the front of the hood.

[BattleFairy]

[StephenG]

While naca ducts look cool, the provide essentially zero positive pressure in the intake. Honestly, I think doing some sort of cowl venting, like on that rx7 there, would do more for your performance by helping to lower engine bay temps.

[iceageg]

Naca ducts most certainly DO provide flow benefits.  The key to getting any benefit out of them is placement.  Put them in the wrong place and all they do is add bling.  Same as the vortilators auto makers have started placing above the rear window (see the Evo MR).  Another limiting factor for most day to day driving is speed.  They will provide little if any benefit until you are up to speed.

[Arro]

^^^what he just said is the most valuable info in the thread so far.

[StephenG]

Naca ducts are designed to provide maximum flow with one exception, that the create zero additional drag or turbulence. They provide zero forced, or ram air effect, for this exact reason. The only REAL performance use you will see them in, with regards cars, is fresh air intakes for drivers and intakes on the bottoms of race cars. They use them there because they do not "scoop" the air, and will ingest much less debris off the road surface.

It looks cool, but it serves absolutely no purpose as an intake system. A small scoop will be much more effective and reducing vacuum in an intake system.

Dont take my word for it. Read the original design studies.

[Arro]

The NACA duct on a 280ZX is designed to cool the turbocharger, not to take in air. Underneath na din the engine bay there is a metal air deflector that routes the intake air down onto the exhaust turbine housing.... when you shut the hood, the NACA feeds directly into this deflector.

The 280ZX NACA is also louvered on the back end in order to allow hot air to vent the engine bay. There is also a second louver duct on the opposite side of the hood.



Because the two louver ducts allow the hot air to vacate the engine bay, there is not a negative pressure situation inside the inlet scoop (triangle), so you do actually get positive airflow. So given you ran with both the 280ZX NACA and it's accompanying second louver vent (or a generic NACA and your own custom louver vents), you could conceivably use it as a positive pressure air intake.

[iceageg]

Naca ducts are designed to provide maximum flow with one exception, that the create zero additional drag or turbulence. They provide zero forced, or ram air effect

All correct.  If I gave the impression that naca ducts would create a ram effect greater than that of a traditional scoop . . . it was not my goal.  I was speaking to the flow advantages they offer.  When placed in a good clean airflow they allow the incoming air to maintain velocity.  While on cars the aerodynamic effect is usually unimportant from a performance standpoint, maintaining the velocity of a fluid (in this case intake air) is invalueable.  Velocity is the sultry mistress of pressure.  Gotta have both or your intake/forced induction/exhaust/etc. will never work optimally.

More to the original topic, if you do like the idea of a naca duct make sure the portion of the hood you intend to put it on has a unidirectional flow against the sheet metal.  You would be surprised how much swirling the air does between the windshield and the hood of most cars within an inch of the surface.  A traditional scoop sticking up will catch the air farther up making placement less critical and therefore much easier with a higher likelyhood of success.

[Arro]

I reitterate, IF you use the two pieces from the hood of a 280ZX or set up your own vents with a single NACA, it WILL see positive pressure from the NACA, because you reopened the airpath.

[StephenG]

Well, I apologize for over reacting a bit there. I get so tired of these honda guys thinking naca vents are the godsend epic ram air intakes that make fast cars faster. I should have been slower to assume you were part of that group.

I still don't know if I would go so far as saying they benefit the velocity of the incoming air. They flow very little volume for their size, because they exploit the less turbulent boundary layer that sticks close to the hood. The back of a car's hood is already in a turbulent state, thus there is very little laminar, high velocity air for the naca to exploit. A similar sized "scoop" that protruded should out perform a naca vent with regards volume and velocity of the air forced into the intake. The advantage of the naca over the scoop is the naca doesnt produce flow seperation behind the scoop, a low pressure are of turbulent air. This has virtually no impact on the air flowing into the scoop.

Note the rear of the hood is nearly half the velocity of the front of the hood.


This is why engineers put these things together:



These type of intakes can exploit that high pressure, high velocity laminar air being pushed over the front edge of the hood. A Naca duct is likely no better, and I personally think it would have to be huge to compete.

[Arro]

You are already over the heads of many people LOL but you're right

[DirtyGaze]

...and I personally think it would have to be huge to compete.

You dont say...

[myREDcarMAN]

So if i understand, this NACA is more of a vent than an intake scoop. but I'm curious as too your guy's opinions now. Vents Vs scoops? Forward facing Vs Reverse facing? If I'm looking for the most benefits, which way?.....  Go!

[Arro]

By "this" you mean the 280ZX version? It's both. The triangular part is the intake, the ventilated part behind that is just what it sounds like -- a vent. There isn't negative pressure because there are two vents on a 280ZX and one inlet. More air can escape than can enter.

You want to run a 280ZX vent facing forward. But you also want to install the companion vent on the other side. Install them both exactly as they are on a 280ZX.