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Homemade Hood Scoop


jjaffe01

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I bought a new factory insert $175 unpainted....then I took modeling clay and set it in to form the new shape, layed fiberglass over the clay and formed scoop. After it was hard, I dug out the clay and popped the bond ( fiberglass does not bond well to ABS)

Then I epoxyed the 2 pieces together and did the finish and paint work.... I never did it before ,so I am very happy with how well all the lines and paint match. It took probably about 20 hrs. worth of work with all of the sanding and shaping...Not ecomomical, but it gave me a hobby and it is the only one in the world exactly like it.:rolleyes:

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Since the standard scoop operates by leveraging the laminar flow of air over the hood, I wonder what this actually does to the amount of air going into the IC ?!?

 

 

So those big words mean the stock scoop works really well and this mod might make it work not as well?

(Updated 8/22/17)

2005 Outback FMT

Running on Electrons

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So those big words mean the stock scoop works really well and this mod might make it work not as well?

 

That is quite possible. Anyone who has studied aerodynamics will tell you that things rarely behave the way you would think!

 

Laminar flow refers to a layer of smooth high-pressure air that runs along the surface of the hood. The scoops on the 05s leverage that phenomenon which allows them to be smaller yet highly effective.

 

Making a change to the aerodynamics of the hood could cause the airflow to go turbulent (hence low-pressure) and greatly reduce the amount of air flowing through. That is why there is a special version of the hood deflector for these cars, designed not to disturb the laminar flow.

 

I'm not saying this is happening, but it is a distinct possiblity. Anyone has access to a wind tunnel?:D

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Neat. I am glad that the spirit of tree-shade mechanic and ghetto engineering is still alive with some of us. Looks good !

 

And speaking of hood scoops...I just spotted a Saabaru...looks like these expensive WRXes have the same hood scoop as the Legacy...Really looks odd !

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That is quite possible. Anyone who has studied aerodynamics will tell you that things rarely behave the way you would think!

 

Laminar flow refers to a layer of smooth high-pressure air that runs along the surface of the hood. The scoops on the 05s leverage that phenomenon which allows them to be smaller yet highly effective.

 

Making a change to the aerodynamics of the hood could cause the airflow to go turbulent (hence low-pressure) and greatly reduce the amount of air flowing through. That is why there is a special version of the hood deflector for these cars, designed not to disturb the laminar flow.

 

I'm not saying this is happening, but it is a distinct possiblity. Anyone has access to a wind tunnel?:D

 

probably an easier test is to put a CPU temperature sensor or something on the intercooler and try em out back to back

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If you notice , I posted this in aethstetics, not as a performance upgrade.

 

I just think it looks meaner......

 

I really have no idea if it is better or worse for flow...althought the laminar air flow stuff sounds official, I suspect that the real reason Subaru went with the type of scoop they did was because the intended audience of the car is more reserved and they did not want too much WRX in the look because they were going more up-class. As far as if small would work better...If you look at the stock Subaru cars....the higher performance the car...the bigger the scoop...so I suspect it was image for the legacy more than any high tech aero dynamic voodoo.

 

Consider how the air intake is done, before you assume that Subaru is making it's design decisions based on max performance.

 

 

I believe that the I/C efficiency is a lot more important than the scoop efficiency..( I saw a very thorough report done with temp sensors on a WRX in another forum once)...since a scoop does nothing for coming off the line (thats why the STI uses a water spray...and by the time you are traveing at any speed the scoop efficiecy is a moot point.

 

I can say I have noticed no appeciable change in performance, I run a cobb stage 1 at 93 octane.

 

As for building one cheaper than $175....that was the cost of the factory blank...besides...if I made a bunch...I would not have the only one....If you want to buy one..AVO makes a bigger scoop...I think it is about $500 unpainted, but I think mine matches the car better.

 

To those that have had kind words.... Thanks:cool:

 

Jim

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Actually the new scoop design is "apparently" more efficient then the WRX one. But the main advantage of a laminar flow design is low drag.

 

Scoop efficiency is not really a moot point at speed. If not designed properly, it could actually create a zone of high-pressure in front of it and you can end-up having no air at all coming through. That is why airplanes use NACA scoops, which are mounted below the surface and provide low drag and efficency at speed.

 

Once again, I'm not saying that your scoop is bad, just wondering what it actually does to the efficiency, and pointing out that just because it is bigger doesn't mean it is necessarily better.

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And speaking of hood scoops...I just spotted a Saabaru...looks like these expensive WRXes have the same hood scoop as the Legacy...Really looks odd !

 

They're close, but they're actually alot bigger than ours. Taller opening.

(Updated 8/22/17)

2005 Outback FMT

Running on Electrons

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jjaffe1- very nicely done. There is great pride in knowing that you have built something that is a one of a kind. If you call it an CIA you can claim an immediate 22 horsepower increase. (smiley face)

 

Do you hear any additional wind noise from teh scoop at High speeds?

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Sduford...... I do not recall anybody at any time saying it was better...and I get your point about the airplanes....that must be why top-fuel cars and funny cars have those concave hoods;)

 

I will restate... I built it because it looked cool....

The stock legacy scoop is not cut below the surface..(Just look at the car from the front) It is just short.

 

The negative pressure condition would likely only be an issue at very high speed.. ( I am sure with your knowledge of airflow...you know that the response will change based on the speed of the flow) The faster the air the larger the area of turbulence.

 

But now I am tempted to do a backyard test with a fan and a smoke bomb.

 

But really I think you are just HATE'N , It would look good on a wagon too.:)

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