Take a look at the opeining for the fog light, in my car there is a separate vent below the foglight that runs to the brakes. With my design 'dust pan shaped' went on top of that vent so the brakes would get cooled properly.

 

Has any seen the Bonez fresh air headlight cover, I got one off RX7.com and although it may not be as good as ram air, it does provide some fresh air into the intake, and it couldn't be easier to install.

 

Hey guys i think the diagram is just showing the force of the air on the body of the car. like downforce. that would explain why the front of the nose has a lot of force on it and the top of the windshield has the same.

that would make sense to me

Justin

 

i didnt read njdave's last message, but i think i am seeing the same thing he is but without all of the fancy terms. i guess architect dont understand airflow as well as aeronautics people.

Justin

 

Well, I had an architect as a roommate in college. All I know is he worked harder than I did!

 

Dave,

I know it depends on the size, shape, and position of the scoop, but how would it affect the flow pattern if you just extended the stock hood scoop to open at the front of the hood? Would that help flow to the stock IC?

Would the flash-to-pass or headlight cover NACA duct work better for a ram-type air intake?

Also, RX-7's were available with two different types of rear spoilers. One was a small one that came straight off the rear, like an old 200SX. The other was the one you see everywhere. Which do you think would be more effective at reducing drag and increasing downforce?

If the windshiled area is a low-perssure zone, how does cowl induction work?

Does the speed of the car have an effect on the shape of the curve?

I realize you weren't on the design board, and this is all conjecture and speculation, but I don't have any fluid dynamics under my belt (yet) and would like your opinion.

Ren

 

NJDave did not explain the Bernoulli's principle is only a part of the lift force a wing provides. The laminar flow over the top of the wing follows the profile of the wing. So the air over the trailing edge continues to flow downward and "pushes" the wing up. Look at the way the air follows the contour of the rear glass and would continue to flow downward! He said it was a crude explanation on his part and this is just an FYI. I think he is right about the pressure vectors relative to the surface. That's the way I saw it also.

Tweaked, your idea about reducing "frontal area" is off-base. Frontal area is not the area at the front of the car. Frontal area is the total area that the car presents to the wind from the front. (The way it is measured helped my understanding of it.) A light is placed in front of the car a ways. The shadow is projected rearward onto a wall. The "area" of the shadow on the wall is the frontal area. Therefore, you can reduce frontal area by chopping the top, channeling, using smaller mirrors, lowering, etc.

 

This guy has a great idea for an intake with a scoop. The thread is kinda long, but the pics are excellent. I'm considering this instead of a frontal CAI tube.

https://www.rx7club.com/vforums/show...threadid=37840

 

[QUOTE]Originally posted by turboren
I know it depends on the size, shape, and position of the scoop, but how would it affect the flow pattern if you just extended the stock hood scoop to open at the front of the hood? Would that help flow to the stock IC?

There would be no benefit to extending the scoop to the front of the hood. In fact, you might lose some air due to the fact that the laminar air flow moving over the hood would be slightly denser than that at the front of the hood. But this would be negligible and, in fact, you wouldn't notice a difference probably.

Would the flash-to-pass or headlight cover NACA duct work better for a ram-type air intake?

I don't believe so. A good ram air system forces laminar air directly into the engine intake. It is preferable to have as little distance between the source of air and the intake (hence, the use of hood scoops) and it is very preferable to have no sharp curves in the piping that delivers the air to the intake (to avoid turbulence). Unfortunately, the opening on the TB on the FC is 90 degrees from the direction the air is coming from. Given the stock intake, forcing any turbulent air into the stock intake will result in turbulence at the bend right before the intake.

Also, RX-7's were available with two different types of rear spoilers. One was a small one that came straight off the rear, like an old 200SX. The other was the one you see everywhere. Which do you think would be more effective at reducing drag and increasing downforce?

You get different kinds of drag with the two different types of spoilers. With the short one (if I am picturing the right one), laminar air comes down from the rear hatch and hits this obstruction sticking up in the wind flow. The air hitting this obstruction results in significant drag, I am sure (sort of like putting your hand out the car window with your palm facing forward). The other type of spoiler is a sort of upside down wing. Air stays laminar over the wing. (picture your hand out the car window with the edge facing the air flow). Just like an airplane wing results in a vertical lifting force, an upside down wing would create a verticle downward force. There is drag here also, but it results from the laminar flow over the spoiler. Laminar flow results in more drag because it is denser and, as a result, more air molecules "touch" the surface of the wing. (Have you ever seen little metal "walls" on airplane wings facing the air flow? These are there to, among other things, create turbulent flow over part of the wing to prevent drag).

All things being equal, the wing would probably have less total drag than the lip-type spoilers.

If the windshiled area is a low-perssure zone, how does cowl induction work?

Cowl induction is not a ram air method, although I think air entering the cowl will be at slightly higher pressure. Similarly to what happens when air passes past the rear end of the car, air passing over and around the cowl will tend to try to follow the curvature of the hood. As it passes by the opening of the cowl scoop, therefore, it will tend to curve in the direction of the scoop opening. I think the main benefit of cowl induction is, however, the cold air that enters the engine bay close to the intake.

Does the speed of the car have an effect on the shape of the curve?

Yes, I would expect that it would. As the car moves faster, I would expect that the pressure vectors in places where the flow is very laminar (e.g., the hood back part of the roof, rear glass) would drop further in magnitude (Drag would increase over these parts of the car). Pressure on the front of the car, the top of the windshield, and the rear of the car would rise. At very very high speeds, I would anticipate that the car would tend to be light at the front end, making steering difficult - the pressure on the hood would drop so low that it would be just like a wing and the air passing under the car would be exerting more pressure upward than the combined weight of the engine and front end and would cause the front end to rise somewhat (hence the reason why, on high speed cars (e.g., Nascar) you see front lower air dams - they are attempting to keep air from getting under the car). [/B]

Dave