Fordnatics List Archive

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Mail From: Ted Mittelstaedt <agora!toybox.central.com!tedm>


Hi,
Here is my 2 cents on the air scoop thing:

On my 68 Torino, I have a 69 factory hood and scoop. The scoop is facing
forward and has a large hole in the hood that is right over the air cleaner.

I picked the hood and scoop up in a wrecking yard, and didn't get the air
box. Instead, I took a 66 Mustang factory air cleaner box, and cut away
part of the top of it that surrounds the air filter. In the 66's the air
cleaner is a smaller diameter than the 67's and later.

I have found that I need to remove the fabricated air box assembly in the
winter time and replace it with the stock air cleaner which is completely
closed to the outside air, because otherwise the carburetor will ice up.

This occurs at speeds "greater than 50MPH" so, obviously regardless of the
fact that the air scoop is facing the "wrong way" the air in the engine
compartment is hotter than the air above the hood, even at 50 MPH.

Also, I noticed that when I was dragging the car in the quarter mile at the
local track that I got an average of a .25 second decrease in times with the
air scoop.

In my opinion, it doesen't matter which way the air scoop faces, or whether
the air is "rammed" in to the carb or not, what matters is that the air
intake is as cool as possible, as the denser air obviously contains a greater
amount of oxygen for the burn.

My advice is to make the air intake as short as possible, and as high as
possible, what you want is to get the filter as close to the carb or the
injectors as possible, and the air intake as close to the filter as possible.
Also, make as large a hole as you can for the air intake.

I also was given an idea that with my round airbox that I can stack the
airfilters, to get double the filtering space, thus less resistance from
the filter, but I haven't done this. The current airbox I made an air seal
for out of that insulation you put around pipes to keep them from freezing,
the seal I just put over the rim of the airbox, and when the hood is closed
it presses down on it and seals the airbox to the hole in the hood under
the scoop.

I would think that by putting the air intake down in front of the car, or
in the wheel well that it would be too close to the surface of the road, and
espically on hot summer days the air close to the road would be really hot
from the sun beating down on the pavement. Also, running the air intake
through hose is going to increase the chance that underhood heat is going to
heat the air, not to mention the air resistance of sucking air through that
length of hose.

Ted

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Mail From: (email redacted) (James W. Swonger)

Another perspective, for yer amusement.

Take a vehicle @ 60MPH, perhaps 600CFM of draw @ WOT.

Said vehicle is moving 5280 ft/min. At this speed you would need an orifice
of .11 ft2 to pass the intake air, presuming no stacking; that's about
1-1/2" x 12", a BMF hood scoop. Something less than this will be less than
ideal, but probably better than nothing at all.

This is one reason you see things like cowl induction, and spoiler
mounted scoops, to take advantage of larger frontal features to
concentrate the air, a larger effective orifice.

The underhood area, in addition to being hot, is also often a low
pressure region, supplying makeup air to the underbody low pressure
induced by ground effects, spoilers, etc. So open air or ram air
induction may be beneficial at high speeds simply because you don't
incur a vacuum penalty.

Many cars use a feed from in front of the core support, which
is reasonable if done well; there will be some elevated pressure there
and the air will be cool. The feed is often restrictive and indirect
however. A problem here is that the automakers love to minimize this
pressure in the name of highway MPG.

I have seen fiberglass cowl induction hoods for MustangIII bodies;
have not seen any advertised air cleaner/duct setups to properly
pull the air though.

This read-only message was archived from a public mail list.
Mail From: (email redacted)

>I would think that by putting the air intake down in front of the car, or
>in the wheel well that it would be too close to the surface of the road, and
>espically on hot summer days the air close to the road would be really hot
>from the sun beating down on the pavement. Also, running the air intake
>through hose is going to increase the chance that underhood heat is going to
>heat the air, not to mention the air resistance of sucking air through that
>length of hose.

>Ted

- --------------------------------------------------

Interesting thought about air close to the road being hot. OTOH, the long
hose on the mustang runs through the wheel well (which is semi-enclosed) and
does not pick up engine heat. I would say most engine heat picked up is from
the MAF (and it's hosing) which sit above the pass header! I think I'm gonna
try ceramic headers.

-Tom

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Mail From: (email redacted)

Ok, here's the scoop (no PUN INTENDED) on my RAM AIR project for my 93 Cobra:

I had fabricated a pretty nice IMHO ramair for the car. When I put it
on, I could feel no difference in the seat of the pants. I also feared
it might actually be hurting low speed performance. Again, couldn't
really tell.

Asking around, you get every response, from - gotta have it, gave
me 2 tenths, to just the opposite.

So I went to the science forum on CIS and got the following
formula:

>> Does ANYONE know any pressure formulas? <<

F = - Rho Area V^2

Rho = air density = unit of mass per cubic unit of space
(e.g. Kg/m^3 or slug/ft^3); varies with altitude, temperature,
and atmospheric pressure; sea level condition: 0.00238 slug/ft^3

Area = Square unit of space (e.g. m^3 ot ft^3)

V= Velocity of air = unit of space per unit of time (e.g m/s or ft/s)
60 MPH = 60 x 5280 ft/3600 sec = 88 ft/sec

4 inch diam = 2 inch radius => Pi r^2 = 3.1416 X (2/12)^2 = 0.087 ft^2

F = - 0.00238 slug/ft^3 X 0.087 ft^2 X (88 ft/s)^2 = 1.6 lb of force

If you want it in PSI, you need to find how many square inch for the 4
inch diameter (2 inch radius):

Area = 3.1416 X 2^2 = 12.57 sq.in.


1.6lbs/12.5sq.in. = 0.127 psi @ 60 mph


- ------------> While cfm might be more useful, I decided that this was
enough proof for me, and removed it.

BUT I did enlarge the hole as follows.

Take out your air cleaner and look,

you will see a racetrack shaped hole going into the wheelwell.

x x
----------------------------------------
/ \
/ \
| |
\ /
\________________________/

(these things never work on here- wish me luck)

however, the air box's hole is bigger than the hole in the
wheelwell.


x x
---------------------------------------- - - - -
/ \ m \
/ \ e \
| | t |
\ / a /
\________________________/_ _ l_ /

It is easy with a hammer and chisel or a hacksaw to get
another 2-3 square inches of hole. This cannot hurt
performance and will definitely allow for more air at high rpms.

This was my solution based on the above formula, Super Ford's
ram air tests showing the stock box with K&N filter and no
noise dampner flowing better than ram air and no change in seat
of the pants feel.

2 more cents.

-Tom