I thought about that but in the end, it pretty tight, just the small openings where the refrigerant lines go thru. I also like to keep the ducting easily detachable for cleaning or if I need to remove it to work around that area.I don't think there is enough ram air entering the duct that would provide enough positive pressure that would require sealing up the duct. I worked as a A/C install and repair tech for most of my younger days and switched careers for computer networking. Makes as much or more money for next to nothing hard labor.

 

Why not take the next step
and start measuring your IAT and MAP sensors
to see whether there is an actual improvement
with this modified air intake?

The intake air temperature sensor
and the manifold absolute pressure sensor
tell you
"the truth"
about intake modifications.

old posts that might be of interest:
=====
Page 415 of the Bosch Automotive Handbook, 5th edition

http://tinyurl.com/yplr3d

has the two equations you need
to see how horsepower and torque change
when either temperature or pressure change.

For temperature the offical equation
used by Americans (SAE) Europeans (ISO) and Japanese (JIN)
is:

{ Temperature Before + 460/Temperature After +460} raised to exponent 0.6

you need a scientific calculator to do this
but there is one built into every Windows computer
under Start...Accessories

As an example,
say that your re-locate your air inlet to a spot where the air temperature
drops to 80 degrees
when before the air coming in had been 100 degrees.

{100 +460 divided by 80 + 460} raised to exponent 0.6

={560/540} raised to exponent 0.6

= {1.037} raised to exponent 0.6

= 1.022

You mulitply this number times your horsepower or torque
so if your engine.
If your engine makes 230 hp at peak
1.022 times 230 = 235 horsepower with the 20 degree lower air temperature.

You may have heard the 'Rule of Thumb' that each 10 degree F reduction in air
temperature improves horsepower by 'about' 1% and the equation above is where
that comes from, but is more accurate

For corrections when the pressure changes
the following equation is used:

{absolute pressure after/absolute pressure before} raised to exponent 1.2

As an example
say that the weather is changing where you live
and one day the weatherman says the pressure is
29.5 inches of Mercury as a stormy "Low" passes over
then the next day a clear sky "High Pressure Area" passes over
and the pressure rises to 30 inches of Mercury

{30/29.5} raised to exponent 1.2
{1.0169} raised to exponent 1.2
= 1.0204

It is important to realize
that built right into your engine
are IAT (intake air temperature)
and MAP (manifold air pressure)
sensors.

Your IAT and MAP sensor outputs can tell you whether an aftermarket air intake
has helped or hurt your power output. You can read these sensors
yourself by using an OBD-II scanner, or a cheap electrical multimeter.

You are correct to suspect that most CAI's
only make more noise and have flashy colored parts.

Want confirmation about this from a CAI manufacturer?

Well right now KN Filters is running an advertisement in the various hot rod
magazine saying that a typical paper air filter from the factory creates a
restriction of about 2.8 inches of water....and when this filter gets really
dirty the restriction rises to about 12 inches of water restriction. The KN
advertisement has a dyno graph showing that this can cause about 11 hp power
loss on a high horsepower engine.

The pressure of the air around us is about 404 inches of water
so KN Filter is saying that the pressure is changing from
404 - 2.8 = 401.2
to a new pressure of
404 - 12 = 392 inches of water

Play around with the equations above
and you can find out what the actual horsepower of the engine KN was using
was....and then confirm it by looking at the dyno graph in the advertisement.
=======
Heard of the 'Ram Air' effect where the speed of the air hitting the vehicle
builds up pressure in a forward facing air duct and helps 'supercharge' your
engine a bit. ?

Well, at 'typical' street speeds the effect is very very small.

The formula for that is:

Inches of water pressure from Ram Air = (mph) times (mph) divided by 2025.

So at 70 mph the ram air effect is:
(70 mph) times (70 mph) divided by 2025 = 2.4 inches of water.

So the very best possible air inlet tube designed for Ram Air would actually
have a positive pressure of 2.4 inches of water.

How much pressure is an inch of water ?

One psi of pressure is equal to about 28 inches of water.

You can get this by dividing the cubic inches in one cubic foot ( 12 x 12 x
12 ) by the weight of one cubic foot of water ( 62.4 lbs).

The air pressure around us is averages about 14.5 psi at typical heights above
sea level.

So another way of looking at it is that the air pressure around us is about
400 inches of water. ( 14.5 x 28).

So the best Ram Air system at 70 mph gives you a boost of about 2/400 or one
half of one percent. Small.

Ram air started in airplanes where it means more. An airplane going 300 mph
gets a boost of:

300 x 300 divided by 2025 = 44 inches

This is a percentage boost of 44/400 or about 11%

Want a challenge?
Consider your tires.
Some strange facts:
At 70 mph the center of your tire is moving 70 mph.
The bottom of your tire where it 'grabs' the pavement is moving at 0.1 mph
The top of your tire is moving forward at 140 mph.
If you could put a 'Ram Air' inlet right at the top of the tires (where it is
horribly dirty and wet) you could get a significant air pressure boost.....

 

Man, I love you geek engineers! I am a geek at that stuff myself and now you got my mind all pondering over this techno stuff.

 

I have decided to build an intake for my self and i hope to have a pic up soon no money will be spared

 

I did the same thing (all most) I love the power gain. I run a drop in K&N and find I have to clean it about every 2 oil changes. A lot of crap gets on the filter. I havn't had the air filter plug up with water or snow yet. I would be more wery about the snow tho.

 

Hank,

1/2 of one percent is still a good positive. As air being sucked in to the engine behind a filter is in a negative pressure vacuum state. So with RAM air effect, if we can bring that negative vacuum state to a positive state, even 1/2 of one percent, that is still some good power gains.

 

I do agree that if we are talking about racing
a vehicle with even the slightest advantage
will win races more often.

If we are taking about getting a pickup to do a better quartermile
and...like many at this forum...intend to trade the truck in a few years
then it makes sense to remove the air filter completely at the track and gain 3 to 4 inches of water more air pressure into the throttle. You can use the equation above to calculate how much horsepower you will gain when the air pressure rises from 396 to 400 inches.

At the race track
the guy who removes his filter completely
and has a simple forward facing duct pick up the air in front of the grille
will beat the guy with the expensive aftermarket CAI
something like 4 out of every 5 runs.

He won't beat the CAI owner every time
simply because traction at the starting line on trucks/suv's is so iffy
that it adds uncertainty to each quartermile run.

One sign that owners at forums concentrate on the wrong mods
is that there are hundreds of posts on CAI's, throttle body spacers, etc.
and very few posts on traction enhancing mods to the suspension.

 

I do agree with you on a racing standpoint that traction is a very big deal, however 99% of Durango owners don't race. We're looking to pick up a few mpg or some throttle response, not shave a tenth off our 60 foot.

 

I can say that traction is not an issue for R/T owners. We have full time AWD so all 4 tires are planted when we nail the gas pedal. I not even get a chirp off the rubber when I go full throttle.

but yes, we are mainly more interested in fuel mileage savings and some Extra Umfph when we are cruising on the highway.

 

Please don't get the impression that I advocate drag racing pickups or SUV's.
I am firmly in the
'trucks are made for hauling stuff safely and economically'
camp.

Even when testing for engine improvements
I prefer accelerating up the same steep hill as a test
at legal and safe speeds.
This can be even more sensitive and accurate
than quartermile runs
because it stretches out the time
so that smaller improvements
can be more easily spotted.