Modification of the Stock Air Box
Installation of the K&N "Filtercharger" and
My "$4.97 Cold Air Set-up"
Note: This was smashed off the front of the car on day 2! So
there will be no "new" photos that are not blurry!
All images on this page link to larger images - not for the faint of
bandwidth... use your back button where applicable.
Sorry that some of the images are blurry - but the camera I use cost
about $1400 and with grungy "garage hands" there's little opportunity for
re-takes....
Basic Info:
Here's what I did to gut my stock air intake, install a K&N filter
(which WILL NOT fit without modification) and the (short lived) "ram-air"
set up I made with the stock pieces. I will not get into a big physics
dissertation here - but regardless of what anyone tells you or what you
choose to believe it is NOT POSSIBLE to get a "ram-air" set-up on a car
short of an NHRA sized scoop and appropriate ducting. You can, however,
get lots of fresh cool air into the engine, and that's what this mod is
all about. One of the Mustang rags and Steeda or Saleen or somebody did
dyno runs with a fan in front of several popular "ram air" kits for the
Mustang (and F-Bodies I believe) the results showed that the effect of
wind and the "ram air" scoop was negligible beyond the basic benefits of
just getting fresh air into the intake.
Don't send me emails - I don't wanna hear it - it's PHYSICALLY IMPOSSIBLE
to ram air into your engine from a little 10 square inch duct under your
car. Do some research, hop on the Cobra Owners email list and ask
one of the propeller heads that lurks there to give you the empirical data
on air flow & ram effect. Just remember who told you that "ram
air" as a means of boosting performance is a crock of $h!t. Cold
air is all you'll get - but that's a good thing!
Lastly, the idea of this page is to have you learn from my mistakes - poor
choice of adhesive, poor selection of a mounting point for the snorkel
(as seen above) and poor judgment when crossing a divided highway separated
by a large high-point in the road which led to quick demise of this VERY
cool looking and functional mod. But it WILL be back......
Originally posted at: The
TCCOA Tech BBS
What you'll need:
11 mm socket
Phillips & Flat Blade Screwdrivers
Small Pry Bar
Box Knife with NEW Blade
Dremmel Tool or Die Grinder w/ Small Barrel Stone
4" Flexible air duct: Deflect-o Corp. Part No. A038/16.
K&N Filter (P/N 33-2033)
Good RTV (room temperature vulcanizing) Silicone
Adhesive (NOT caulk)
Small Bolt, Nut, and Washer
Step One:
Remove the stock air box top & your air filter. If all you're
doing is installing the K&N you'll need to perform the mods below to
get it to fit without the risk of damage to your air box.
Remove the bottom of the air box from the car. Some folks may find
it easier to remove the 2 wire harness connections into the air box top
- mine were long enough to allow me to work with them in place. You'll
need an 11mm socket for this (note my "SideWinder" ratchet - well worth
the money!!) Once you get the 3 nuts off, the lower portion of the
air box will lift right out. Take your grinder (I used one of the
little jobs in the Sears Versa-Pack tool kit) and buzz about 1/8 inch from
the 3 tabs you see illustrated above. It should take you less than
5 minutes to do this. Clean everything. The illustration on
the right will show you the new clearance that will allow your air box
lid to go back on with minimal effort or fear of snapping something (which
many have done). Sadly, I did not get a snap of the poor clearance
the filter presented before the mod to the box bottom with the grinder........
but it was bad.
You'll see in the picture of the filters that the K&N is a little bit
larger than the stock filter on the outside dimensions. This is really
not the problem - what you don't see it that the K&N piece is nearly
TWICE as thick as the stock filter. The stock filter (Motorcraft
FA1061) is 9.5"x9.5"x3/8" - the K&N is 10"x9 7/8"x1/2". So much for
an "exact fit". What I did was to get a VERY sharp box knife blade an carefully
trim the entire top ridge off the K&N. Use a really sharp blade
& take your time - this thing is like raw gum rubber and it's really
hard to cut and a slip will injure you real bad. As you can
see I was able to get the gasket off almost in one piece. Above the
K&N you'll also note the 2 small tabs that absolutely must be trimmed
for this thing to fit - B-Bye Warranty!! Nice feature.
There are those that argue that this was a "drop in" installation for them
- and I'm really happy for them. All I can tell you is that
on my 1997 T-Bird there was no way this thing was going to fit w/o
trimming some of the height down. YMMV.
If you're only adding the K&N then bolt everything back together &
button it up - you're done. Be sure to note your mileage somewhere
for reference. I tend to clean my filter a bit more often that spec'd
- about every 3rd oil change (15K miles)
If you're going onward to remove the stock air silencer than read on.....
Step Two:
Now that the air box is out of the way we can get at the air silencer -
a major source of intake restriction IMHO. With the lower air box
gone you'll see 3 plastic "nut-like" fasteners - through which protrude
the 3 studs that both hold the lower air box in place and keep the air
silencer (in the fender well) snugged up to the fender. You'll need
to unscrew those completely so that the air silencer is free to fall into
the fender. In the illustration below the silencer is already gone,
and you can see all the way to my garage floor.
At this point you can either pull out the studs from the factory air silencer
structure & put the lower air box back in & button it up - or you
can continue on & create the ducted cool air intake that I did.
Either way - you need to pull open the fender liner to get the stock silencer
out of the fender.
To do this all you need to do is pull 5 screws (2 underneath, 3 in the
front of the wheel well) and remove one press-in trim panel fastener.
(If doing the cold air mod read below - you need to cut a hole first) To
get the screws out in the wheel well you'll need a stubby screwdriver -
or simply fire up the motor and crank the wheel to the lock. I don't
see much harm in running the car for the 15 seconds it will take to do
this - but by no means should you run the car for an extended period without
an air filter or the MAF harness connections off. Just say no....
Getting the trim fastener out is a dicey operation and should be done gradually
to work this thing out. A long time ago I bought a $2 pry bar from
Big Lots - it works great here, but any small nail puller will do, or a
broad bladed screwdriver. Even if you're cautious it's possible that
you'll destroy the fastener. You'll see in the image above that the
fastener consist of nothing more than a "friction fit" piece that expands
when you shove the plug into it. Be advised, these are a BITCH to
get back in, and really aren't meant for repeated use - you may even find
that even though you got it out just fine you can't get it to go back in.
This was, by far, the most aggravating piece of the removal/installation.
Pull open the plastic fender liner & the stock piece will come out
with a little twisting and turning. You'll see why if you look a
the shots of the stock parts below...
FWIW - I believe that my car ran better with nothing below the air box
bottom. I'd really need to see dyno numbers to prove anything out,
but the "seat of the pants o-meter" tells me it ran better with just the
K&N and the stock air box with nothing under it. I can say that
the car DEFINITELY had a much more aggressive sound to it when the air
box bottom was open. Don't ask me why or how - all I know is that
when I had the stock exhaust and the "open" air box bottom it sounded much
more aggressive than the ducted set-up and the Dynomax kit. Either
way the car Hauls Ass....
So if you're not going to do some kind of cold air modification as I have
below simply cut off the 3 studs mounted in the rubber isolators you see
in the image below. Use these to re-assemble the lower air box into
the car, add filter & box top and off you go. Or.............
Step Three:
Now you'll see where the big restriction in this system comes from.......
The illustrations above show the stock air silencer as it comes out of
your fender. Actually, that's not quite correct as I have already
removed all of the milky-white caulk-like sealant on the 2 "joints" that
hold these pieces together - you can see a piece of it I placed on the
seam in the photo on the left. You'll need to take a flat blade screwdriver
or small chisel and work all this "glue" off so that you can separate the
3 pieces - you'll re-use the piece that goes on the bottom of the air box
and the angle cut snorkel piece. Mine came off fairly easily, and
there's a few tabs & teeth that hold the pieces together, but you'll
see them when you start to work on it and you'll know what to do.
The idea here is to get rid of the piece in the middle.........
As you can see the middle section present quite the restriction to airflow.
I've no idea why FoMoCo designed it this way, but popular theory is that
this creates some sort of "Bernoulli Effect" to increase intake velocity.
Who knows - it's just way bad......
Another thing to note in the image above is the area that I've "ground
flat" on the angled snorkel piece. This is to allow me to provide
a flat area for mounting this piece under the fender on the opposite end
of the duct that leads to the bottom of the air box. You'll need to drill
a small hole in this snorkel piece to use the small nut-n-bolt that hold
this to the bottom of the car.
Step Four:
Now you need to saw a hole in the lower trim of the car to place the snorkel
in the air path. The image might be a bit confusing at first - just
realize you looking at the underside of my car. I used a hand saw
(pictured) from the Versa-Pack - it took me all of 30 seconds, and the
image below will show the "random precision" I used to get an opening large
enough to accommodate the back of the snorkel pictured above......
Clean everything. One word of caution - keep this hole as far back
as you can - the vapor canister is right above and you don't want to create
any interference problems. You also have to worry about smashing
this thing into the ground - which I did....... And yes - the piece smashed
so completely I couldn't even find any pieces later the same day.....
Step Five:
Now you'll need to join the 2 pieces of the stock air silencer back together
- using the flexible 4" duct I outlined above. I got mine at Home
Depot - so it should be easy to locate. I made the mistake of using
a caulk/sealer to glue the duct into the piece that goes below the air
box (you'll want to do that first) - be sure to use a really good RTV silicone
glue. I found that mine came apart even after a night to cure - it
just wasn't made for this kind of application. The 4" duct will fit
into the stock pieces with a bit or room to spare. If I was
doing it again I'd probably use 5" duct - but they didn't have it when
I went and the 4" seemed nice & sturdy & certainly better than
the stock crap! A five inch duct would go over the outside of the
stock pieces as opposed to the inside which is how the four inch connects.
Bigger, Better Faster, MORE! Anyway - the image below will show you
what the duct & lower air box funnel piece look like once you've joined
them. Now you need to get back under the car & work the piece
back into the fender cavity. Since you've cut a hole & have everything
apart it should go in with a minimum of coaxing. You'll be able to
duplicate the nice "gentle bend" in the photo below. The huge (dirty)
black thing in front of the duct is the aforementioned fuel vapor canister
- one of the reasons you want to cut the hole for the duct far back towards
the wheel. The other reason to do this, as I was to find out 2 days
later, is that the "intake" portion of the duct will sit fairly far forward,
and it's going the be quite susceptible to "road geography" and you run
a good risk of bashing it to bits as I did here on the far-too-hilly roads
of PA.
After you glue the duct into the lower air box piece & let it dry you'll
have to work it back into the fender and go through the process of first
working the studs into the plastic retainers and then replacing the bottom
portion of the air box and the 3 nuts that then hold THAT piece in place.
You can also go ahead & install your K&N or (gag) stock filter,
and snap the lid back on the air box. DON'T FORGET to reconnect your
MAF & Temp harness connections if you pulled them to get the air box
top out of the way....
Step Five:
Now you've got to get back under the car & trim the duct to length
& get the intake screwed/glued in place. All I did was "eyeball"
the plastic duct piece, and buzz a screw hole in the lower fender liner
& the duct itself so that when attached the alignment was such to give
the duct, which has a nice angle cut to it, a decent "scoop" of the airflow
as it passes under the car. The photo at the top
of the page should explain this fully. I used a small machine screw
with decent sized washers (to spread load) on either side. I also
used a decent bead of silicone, but again, it wasn't the correct type for
this application. If I were putting in a tub surround I'm sure that
it would have been fine - unfortunately I was not putting in a tub surround
and the stuff was far too "soft". The idea here was to give the duct
a slight bit of "give" so that it could withstand the occasional low speed
meeting with a parking bump, etc. However, it was not sufficient
give to allow for a 40 MPH meeting with a large "hump" I have to cross
when heading into work. It splattered so completely that I couldn't
even find pieces of it later in the day....... all I have left is the small
piece that remained under the machine screw...
Anyway - the duct is easy enough to trim - all you have to do is "unwind"
it to a spot fairly close to the bottom of the fender. Try not to
unwind too much, but if you do don't worry - keep in mind the duct is a
collapsed 8 foot pipe! I was able to trim this with a pair of heavy
duty shears.
Step Six:
The last step is to glue the lower portion of the duct into the snorkel
piece, and attach the snorkel with the small nut & bolt. I left
a decent amount of duct below the fender as you can see in the photo above
(actually a little less), and this tucked neatly into the snorkel piece
& gave me a decent area to apply my ineffective glue. Now simply
button everything back up & you're done. Viola! (or "whola" as
the case may be) you've got a means for getting plenty of cool fresh air
into the engine.
Comments:
Above is a photo of the stock MAF, and the convoluted air path that goes
into it. While it's not the best angle, you can see the HUGE amount
of scrap metal in the center post - this is part of the MAF mod that's
detailed at The
MN-12 Performance Site as well as many Mustang sites. This certainly
seems to be a worthwhile modification and will be next (or nearly next)
on my list.
There you have it - one man's story of a cold air conversion - from stock
to ROCK!
