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DIY Ram Air Duct for Cold Air Intake

If you already have a front mount intercooler and a cold air intake, you can add a ram air duct to take it one more step. This will further isolate the intake air from the heat of the engine air take advantage of compressed in front of the car to force more air into the intake.

Fiberglass Cloth and Resin
Sheet Metal
Flexible Tubing - 4” ID about 2 feet length
Hose Clamps – (2) 4”
Foam Blocks (I like the green floral foam)
Duct Tape
Sheet Metal Screws
Spray paint – Flat Black
Glue- Hot glue gun preferred
Electrical Tape
Sharpee marker

Screw Drivers
Drill and 1/8” Bit
Tin Snips
Utility Knife
X-Acto Knife


Make the Intake Funnel

1. Glue 2 floral foam blocks together to form one larger block. I like hot glue.
2. Remove the paisley shaped bumper cap and use it for a template. If you don’t have a Right one you will need to trace the left one and reverse it.
3. Using a Right cap, simply press it into the foam to leave an impression or use a tracing from a left cap reversed and trace it onto the foam. IMPORTANT: Draw a line all the way around the impression spaced ¼” out. This will leave room for the funnel to fit around the bumper opening.
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4. Fit a rolled piece of sheet metal or rigid cardboard into the 4” tubing you will be using and tape it to form a ring.
5. Use the ring to create an impression on the other side of the foam block. Be sure to align it so that the funnel will not interfere with intercooler piping behind your bumper.
6. Use an x-acto knife to cut straight down all the way around both the paisley shape and the round shape. This will shape your mold to allow about a one-inch straight section to fit over the bumper opening and a section for tubing attachment on the other side.
7. Use a long, thin knife to shape the mold for the funnel. Smooth it out until you are happy with the shape.
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8. At this point, I recommend wrapping the mold with electrical tape for easier release. I did not and got a somewhat rough texture.
9. Precut fiberglass fabric with a utility knife into strips 2” wide. Then cut into pieces 6” long.
10. Cover the mold with fiberglass strips and resin. I recommend strips 2 inches wide and 6 inches long going top to bottom, overlapping about 75% of each strip. This will result in about 4 layers of fabric. This is minimum and will result in a very light and somewhat flexible funnel. Use more strips and overlap more if you want a heavier piece. You can insert a scrap of wood or metal into the mold and clamp it to keep it still while you apply the fiberglass.
11. Let it cure.
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Make the upper hose attachment point
1. Cut a strip of sheet metal about 13” long and 4” wide.
2. Roll it so that it fits into the end of the flexible tubing.
3. Leave it in the tubing and drill a hole about ¼” from the edge in the overlap area.
4. Rivet it.
5. Remove the ring and squeeze it so that the un-riveted end is somewhat smaller. Compare the size and shape to the oval hole in the in the shelf under the air filter. Bend the ring until you have the shape very close.
6. Drill and rivet about an inch from the first rivet.
7. Draw a line around the outside of the ring with a sharpee.
8. Cut slits from the outside edge to the line. When mounted under your air cleaner, this will allow the fitting to angle away from the fender splash guard and toward the bumper opening. Cut the slits about ¾” apart and cut at an angle removing a thin triangular piece between each tab.
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9. Bend the tabs in at about a 45° angle.
10. Fit the piece into the air filter shelf opening from the under side and bend all the tabs over on the top side.
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11. Tape off the opening on the side going into the fender. Close other openings. Consider stuffing the openings with foam or similar material so that it can pop out and provide an alternative air source if you should ever drive you bumper under water.

Finish and mount the Funnel
1. Cut excess fiberglass material from the ends of the funnel mold.
2. Chip out the foam mold.
3. Clean it up if needed.
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4. Spray paint if desired. The inside only will be visible.
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5. Fit the funnel over the bumper opening from behind.
6. Drill a couple of inconspicuous holes and secure with sheet metal screws. I found the only easy way to do this is from the front of the car drilling through the inner part of the bumper opening, then though the fiberglass funnel.
7. Secure with sheet metal screws.
8. Cut the flex hose to the right length. Estimate to the longer side, obviously.
9. Secure the hose to the upper mounting point you created and to the back of the funnel with hose clamps. You will probably need to remove the fender splash guard (I did).
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10. Reattach the air filter.
11. Close the hood.
12. Drive

Ron Tew

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