Cowl Induction

Ok so I want to cut this weekend but it's going to rain. In order to work in the garage I'll need to run the motor. Given the dirty state under the hood I'd rather not do this without an intake filter in place. So before the sparks can start flying I'll need to address the intake issue.

This is another project that has been thoroughly written up elsewhere. After relocating the windshield washer reservoir (Wheel Well Trimming Part 1) into the space previously occupied by the stock air box I needed somewhere for the little 4.0L to get air. This modification allows the dry side of the cowl to act as an air box. The benefits are twofold: 1) ambient temp air is collected vs hot engine bay air (hence the term 'cold air intake') and 2) the set up acts like a snorkel by relocating the intake to the hood level allowing deeper water crossings.

Finished product:

Parts for this project:

-Spectre 3" OD intake flex tube (linky)

-Spectre 3"OD x 6" intake tube

-Random air hose connector I had laying around

-AirRaid cone filter (linky)

-Frost King EPDM 1/4 weather seal from Home Depot

-Door edge trim from Auto Zone

Not many pictures on this one as most of the work was done at night. Pretty straight forward though:

1) Remove wiper arms and cowl cover. Notice the passenger side has a solid plastic backing creating the 'dry side' of the cowl. The reason for this is the cabin air intake vent is located over here.

2) Cut out the rectangular depression to allow access to the cowl. Should be about 5" wide to allow the filter element to fit. In hindsight I should have taken the extra metal out of the windshield side where there is a giant rubber gasket to provide cover. As it turns out I went towards the hood creating a small exposed gap. This will be addressed with the weather seal later.

Gap where I should NOT have cut:

Here the hood (top of the pic) is in the up position partially blocking the shot. The actual cut out extends towards the top of the picture a bit more than shown:

3) Cut a 3"-ish hole in the firewall. Widen just enough to pass the flex tube through. Hit with some rattle can (black truck bonus!) and trim out with the door edging to protect the plastic tube.

4) Connect everything. The outer diameter (OD) and inner diameters (ID) don't match up well. I used a couple turns of Gorilla tape around the OD to make up the difference then tighten everything up with hose clamps. 

5) Line the outer edges of the cowl cover with the EPDM weather seal. This is just extra protection from any water that may try to get into our new air box. Rain, snow that intrudes on the drivers side will flow out without (hopefully) wetting the filter. Also why I chose the oiled over dry filter in this application.

Here's a shot of the weather seal installed:

6) Drill a hole for the air hose fitting into the solid tube. This will be your new CCV tube connection. I used some random tubing I had laying around cut down to size. Fits tightly over the air hose connector and inside the existing CCV tube.

The additional interior noise from the intake is minimal at low throttle. I only hear it with the windows up, radio and fan off. Even then it reminds me of having static on the radio at a low volume. No whistle that I notice. Now, when you lean into the skinny pedal there is a very audible roar. I think it sounds beastly. ROAR!!!

Project Cost: $100

Total Build Cost: $3,655