Another Cowl Air Intake write-up

[EricsXJ]

I just added the following write-up to my website. I thought I would add it here so here is a copy and paste version:

Cowl Air Intake
3/28/09

For several years I have had an ARB Safari snorkel as my intake. It just so happens that the cage I am getting ready to build is going to have a tube running up the outside of the A-pillar, right where the snorkel is. So as much as I like having the snorkel, it has to go. That left me with a new problem - what to do for an intake? I didn't want to go back to any intake (stock or cone filter) that gives up the ability to cross deep water. After looking at what several other people did, and concluding that no matter how I tried I would not be able to keep the filter dry if it was inside the engine bay, I decided to relocate the filter to inside the cowl.

The "cowl" is the hollow area between the dash and the engine compartment. Inside the driver-side section of the cowl is where the windshield wiper motor is. The passenger-side section of the cowl is mostly vacant and that is where the HVAC system draws air from. As seen in the photo below with the cowl grill removed, the driver-side is open (for air to enter) but the passenger side is not open on the top (to prevent water from entering right over the HVAC duct).



The passenger-side cowl is an ideal spot for the filter, however to get it in there we need to cut a hole in the top.



Even though a hole was cut in the top, not much water will enter here because the cowl grill does not have any vent holes on that side. You can see the underside of the cowl grill in the photo above. Mine is a 2000 and older models may have vent holes here (I'm not 100% positive). But if that is true in your case you could find a way to seal them off, leaving only vent holes on the driver-side.

Now before going any further, let me give you a parts list of what I used. You may be able to find this stuff cheaper, but I chose the convenient route and bought the main parts at Summit Racing since their warehouse is close by.

item part # cost
Airaid cone filter Simmit AID-700-430 $31.95
3.0" OD exhaust pipe Summit SUM-640030 $12.95
3.0" ID connector Summit WLK-41892 $15.95
3.0" x 30" Spectre flex tube Summit SPE-8741 $25.99
3.0" black ABS pipe Home Depot $5
misc hose fittings and clamps Home Depot ~ $10

I also found this write-up http://www.cardomain.com/ride/325707/7 (thanks Balloo93) which gave me the idea to use the 3.0" exhaust pipe. I found a slip-fit pipe like his but it was only 10" long. I needed about 2 feet which is why I ordered the pipe from Summit. In hindsight I could have saved a lot of money by ordering the 10" slip fit piece and using the full length of the 30" flex tubing, but oh well.

Here is the Airaid cone filter. I chose this filter because of its dimensions. It has a 3 1/2" flange, 4 5/8" base, 3 1/2" top, and is 7" long. It fits just inside the cowl, but it isn't too small of a filter either. I mounted it to a short section of 3.0" (ID) black ABS pipe because this pipe has an outside diameter of 3 1/2". Then added a short section of exhaust pipe for the flex hose to mount to.



Here it is tucked into the cowl.



Here is the flex hose coming through into the engine bay. I used a 3" hole saw for the opening and had to open the hole up a bit more to fit the flex hose through. Also to make room for the tube I had to relocate the under-hood light, relocate the EVAP purge solenoid, and move the large loom of wires out of the way. It was not hard.



And here is the rest of it going to the throttle body. As indicated by Balloo's write-up, the diameter of the exhaust coupler I used is exactly what you need to attach the stock "accordian" throttle body tube. I welded the coupler in place but it was such a tight fit I think it would have been just fine without welding it. I also plumbed the CCV tube like in Balloo's write-up.



Impressions

I was told by a friend who also had his intake set up this way that it might be loud inside the cab. He was right! When I first started the engine I was shocked at how loud the sucking sound was coming through the vents. After a few seconds the sound diminishes to where you can barely hear it, but I was still concerned that the sound might be an annoyance. Well after driving on the highway and on a trail ride, I had completely forgotten about the sound and didn't notice it at all. For the person who is overly concerned with noise in the cab, this modification might not be right for you. As far as any "performance" gain, I didn't notice any increase or decrease, but I wasn't expecting any either. As side benefits to this modification, I am still sucking cold air and I can get rid of the stock airbox, creating more room in the engine bay. Overall I am very happy with this modification.

[Jameslol]

The only problem i see there is the metal tube sitting on the engine, its just gonna heat the crap out of the air.

[nrpalmer32]

I like how it goes straight from the TB to the passenger side, good twist to the cowl intake. Definitely the shorter the better throttle response. When I get home I'll have to look into that, I'm not a fan of running it to the driver side area. Oh and my '87 has the same closed section on the cowl like yours, its only vented on the driver side.

[EricsXJ]

Originally Posted by Jameslol

The only problem i see there is the metal tube sitting on the engine, its just gonna heat the crap out of the air.

Actually no it doesn't. The hottest part of the engine is directly over the exhaust manifolds. This is on the other side of the engine and the metal tube just barely rests on the valve cover. After running the engine you can put your hand on the tube no problem. It does not get hot.

[RWKXJ]

Looks good Eric! I may have to re-instate my cowl filter, my k&n never fit in there really great, but that filter looks like it fits good! I never minded the extra noise too much, but I am not sure the lady liked it too much! Can't wait to see the cage that we will likely end up duplicating in my rig!

[3xratedxj]

Enough about this cowl filter... Lets get into the cage goodness

[hotrod_hooligan]

I had been passively looking at this mod, but hadn't seen a way to keep the filter dry. Definitely going to look deeper into this now.

[SHUG]

wouldnt rain water get down in there....

[conrasm]

I was thinking that too.

[nrpalmer32]

Hey Eric, now that you've cut into that passenger side, do you think a filter that has a base filter dimension of 5" would fit in there?

[EricsXJ]

A few things:

Going back to the heat issue - I drove the Jeep home from work today (20 minutes highway) and after getting home I popped the hood and put my hand on the tube. Most of the tube was surprisingly COOL to the touch. The portion of the tube right above the valve cover was only luke-warm at best. No way it is heating up the air flowing through the tube...

Water. Rain is not going to be an issue. Even if the filter was right beneath the vent, a little rain water will not hurt. Moisture mixed with air can go right into the engine no problem. A solid wall of water cannot. Remember the cone filter, as most are, is cotton-gauze material which won't be damaged if it gets wet. A paper filter will get damaged if wet. Also realize that water regularly gets into that cowl area anyway and drains out in a few places.

Originally Posted by nrpalmer32

Hey Eric, now that you've cut into that passenger side, do you think a filter that has a base filter dimension of 5" would fit in there?

In mine it won't. You might be able to physically get it in there if you squish it to get past the opening that you cut, and then attach it to the hose. The way I made mine was to be able to pull the flex tube out a little, attach the filter, and then insert it in there. By doing it this way I can't squish it to get it in there. If you look around the perimeter of my cut, you will see a section I had to cut a little wider. That was to be able to fit it in without squishing it.

[Gman_VIMB]

Nice work... looks like a good way to get dry cold air in the XJ with a higher flow filter and really few downsides.

Nice mod!

2000 XJ you say....hmmmm.

[EricsXJ]

Originally Posted by RWKXJ

Looks good Eric! I may have to re-instate my cowl filter, my k&n never fit in there really great, but that filter looks like it fits good! I never minded the extra noise too much, but I am not sure the lady liked it too much! Can't wait to see the cage that we will likely end up duplicating in my rig!

Thanks for the inspiration!

[Teal96XJ]

Awesome wright up!!!!!

I have been thinking of doing this myself because my cone filter gets wet pretty easily.....

[nrpalmer32]

Yeah I noticed the little extra cut along the front side of the cowl to fit the filter. I was originally looking at the AEM Dryflow filters but they have a really wide diameter of 6 1/8" at the base, then looked at a couple other brands. Finally I found the one I want, the good old K&N. Its a little shorter than yours but it has the inverted filter end on it. It has a 3.5" flange, 4.75 base diameter, 3.5" top diameter and 5" long, so that should fit about the same as yours? What do you think? Also I wanted to thank you for all your write-ups and stuff! I, as well, am really looking forward to your roll cage!