Help with Cowl Intake - Page 2 -
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post #16 of 23 Old 08-10-2005, 07:55 AM
i wear foil underwear too
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i think that you guys are overthinking this.

anyway, you could use the stock airbox top to protect the filter.


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post #17 of 23 Old 08-12-2005, 11:39 PM
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sorry for not contributing to this earlier, been real busy

anywho, I got my airbox from a '92 Buick Century (I think) with the 3300 engine. I also grabbed some airbox tubing from another buick (a regal of the same era). Both sides of the box are 3" diameter which is actually too large for a 2.5L Jeep imo (more on this later).

From the TB, I used the stock 2.5" rubber flex piece which is about 4" long, then connect to a 2" to a 3" PVC converter. Then a 3" 90' corner. Then a 18" piece of 3" PVC pipe, then a piece of that Regal flex hose, then the airbox.

From the airbox, I put another flex piece on, then a 6" piece of PVC that goes through the firewall, then a sharp 90' and now a 3" to 2" reducer.

Now what I did wrong;

1) 3" is too large for the 2.5L as it just doesn't need that much air and it causes the air to slow down too much, thus allowing too much sound to escape the air intake system. That is why I now have the reducer on the end. Before the reducer the sound was extreme! At 1/3rd throttle there was a deep rumble that was like a V8, at 2/3rds the whole Jeep started vibrating badly. The reducer removed most of the vibration, the sound has grown on me

2) This maybe related to the 3" as well, but every once in a while, I'll have a small backfire. Doesn't cause any CEL or other problems, but it started right after the install.

Things, I'd change ;

Obviously, I'd use 2.5" plumbing and have enlargers just at the airbox. I'd also increase the length of pipe used in case that's the reason for the backfires. (no too sure about that one)


- Watch the height coming off the TB
- after the firewall, I made a hard right turn to turn the air flow towards the vent opening, but that can interfere with the wiper arms if you're not careful.
- At the end of the tube in the cowl, I cut the pipe at a 45' so it made a overhang at the top, just in case water came straight down onto the pipe it would have less chance of getting into the airstream. BTW, I live near Vancouver B.C., a MAJOR rain belt... I have driven through SERIOUS rain storms with this setup and never had any problems. Water does NOT get in... period.

post here for addtional questions,... I'll follow this thread.
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post #18 of 23 Old 08-13-2005, 12:10 AM
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Has anyone thought of making a setup with detachable pieces to run the intake under the hood on the street, but then through the firewall into the cabin for offroad?

99' Sport: 33's with 3.5" RE & 8k lbs winch
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post #19 of 23 Old 08-13-2005, 12:21 AM
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if you read my post above, I mentioned a problem with noise. If you ran the intake into the cab, I'd think the noise would be so bad, you couldn't hear much when you stepped on it. Take some dryer vent hose and run it into the cab with the engine running to hear what I mean.

Also, you might have bad smells coming back from the system (from the CVC (PCV) system for sure).

I haven't heard of anyone doing that, doesn't mean you shouldn't but I'd consider the above first.
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post #20 of 23 Old 08-13-2005, 09:36 AM
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Can you post any pictures raskal????

1999 Jeep TJ on 1 tons (OLDER)
2003 Jeep Rubicon (OLD)
2008 Jeep Unlimited X (NEW)
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post #21 of 23 Old 08-13-2005, 10:45 AM
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what the heck, it's 9am I can go outside in my gonch and take pics on my heep, the neighbors won't mind

If you want clarification of any pics, please ask but I never took any pics inside the cowl because I don't feel like taking it all apart again, it's not that exciting anyways. The only exciting part of that is when you just figured out you drilled a big *** hole in your Jeep's firewall!!! (future holes become much easier)
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post #22 of 23 Old 08-13-2005, 04:43 PM
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I didn't want you to take it apart, I just wanted a pic of how your system looks in the engine comparment and where you went through the firewall at to the cowl.....

1999 Jeep TJ on 1 tons (OLDER)
2003 Jeep Rubicon (OLD)
2008 Jeep Unlimited X (NEW)
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post #23 of 23 Old 08-14-2005, 08:21 AM
rock dawg
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Originally Posted by bondo303
A guy in my club just did this.

so that jeep cant be driven in the rain right?
Thats My Jeep So I can answer a couple of questions.
The air filter is to the right of the cowl grates so rain drips right next to it.
The drain is lower than the filter(that took a lot of beating to the cowl floor) so the water runs away from the filter.
I used a dual cone filter(look at the pic) to get the airflow I neded.
I used an outerwears pre-filter over the airfilter. you could spray water at it and it runs right off.
As far as driving in the rain - No problem.
The performance benefit of getting cool fresh air is very noticable, especially in hot weather.
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