I'm looking at modifying the bottom part of the factory air box and putting a truncated cone Spectre air filter in there. Just trying to figure out the plumbing. I noticed a square panel in the bulkhead behind the left headlight that looks to be a match up to the square entry hole in the factory airbag. Did they have a tube that ran between the two in earlier models? I know my '87 FSJ GW has a connector from the air cleaner box to a hole in the bulkhead.

IN the interest of getting more cold air into the intake area I am wondering about replacing the large square turning lights with something physically smaller, maybe some sort of LEDs. Then using the rest of the opening as an air intake area. has anyone else tried this on a DD.

Still tinkering, plotting, and prioritizing.

 

A cowl intake will work better and you can buy one from two different companies.

 

X2 Or make your own for less than $20. Plenty of how-to's on the subject if you search for it.

 

But most of those diy types look like crap,They use pvc pipe or the flex hose that looks like something off a clothes drier.

 

I initially considered a cowl intake and decided against it very early on for my Highway/daily driver Cherokee.

To me the point of a COLD air intake is to deliver cooler O-rich denser outside air to the combustion chamber. The cowl intake systems DO deliver outside air from the areodynamic high-pressure area at the base of the windshield. However the longer required metal or plastic ducting passes over the main source of heat in the vehicle---the engine. So it actually delivers engine heated air to the throttle body unless it is carefully insulated---and there goes the COLD air advantage. To me the biggest advantage cowl system is that it frees up the air box space for on-board air compressors or welders or other stuff that serious off-roaders find necessary, or that it just looks Off-Road Cool. I have also been informed that it is also rather noisy especially for a heavy use daily driver.

I'm not terribly interested in arguing the aesthetical values of commercial systems versus DIY. I was asking about the use of the use of potential front openings on the drivers side of the engine compartment. I'm assuming that it represents the most efficient path with the minimal exposure to the hot engine compartment environment. As my own Cherokee is a daily driver with relatively little deliberate off-road use I don't need to free up that space for equipment I don't need. And I'm an old guy with little care about "appearances". There might be some advantages with a higher air intake placement perhaps not sucking in water and debris as much as a a lower one might; but if the water in the streets and roads is gonna get that deep, I'll just stay home.
I have done some work with engine compartment airflow management for EAA aircraft where ducting and moving cold outside air is critical to the survival of air-cooled engines. I have never seen any actual measured air delivery figures with volume pressure and temperature for Jeep systems. I know the carbs used to have CFM figures but don't recall seeing that for injector systems. I suspect that our 4.0 injected engines manage to "suck" all the air they need and "ram-air" effects are really not a big factor. (For what it worth to the discussion I have a supercharged 98 Buick Regal and participate in an E-forum or two for them. the serious racer-types among them use either a low front end or even a port through the fender liner for a cold air intake---and they suck a WHOLE lot more air than our injected engines. However they are not intentional off-road vehicles).
Cold air induction simply provides a source for higher O-density air rather than using the hot engine compartment air. I have chosen to use the factory air-box area for that purposes

 

Not true..here is a vid of my engine shot with a thermal cam. The engine has been running for a while in a hot garage.. You can see that the Spectre cowl intake is cool to the touch while running.. Yes it gets a little warm when it just sits and motor not running. But once you start the Jeep it cools down to the touch in less then a minute because of the cold air from the cowl cooling the cowl intake down.

Time 0:24 see how cool it is.


My Jeep is a DD, Its only loud when getting on the gas hard..most of the time you hear just a sucking noise, but real faint. I don't really hear it anymore, You get use to it.

You can hear how quiet it is when I let off the gas at the end of the vid.
The Jeep also has a 62mm throttle body from Jeepers and creepers

 

THANK YOU!!! now that is informtion that is useful with some reasonably well backed facts. I appreciate that very much. I'll check out their site. I'm sending you a PM.

Edit: they don't list a Cowl kit, but a lot of parts. I'm not quite ready to tear the cowl cover off quite yet, I'd need to get all the parts together first and do it all in one day----It IS my daily driver right now. Can you tell me what the dimensions of the cowl space are----or which Spectre filter you were able to fit in?
I have a few parts I was going to use on the airbox modification that I might be able to use or exchange.

Do you have to disassemble the whole cowl top to clean the filter or have you split it into two sections?

 

Here are the pics of what the Spectre cowl air intake looks like. I think ppl are finding it hard to find, something to do with out of stock and discontinued, not sure on that.





The filter on the Spec is in the middle.. the big pill looking thing.




But you can see how people have done the DIY way and it works just as good.





Hope this helps..

here read this>>>>>>>> this way allows you to keep the stock box and filter

 

You say the hottest area is over the engine that is not correct. The hottest area is on the drivers side over the exhaust manifold and headers (check with an IR temp gauge).


One of the nicest looking homemade cowl intakes are made using turbo materials silicone and aluminum very little heat soak. But Duma has many times shown the results over what some claimed were not true.

 

As the video shows, the air isn't heated because it doesn't sit in the intake long enough to absorb any engine heat. The cowl is actually a very good place from which to pull air because of the back pressure against the windshield. The vehicle is designed to take advantage of that high pressure area to help pump air into the cabin, and the cowl intake takes its air from right next to the cabin air intake.

The Spectre intake is out of stock at the manufacturer. The last word I saw posted was that they are supposed to have a new supply by October 1, but they also declined to guarantee that date. So you can wait a month or so and see if they start up production again. If they do, the best deal I have found was to buy it from Advance Auto with one of their coupon codes. I got mine for $117 shipped to my door.

Trail Head Off Road (THOR) also makes one that is slightly different. The Spectre puts a reusable cone filter in that big pill you see in the middle of the pipe. The THOR intake puts the filter in the cowl itself, making it a little more difficult to reach for maintenance. However, the THOR uses smoother turns and should perform just as well as the Spectre. The THOR intake is also apparently on back order, but there was a message on their site that said they're still taking orders and will resume shipping soon.

You also have the option of buying pro parts and making one yourself. I'm not talking about the homebrew DIY stuff you see. If you have a little bit of fabrication skill, you can buy most of what you need from an exhaust parts supplier like Silicone Intakes. I totaled it up a while back, and it comes out pretty close to what you would pay for the Spectre or THOR.

On to your original post...

There's no point in doing that. If you want to replace the filter, just use a drop in panel filter instead. You get no advantage from putting a cone in the same airbox. A cone will not flow any better than an aftermarket drop-in panel. Also, part of the purpose of that airbox is to give the panel a protected area where detritus and water can settle to the bottom without being sucked into the filter. Relocating your filter further down defeats the purpose of that design.

As a matter of fact they did, on some Jeeps. The earlier ones had a hole there from the factory. The later ones had a solid bulkhead without the hole. Some of them had a connector pipe that went from the hole to the intake box, but not all. I'm not sure what years or models had that pipe, but they seem to be pretty rare. I've never once seen one of those connector pipes in the junk yard.

In the later XJs they filled in the hole in the bulkhead in order to prevent cold air from reaching the intake box. In fact, on some of them Chrysler put a pipe in the front of the airbox that wraps back around the side of the box to pull air from next to the exhaust manifold. I found one of those in the junk yard and grabbed it just for giggles, because otherwise people might not even believe Chrysler did something that stupid. This was all done for emissions purposes, to get the engine up to operating temp as quickly as possible.

I think you'd get better results with a lot less effort with the cowl intake, with the advantage that your intake is higher and less likely to ingest water or become obstructed by snow or bugs.

 

All good points. I'm pretty well convinced to go with the Cowl system. though that one running form the back of the box to the cowl on there drivers side was a pretty slick installation too.
I'm looking at the Spectre parts at local branches of a couple national DIY car part shops. I'll have my local muffler and suspension shop cut me a piece of 3" seamless tubing for the long runner. But he can't do good 90-degree bends with 3" I may be able to get him to make the bend on the end of the runner piece to go up against the cowl bulkhead though and have him weld a small bung in for the PCV tube connector. Unfortunately the nice shiny Specter elbows and other parts all look to be chrome flashed plastic of some sort. the part I found to mount on the Bulkhead seems to be metal and it has a capped port for an O2 sensor. then I'll need another short 90 elbow and a connector to mount to the filter. I have found 2 sizes of cone filters, one is Spectre with about a 6" diameter and then there is a K&N with a 4 " diameter (at half again the price) that I know will fit. I'm just not sure about the 6" one. { Is a K&N REALLY that much better than the Spectre oiled fabric filters?}
The steady speed hiss wasn't too bad on a couple of the vid-clips but the roar on acceleration might get wearing after 4 or 5 hours behind the wheel. I like extra performance---but I like a stealth mobile----not something that catches the attention of every bored cop in the streets. I suspect a bit of acoustic insulation on the back wall of the cowl cavity might cut some of the down

I also have one of the new J&C throttle bodies on the way--might get here tomorrow or tuesday.
Then off to a few local auto salvage for mirrors, seats (I hope) and some roof rack stuff and other odds and ends. right even find some neon injectors LOL

 

Wow. Lots to address.

The passenger side is preferable because that side of the cowl is covered and protected from rain, mud, debris, etc. The driver's side has a big 'ol hole in it. Lookit:



See where the arrow is pointing that says "COWL PANEL"? Under that solid area is where you cut your hole for the intake.

You can buy silicone elbows and 3" aluminum pipe from Silicone Intakes, which I linked above. The silicone parts are made for building out turbos, so they should be fine for this purpose. If I were going to make one myself, that's what I would do rather than trying to source metal elbows. You can run one of the elbows into the cowl and install a generic 3" K&N filter mount on the end of it.

Here's a thread where I was pricing out the parts. You might be able to find them cheaper than SI.

Nope. The tubes and elbows are all metal. They actually did their bends with welds, by cutting straight pieces at an angle and mating them up. There are some rubber joints, but no plastic anywhere.

Spectre is owned by K&N, and the "Spectre" filter is actually a K&N filter. I ordered a spare (so I can just swap them out when it's time to clean them), and the spare came in a K&N box. As far as the loose "generic" sizes go, I'm not sure if there's any difference between the ones being marketed as Spectre and the ones under the K&N name.

Several people have done their own. I would suggest searching the board to see what filter others have used in the cowl.

The roar you hear is only at WOT. Out on the highway it settles down and is fairly quiet. It's not going to attract the cops' attention unless you're romping on it.

Doubtful. The reason it's loud in the cabin is that the hole you cut in the cowl is right next to the cabin air intake. So what you're doing is piping intake noise right into your cabin. Insulation in the cowl would not work unless you plugged your air intake, which would make it rather stuffy inside.

Additionally, I wouldn't put any additional foreign material in the cowl. The one situation where the cowl intake can ruin your day is if you let your cowl drains get clogged so that water doesn't run out the bottom of the fenders like they're designed to allow. If you put insulation in there, and it comes loose somehow, it could either clog the drains or clog the intake itself. It's better just to leave it open. It's not really worth it when it won't work anyway.

Happy hunting.

 

I agree the factory system with the mid-runner filter Pod is welded up steel or AL. looks like it has 500 bucks worth of welding in it. it was the parts store Spectre elbows that look/feel/sound like chromed plastic to me. I m assuming their will work OK. I just would rather have something a bit more solid and kind of hate to use the heavy ribbed rubber. after working on a few airplane are intake systems I much prefer to have mine as slick and smooth inside as possible---makes for a less turbulent airflow----and they have a LOT of vacuum suction plus a lot of ram--effect.

 

Not to sound like an Azz Hole but you have been told several times where to get good parts for a DIY job a top notch one. To be blunt I have a Twin 77mm Turbo SBC 381ci. Dart block/heads, air to water intercooled street wagon now. I have used all of these parts on my car they are NOT cheap junk and flow very well as well as look good.


extrashaky told you several times as did I you need to look at some of these then post on looks and such.

 

I'm terribly sorry, I certainly did not mean to offend you. I certainly do not doubt or disrespect you or your level of expertise and experience.

However I am trying to learn about this stuff since much of it is new to me and to me learning means looking at differing options and listening to differing opinions. I also have to figure out how to accomplish my personal goals factoring in my own resources, skills, and schedules.