Topic: Installing aftermarket air intake on 90 YJ

[C.Redbeardd]

what is the restrictor in the back of the airbox? I see three tubes going in back there.

[sharpxmen]

what is the restrictor in the back of the airbox? I see three tubes going in back there.

inside the outlet tube (the thick tube that is connected to the throttle body with the rubber hose) there is a velocity tube inserted - i think someone mentioned that yours might not have it, measure the inside of your outlet from the airbox and you'll figure out if you have it or not should be close to 2.5'' (a little less but i'm not sure how much less). i think you're at 2'' or so if you have the restrictor/velocity tube in there.

[C.Redbeardd]

I think I do have what you mentioned but ill check it out after class.

[vprsrul]

I will do everything but the k&n.  I wouldnt ever waste my money on that garbage again!  they let too much debris through and the flow values are no better than a oem when it is filtering correctly, ie 60% restricted with dirt it filters 94% what your oem will even less when its nice and clean.  The oil used on the filter will damage you maf and turbos as well. I recently sold my 03 duramax and this was a huge stink on forums for diesel trucks.  You are definatly right about gutting it though.  ps amsoil makes a nanofiber filter that outflows oem but still actually filters the air a small amount better than oem...

[sharpxmen]

I will do everything but the k&n.  I wouldnt ever waste my money on that garbage again!  they let too much debris through and the flow values are no better than a oem when it is filtering correctly, ie 60% restricted with dirt it filters 94% what your oem will even less when its nice and clean.  The oil used on the filter will damage you maf and turbos as well. I recently sold my 03 duramax and this was a huge stink on forums for diesel trucks.  You are definatly right about gutting it though.  ps amsoil makes a nanofiber filter that outflows oem but still actually filters the air a small amount better than oem...

there's a relation between CFM, pressure drop and size of the filter - you would need a really large filter to have a pressure drop that is the same as a high flow filter one, of course it will let larger particles in, there is no way to use the same fabric and have higher flow in the same design filter - the downside of the KnN is that you have to clean it more often (rather than discard it and buy another cheap one) and reoil it. try this - lift the airbox cover, flip it around and lay the filter on top - open the throttle and see what happens - you will see the filter getting sucked in - now try the same with a high flow filter (doesn't have to be KnN and i am not saying it's the best filter out there either) - you'll see the deflection is way less that the stock filter -  that's your pressure loss behind the filter. Like i said, ideally you should get a bigger box from a junkyard so your filter surface area is larger.
there's really no compromise, the better filtering capabilities the more loss and less performance, better flow is either using a really large airbox (some of the diesels have really big ones) or a high flow with the downside of letting in more particles.

[C.Redbeardd]

inside the outlet tube (the thick tube that is connected to the throttle body with the rubber hose) there is a velocity tube inserted - i think someone mentioned that yours might not have it, measure the inside of your outlet from the airbox and you'll figure out if you have it or not should be close to 2.5'' (a little less but i'm not sure how much less). i think you're at 2'' or so if you have the restrictor/velocity tube in there.

so this THICK TUBE CONNECTED TO THE THROTTLE BODY WITH THE RUBBER HOSE is the restrictor?

[chardrc]

this is a picture of my 1990 air intake.. what thick tube are you talking about.

[C.Redbeardd]

I dont know. Thats why i am asking, But I cant really see much of your airbox. My 90 has three tubes coming out the back. Two thin and one thick.

[sharpxmen]

I dont know. Thats why i am asking, But I cant really see much of your airbox. My 90 has three tubes coming out the back. Two thin and one thick.

the outlet on the cover of the airbox that goes to the tube which is connected to the t/b - on 91-95 inside there's a restrictor tube - so you need to take the cover off and look towards the hose that connects to the t/b - but someone said that the tbi does not have the restrictor (or velocity) insert.

[Jeffy]

http://4bangerjp.com/forums/index.php/topic,3595.msg27785.html

I don't see any reason for a TBI to have it since the CCV doesn't go to the airbox.

[sharpxmen]

http://4bangerjp.com/forums/index.php/topic,3595.msg27785.html

I don't see any reason for a TBI to have it since the CCV doesn't go to the airbox.

for some reason i thought is for the evap canister not for the valve cover vent bu again dunno if the tbi has it or not.

[vprsrul]

there's a relation between CFM, pressure drop and size of the filter - you would need a really large filter to have a pressure drop that is the same as a high flow filter one, of course it will let larger particles in, there is no way to use the same fabric and have higher flow in the same design filter - the downside of the KnN is that you have to clean it more often (rather than discard it and buy another cheap one) and reoil it. try this - lift the airbox cover, flip it around and lay the filter on top - open the throttle and see what happens - you will see the filter getting sucked in - now try the same with a high flow filter (doesn't have to be KnN and i am not saying it's the best filter out there either) - you'll see the deflection is way less that the stock filter -  that's your pressure loss behind the filter. Like i said, ideally you should get a bigger box from a junkyard so your filter surface area is larger.
there's really no compromise, the better filtering capabilities the more loss and less performance, better flow is either using a really large airbox (some of the diesels have really big ones) or a high flow with the downside of letting in more particles.

I understand what your saying, but they do not filter until they are more occluded than an oem and flow identical.  On top of that dyno results from a drop in filter are little to nothing if anything at all.  when i had my duramax dynoed I saw no gain in power with a complete intake that is until I was making 900 whp, then i needed more flow and saw a 8 hp increase after reinstalling the intake.  I may be fairly new to the jeep side of the house but drag racing and pulling are my expertise.  We have tried all types of filters and unless your making tons of power you will see no gain in filter media.  especially in an offroad vehicle!

[dwtaylorpdx]

Ok NO K&N wars, its a religious issue.  And BOTH sides are right on about 1/2 the issue...

My 2.5 just ate another paper filter(2), I dropped the K&N I had and it got a hole in it,
so I had replaced it with paper...

Dave

[sharpxmen]

I understand what your saying, but they do not filter until they are more occluded than an oem and flow identical.  On top of that dyno results from a drop in filter are little to nothing if anything at all.  when i had my duramax dynoed I saw no gain in power with a complete intake that is until I was making 900 whp, then i needed more flow and saw a 8 hp increase after reinstalling the intake.  I may be fairly new to the jeep side of the house but drag racing and pulling are my expertise.  We have tried all types of filters and unless your making tons of power you will see no gain in filter media.  especially in an offroad vehicle!

let me get this straight - you're telling me that you're using the same filter in your 900hp (sorry, whp) that you use in your Jeep? Are we talking nitro? Just because in that case your oxygen is coming from the bottle and not thru your air filter and the dyno is completely irrelevant. not sure what we are comparing here. and no, you cannot possibly have 2 filters that have different filtering properties with the same flow rating, it's not possible (same size filters) - as for filtering properties that is a downside, no question about that but you compare a plugged filter with a brand new one which is defeating the point, compare 2 old ones or brand new ones. 

[dwtaylorpdx]

I think the biggest issue is that too many people don't/did not care for the K&N correctly,
Don't take care of the paper filter in other words are not scientific samples of the subject.

I do know this:
Caterpiller found the K&N was inferior to their centrifical + paper
filters for stopping dirt, on silica, in the micron range.

I've run K&N filters since the 80's and they worked well, I define
well as no dirt past the filter I can see. I religiously maintained them
exactly like my original one required. I have sold all of my cars with
200+K miles and I am an avid off-roader so they see dirt a lot.

K&N filters will usually stop your engine from inhaling water in my limited experience.

I really like the outerwear foam wrap on the K&N for the sand.

The only filter that reliably stopped volcanic ash (I lived 10 miles from St Helens)
Was a K&N wrapped with a nylon stocking (4 layers/stocking.,)
Paper did not work because it sucked in when it plugged, this was
back when most rigs had the old round filters and carbs still.

I frankly don't care if they K&N flows any better or not, I use it to
stop a few more filters form hitting the land fill... My little contribution...

Dave