Custom air intake

L

lostcreek21

NAXJA Forum User
Location
Gresham oregon
Hey guys. I was looking around at the K&N intakes and I decided that they're too much and I can just make my own. I have some ideas but I need to know if I have to move any sensors or airlines. I have an 87 with a 4.0L. I'm going to take my stock air box out and use my existing tube and connect a filter to it. I'm loking for the cheapest way. If anyone has any ideas I'd love to hear them. Thanks
 
well i took my dad's leaf blower and cut a big piece of tubing off it for my intake pipe and put a big k&n on it, he was'nt happy but it worked really well, i make a nice heat shield for it from my old box and hacked up my header panel and bottom of the fender and put a cold air pipe in it, as for the vacuum tubes and emissions tubes well i removed all the emissions from my '91 so that was'nt a problem

eric
 
I have done something like that but i use aluminized exhaust tubing and welded heater fittings to it for the emissions lines.
 
eric91xj said:
well i took my dad's leaf blower and cut a big piece of tubing off it for my intake pipe and put a big k&n on it, he was'nt happy but it worked really well, i make a nice heat shield for it from my old box and hacked up my header panel and bottom of the fender and put a cold air pipe in it, as for the vacuum tubes and emissions tubes well i removed all the emissions from my '91 so that was'nt a problem

eric
Click to expand...

I'll bet he locks his tools up now huh?
:D
 
1053042216_airtube2.jpg
 
I made this one out of 3" steel exhaust tubing(not aluminized) and 3/16" plate for the flange. I had to weld in two 1/2" tubes to attach the breather tubes. Next time I do one, I'll angle the tube in the direction of the air flow so they'll draw better vacuum. The ones in the picture are attached at a 90° angle to the main air tube.

Jeep_AirTube_finished.jpg
 
Mine looks just a bit like Max's :D Made from 3" exhaust tubing. 1 90*, 1 45* and a small straight section between. Wish mine was powdercoated pretty red too. Mine is just flat black krylon

Underhood.jpg
 
Looks good, Willis. Mines black too, it's just glowing red from all the hot air! :)

How's your breather tubes working? When I pull the hose off mine, they don't seem to be drawing air in too much. That's why I'd like to angle them towards the air flow.
 
I'm kind of new to the forum, but I also am looking for an intake solution and I came across this on e-bay Ebay intake aution Is this a good deal? Buy it now is only $29.00. He has some other auctions where he includes the filter and some other stuff. I was going to purchase one, but wanted to check w/ the experts first.:worship:

Love this forum. I own 2 XJs and have just recently gotten into adding some modifications to mine(her's is only 2 WD, lol). Starting out slow due to $ situation, but good things come to those who wait.

K9Cop
 
I wouldn't buy it. You could probably grab a chunk of plastic tube and hose clamp at your local Home Depot for under $10.00 and do the same thing. Besides, from the looks of that picture, his hood won't close. If you notice mine and the one Willis built, they both have a 45° bend to get the filter down low enough to close the hood. The tube going over the top of the valve cover just barely clears on mine.

The performance gains are questionable as well. What you gain in air flow, you prabably lose due to heat gain. The stock airbox draws cooler air from a hole in the front bulkhead, behind the grill.

Do a search here on NAXJA for air tubes and filters. You should come up with several versions of air intake. These range from replacing the stock filter with a similar to K&N to completely fabricated air tubes and heat shields.
 
Was still able to stick a second battery w/functional heat shield in front of kn8010. Gonna try to make something like Michael Flower's shield, more heat it seems on this side of motor due to exhaust.

click here for pix of setup: www.stayvertical.com
 
Hey, K9Cop. Nice to see someone from the midwest. I don't think we have too many folks from Arkansas. You may not realize it yet, but as soon as we get your XJ in shape, we're going to have you invite use down there for some Arkansas wheelin'.

If I remember right, the only vacuum lines I had on mine ('90) were to control the vacuum motor on the preheat stove. I coupled those together as my air tube has no flap valve to source its air supply (hot vs cold). The only hoses left to deal with are the two 1/2" breather hoses. One goes to the top of the valve cover and one wraps around the firewall behind the engine and vents the crankcase, I believe.

FYI: I monitor my intake temp and it is typically 40° or more above the outside temp. A good cold air source would return 4-5% more horsepower. The usual answer being a snorkle.
 
MaXJohnson said:
I had to weld in two 1/2" tubes to attach the breather tubes. Next time I do one, I'll angle the tube in the direction of the air flow so they'll draw better vacuum. The ones in the picture are attached at a 90° angle to the main air tube.
Click to expand...


The tube to the forward hole on the valve cover is supposed to draw filtered air from the air tube and deliver it to the crankcase, with the rear CCV manifold tube providing the low crankcase pressure motivation. The factory aids this action by decreasing the velocity at the air collection point of the air tube (low velocity = high pressure) in an attempt to keep the intake pressure at the air tube collector entry higher than the crankcase pressure (this is the opposite of what they do for the emissions vapor canister with the venturi).

Increasing the collection tube diameter at the point of entry (a simple bell fitting to 1" or larger) or adding a 45 degree inlet sweep to the existing 90 degree point of entry (both achieve a greater inlet area cross section), will slow the velocity at this entry location and increase the pressure to assure the air (and oil) flow is motivated into the valve cover, as opposed to into the intake tract above the TB butterfly and IAS.

The only tube entry I would point in the direction of airflow is the emission vapor canister intake where you desire the high velocity/low pressure to draw the vapors off the canister and fuel tank.

Just some help if you plan on an air tube improvement.
 
MaXJohnson said:
How's your breather tubes working? When I pull the hose off mine, they don't seem to be drawing air in too much. That's why I'd like to angle them towards the air flow.
Click to expand...

Ed pretty much covered it. You do not want to create a venturi effect for the tube on the front of the valve cover. As designed air flows from the intake tube into the valve cover, then sucked through the valve cover into the intake by the smaller hose at the rear of the valve cover. You could angle that one up like a scoup in the air flow, and the one for the charcoal canister (that one at the back of the engine bay) could be angled down to try to suck more air, but not really that important. I have been thinking of changing that small vacuum hose at the rear of the valve cover to a larger size to get rid of some of that oil that seems to work its way into the intake tube.
 
The EGR mounts on the manifold, and the exhaust supply tube hooks to the manifold. If you are talking about that 2ish inch 'accordian' tube from the exhaust to the box, that just supplies warm exhaust manifold air to the intake for cold start up and opperation. Just remove that.
 
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