Topic: 4.0 TB ?

[bhelzer01]

When i install my 4.0 tb do i need to get a 4.0L intake as well? If so does that mean i can get a 4.0l cold intake

[FourbangerYJ]

When i install my 4.0 tb do i need to get a 4.0L intake as well? If so does that mean i can get a 4.0l cold intake

It take it you mean air intake. Not intake manifold.
The air intake is the same dia. for both the 2.5 and the 4.0 so you can use the one you have.

[andpgud]

How does the 2.5 sound with a CAI?

[sharpxmen]

How does the 2.5 sound with a CAI?

if you mean with a cone filter in the engine bay - it's loud but not unbearable. Mind you that's not really cold air intake, more of hot air intake (and it takes a toll on power output, so might want to reconsider).

[andpgud]

So you dont recommend doing anything to the air intake? Just keep it stock

[sharpxmen]

So you dont recommend doing anything to the air intake? Just keep it stock

if you can get outside air then you're fine (like using a shield to seal around the filter and pull air from the front of the grill or even better a snorkel), if not you can keep the stock airbox, remove the venturi/restriction tube insert in the outlet of the airbox, use a fram air-hog (cheaper) or KnN high flow filter - also might want to enlarge the inlet of the aribox and have a tube going thru the sheetmetal under the headlight (behind the grill).

hot air from engine bay kills your power, makes a big difference to get cooler air in the intake.

[RT]

An intake really does help, so get a kit, or go down to pepboys and get their spectre parts and make a short ram with ducting running to where there's cold air.

[FourbangerYJ]

I went from a Rockit city air intake tube with a fancy K&N filter to a factory TJ set up with a cheap paper filter. I did not notice any loss in performance.
I got tired of cleaning the K&N all the time.

[stan98tj]

if you can get outside air then you're fine (like using a shield to seal around the filter and pull air from the front of the grill or even better a snorkel), if not you can keep the stock airbox, remove the venturi/restriction tube insert in the outlet of the airbox, use a fram air-hog (cheaper) or KnN high flow filter - also might want to enlarge the inlet of the aribox and have a tube going thru the sheetmetal under the headlight (behind the grill).

hot air from engine bay kills your power, makes a big difference to get cooler air in the intake.

i agree that the air from a cone or "cold air" intake isnt as good (temp wise) as you would get from a snorkel, but i actually gained a bit from the AEM intake i installed when i got the jeep. I gained 1-2 mpg and a slight bit of pep. it got better with the 62mm TB and spacer-but not by much- the spacer seemed to position the intake better and you can hear it drawing in the air a bit more cleanly than before.... This is NOT a life changer but a good cold air intake can help a bit. And in my experience, it is not loud at all. When you mash the pedal down, you can hear it draw in air (almost sounds like a turbo blow valve but waaay quieter). If i could do it again, i would consider a snorkel, but only if i were absolutely sure that the snorkel's design wouldnt hinder air flow. Snorkels in general have sharp turns and seem like they wouldnt provide a great flow of air...but some brands claim they provide better flow.

[sharpxmen]

i agree that the air from a cone or "cold air" intake isnt as good (temp wise) as you would get from a snorkel, but i actually gained a bit from the AEM intake i installed when i got the jeep. I gained 1-2 mpg and a slight bit of pep. it got better with the 62mm TB and spacer-but not by much- the spacer seemed to position the intake better and you can hear it drawing in the air a bit more cleanly than before.... This is NOT a life changer but a good cold air intake can help a bit. And in my experience, it is not loud at all. When you mash the pedal down, you can hear it draw in air (almost sounds like a turbo blow valve but waaay quieter). If i could do it again, i would consider a snorkel, but only if i were absolutely sure that the snorkel's design wouldnt hinder air flow. Snorkels in general have sharp turns and seem like they wouldnt provide a great flow of air...but some brands claim they provide better flow.

it's about air mass, hotter air means less density and therefore less mass (and less oxygen along with it). Check Chad's dyno runs (in member's projects) with the hood open vs. pulling hot air to see the difference. Whatever the snorkel design would lack regarding smoothness would still be better than hot air.
you can even calculate it, for example you lose about 6HP between 70F and 100F air temperature if you take 120HP base for the Jeep - go here http://www.msdfuelinjection.com/MSDInjectorV1/main.html and put in the numbers for the jeep then change the air inlet temp to see how the output changes.

[chrisfranklin]

I've got some "ferrari" headers (pacesetter) on the way and I'm trying to figure things with the intake. 

The intake I pieced together awhile back  pulls from a 3" hole in the front grill.  The hose from the filter to the grill hole is 3" in diameter.  I figure the 62mm TB is about 2.5" in diameter. 

I was under the impression that the 2.5L and 4.0L engines adjust based-- amongst other things --on MAP sensor readings/air pressure in the intake. 

You use a wide intake tube, perhaps that sets things up so that you lose air pressure some at the low end. 

Well, the tube I've been using is probably 3.5" to 4.0" -- pretty sure it's 4.0".  Even though there are restrictions down from 4" on both ends -- the TB diameter at 2.5" and the grill opening at 3" -- I still get the impression that maybe its the intake tube that is forcing the power curve up a bit in to the rev range on mine.  I guess I'll have to experiment with a different diameter tube. 

[RT]

if you're trying to keep temperature down in the engine bay, could you wrap the header and downpipe in thermal tape? I'm sorry for kind of jacking the thread but a big reason why you'd be sucking hot air is from radiation from the exposed exhaust system...