keep your airbox?

[j99xj]

http://www.thunderproducts.com/AirboxesDynotech.htm

What do you all think?

Why is there such a knee-jerk reaction to throw away the airbox when doing engine performance upgrades?

[yossarian19]

I think it sounds like this guy has done more research than I have.
I wonder, though, if our XJs have tuned airboxes or just whatever the factory thought was cheap. I suspect, given the uniformity of airboxes from 80-something to 01, that we have the sort of airbox systems that can benefit from after-market cutting, modding, replacing, etc.

You wouldn't catch me hacking up the air cleaner on an Infinity G35 or a 09 Camaro, but the XJ? I doubt they had performance in mind when they threw the box in these things.

[Talyn]

XJ.. Tuned air box... AAAAAAAAAHAHAHAHAHA.. its what has cheap and fit in the space.. that corrugated tube is in no way tuned.

[XJRunner]

I'm keeping my stock airbox with my bored our engine and header. To me I'd rather have a restrictive air intake that actually filters the air then a free flowing one that doesnt considering i'm building a prerunner lol

[n1ywb]

I'd like to use that space for a second battery.

[yossarian19]

I'd like to use that space for a second battery.

And I'd like a pony but I ain't gettin that now, am I?

[Talyn]

If someone made a air box that actually helped in that method I would buy one... until then its all nice in theory.

[wolfpackjeeper]

I like the stock XJ airbox. It keeps heat and water out. both things my intake is not very fond of.

[BBeach]

I like to keep the stock box on most vehicles i have whether the jeep or the vw. When you cut them up (which i did to both), sounds pretty close to a short ram / cold air intake and gives comparable performance. Especially with puddles and/mud is it worth the extra couple hp to have an exposed filter (without heat shield)?

[FlexdXJ]

mine sees trail duty I'll keep my airbox thank you :D

[seanyb505]

When I look at my bikes airbox it does look like some thought went into it. I cant say the same for the XJ box.

[DCB]

I just took my stock box out a drilled a number of holes in the bottom of it... best of both worlds.

Peace

[pierrexj]

DCB, I think i did something similar to you,I cuted a hole on the base of the airbox right through the metal wher it stands and covered it with mesh, i guess I'm getting fresher air from under the mudguard,I know the problem should be water but I use my XJ in the street mostly,If this doesn't work I can cover the hole easily ,I also plan to use one of those less restrictive factory type air filters(not the conical's I mean),so far it works fine,didn't drive it long enough to tell if there is much difference,just wanted to experiment a little getting colder air into the factory airbox.
On the other side on my 93 Grand ,I just had a piece of PVC pipe and insulated with that heat resistant material and put it through the box's hole ,but the pipe goes all the way to the grill,that seemed to work since the engine runs now usually one notch below 210(it use to stay at 210 all the time),and it's hot here,again water should be the problem but the pipe is at the top of the front grill ,more than enough for me as I don't get much into water...

[Talyn]

That is an idea I am tossing around on my XJ.. but different. I'm looking at after market intakes and thinking about cutting a hole in the horizontal area where the stock air box mounts. However, using the stock air intake still leaves that corrugated flex tube in place, which has been cited as the main restriction in the intake. Don't know for sure though but makes sense.

[pierrexj]

Talyn,If I understood right you want to make a hole where the airbox stands,as I did, but put a conical filter to breathe air from there,just above the wheel...I think this would be good as for what I read the K & N type of air intakes are not really "cold intake filters" as they still breathe hot air from underneath the engine bay...I didn't know the corrugated hose was so restrictive,is it by the material,shape or both?
Maybe i could change this hose for a K & N type one, and still leave the airbox,would that make any sense?

[DCB]

I got 1 mpg average better after I did mine. I also did the same thing on my van... same results.

Peace

[Talyn]

Talyn,If I understood right you want to make a hole where the airbox stands,as I did, but put a conical filter to breathe air from there,just above the wheel...I think this would be good as for what I read the K & N type of air intakes are not really "cold intake filters" as they still breathe hot air from underneath the engine bay...I didn't know the corrugated hose was so restrictive,is it by the material,shape or both?
Maybe i could change this hose for a K & N type one, and still leave the airbox,would that make any sense?
Its the shape of the corrugation or bellows that allow it to flex that makes it restrictive. I don't think you could fit a K&N (unless you are talking about the drop in panel type) with a K&N FIPK. The K&N FIPK does come with a heat shield, although a simple one. I believe that there is a CAI that keeps the bottom part of the air box.. but I can't recall which one does that right now.

[Boostwerks.com]

I'm keeping my stock airbox with my bored our engine and header. To me I'd rather have a restrictive air intake that actually filters the air then a free flowing one that doesnt considering i'm building a prerunner lol

Finally... someone who makes sense.

1-5 more HP VS more + smaller particles filtered.

Hrmm. Thats a hard one.

Nothing will filter better than a restrictive OEM paper filter.

[Timmy2XJS]

on my 88 i build a cold air intake with a heat sheild, cut out behind the headlight, and made it with a smooth pipe all the way the the throttle body. all of it is heat shielded. i run a A&M filter on the end with a pre-filter sock on it. i saw a 5 hp gain and lots more pick up. its my street toy

my 99 is the trail beast and i went another way with it. i made the tube from the throttle body outta smooth intake piping, ran it in to a stock airbox that i sealed at the front fut out breathing holes on the top and mounted an A&M filter inside the box. i did it that way so that the box could protect the filter some from the muck and funk while wheeling, but when its all highway stuff, i disasemble it and remove the bottom of the box compleatly and now i have a some what cold air intake. makes a coupla extra mpg.

[pierrexj]

I just took my stock box out a drilled a number of holes in the bottom of it... best of both worlds.

Peace


I did the same...did you notice any improvement ?

[maybe2fast]

XJ tuned box...hahahahahahahah right...no

[badron]

Years ago I tried back to back 1/8 1/4 and 30 to 70 MPH 4 gear only test. No improvement was to be had by removing the air filter. This was on another wise bone stock 01 5 speed. It was also tried on a 89 auto with a low resistance muffler. Also no improvement.
We also tried TB spacers of 1/2 inches , 1 inch. 1 and 1/2 inches and a 2 inch spacers.(home made wood) A note: Becouse the hood would not close with the 2 inch spacer and stock air cleaner in place. The hood was removed for test with this configuration. But new baseline runs were made with hood off so I feel the comparisons are valid. No improvement was found.
Same for TB will the bulge removed and some combinations of all three mods still no help.

[seanyb505]

Years ago I tried back to back 1/8 1/4 and 30 to 70 MPH 4 gear only test. No improvement was to be had by removing the air filter. This was on another wise bone stock 01 5 speed. It was also tried on a 89 auto with a low resistance muffler. Also no improvement.
We also tried TB spacers of 1/2 inches , 1 inch. 1 and 1/2 inches and a 2 inch spacers.(home made wood) A note: Becouse the hood would not close with the 2 inch spacer and stock air cleaner in place. The hood was removed for test with this configuration. But new baseline runs were made with hood off so I feel the comparisons are valid. No improvement was found.
Same for TB will the bulge removed and some combinations of all three mods still no help.

Maybe the air filter wasnt the restrictive part of the stock setup?

That article was talking about sportbikes in which case it has a point. A giant rectangle with corrugated tubing? I dont think too much frequency tuning went into it.

[JNickel101]

Nothing will filter better than a restrictive OEM paper filter.

I dunno, the AMSOIL cone filter I have is pretty awesome. xEleventy billion times better than the K&N one....its not an oiled gauze one...

[Talyn]

I dunno, the AMSOIL cone filter I have is pretty awesome. xEleventy billion times better than the K&N one....its not an oiled gauze one...

You have the Amsoil EA filter or the older oiled foam one?

[Gravesdiggerxj]

Finally... someone who makes sense.

1-5 more HP VS more + smaller particles filtered.

Hrmm. Thats a hard one.

Nothing will filter better than a restrictive OEM paper filter.

WOW... uninformed much? :roflmao:

take a look under the hood of a prerunner, drag car, mud truck, comp rock buggy... what do you see? probably not a stock airbox... but I'm just guessing. :wave1: :peace:

[CSaddict]

I have a turbo where the stock air box was.....

[maybe2fast]

mines in the landfill

[kf_chris]

had a Rusty's intake then went mudding in FL
after 4 hours of unbolting intake parts and drying them out (luckily didn't hydro) I didn't hit anything big and deep
put the stockie box back on with a k&n filter ant cut a corner out of the front. I'm not running the risk of water again from under the hood. just my opinion and my setup

[Talyn]

(luckily didn't hydro) I didn't hit anything big and deep

I did... thought I was chasing a lifter tick.. a few months later and I have parts of a piston in the oil pan.

[bjoehandley]

I just hacked open the front of a boneyard XJ airbox and used a drop in K&N (street driven XJ) and would like to eventually put a smooth silicone tube on place of the stock corregated piece. I've just not had the chance to measure it, and have been spending too much cash on gas and RC rock crawler stuff:wow:

[DeathValleyPaul]

Louvering the hood above the throttle body lowered the temp at the throttle body, thus providing cooler air. The temp at the throttle body is just too damn hot as it is.

[sharq]

i do know one thing. a K&N/tube sure made my jeep sound meaner.

[bjoehandley]

i do know one thing. a K&N/tube sure made my jeep sound meaner.

Just cutting the front of an airbox and using a drop in K&N makes a difference in sound......not that I'm complaining:D

[2001XJ]

What about jeeps that see mostly woods, logging trails and 2-tracks......mainly MINIMAL dust, mild mud (not enough to worry about) and logs and rocks. Would one of the rock-it, rusty's or K&N filter kits that eliminate the box be beneficial? I always see a lot of guys complaining about maintenance on openair intake systems with oiling, dust, etc etc.

Advice?

TIA

[1bolt]

The main reason not to throw away the air box is that having a cone filter sucking hot engine bay air will LOWER your power, to the tune of 1% per 11* increase in air temperature.

If you do the math, a K&N with the airbox deleted will lose power... I had a thread about this where I measured intake air temps and found an average of 65* hotter intake air from deleting the air box... That's about 6% average LOSS of power and torque through the entire power band. Which is well over what a K&N is going to give you. And a K&N is mostly going to give you a small increase at PEAK. not a 6% increase through the entire curve.

So if you want less power and more particulate matter sucked into your engine, delete the air box and put a K&N in.

I don't have the link but if you search for "home brew cowl induction hood" the first link should be my writeup (different username at the time)

If you want to upgrade your induction system, that thread will help. Most of it is also duplicated over on Jeepstrokers.com in my project thread.

[Talyn]

You are aware that on the late model XJs that the air box is sucking in hot engine bay air?

[gradon]

Here's what I did with mine:
http://i248.photobucket.com/albums/gg166/gradons/p5210084.jpg

Can't find a pic of the intake, but it's a FIPK w/ an amsoil eeau3090 filter on it and boxed in w/ a sunscreen visor. Course mine had the plastic cap there in front of the box, and yes, the stock box does suck in hot engine/radiator air. I vaguely remember my 88 or 92 having a tube connecting the hole and airbox.

[1bolt]

You are aware that on the late model XJs that the air box is sucking in hot engine bay air?

No I'm not aware of that, I have a 97 that goes to the square hole in the header panel, which year was it that doesn't have a hole that is more or less at the header panel opening? 2000 to 2001 I'm guessing? Those are the only years I don't have any real hands on experience with. Can you post a pic? Where did they relocate the inlet?

Anyway assuming you're right whats the point? that the factory can screw something up after 15 years of getting it right?

You don't have to take my word for it though, I recognized that there were a LOT of NAXJA users throwing away power back when I was moding my own (and a lot still doing it). I knew I might get some flack from the odd person who stuck a K&N on the end of their intake tube. So I took more or less rigorous scientific intake air temp readings documented as much as I felt was necessary to prove my point and put it in that thread.

[1bolt]

Gradon the sunscreen visor heat shield sounds like Dino's

[hubs97xj]

My 97 has a solid header panel- no hole in it like my buddy's 96 has (which, incidentally, was blocked from the factory with a plastic cover), and my other buddy's 2000 is, IINM, identical to mine. So, basically, the factory airbox had to breathe the same air from the same place that my open element filter does- I'm a little skeptical about the power loss claims, as the XJ seems livelier than ever, and my mileage improved as well.

Where's that thread on temps?

[1bolt]

I wouldn't expect anyone who has a cone filter breathing an XJ's notoriously hot underhood temps to think he's pulled off anything but a super-duper butt dyno upgrade. For the same reason that people put Acetone in their gas and have illness' healed by a sugar pill.

Air temperature is air density (simplified version) this is why legit cold air systems breath from a fender well, or another opening. I didn't make up the 11* = 1% power rule. Its a rule of thumb used by Drag racers who can see on a daily basis that it's true based on the tenths they gain or lose at the track as the air changes temp.

I don't know how I got a 97 XJ that still has the opening through the header panel. I don't have two buddies with late model XJ's I can go look at, or that I just happen to remember odd details about. Regardless I'll just take your word at face value...

Are you saying that every move the factory makes is better for performance? Did the factory remove the outside air inlet because it wasn't good for performance? Or is there a more likely reason?

Do you think they capped that hole so the engine would have to breath hotter air because hotter air = more power? It's not like they've never put something restrictive in the intake track To (for example) lower noise... Like that cone that's just above the air box inside the plastic tube the hose connects to? (it's a nozzle silencer). How about the soft rubber tubing with ribbing which does a good job absorbing noise. But is absolutely woeful for air flow... Some day I'll put that crappy thing on my flow bench and measure the difference between it and a smooth pipe of the same diameter..

All that said, I wouldn't be surprised if they capped that hole because there's a pressure drop where the hole is (basically the reverse of ram air), created by the high depression at the front of the grille and the low depression in the engine bay pushing air through the larger radiator opening... I've long suspected this might be case, and I even have a nice new Magnahelic gauge I intend to check this with at some point. (I didn't get the gauge for that, I'm not that big a geek, I got it to test the best location for a top mount intercooler, and then test the pressure drop across it after it's installed).

Regardless, 60* higher intake charge is roughly 11hp (flywheel numbers) on a bone stock 4.0, if it's got more bolt ons then it'll be more than 11hp. the best K&N dyno result I've ever seen (alone without a FIPK) was just under 6hp. So net "on paper" result from deleting the air box with no other mods =
-6 hp

[hubs97xj]

Did you test stock and aftermarket setups, or just your own? I'm a bit of a skeptic, no offense intended. You may well have debunked the biggest myth in the automotive world, but I'd like to see some tests to back up the claims that a CAI robs power. I don't see them in that thread, but if you have them, please share- no one likes throwing money away.

[1bolt]

You realize the C in CAI means cold or cool right? As in; not engine bay heat :) Look i'm not trying to be a sarcastic dick or anything but the power in a CAI is in the fact that it's breathing air from outside the engine bay... What I'm pounding on here is that putting a cone filter where the air box used to be; is self defeating. Unless there's a source of cool outside air which is what the factory air box is trying to do through that square hole in the header panel.

I'm not going to say the factory succeeded, I'm saying that was the point of it even if it is restrictive to the point of defeating the purpose. As I was saying there may be such a big depression behind the headlights from the air crossing the radiator that the factory setup was later found to be counter productive.

If you want cool air, extend the intake tube over to the cool side of the engine, and heat shield it:
http://img253.imageshack.us/img253/7340/newpipe02yt0.jpg
http://img252.imageshack.us/img252/4994/newpipe01sh4.jpg
http://img262.imageshack.us/img262/5130/coatediy8.jpg
If you want even cooler air, box the cone filter onto an opening like a cowl hood:
http://img244.imageshack.us/img244/5763/ourpicsusa988dp1.jpg
crush template
http://img489.imageshack.us/img489/3787/ourpicsusa033ng0.jpg
steel box
http://img180.imageshack.us/img180/1879/ourpicsusa032nq0.jpg
test fit
http://img201.imageshack.us/img201/8246/ourpicsusa038ri8.jpg
finished product
http://img358.imageshack.us/img358/5258/ourpicsusa024gv4.th.jpg (http://img358.imageshack.us/my.php?image=ourpicsusa024gv4.jpg)http://img516.imageshack.us/img516/1522/ourpicsusa022ul3.th.jpg (http://img516.imageshack.us/my.php?image=ourpicsusa022ul3.jpg)
thumbnails of the weather strip sealing to the hood when closed visible through the cowl opening. I'd estimate I got it about 95%-98% sealed from the engine bay, only holes are in the corners where the weather strip wouldn't bend sharply: Cowl hood:
http://img160.imageshack.us/img160/4254/1001178bz3.jpg

[sharq]

1bolt, where did you get the tubing for the intake?

[hubs97xj]

Yeah, I'm aware of what CAI stands for, but I get tired of typing "open filter element and tube". I'm sure a real cowl hood is much better, but here, for a DD, I'm not sure that's the most practical solution for me.

I would like to see some actual numbers of a stock and aftermarket kit- so we'd have apples vs apples vs apples. Maybe the mileage gain I've seen is simply the PCM leaning the mixture out due to hotter air, or maybe it does actually make more power- without some good numbers, I don't know, and until I get an infrared thermometer and a scangauge or something to monitor in real time, I won't.

Slightly OT- here's the cowl hood thread- it's pretty neat.
http://www.naxja.org/forum/showthread.php?t=100961&highlight=cowl+induction+hood

[ricot83]

I threw on a cowl snorkle for a while, then took it out and but a high mounted cone filter.

[1bolt]

it's a single mandrel bent U bend off Ebay, 2.5" aluminized exhaust tubing, it was a prototype for the stainless steel version. I had to plan the cut carefully to get the angles and curves to be nice. basically once I figured out where to cut the U bend in half to actually get the pipe to point in the direction I wanted with a very smooth compound curve (I only had one U bend to play with and I didn't want to wait for another one to ship to me) the hard part was over.
The cowl induction hood up is here:
http://www.naxja.org/forum/showthread.php?t=100961&highlight=home+brew+cowl
The air box stuff is later in the thread, I never did get to remaking it in 3.5" stainless tubing, the Aluminized held up very well, even the weld inside the tubing didn't rust.

At the end of the thread you can see that the whole setup migrated over to my MJ, the Cherokee is slated to be the test mule for a whole different setup.

[1bolt]

One other thing, the intake temp testing I did in that thread (around page 3) was three different configurations none of them were with the filter in the stock air box location... the worst (hotest) configuration.

The test where I get an _average_ while hiway cruising of around 60* hotter than ambient temp was with the filter on the passenger side of the engine and the cowl opening taped shut. A setup hanging where the airbox used to be should be considerable hotter due to the headers being so close. I've done "informal" tests with filter there, and found peaks over 100* hotter than ambient air (i.e. over 200* degree intake temps on a ~95* day)

[EricsXJ]

1bolt,

You have what I think is the most ideal intake setup and it looks very well done! Awesome job. One of the reasons I stumbled into this thread is I'm coincidentally planning to do the same thing with mine, with a couple big differences of course. I already have the sheet metal for my box in the garage. My challenges are going to be doing this without a cowl induction hood. I know I am going to have to relocate some of the heater/AC junk on that side and the wiring harness. Mines a 2000... I was hoping to make a completely sealed box drawing air from the cowl similar to your snorkel setup. We'll see how it goes, but thanks for giving me lots of hope by seeing that someone has already done something very similar.

Also I agree with you 100% on all the "hot"-air intake crap that's out there.

[Talyn]

No I'm not aware of that, I have a 97 that goes to the square hole in the header panel, which year was it that doesn't have a hole that is more or less at the header panel opening? 2000 to 2001 I'm guessing? Those are the only years I don't have any real hands on experience with. Can you post a pic? Where did they relocate the inlet?



They located the inlet in the same area... so, the stock air box was pointing at a solid wall. If I can get to the storage unit I will snap a pick.


Anyway assuming you're right whats the point? that the factory can screw something up after 15 years of getting it right?


the point is that not all the factory setups actually pull in cold air.

[Talyn]

Here's what I did with mine:
http://i248.photobucket.com/albums/gg166/gradons/p5210084.jpg

Can't find a pic of the intake, but it's a FIPK w/ an amsoil eeau3090 filter on it and boxed in w/ a sunscreen visor. Course mine had the plastic cap there in front of the box, and yes, the stock box does suck in hot engine/radiator air. I vaguely remember my 88 or 92 having a tube connecting the hole and airbox.

That is what I am planning on doing with mine, although not such a big hole. I just need to decide what i want to use for an air box. I really don't want to go the route of the sun visor though. And I would also like to get rid of the corrugated air tube. I think I may go with an S&B intake, which actually has a box, or the AFE intake, which has a shield that I would mod to be more enclosed.

[gradon]

I already had the k&n fipk- it doesn't come all the way to the hood and there are gaps/holes where hot air gets blown in by the e-fan and air from the header can enter when stopped. I cut the shade and it fits inside the walls of the fipk and covers the top. Air has to enter from the header panel behind the headlight. I can open it up when I want to check coolant or fool with the pcm. It works for now(and for $5), but maybe someday I'll make a nicer box.

[FlexdXJ]

You realize the C in CAI means cold or cool right? As in; not engine bay heat :) Look i'm not trying to be a sarcastic dick or anything but the power in a CAI is in the fact that it's breathing air from outside the engine bay... What I'm pounding on here is that putting a cone filter where the air box used to be; is self defeating. Unless there's a source of cool outside air which is what the factory air box is trying to do through that square hole in the header panel.

I'm not going to say the factory succeeded, I'm saying that was the point of it even if it is restrictive to the point of defeating the purpose. As I was saying there may be such a big depression behind the headlights from the air crossing the radiator that the factory setup was later found to be counter productive.

If you want cool air, extend the intake tube over to the cool side of the engine, and heat shield it:
http://img253.imageshack.us/img253/7340/newpipe02yt0.jpg
http://img252.imageshack.us/img252/4994/newpipe01sh4.jpg
http://img262.imageshack.us/img262/5130/coatediy8.jpg
If you want even cooler air, box the cone filter onto an opening like a cowl hood:
http://img244.imageshack.us/img244/5763/ourpicsusa988dp1.jpg
crush template
http://img489.imageshack.us/img489/3787/ourpicsusa033ng0.jpg
steel box
http://img180.imageshack.us/img180/1879/ourpicsusa032nq0.jpg
test fit
http://img201.imageshack.us/img201/8246/ourpicsusa038ri8.jpg
finished product
http://img358.imageshack.us/img358/5258/ourpicsusa024gv4.th.jpg (http://img358.imageshack.us/my.php?image=ourpicsusa024gv4.jpg)http://img516.imageshack.us/img516/1522/ourpicsusa022ul3.th.jpg (http://img516.imageshack.us/my.php?image=ourpicsusa022ul3.jpg)
thumbnails of the weather strip sealing to the hood when closed visible through the cowl opening. I'd estimate I got it about 95%-98% sealed from the engine bay, only holes are in the corners where the weather strip wouldn't bend sharply: Cowl hood:
http://img160.imageshack.us/img160/4254/1001178bz3.jpg

Thats a good idea for the intake man! I would totally buy one!

[sherman08]

So ive been kicking around the idea of putting the intake cone in the cowl, like the snorkel setup, ive seen done on here before. It would look alot like 1bolt's but the tube would enter the back of the engine bay and sit in the cowl. One of the big things ive run into is that it seems like the airbox in my 88 I6 is doing a heck of a lot more than holding the filter you know what i mean? It has a lot of vacuum hoses hooked to it, and a vacuum motor?, i dont even really understand what this thing does. I was wondering how some other people had set up there custom intakes, as it seems that its going to need to be more than just a tube.

[Talyn]

I already had the k&n fipk- it doesn't come all the way to the hood and there are gaps/holes where hot air gets blown in by the e-fan and air from the header can enter when stopped. I cut the shade and it fits inside the walls of the fipk and covers the top. Air has to enter from the header panel behind the headlight. I can open it up when I want to check coolant or fool with the pcm. It works for now(and for $5), but maybe someday I'll make a nicer box.

I know, that is why I would mod one buy sealing it more and cutting a hole like what you did. I have access to cheap plexi, so I will be using that. I found a few K&Ns and other brand on ebay that are used, one of which doesn't have the shield which I am bidding on.

[Bville99gt]

I got my K&N system from a 99 chev blazer and modify it a bit... here is my POS but hey it works...


http://img214.imageshack.us/img214/4058/dscn0776as5.jpg (http://imageshack.us)

[1bolt]

I know, that is why I would mod one buy sealing it more and cutting a hole like what you did. I have access to cheap plexi, so I will be using that. I found a few K&Ns and other brand on ebay that are used, one of which doesn't have the shield which I am bidding on.


I would get a cheap Magnahelic gauge off Ebay and run some clear PVC tubing from it to the spot between the headlight and where you want to put the hole.

[j99xj]

Just curious....how many people here actually read the article I posted?

[gradon]

I just re-read it. Tuning an airbox would require a lot of trial and error fabrication and dyno time to see if you tuned it to the max at the rpm range you want. Most of us are happy to get rid of the factory intake restrictions and block as much engine heat as possible.

[1bolt]

Acoustic tuning air boxes is usually done to quiet down induction noise. In a few rare cases it is done to make the induction noise sound more racy, and occasionally (motorcycles mostly) for a helmholtz resonance tuning effect that boosts a very small segment of the power band. Usually this is tuned for a troughs (dips) in a peaky powerband band with lots of peaks and valleys to smooth things out and make throttle response more managable.

[1bolt]

I was going to add

The effect is pretty small in terms of power but very noticable on a light bike of a few hundred pounds. Anyway by the time you did enough research, testing and work on one you'd have been better off doing a more effective mod.

[Talyn]

I was going to add

The effect is pretty small in terms of power but very noticable on a light bike of a few hundred pounds. Anyway by the time you did enough research, testing and work on one you'd have been better off doing a more effective mod.

I heard that they tuned the air box on bikes, but they keep calling it ram air.. ugh..

[Talyn]

I would get a cheap Magnahelic gauge off Ebay and run some clear PVC tubing from it to the spot between the headlight and where you want to put the hole.

Are you anticipating a negative pressure zone there? If so.. what about cutting a hole in the fiber glass panel as well?

[XJ98Jeep]

WOW... uninformed much? :roflmao:

take a look under the hood of a prerunner, drag car, mud truck, comp rock buggy... what do you see? probably not a stock airbox... but I'm just guessing. :wave1: :peace:
prerunner, drag car, mud truck, comp rock buggy, Jeep Cherokee.

Which one doesn't fit? I dunno about you, but my Cherokee's engine needs rebuilding a HELL of a lot less than any of those cars does. Their filters don't do as much because they don't need to, because the engines don't last nearly as long. I've seen racecars with wire mesh with bigger holes than a car's grill being used as the only filter medium.

[BobDog]

Well all this airbox on the right stuff is pretty nifty, but what I really like about it is it leaves room to fab up or use a battery tray from a RH Aussie XJ to mount a 2nd battery!:party:

[BobDog]

Well all this airbox on the right stuff is pretty nifty, but what I really like about it is it leaves room to fab up or use a battery tray from a RH Aussie XJ to mount a 2nd battery!:party:

[2001XJ]

I know some of you guys advocate removing the airbox and others don't BUT if one were going to what do you think of this kit? It seems to keep most of the OEM airbox design, except it allows more air in.....I think it is a better design and sort of mimics what some of you guys are doing with cutting or drilling stock airboxes?

http://www.autopartswarehouse.com/details/QQJeepQQCherokeeQQAiraidQQCold_Air_IntakeQQ1991200 1QQA86310136.html

[Talyn]

I don't like that airraid kit for several reasons. 1) it doesn't eliminate the corugated rubber tube, 2) for what you are getting you are paying too much, and 3) same sealing to thehood as the rest of the kits.. poor seal.

I purchased a S&B CAI kit for $100 new on ebay. It has its own air box which is only open to the front, which I will be sealing better to the outside air.

BTW, nice sig.. I like this one better though "And though I can hide my cold gaze, and you can shake my hand and feel flesh gripping yours and maybe you can even sense our lifestyles are probably comparable... I simply am not there. "

[2001XJ]

I don't like that airraid kit for several reasons. 1) it doesn't eliminate the corugated rubber tube, 2) for what you are getting you are paying too much, and 3) same sealing to thehood as the rest of the kits.. poor seal.

I purchased a S&B CAI kit for $100 new on ebay. It has its own air box which is only open to the front, which I will be sealing better to the outside air.

BTW, nice sig.. I like this one better though "And though I can hide my cold gaze, and you can shake my hand and feel flesh gripping yours and maybe you can even sense our lifestyles are probably comparable... I simply am not there. "

Thanks, will take note of the S&B kit. Thanks for the remark on the sig.....yeah I like that one as well.........LOVE that movie, Christian Bale is the shit, he should have got an award for that movie......very under appreciated actor if you ask me.

[ChevelleSSLS6]

You wouldn't catch me hacking up the air cleaner on an Infinity G35 or a 09 Camaro, but the XJ? I doubt they had performance in mind when they threw the box in these things.


They're designed to be quiet, fit in the application, be cheap to make, and cheap to install. Not to mention help keep the EPA happy with the cafe standards. Honda and other motorcycle makers do the tuned airboxes, but even they're facing government restrictions, so complying comes first, then producing a good product.:soapbox: <insert my rant here about the EPA making autos more complicated and less reliable (regs killed any hopes for a US market JK diesel, and check out the current diesel trucks if you don't believe me on complexity), and making it expensive for automakers to do business.


I took a dremel to my airbox... from the top of the stock hole I went around to the 'fender' side and back... did the same on the bottom, and connected the two with a diagonal cut along where the airbox 'cuts in' for fender room.

[BobDog]

Man if u think we have tough regs....just check out what they have do in Germany...
check out http://www.xxxpedition.com

:banghead:

[martness]

You would probably get better results from getting rid of the corrugated tube and replace it with smooth. I seem to remember reading that a corrugated tube has the effective air flow of a tube = to depth of corrugation - ID what I'm trying to say measure the depth of the corrugation subtract that from your smallest ID thats the effective diameter. I might be wrong on this it's happened once before