keep your airbox?

[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:

If you want even cooler air, box the cone filter onto an opening like a cowl hood:

crush template

steel box

test fit

finished product

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:

 

[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:

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:

If you want even cooler air, box the cone filter onto an opening like a cowl hood:

crush template

steel box

test fit

finished product

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:

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...

 

[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.