Hey everybody, I've been reading LOTS on this site for a while now, but thought I would post my first message to report on the "unexpected" result of my first step in trying to wake-up my '02 Tracker's 2.0L.

Looking under the hood, it seemed like the tube that pulls air from inside the fenderwell to the stock air-box was really small and "squished" by design (restrictive).  When I pulled my regular ol' paper air filter out, you could tell that all of the air was going through right next to the corner where that tube came it, since that was the only discolored part.

So, I pulled out the dirty side of the air box, and drilled about 15 or so 3/8" holes spaced-out around three sides of it (couldn't really drill the side with the intake tube attached).  Figured this would give more air, more evenly distributed.  Shouldn't be too hot, either, since this model has the air box on the exact opposite side of the engine bay from the exhaust manifold.  Put it back together in the garage, started her up, revved a little, and really couldn't tell any change in sound or anything.  Not too surprising for a free, 15 min. mod.

THEN, this morning, I got in it to leave for work.  Pulled out of the driveway, and as soon as I got the throttle to about 40% or so, HOLY COW!!!  It sounds like a custom exhaust UNDER THE HOOD!  It's a VERY NOTICEABLE sound up through the RPMs as long as the throttle is around half open or better.  Then, once you back off (highway cruising), the sound COMPLETELY goes away.  Thus, I have created an air box which is whisper quiet at idle and cruising, but makes a real roar under acceleration or hill climbing.  Didn't really notice any performance gain, but to be honest, I didn't really expect to.  I was more thinking that when I add a K&N filter and eventually cat-back exhaust, it will need more air than the stock tube could provide.

I think I like the sound, but my wife will frown.  At least she doesn't drive it very often . . .

I have a drop-in K&N on order, so we'll see how that changes the tone when it goes in.  Then, later on, the cat-back exhaust will probably drown out the intake anyway . . .

Anyone else had this experience with their air box?  Different sound with K&N vs. paper in stock box?

This was an old dirt bike trick, drill the intake filter box for more flow, I tried
it on my 1.6 Sidekick and got the same results, about nothing, except more
dirt and water now can get to the filter, never had any problems, but now
it can happen easier than before

Wild

Update:

Got the K&N filter installed last night.  No noticeable change in sound, and nothing OBVIOUS in the power department.  But, in morning traffic, I wasn't really able to push it.  We'll see how it does on the infamous uphill freeway ramp this afternoon. . .

Most of what you gained in extra flow from the holes is lost to the hotter under hood air temperature.

To make real gains (usually about 5hp), you need to set it up so the inlet draws pressurized cold air (from the truck moving) in from either the grill or the cowl with no sharp turns.


K&N filters flow more air because the filter has bigger holes in it.
This means it lets more dirt through as-is compared to a top quality paper filter unless meticulously maintained with proper cleaning and oiling.
Usually not too big a problem for cars, but not so good for off-roaders.

It's a good idea to add the extra foam pre-cleaner cover made for 4x4s
http://www.knfilters.com/airforcewraps.htm