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Old 05-01-2007, 11:52 AM   #1
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Default Worthwile to gut the airbox?

I've been doing some searching on the topic of gutting the airbox after thinking of doing it with mine. It seems that just about all the threads I found involved people with supercharged engines. Some added hp would be nice, but I'm mainly after increasing gas mileage since I put on 16,000 miles a year. Right now I drive 300-350 miles per week, with about 220 of it being strictly highway. Even one mpg increase would be worth it assuming there are no adverse affects. I'm assuming it is also of benefit to an NA car, but just want confirmation.
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Old 05-01-2007, 11:54 AM   #2
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There'* little to gut on your 2000 IIRC, a K&N only would probably be the better way to go.
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Old 05-01-2007, 11:55 AM   #3
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I don't see why you wouldn't gain a MPG or 2. Car companies resonate airboxes to make them quiet, and it sacrifices 1 or 2 MPGs and some HP. For example, we gutted my dad'* airbox and removed the large resonator on his '03 Durango. On average, he gained 2-3 MPG, and it def. feels more powerful. So I am a strong believer that gutting a airbox does help. But if I recall, the Airbox on yours is fairly open.
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Old 05-01-2007, 12:35 PM   #4
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Quote:
Originally Posted by Bonneville94V688
I don't see why you wouldn't gain a MPG or 2. Car companies resonate airboxes to make them quiet, and it sacrifices 1 or 2 MPGs and some HP. For example, we gutted my dad'* airbox and removed the large resonator on his '03 Durango. On average, he gained 2-3 MPG, and it def. feels more powerful. So I am a strong believer that gutting a airbox does help. But if I recall, the Airbox on yours is fairly open.
I don't know if the Durango'* airbox or filter size is a restriction, so I can't comment on that.

As for our H-bodies...I'm still waiting for someone to post data proving an increase in mpg (or performance) with a gutted airbox (or ricepipe, or whatever) and/or a K&N (or similar) filter, on an otherwise essentially stock n/a 3800 (stock cam, stock rockers, stock TB, stock LIM).

Just running the numbers, on a stock n/a 3800, the first restriction you're going to find in the intake system is easily the LIM-to-head ports--that'* been proven to my satisfaction on this board, and is fixed by (gently) porting the LIM. After that should be intake valve lift (fix with rockers or a cam and valvesprings). After that should be TB bore (fix with a bigger-bore TB). ONLY after all that should the hole in the front of the airbox become a restriction, and more so on the 99 and older-style airbox (fix by modifying the front half of the box). Only after all THAT should the OEM-style filter become a restriction, and only if you believe it flows 20% or less (if I recall my calc'* correctly) of the air that hits it.

(I'm not sure yet where ported exhaust manifolds fit into all this...the numbers say somewhere between rockers and needing an oversized TB)

After all that, you're getting into bigger valves, way-hogged-out heads, super-aggressive cams, headers, and other big-ticket items that are way beyond anything I want or need on my daily driver...these things might actually benefit from aftermarket intake mods.

To make a long story short, just gutting the airbox and installing a K&N shoudn't gain you squat, unless you've done some of the other items already. And frankly, there just ain't no data nowhere that demonstrates otherwise.

In the end, my guess is that most people who see something with a K&N filter (or with typical intake mods) are simply replacing a clogged-up OEM filter that needed to be replaced 20,000 miles ago anyway.
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Old 05-01-2007, 02:15 PM   #5
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Generally speaking, I believe gutting an airbox will gain you something, at LEAST some horsepower (may or may not be 'noticeable' hp). IMO, the FIRST restriction is where the air ENTERS the car - naturally - which would be the intake/airbox. You can have matched ports on everything, but if you have an airbox that is designed like a maze, it will hurt you. I don't have data here to prove that, I'm just making some educated guesses on what I know.

If you know what the L27 airbox looks like, it'* pretty restrictive, not to mention the 5 resonators on my 94 L67 stock airbox.

Replacing the stock airbox with a cone filter intake will show gains on a totally stock (nothing ported) engine, so I'd definitely say a gutted airbox is an improvement, if only a small one.

Bill W gutted/added tubes into Zilla'* stock airbox (years ago ) and I guarantee that showed some hp gains and fuel mileage gains when he wasn't on the throttle.
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Old 05-01-2007, 04:13 PM   #6
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I am working on testing a gutted airbox vs a 3" warm air intake (w/ K&N 9" cone) vs a Intense 3.5" FWI on a 2002 Park Avenue Ultra.
Was getting 20 mpg average with the WAI over the winter and swapped to the FWI and on the first tank, driven very conservatively we noticed only a .2 mpg increase -so small it is hard to say what made the difference.
Running the FWI on it'* second tank and so far it hasn't changed much, and as soon as this tank is done the gutted stock air box with K&N drop in is going back on.

Will update from there.... sorry, I don't have a stock air box to use for a base comparison.
I may have to do the test over as it looks like the car still has it'* original plugs and wires in it at 80k miles.
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Old 05-01-2007, 04:26 PM   #7
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put that WAI on in the summer and it will kill you.. thats why we need the FWI
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Old 05-01-2007, 05:19 PM   #8
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Not that I have the data to prove, but doesnt more air mean more fuel which means more HP in the end result? I mean thats what the PCM does doesnt it? Adjusts the fuel to air mixture depending on how much air is being brought into the car? I noticed an improvement just jumping on the pedal. Even more so now that I have a 3.4 on the SC.
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Old 05-01-2007, 05:36 PM   #9
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i did gut my air box on my regal, beside the sound on a cool start and at WOT i did not see much improvement but mine was really bad the way it is stock whit 2 90degrees .but it did feel a bit better on gaz .so do it for sure you wont loose anything
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Old 05-01-2007, 05:50 PM   #10
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Without other mods first, the L36 just doesn't suck enough air for anything from the airbox to the UIM to be a restriction.

Compared with the L36 guys, you L67 guys (at least from about '96 up) have a much larger TB bore from the factory, plus your engine has a good 15-20% higher Volumetric Efficiency with the */C blowing. Unlike an L36, I expect you guys would benefit from a gutted airbox (or other intake option) as a very first mod. I would think this would especially apply in the model years '96 to '99, as you would have both the larger TB and (from what I've seen) a more restrictive stock airbox.

That'* why, after a ported LIM, rockers and a front PEM, I'll likely be at the point of looking at modding an L67 TB to fit my '98 L36, and using an airbox gutted in the front half. That should be enough to get me through any further mods I might contemplate for this car.

P.*., about the noise, I have discovered that gutting the baffle from JUST the front half is far less noisy than gutting both the front AND the rear (I have both a full unmodded stock and gutted stock airbox for the '98, and I've been playing around with interchanging the halves). As the tube in the rear half is far larger than your stock TB bore already (n/a or */C), there'* no significant restriction there and thus no need I can see to gut it.

EDIT: I really should get some data on this, so I can shut up.
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