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Old 01-26-2003, 05:10 PM   #1
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Default Factory Airbox on SC engine

Guys, I was checking filters and such yesterday, and decided to have a good look at the inside of my airbox. I found my MAF screen had some of its fins bent. Looked like someone ran a screwdriver accross it or something. So, I removed it. Once the C clip was out, it didn't take much work to carefully work it out.

The next thing I did was take a good look into the TB, and then back through the airbox. The whole thing looks like it was pretty well engineered, in terms of the air pathway and size of the tubing that feeds the TB. Is a CAI really reeded on this car? The stock system doesn't look very restrictive at all, except for the paper filter.
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Old 01-26-2003, 05:42 PM   #2
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You want volume, yes, but you also want LAMINAR velocity. I've heavily modified my airbox, and have been assured that the ADTR intake will still improve performance. You can see my airbox on my website.
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Old 01-26-2003, 08:57 PM   #3
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Laminar, I assume means straight or layered uniformly. I would guess this means more air is able to get through faster due to less turbulance?

Anyhow, sounds logical, Will, and maybe I'm splitting hairs, here, but you have a different generation Bonnie than I have and I am wondering if there might have been some differences.

I don't mean to challenge you guys, at least not for anything other than to learn a thing or two from you. I am just wondering what the difference, in terms of measurable performance, might be with say, Hector'* intake vs. the factory box with a K&N filter.

In any event, I'm guessing, this isn't the most critical area. I'd bet the exhaust manifold, pulley and coils might make a bigger difference than the intake. The down-pipe from the exhaust is a good 3 inches, and the pipes from there back look almost as big. The TB, and the air intake in the factory box, hell i could fit most of my forearm in there, and I'm not a small guy.

Feel free to shoot me down here, cause I hope to learn from your experience.
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Old 01-26-2003, 10:33 PM   #4
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I just changed out my factory air box with a 4" PVC piped cone filter.
The biggest hurdle was adapting the 4 1/4" ID PVC 45 elbow connector to the 3 3/4" throttle body OD. I used some 1/4" sheet rubber and it works like a charm. I also bought a separate computer relocation box from Extreme Performance and a 7" long * & B cone filter with a 4" connection. A 4" pipe to 4" hose PVC connector adapts perfectly to the filter.
It did make a noticeable difference even though I retained the MAF screen on the throttle body. I plan to remove it later to see if it affects the idle quality. From other posts it is supposed to restrict WOT air flow by 15%.
The biggest difference is the sound when I put my foot into it. Awesome. Sounds like a jet engine winding up. Very cool. Even my wife likes the sound. It is hardly noticeable at idle.
My 0-60 times improved by a tenth or two.
I was a sceptic like you at first but now I am a believer.
Try it. You can always change it back if you don't like it but my bet is you won't.
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Old 01-27-2003, 12:19 AM   #5
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Thanks for the feedback. You are saying the screen restricts WOT flow, right? Not that removing it does? Anyhow, the idle seems fine. I ran it on the expressway last night, but my wife and I were on a date, so I didn't romp very hard. I'll have a better feel tomorrow when I go to work.

I'd been to Home Depot this weekend, and scoped out some plastic pipe and such. There were even some interestingly shaped central air ducting pieces that might make a good scoop for under the air dam or something.
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Old 01-27-2003, 10:28 PM   #6
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Yes the screen when installed is supposed to restrict at higher flows. Apparently it is there to smooth out the air flow so the MAF sensor can take accurate readings.

Some guys have experienced a rough idle when they remove it and stay with the factory air box and turbulent rubber bellow connector. I would think though that the turbulence should increase with WOT flows. That'* why for now I have left it in place....for now.

I was going to plumb some cold air up to the cone filter thru the existing hole in the fender that the stock air box connects to. Unfortunately the computer box gets in the way. You would have to strap the computer down somehow without the relocation box, but then it would not be covered.

I decided to fab up a simple heat shield using silver reflecto insulation. I shrouded the cone on two sides up to the underside of the hood and it is successful in reducing the air temperature that the cone sees from 130 F down to 85 F. It draws most of the air from the holes in the fender.
Remember 1% hp increase for every 10 F temperature decrease, but more importantly for supercharged engines, knock retard.
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Old 01-27-2003, 10:48 PM   #7
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So can we finally put the whole "is the factory airbox restrictive thing" and put it to rest? It'* amazing that this question is asked every week. I would not offer an intake if I did not believe it made a big enough difference. Basically if you have ever noticed, the factoyr intake restricts because it is made to be silent but also chokes the car at 5000+ rpm'* which is not good. Using 4" PVC..... alrighty.

ADTR is all about performance, we are different from other shops. We dont really care about looks but all power. That'* why I am having trouble deciding on a cat-back system for Bonneville'* because I want to squeeze as much power as possible out of it but people want sound I can't guarentee that with maximum performance.
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Old 01-28-2003, 01:49 AM   #8
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Article #18 in Techinfo, Tech know-how. Anyone who hasn't read it should do it!
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Old 01-28-2003, 01:52 AM   #9
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I'd like to put it to bed. I'm certain that CAI would be a good thing, and I'm sure you make a good product. Just trying to get to the meat of what the difference is, in terms of numbers. I can't speak for anyone but myself, but am guessing that it gets asked often because the claims made about such mods are usually pretty general in nature.

I really don't mean to beat a dead horse. I was hoping to learn some CFM rating, or similar comparison. One thing that did strike me when I had it apart was the size and shape of the sensor. Almost looks to me like it would mess with the airflow even if I had a straight pipe from outside the engine bay into the TB. Has anyone used one of those Tb airfoils? I've seen them in Jegs and Summit catalogs, and wondered if they really help.

Again, sorry to keep dredging this up. I'm just trying to get up to speed on it all. Thanks!
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Old 01-28-2003, 02:00 AM   #10
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If you had TBI or Carburation, the Vornado thing might help. You have a TB and multi-port.......our intake setup demands laminar velocity. Disrupting it would be like putting sugar in your tank. Yes, you could do it, but why would you want to? Your MAF sensor must be capable of reading the volume of air, and it must therefore NOT be turbulent. If you induce turbulence, the MAF will read low, and it will lean out your mixture.

To be honest with you, I haven't heard a single success story from anyone who'* tried the Vornado in any type of intake, and when I asked our local NAPA guy, he said he'* had more than 50% returned in disgust.

The article up in Techinfo was a compilation of knowledge that some of us gained (about 12 people had input, and there was general consensus on all points) over a period of years with other cars, and more specifically the Bonneville. In many respects, the bonneville is unique.
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