[lbpesq]

After reading this, I turned on my sound meter app on my cell phone while driving last night and found that at about 70 mph in 6th gear, the sound level inside my Cab was about 80 db. And I've got the airbox mod (with trim rings). I can't imagine driving a car that dumps 109 db of volume into the passenger compartment. That's the equivalent of a rock concert!



Bill

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[Rap]

Rock on Garth!

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[Rap]

Ibpesq, is that an iPhone app?

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[lbpesq]

Droid. It's called "Sound Meter Lite" and it's free. I'd expect there must be something similar for iPhone. It's a pretty cool little app.



Bill

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[Rap]

Thanks

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[DaveN]

As Electonics Technologist for the last 30+ years I wouldn't put my faith in an uncalibrated free Android app running ona cell phone <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" /> <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

You may be off by 20 dB due to the programming of the app and the quality/sensitivity/freq response of the microphone.

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[Rap]

Dave no doubt some validity to that statement. I downloaded a free iPhone db app. With the windows open and shut pretty close to equal reads 70-80. Lot to be said for free!

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[lbpesq]

I don't expect my free app to be the most accurate sound meter available, but it does seem to be in the same ballpark as others I've compared it to. It certainly isn't 20db off. . Nevertheless, as a musician I am somewhat familiar with sound levels and 109 db is very loud - the typical rock concert is in that range. My Cab isn't (except when I have the Grateful Dead station on!) <img src="/forum/images/smilies/968/rock.gif" class="smilie" alt="" />



Bill

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[Lear35A]

Is the air box mod article still available? The link doesn't work for me.

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[Cloud9...68]

Lance,



I have a PDF copy of the entire magazine, but it's 15.9 Mb, and I can't copy just the airbox mod article. I could email the pdf to you, if you'd like, but it's a huge file. Let me know.

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[tamathumper]

@Cloud, you can cut the pages out of the PDF with a free app like PDFTK, or with the website PDFEscape.com.

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[DaveN]

Ahhh the Dead <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />

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[Cloud9...68]

Tama,



Amazing - seems like all you have to do is imagine it, and - poof - there's a web site or app that does it! Still waiting for one that will fix a sprinkler head, time a 968's cams, or correct an alignment issue on an BMW E46, though...

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[flash]

i fixed the link.

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[986boxster1998]

I remeasured today and I stand corrected, my new measures are not nearly as loud. The application I was using (dB Meter Pro) must not have been calibrated correctly. Here are my new findings for Air Box Mod volume levels:



Temperature: 39 degrees (engine at operating temp just above the first bar)

1(Car off): 67dB

2 (Idle): 68dB

3 (3,000 RPM in 6th gear @ 72MPH): 70dB

4 (6,400 RPM in 1st gear): 73dB

5 (7,500 RPM in 2nd gear): 74dB (I have the Promax 7,700 RPM chip but hate even going up this high)



I still believe the 6% increase in volume that was previously recorded (103-109) should be fairly accurate; I dont have a base line for the new measures but can swap airboxs with a friend in the future.

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[lbpesq]

So the coupe really is quieter than the Cab. <img src="/forum/images/smilies/968/EmoticonCar.gif" class="smilie" alt="" /> It didn't seem to make sense the other way around.



Bill

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[986boxster1998]

Bill,



Your absolutely correct; I appreciate you bringing the erronious measurements to my attention. I had a 944 S2 cab a few years back and remember it filtering out noticably less then the coupe.



Thanks again, Dan

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[BeBe]

I have some 2x2-1/2 speaker port tubes (and a K&N filter) on the way to me and hope to do the airbox mod over the holidays. I see in the picture with the 9magazine article that the "flange" is up against the outer wall of the airbox. However, some of the "here's how mine looks" pictures have a "stack" outside the box. I'm trying to decide if I should cut the ports so that the flange is against the outside of the box with 1/2" to 5/8" inside or leave as is and have the remaining 2" outside the box. I don't remember much about fluid dynamics. I assume that the incoming air flow would get less turbulent as it went down the length of the tube, but in this case, the length is hardly bigger than the diameter so it shouldn't make much difference. To cut or not to cut? Opinions?

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[flash]

lol - we looked at that. the problem was space availability, and airflow in front of the box. the determination was that the small amount of added length was not effective in improving flow. now, if you could add about 3 inches, and then flute it...........



but still you would not be adding much. that's why we didn't go to a larger hole either. there was no gain. we already achieved zero negative pressure. without increasing the flow behind the airbox, there was no gain to be had by further altering the entry to it.

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[BeBe]

So there's no performance benefit. Anyone ever hear a difference between a flush mount vs. stack mod?

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