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Old 04-17-2016, 01:51 PM   #1
TiJohn
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Default My CAI isn't so loud (anymore)

When I first put my CAI on my car, I was quite surprised by how loud the "air sucking" noise was. I was expecting a new CAI "growl tone", but not the loud "air sucking"

After checking and checking for a coupler leak, I determined I don't have a leak. On the forums, it seems like a lot of people are complaining about how loud the CAI's are.

I started to wonder if there was effectively a sound-pipe type phenomenon happening that was bringing the noise generated by the air filter into the cabin. After only a few minutes testing, I determined there most certainly is!

Here was my test: With my wife sitting in my car and the windows up, I removed my intake, and played some music on my cell phone. I moved my cell phone around to all of the locations near my intake. When I pointed it up through the fender, my wife started knocking on the window, telling me that she could REALLY hear the music at that point.

So, I have made a prototype sound blocker/insulation from some flexible PVC sheeting that you can buy at home depot. It blocks the path to the fender, so the sound can't enter the fender area. After a single drive the change is amazing. The "air sucking" noise is reduced drastically! The CAI "growl" is still present, and now its more noticeable.

Side note: I think this is a reason for the stock pieces under the hood that fit the fenders and go around the hood strut mounts. I think those are there to block the engine noise to the cabin.

I am hoping some other people try this and find a more elegant solution. Mounting the PVC sheet is currently just done with cutting slits in the material and zip ties. Although everything is hidden once the intake is installed, I want to make a solution that is more robust.

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Old 04-17-2016, 02:21 PM   #2
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Good detective work.
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Old 04-17-2016, 02:44 PM   #3
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i wonder if there is a "sound" tube like in the BRZ/FRS
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Old 04-17-2016, 02:59 PM   #4
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Quote:
Originally Posted by crankWRX View Post
i wonder if there is a "sound" tube like in the BRZ/FRS
Not on the WRX, I think there is one on the STI. My WRX has a plug in the fire wall where the tube would go.
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Old 04-17-2016, 05:05 PM   #5
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Good job, I had the same thing going and had put 2 layers of dyno mat inside the box and in ever nook and crany I could fine. I love the growl and hated the suck.....
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Old 04-17-2016, 05:21 PM   #6
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Good find!
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Old 04-17-2016, 07:38 PM   #7
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Very interesting ! Love the idea. I've seriously been thinking about taking my cold air intake off and going back to the stock intake next time I tune w/ some more mods.
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Old 04-17-2016, 07:54 PM   #8
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I thought about doing this when I installed my CAI. I determined the same as you that the fender is not sealed. If you open your door, you can see the gap right through.

I Dynamatted my doors for my sound system and got an improvement, so never really bothered blocking off the fender. I still might later on though.
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Old 04-18-2016, 01:50 AM   #9
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Subbed
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Old 04-18-2016, 09:14 AM   #10
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Great find. I had been working towards fabricating a box, but this is way simpler.
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Old 04-18-2016, 09:44 AM   #11
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Nice find! I actually ended up going away from the ETS intake and back to stock since the damn thing was so loud.
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Old 04-18-2016, 09:46 AM   #12
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so even the ones in a sealed box are loud?
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Old 04-18-2016, 09:53 AM   #13
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Quote:
Originally Posted by jobber View Post
so even the ones in a sealed box are loud?
I had the boxed ETS one, and yeah, it was pretty gnarly. I suppose it could have been *worse* without a box. The positioning of it, plus the cars "newness", where stuff just seems to reverberate a lot more due to 'tightness', made it even worse IMHO. It felt insanely rice-burner in my mind.
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Old 04-18-2016, 09:57 AM   #14
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Quote:
Originally Posted by hotdog View Post
I had the boxed ETS one, and yeah, it was pretty gnarly. I suppose it could have been *worse* without a box. The positioning of it, plus the cars "newness", where stuff just seems to reverberate a lot more due to 'tightness', made it even worse IMHO. It felt insanely rice-burner in my mind.
damn... i was pretty stoked to try an intake soon.. even putting dynamat on the inside walls of the box? i guess that wouldn't really do anything, as its a different kind of noise..
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Old 04-18-2016, 10:00 AM   #15
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Never did Dynamat inside, but that obviously couldn't hurt. Getting *inside* the box might be a little tricky; not sure of how it's laid out internally, but not sure if you could really get Dynamat positioned. If you could, plus dynamatting the area that the OP showed, it certainly would help.
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Old 04-18-2016, 10:27 AM   #16
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I'm going to assume, since I don't have one and haven't researched because I don't intend to get one for my car... that the subject CAIs get their air intake from the passenger wheelwell area.

If so, I'll throw this out for consideration: You may find your MAF calibrations are no longer accurate... at speed. This does not apply to static calibrations, low (sub 65-70 mph) speeds, or those determined on a dyno... just at speed, and the faster the speed the more the calibrations are affected.

To elaborate, on my '11 STi I did extensive modifications and testing with an AEM intake. The end product was a true COLD AIR (as in true ambient, or outside-the-car) intake. I sealed that wheelwell... pretty much totally... from all air except frontal air that I directed by ducting into it. This kept my AIT in concert with the OEM front temp monitor in the grill when moving. It also, after extensive recalibrations of the MAF, extended top-end power... I made more power the faster I went. The HP curve flattened out on the top-end as speed increased, in other words. This is because the air intake became pressurized. In addition to other affects the turbo compressor efficiency is increased. I have a detailed thread on this on another Subaru website.

But to make this work, took a lot of work with the MAF calibrations. It was worth it. Along with the other mods, some also unique, my STi ran away and hid from a big modern motored hotshot from 70 up to 135, where the gap was rapidly widening.

Remember, while it isn't apparent part of the car's total airflow picture is the fenderwell "ducting." Opening up the outlet holes at the rear of the fenderwell was a common mod for the GR. A byproduct is the fenderwell doesn't get pressurized by frontal air at speed.

THE POINT of this post is... things may change when you have a CAI in the fenderwell and you block off the rear venting of said fenderwell.

Some reading that corroborates the above; http://www.cnlperformance.com/MAF_info.php?section=15
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Old 04-18-2016, 10:44 AM   #17
jobber
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Quote:
Originally Posted by SeeeeeYa View Post
I'm going to assume, since I don't have one and haven't researched because I don't intend to get one for my car... that the subject CAIs get their air intake from the passenger wheelwell area.

If so, I'll throw this out for consideration: You may find your MAF calibrations are no longer accurate... at speed. This does not apply to static calibrations, low (sub 65-70 mph) speeds, or those determined on a dyno... just at speed, and the faster the speed the more the calibrations are affected.

To elaborate, on my '11 STi I did extensive modifications and testing with an AEM intake. The end product was a true COLD AIR (as in true ambient, or outside-the-car) intake. I sealed that wheelwell... pretty much totally... from all air except frontal air that I directed by ducting into it. This kept my AIT in concert with the OEM front temp monitor in the grill when moving. It also, after extensive recalibrations of the MAF, extended top-end power... I made more power the faster I went. The HP curve flattened out on the top-end as speed increased, in other words. This is because the air intake became pressurized. In addition to other affects the turbo compressor efficiency is increased. I have a detailed thread on this on another Subaru website.

But to make this work, took a lot of work with the MAF calibrations. It was worth it. Along with the other mods, some also unique, my STi ran away and hid from a big modern motored hotshot from 70 up to 135, where the gap was rapidly widening.

Remember, while it isn't apparent part of the car's total airflow picture is the fenderwell "ducting." Opening up the outlet holes at the rear of the fenderwell was a common mod for the GR. A byproduct is the fenderwell doesn't get pressurized by frontal air at speed.

THE POINT of this post is... things may change when you have a CAI in the fenderwell and you block off the rear venting of said fenderwell.

Some reading that corroborates the above; http://www.cnlperformance.com/MAF_info.php?section=15
great post, i will read that later. makes sense that blocking that rear air path with a pic sheet could effect something or other..
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Old 04-18-2016, 12:18 PM   #18
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Quote:
Originally Posted by jobber View Post
great post, i will read that later. makes sense that blocking that rear air path with a pic sheet could effect something or other..
Could is the right word. After thinking it over I'd guess there are enough leaks in the wheelwell void to vent most extra air. It is still something to consider, however.

I sealed all those leaks... because (and I hate to open this subject) underhood heated air invades that space and affects AIT. That was what spurred my initial sealing mods. I wanted my AEM to be a CAI but found (because I had multiple temperature probes) that hot engine air was being vented, purposely, partly through the fender venting. It was only after I'd succeeded in that aspect that I found the influences that made on my calibrations. Also, anytime the fans are on the engine bay is "pressurized," forcing the heated air to escape through any means possible. That means through the wheelwell and into where everyone thinks they have a CAI. lol

Hopefully, few drive their cars at super illegal speeds, but if they do and have a blocked wheelwell with a boxed CAI in it... it may, or may not, be an issue. I'm just saying, be aware of that possibility. It could be a bad thing.
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Old 04-19-2016, 12:40 AM   #19
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Quote:
Originally Posted by hotdog View Post
I had the boxed ETS one, and yeah, it was pretty gnarly. I suppose it could have been *worse* without a box. The positioning of it, plus the cars "newness", where stuff just seems to reverberate a lot more due to 'tightness', made it even worse IMHO. It felt insanely rice-burner in my mind.
I had the Cobb intake w/ box and now have the PRL w/out box. Cobb with box was much louder. In all honesty after seeing this thread and how the sound travels thru the fender it makes sense that the boxed intake was louder.
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Old 04-19-2016, 01:23 AM   #20
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Quote:
Originally Posted by Nuked View Post
I had the Cobb intake w/ box and now have the PRL w/out box. Cobb with box was much louder. In all honesty after seeing this thread and how the sound travels thru the fender it makes sense that the boxed intake was louder.
wow. so the opposite.. boxed intakes are LOUDER?? good info.
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Old 04-19-2016, 01:48 AM   #21
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Quote:
Originally Posted by jobber View Post
wow. so the opposite.. boxed intakes are LOUDER?? good info.
The box just makes the filter get all the air from the fender void. Of course it is louder. It's the fender void where all the noise gets directed to the cabin. The 'boxes' aren't sealed.....
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Old 04-19-2016, 02:27 AM   #22
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Quote:
Originally Posted by -Raven- View Post
The box just makes the filter get all the air from the fender void. Of course it is louder. It's the fender void where all the noise gets directed to the cabin. The 'boxes' aren't sealed.....
i thought it gets the air from that scoop at the front grill, if the intake uses that stock piece. i have to look at the setup soon, to really understand about this fender thing.
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Old 04-19-2016, 06:54 AM   #23
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Quote:
Originally Posted by jobber View Post
i thought it gets the air from that scoop at the front grill, if the intake uses that stock piece. i have to look at the setup soon, to really understand about this fender thing.
Yeah they aren't a fully sealed box like OEM, just more of a heat shield from the heat of the engine bay. Some do utilise the stock intake scoop like the Process West one I have.
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Old 04-19-2016, 06:56 AM   #24
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Quote:
Originally Posted by -Raven- View Post
Yeah they aren't a fully sealed box like OEM, just more of a heat shield from the heat of the engine bay. Some do utilise the stock intake scoop like the Process West one I have.
are there any that are a true sealed box aftermarket system?
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Old 04-19-2016, 07:37 AM   #25
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Quote:
Originally Posted by jobber View Post
are there any that are a true sealed box aftermarket system?
Not that I am aware of off hand.

Like Raven said, the box is only 4 sides (front, back, top and one side), The factory intake is used on most, but again thats only a small 5"x5" (apx) opening compared to the open bottom and side.

I really like Seee Ya's idea and have been considering doing something similar. Just one of those projects to tackle when I get a week off work. With the way the fog light housing and lower splash shield is oriented, you could probably make a nice sealed unit with ducting to provide a true cold air intake.
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